Science.gov

Sample records for triplet state spectra

  1. The Triplet State

    NASA Astrophysics Data System (ADS)

    Zahlan, A. B.

    2010-01-01

    Preface; List of participants; Part I. Spin-orbit Coupling and Intersystem Crossing: 1. Spin-orbit interactions in organic molecules; 2. Singlet-triplet transitions in organic molecules; 3. Triplet decay and intersystem crossing in aromatic hydrocarbons; 4. Statistical aspects of resonance energy transfer; Discussion; Part II. Magnetic Resonance and Magnetic Interactions: 5. Magnetic resonance spectra of organic molecules in triplet states in single crystals; 6. Magnetic interactions related to phosphorescence; 7. ESR investigations of naphthalene-d8:Naphthalene-h8 mixed crystals; 8. Biradicals and polyradicals in the nitroxide series; 9. Changes induced in the phosphorescent radiation of aromatic molecules by paramagnetic resonance in their metastable triplet states; 10. Paramagnetic resonance of the triplet state of tetramethylpyrazine; 11. On magnetic dipole contributions to the intrinsic S0 = T1 transition in simple aromatics; Discussion; Part III. Photochemistry: 12. The kinetics of energy transfer from the triplet state in rigid solutions; 13. Triplet states in gas-phase photochemistry; 14. Biphotonic photochemistry, involving the triplet state: polarisation of the effective T-T transition and solvent effects; 15. Direct and sensitised photo-oxidation of aromatic hydrocarbons in boric acid glass; Discussion; Part IV. Radiationless Transitions: 16. Radiationless transitions in gaseous benzene; 17. Low-lying excited triplet states and intersystem crossing in aromatic hydrocarbons; 18. De-excitation rates of triplet states in condensed media; 19. Lifetimes of the triplet state of aromatic hydrocarbons in the vapour phase; Discussion; Part V. Triplet Excitons: 20. Some comments on the properties of triplet excitons in molecular crystals; 21. Exact treatment of coherent and incoherent triplet exciton migration; 22. Magnetic susceptibility of a system of triplet excitons: Würster's Blue Perchlorate; 23. A study of triplet excitons in anthracene crystals under laser excitation; 24. The electronic states in crystaline anthracene; Discussion; Part VI. Delayed Fluorescent and Phosphorescence: 25. Delayed fluorescence of solutions; 26. The kinetics of the excited states of anthracene and phenanthrene vapor; 27. Optical investigations of the triplet states of naphthalene in different crystalline environments; 28. Excitation of the triplet states of organic molecules; 29. The delayed luminescence and triplet quantum yields of pyrene solutions; 30. Triplet state studies of some polyphenyls in rigid glasses; 31. Decay time of delayed fluorescence of anthracene as a function of temperature (2-30ºK); 32. Energy transfer between benzene and biacetyl and the lifetime of triplet benzene in the gas phase; 33. Charge transfer triplet state of molecular complexes. 34. Flash-photolytic detection of triplet acridine formed by energy transfer from biacetyl; 35. Extinction coefficients of triplet-triplet transitions between 3000 and 8800 A in anthracene; 36. Anthracene triplet-triplet annihilation rate constant; Discussion; Part VII. Triplet State Related to Biology: 37. ESR and optical studies of some triplet states of biological interest; 38. The triplet state of DNA; 39. Some characteristics of the triplet states of the nucleic bases; Discussion; Indexes.

  2. Singlet and triplet state spectra and dynamics of structurally modified peridinins.

    PubMed

    Fuciman, Marcel; Enriquez, Miriam M; Kaligotla, Shanti; Niedzwiedzki, Dariusz M; Kajikawa, Takayuki; Aoki, Kazuyoshi; Katsumura, Shigeo; Frank, Harry A

    2011-04-21

    The peridinin-chlorophyll a-protein (PCP) is a light-harvesting pigment-protein complex found in many species of marine algae. It contains the highly substituted carotenoid peridinin and chlorophyll a, which together facilitate the transfer of absorbed solar energy to the photosynthetic reaction center. Photoexcited peridinin exhibits unorthodox spectroscopic and kinetic behavior for a carotenoid, including a strong dependence of the S(1) excited singlet state lifetime on solvent environment. This effect has been attributed to the presence of an intramolecular charge transfer (ICT) state in the molecule. The present work explores the effect of changing the extent of ?-electron conjugation and attached functional groups on the nature of the ICT state of peridinin and how these factors affect the excited singlet and triplet state spectra and kinetics of the carotenoid. In this investigation three peridinin analogues denoted C-1-R-peridinin, C-1-peridinin, and D-1-peridinin were synthesized and studied using steady-state absorption and fluorescence techniques and ultrafast time-resolved transient absorption spectroscopy. The study explores the effect on the singlet and triplet state spectra and dynamics of removing the allene group from the peridinin structure and either replacing it with a rigid furanoid ring, replacing it with an epoxide group, or extending the polyene chain into the ?-ionylidine ring. PMID:21452802

  3. 13C isotope shifts of anthracene and naphthalene isomers in triplet state optical spectra

    NASA Astrophysics Data System (ADS)

    Doberer, U.; Port, H.; Rund, D.; Tuffentsammer, W.

    Position-specific 13C isotope shifts in the T1?S0 photoexcitation spectra of anthracene and naphthalene crystals containing 13C substituted molecules in natural abundance and of material enriched with various synthesized 13C isomers are compared. From the spectra of matrix isolated A-h10 in A-d10 and N-h8 in N-d8 the individual isotope shifts U0 of all the 13C monosubstituted isomers are determined (with values U0 between 0·7 and 3·5 cm-1). An additivity rule is established for the U0 of the twofold substituted 13C 13C isomers similar to that found for multiple deuteration. Applying these results also the 13C substructure of the excitonic Davydov components in anthracene and naphthalene crystals is understood quantitatively. A correlation between the specific 13C isotope shifts and the triplet state spin density distribution is discussed.

  4. Triplet excited state spectra and dynamics of carotenoids from the thermophilic purple photosynthetic bacterium Thermochromatium tepidum

    SciTech Connect

    Niedzwiedzki, Dariusz; Kobayashi, Masayuki; Blankenship, R. E.

    2011-01-13

    Light-harvesting complex 2 from the anoxygenic phototrophic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption, fluorescence and flash photolysis spectroscopy. Steady-state absorption and fluorescence measurements show that carotenoids play a negligible role as supportive energy donors and transfer excitation to bacteriochlorophyll-a with low energy transfer efficiency of ~30%. HPLC analysis determined that the dominant carotenoids in the complex are rhodopin and spirilloxanthin. Carotenoid excited triplet state formation upon direct (carotenoid) or indirect (bacteriochlorophyll-a Q{sub x} band) excitation shows that carotenoid triplets are mostly localized on spirilloxanthin. In addition, no triplet excitation transfer between carotenoids was observed. Such specific carotenoid composition and spectroscopic results strongly suggest that this organism optimized carotenoid composition in the light-harvesting complex 2 in order to maximize photoprotective capabilities of carotenoids but subsequently drastically suppressed their supporting role in light-harvesting process.

  5. Excited-state triplet-triplet absorption in. cap alpha. NPO

    SciTech Connect

    Dharamsi, A.N.; Hassam, A.B.

    1987-11-01

    Time-resolved excited-state triplet-triplet absorption measurements in ..cap alpha..NPO solutions were performed. A concentration quenching effect on the excited absorption and fluorescence spectra, due to excimer formation, was seen. A numerical analysis of the results yielded the rate constants for intersystem crossing, triplet quenching by O/sub 2/, triplet self-quenching, and excimer formation.

  6. Triplet state photoassociation of LiNa

    NASA Astrophysics Data System (ADS)

    Rvachov, Timur; Jamison, Alan; Jing, Li; Jiang, Yijun; Zwierlein, Martin; Ketterle, Wolfgang

    2015-05-01

    Ultracold molecules have promise to become a useful tool for studies in quantum simulation and ultracold chemistry. We aim to produce ultracold fermionic 6Li23Na molecules in the triplet ground state. Due to the small mass, small spin-orbit coupling, and fermionic character of LiNa, the triplet ground state is expected to be long lived. We report on photoassociation spectra of LiNa to its triplet excited states from an ultracold mixture. This is the first observation of these excited triplet potentials, which have been previously difficult to observe in heat-pipe experiments due to the small spin-orbit coupling in the system. Determining the excited state potentials is a key milestone towards forming triplet ground state LiNa via two-photon STIRAP. Work supported by the NSF, AFOSR-MURI, ARO-MURI, and NSERC.

  7. Structure of the triplet excited state of bromanil from time-resolved resonance Raman spectra and simulation

    NASA Astrophysics Data System (ADS)

    Puranik, Mrinalini; Umapathy, Siva; Snijders, Jaap G.; Chandrasekhar, Jayaraman

    2001-10-01

    Time-resolved resonance Raman (TR3) spectroscopy has been used to study the structure of the triplet excited state of bromanil. These experimental results were then simulated using parameters from density functional theoretical (DFT) calculations and wave packet dynamics, in order to understand the structure and mode-specific displacements of the resonant excited state. The transition dipole moments and the energy separation of the T1 and Tn states were obtained from time-dependent DFT calculations. We have demonstrated application of the technique to tetrabromo-p-benzoquinone. From our calculations, the observed T1?Tn absorption spectrum has been assigned to the 3Bg?3Bu transition. The geometry has been optimized for the resonant higher triplet state, Tn, and is found to be in good agreement with the predictions of the wave packet dynamical simulations. Mode-specific displacements of the triplet state geometry have been obtained from simulations and these have been rationalized with respect to the molecular orbital involved. Thus, we have demonstrated that from the simulations of the experimental TR3 spectral data, valuable additional information can be derived on the structure of the transient states that may then be used for elucidation of structure-reactivity correlation in the future.

  8. Time-resolved electron paramagnetic resonance spectra of photoexcited triplet states of electron-donor-acceptor complexes in frozen solution: Methylated benzenes and chlorinated phthalic anhydrides

    NASA Astrophysics Data System (ADS)

    Murai, Hisao; Minami, Masashi; I'Haya, Yasumasa J.

    1994-09-01

    Phthalic anhydride (PA) and chlorinated PAs in frozen methyl substituted benzenes provided the time-resolved electron paramagnetic resonance (TREPR) spectra of the electron-donor-acceptor (EDA) complexes. The chlorine substitution of PA reduced the zero-field splitting parameters, D, due to the contribution of the spin-orbit interaction caused by heavy atoms such as chlorine. The increase of the number of methyl group on benzene, which apparently reduced the ionization potential, worked to decrease the D value of the EDA complex. The charge-transfer (CT) ratios were measured more exactly by the absolute value of (Delta m(sub s)) = 1 transition of the triplet states. The major axes of these systems were also safely presumed. The sign of the 100% charge transferred EDA complex was found negative because of the CT ratio plots and the spin-polarization pattern of the TREPR spectra.

  9. Triplet-state optical spectra of highly concentrated isotopically mixed crystals of anthracene A- h10: A- d10

    NASA Astrophysics Data System (ADS)

    Rund, D.; Port, H.

    1983-08-01

    Photoexcitation spectroscopy with a dye laser is applied to study highly concentrated isotopically mixed crystals of anthracene A- h10: A- d10 in the region of the T 1 ? S v 0-0 transition. The spectra of the separated A- h10 and A- d10 subbands are measured in polarized light at 6 K. The concentration-dependent intensities and energetic positions of the subbands are described quantitatively using the moment-expansion method of the mixed-crystal Green's function.

  10. Bright Solid State Source of Photon Triplets

    E-print Network

    Khoshnegar, Milad; Predojevi?, Ana; Dalacu, Dan; Prilmüller, Maximilian; Lapointe, Jean; Wu, Xiaohua; Tamarat, Philippe; Lounis, Brahim; Poole, Philip; Weihs, Gregor; Majedi, Hamed

    2015-01-01

    Producing advanced quantum states of light is a priority in quantum information technologies. While remarkable progress has been made on single photons and photon pairs, multipartite correlated photon states are usually produced in purely optical systems by post-selection or cascading, with extremely low efficiency and exponentially poor scaling. Multipartite states enable improved tests of the foundations of quantum mechanics as well as implementations of complex quantum optical networks and protocols. It would be favorable to directly generate these states using solid state systems, for better scaling, simpler handling, and the promise of reversible transfer of quantum information between stationary and flying qubits. Here we use the ground states of two optically active coupled quantum dots to directly produce photon triplets. The wavefunctions of photogenerated excitons localized in these ground states are correlated via molecular hybridization and Coulomb interactions. The formation of a triexciton leads...

  11. The triplet excited state of Bodipy: formation, modulation and application.

    PubMed

    Zhao, Jianzhang; Xu, Kejing; Yang, Wenbo; Wang, Zhijia; Zhong, Fangfang

    2015-12-21

    Boron dipyrromethene (Bodipy) is one of the most extensively investigated organic chromophores. Most of the investigations are focused on the singlet excited state of Bodipy, such as fluorescence. In stark contrast, the study of the triplet excited state of Bodipy is limited, but it is an emerging area, since the triplet state of Bodipy is tremendously important for several areas, such as the fundamental photochemistry study, photodynamic therapy (PDT), photocatalysis and triplet-triplet annihilation (TTA) upconversion. The recent developments in the study of the production, modulation and application of the triplet excited state of Bodipy are discussed in this review article. The formation of the triplet state of Bodipy upon photoexcitation, via the well known approach such as the heavy atom effect (including I, Br, Ru, Ir, etc.), and the new methods, such as using a spin converter (e.g. C60), charge recombination, exciton coupling and the doubly substituted excited state, are summarized. All the Bodipy-based triplet photosensitizers show strong absorption of visible or near IR light and the long-lived triplet excited state, which are important for the application of the triplet excited state in PDT or photocatalysis. Moreover, the methods for switching (or modulation) of the triplet excited state of Bodipy were discussed, such as those based on the photo-induced electron transfer (PET), by controlling the competing Förster-resonance-energy-transfer (FRET), or the intermolecular charge transfer (ICT). Controlling the triplet excited state will give functional molecules such as activatable PDT reagents or molecular devices. It is worth noting that switching of the singlet excited state and the triplet state of Bodipy may follow different principles. Application of the triplet excited state of Bodipy in PDT, hydrogen (H2) production, photoredox catalytic organic reactions and TTA upconversion were discussed. The challenges and the opportunities in these areas were briefly discussed. PMID:26465741

  12. Toward Triplet Ground State LiNa Molecules

    NASA Astrophysics Data System (ADS)

    Jamison, Alan; Rvachov, Timur; Jing, Li; Jiang, Yijun; Zwierlein, Martin; Ketterle, Wolfgang

    2015-05-01

    We present progress toward creation of ultracold ground-state triplet LiNa molecules. This molecule is expected to have a long lifetime in the triplet ground state due to its fermionic nature, large rotational constant, and weak spin-orbit coupling. The triplet state has both electric and magnetic dipole moments, affording unique opportunities in quantum simulation and ultracold chemistry. Our progress includes the first observation of triplet excited states in this molecule, achieved through photoassociation of ultracold mixtures of 6-Li and Na. We compare experimental results to a variety of near-dissociation expansions as well as ab initio potentials.

  13. Stability of triplet rubidium ground-state molecules

    E-print Network

    Verhaar, B J

    2014-01-01

    Experiments involving ultracold molecules require sufficiently long lifetimes, which can be very short for excited rovibrational states in the molecular potentials. For alkali atoms such as rubidium, molecular, rovibrational ground-states can both be found in the electronic singlet and triplet configurations. The molecular singlet ground state is absolutely stable, however, the triplet ground state can decay to a deeper bound singlet molecule due to a radiative decay mechanism that involves the interatomic spin-orbit interaction. We investigate this mechanism, and find the lifetime of rubidium molecules in the triplet rovibrational ground-state to be about 13 minutes. This is sufficiently long for experimental purposes.

  14. Hydrogen abstraction by triplet flavins. I: time-resolved multi-channel absorption spectra of flash-irradiated riboflavin solutions in water

    NASA Astrophysics Data System (ADS)

    Bernt Melø, Thor; Adriana Ionescu, Maria; Haggquist, G. W.; Razi Naqvi, K.

    1999-09-01

    Multichannel detection with ?s time resolution has been used for recording flash-induced changes in the absorbance of deaerated solutions of riboflavin in phosphate buffer at pH 6.8. By comparing the spectra of solutions containing, in addition to riboflavin (F v), different substrates (ascorbic acid, EDTA, indole acetic acid, tryptophan), and by recording the absorption spectrum of the neutral tryptophyl radical (produced by flash photolysis of aqueous solutions of tryptophan), the absorption spectrum and the extinction coefficient of F vH rad are ascertained. Under the experimental conditions pertaining to the present investigation (solute concentration (7.5±2.5)×10 -5 M, ca. 10% conversion into triplets), quenching of F v† (a riboflavin triplet) by F v0 (an unexcited riboflavin molecule) was found to be insignificant; most triplets appear to decay through triplet-triplet annihilation, the loss of two triplets being accompanied by the gain of one neutral semiquinone radical (F vH rad ). It is proposed that (i) triplets deactivate mainly through triplet-triplet annihilation, (ii) the annihilation event leads to the formation of an ion pair, F v†+F v†?F v++F v-, (iii) the anion rapidly converts to F vH rad , and (iv) the cation ejects a proton and splits into two neutral products, a molecule whose ground-state absorption spectrum resembles that of F v0, and an odd-electronic species containing the remainder of the aliphatic side chain.

  15. Direct Spectroscopic Detection and EPR Investigation of a Ground State Triplet Phenyl Oxenium Ion.

    PubMed

    Li, Ming-De; Albright, Toshia R; Hanway, Patrick J; Liu, Mingyue; Lan, Xin; Li, Songbo; Peterson, Julie; Winter, Arthur H; Phillips, David Lee

    2015-08-19

    Oxenium ions are important reactive intermediates in synthetic chemistry and enzymology, but little is known of the reactivity, lifetimes, spectroscopic signatures, and electronic configurations of these unstable species. Recent advances have allowed these short-lived ions to be directly detected in solution from laser flash photolysis of suitable photochemical precursors, but all of the studies to date have focused on aryloxenium ions having closed-shell singlet ground state configurations. To study alternative spin configurations, we synthesized a photoprecursor to the m-dimethylamino phenyloxenium ion, which is predicted by both density functional theory and MRMP2 computations to have a triplet ground state electronic configuration. A combination of femtosecond and nanosecond transient absorption spectroscopy, nanosecond time-resolved Resonance Raman spectroscopy (ns-TR(3)), cryogenic matrix EPR spectroscopy, computational analysis, and photoproduct studies allowed us to trace essentially the complete arc of the photophysics and photochemistry of this photoprecursor and permitted a first look at a triplet oxenium ion. Ultraviolet photoexcitation of this precursor populates higher singlet excited states, which after internal conversion to S1 over 800 fs are followed by bond heterolysis in ?1 ps, generating a hot closed-shell singlet oxenium ion that undergoes vibrational cooling in ?50 ps followed by intersystem crossing in ?300 ps to generate the triplet ground state oxenium ion. In contrast to the rapid trapping of singlet phenyloxenium ions by nucleophiles seen in prior studies, the triplet oxenium ion reacts via sequential H atom abstractions on the microsecond time domain to ultimately yield the reduced m-dimethylaminophenol as the only detectable stable photoproduct. Band assignments were made by comparisons to computed spectra of candidate intermediates and comparisons to related known species. The triplet oxenium ion was also detected in the ns-TR(3) experiments, permitting a more clear assignment and identifying the triplet state as the ?,?* triplet configuration. The triplet ground state of this ion was further supported by photolysis of the photoprecursor in an ethanol glass at ?4 K and observing a triplet species by cryogenic EPR spectroscopy. PMID:26198984

  16. Direct Observation of Triplet-State Population Dynamics in the RNA Uracil Derivative 1-Cyclohexyluracil.

    PubMed

    Brister, Matthew M; Crespo-Hernández, Carlos E

    2015-11-01

    Investigation of the excited-state dynamics in nucleic acid monomers is an area of active research due to the crucial role these early events play in DNA and RNA photodamage. The dynamics and rate at which the triplet state is populated are key mechanistic pathways yet to be fully elucidated. Direct spectroscopic evidence is presented in this contribution for intersystem crossing dynamics in a uracil derivative, 1-cyclohexyluracil. It is shown that intersystem crossing to the triplet manifold occurs in one picosecond or less in acetonitrile solution-at least an order of magnitude faster than previously estimated experimentally. Broadband transient absorption measurements also reveal the primary electronic relaxation pathways of the uracil chromophore, including the absorption spectra of the (1)??*, (1)n?*, and (3)??* states and the rates of vibrational cooling in the ground and (3)??* states. The experimental results are supported by density functional calculations. PMID:26538051

  17. Room temperature triplet state spectroscopy of organic semiconductors

    E-print Network

    Reineke, Sebastian

    2013-01-01

    Organic light emitting devices and solar cells are machines that create, manipulate and destroy excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device performance in applications like displays and solar energy harvesting. This is complicated if the excited state is a triplet because the electronic transition is dark with a vanishing oscillator strength. As a consequence, triplet state spectroscopy must usually be performed at cryogenic temperatures to reduce competition from non-radiative rates. Here, we control non-radiative rates by engineering a solid-state host matrix containing the target molecule, allowing the observation of phosphorescence at room temperature and alleviating constraints of cryogenic experiments. We test these techniques on a wide range of materials with functionalities spanning multi-exciton generation (singlet exciton fission), organic light emitting device host materials, and thermally activated delayed fluorescen...

  18. Transient EPR Reveals Triplet State Delocalization in a Series of Cyclic and Linear ?-Conjugated Porphyrin Oligomers

    PubMed Central

    2015-01-01

    The photoexcited triplet states of a series of linear and cyclic butadiyne-linked porphyrin oligomers were investigated by transient Electron Paramagnetic Resonance (EPR) and Electron Nuclear DOuble Resonance (ENDOR). The spatial delocalization of the triplet state wave function in systems with different numbers of porphyrin units and different geometries was analyzed in terms of zero-field splitting parameters and proton hyperfine couplings. Even though no significant change in the zero-field splitting parameters (D and E) is observed for linear oligomers with two to six porphyrin units, the spin polarization of the transient EPR spectra is particularly sensitive to the number of porphyrin units, implying a change of the mechanism of intersystem crossing. Analysis of the proton hyperfine couplings in linear oligomers with more than two porphyrin units, in combination with density functional theory calculations, indicates that the spin density is localized mainly on two to three porphyrin units rather than being distributed evenly over the whole ?-system. The sensitivity of the zero-field splitting parameters to changes in geometry was investigated by comparing free linear oligomers with oligomers bound to a hexapyridyl template. Significant changes in the zero-field splitting parameter D were observed, while the proton hyperfine couplings show no change in the extent of triplet state delocalization. The triplet state of the cyclic porphyrin hexamer has a much decreased zero-field splitting parameter D and much smaller proton hyperfine couplings with respect to the monomeric unit, indicating complete delocalization over six porphyrin units in this symmetric system. This surprising result provides the first evidence for extensive triplet state delocalization in an artificial supramolecular assembly of porphyrins. PMID:26035477

  19. Triplet State Delocalization in a Conjugated Porphyrin Dimer Probed by Transient Electron Paramagnetic Resonance Techniques

    PubMed Central

    2015-01-01

    The delocalization of the photoexcited triplet state in a linear butadiyne-linked porphyrin dimer is investigated by time-resolved and pulse electron paramagnetic resonance (EPR) with laser excitation. The transient EPR spectra of the photoexcited triplet states of the porphyrin monomer and dimer are characterized by significantly different spin polarizations and an increase of the zero-field splitting parameter D from monomer to dimer. The proton and nitrogen hyperfine couplings, determined using electron nuclear double resonance (ENDOR) and X- and Q-band HYSCORE, are reduced to about half in the porphyrin dimer. These data unequivocally prove the delocalization of the triplet state over both porphyrin units, in contrast to the conclusions from previous studies on the triplet states of closely related porphyrin dimers. The results presented here demonstrate that the most accurate estimate of the extent of triplet state delocalization can be obtained from the hyperfine couplings, while interpretation of the zero-field splitting parameter D can lead to underestimation of the delocalization length, unless combined with quantum chemical calculations. Furthermore, orientation-selective ENDOR and HYSCORE results, in combination with the results of density functional theory (DFT) calculations, allowed determination of the orientations of the zero-field splitting tensors with respect to the molecular frame in both porphyrin monomer and dimer. The results provide evidence for a reorientation of the zero-field splitting tensor and a change in the sign of the zero-field splitting D value. The direction of maximum dipolar coupling shifts from the out-of-plane direction in the porphyrin monomer to the vector connecting the two porphyrin units in the dimer. This reorientation, leading to an alignment of the principal optical transition moment and the axis of maximum dipolar coupling, is also confirmed by magnetophotoselection experiments. PMID:25914154

  20. Triplet emission from poly(3,6-dibromo-N-vinylcarbazole): Spectra and kinetics

    SciTech Connect

    Starzyk, F.; Burkhart, R.D. )

    1989-01-01

    The triplet delayed emission of poly(3,6-dibromo-N-vinylcarbazole) (PdBVK) in a 2-methyltetrahydrofuran (MTHF) frozen solution at 77K was examined within the spectral and time regimes of 400-570 nm and 0.2-50 ms, respectively. The influence on optical absorption of bromine substitution into the carbazole ring (3- and 6-positions) of poly(N-vinylcarbazole), as well as delayed triplet emission spectra and the kinetic decays, was monitored. The phosphorescence spectra were recorded at different delay times after excitation. The phosphorescence decays were found to be essentially exponential in the wings of the phosphorescence band but showed unusual, definitely nonexponential, behavior in the range 460-475 nm, which is the range of maximum phosphorescence intensity. A resolution of the phosphorescence band into Gaussian components yielded excellent fits by using three components at delay times less than 2 ms and two components for spectra taken at longer delay times. Based upon an average of 12 different spectra recorded at various times after excitation, the calculated wavelengths at maximum intensity for these Gaussian components were found to be 448{plus minus}2 nm, 473{plus minus}4 nm, and 501{plus minus}8 nm.

  1. Long-distance electron transfer from a triplet excited state

    NASA Astrophysics Data System (ADS)

    Murtagh, James; Thomas, J. Kerry

    Electron transfer from the triplet excited state of N,N,N',N'-tetramethylphenylene diamine to phthalic anhydride has been monitored by phosphorescence emission decay. The kinetics of the transfer process were observed directly and the rate constant depends exponentially on the reacting distance, k(r) = 1 × 10 4 exp(-0.58 r) s -1. The electron transfer rate has been found to be invariant over the temperature interval 77-143 K.

  2. The triplet state of tanshinone I and its synergic effect on the phototherapy of cancer cells with curcumin.

    PubMed

    Zhang, Chenchen; Jiang, Shan; Li, Kun; Wang, Mei; Zhu, Rongrong; Sun, Xiaoyu; Wang, Qingxiu; Wang, ShiLong

    2015-11-01

    The excited triplet state of tanshinone I (Tan I) extracted from the traditional Chinese medicine Salvia miltiorrhiza Bunge was characterized by laser flash photolysis. The synergic effect of Tan I on the phototherapy of cancer cells with curcumin (Cur) was also investigated by MTT assay because the excited energy transfer from the triplet state of Tan I ((3)Tan I(?)) to Cur occurred. At the same time, the characteristic absorption spectra of (3)Tan I(?) were recorded, and its molar absorption coefficient and rate constants for several excited energy transfers were obtained. The photo-therapeutic effect of Cur is enhanced by combination with Tan I. PMID:26046496

  3. Room temperature triplet state spectroscopy of organic semiconductors

    PubMed Central

    Reineke, Sebastian; Baldo, Marc A.

    2014-01-01

    Organic light-emitting devices and solar cells are devices that create, manipulate, and convert excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device performance in applications like displays and solar energy harvesting. This is complicated if the excited state is a triplet because the electronic transition is ‘dark’ with a vanishing oscillator strength. As a consequence, triplet state spectroscopy must usually be performed at cryogenic temperatures to reduce competition from non-radiative rates. Here, we control non-radiative rates by engineering a solid-state host matrix containing the target molecule, allowing the observation of phosphorescence at room temperature and alleviating constraints of cryogenic experiments. We test these techniques on a wide range of materials with functionalities spanning multi-exciton generation (singlet exciton fission), organic light emitting device host materials, and thermally activated delayed fluorescence type emitters. Control of non-radiative modes in the matrix surrounding a target molecule may also have broader applications in light-emitting and photovoltaic devices. PMID:24445870

  4. Excited triplet states as photooxidants in surface waters

    NASA Astrophysics Data System (ADS)

    Canonica, S.

    2012-12-01

    The chromophoric components of dissolved organic matter (DOM) are generally the main absorbers of sunlight in surface waters and therefore a source of transient reactants under irradiation. Such short-lived species can be relevant for the fate of various classes of chemical contaminants in the aquatic environment. The present contribution focuses on the role of excited triplet states of chromophoric DOM, 3CDOM*, as transient photooxidants initiating the transformation and degradation of organic chemical contaminants. An early study [1] indicated that 3CDOM* may play a dominant role in the photo-induced transformation of electron-rich phenols, a conclusion which was later fortified by the results of transient absorption investigations using aromatic ketones as model photosensitizers [2] and by a recent careful analysis of the effect of oxygen concentration on transformation rates [3]. The variety of aquatic contaminants shown to be affected by triplet-induced oxidation has kept increasing, phenylurea herbicides [4], sulfonamide antibiotics [5] and some phytoestrogens [6] being prominent examples. Recent research has shown that the triplet-induced transformation of specific contaminants, especially aromatic nitrogen compounds, could be inhibited by the presence of DOM, very probably due to its antioxidant moieties [7]. While such moieties are not relevant for the quenching of 3CDOM*, they are expected to react with it in a similar way as the studied contaminants. Analogous reactions can be postulated to occur in liquid or solid phases of the atmospheric environment, as demonstrated in the case of HONO formation [8]. References 1. Canonica, S.; Jans, U.; Stemmler, K.; Hoigné, J. Transformation kinetics of phenols in water: Photosensitization by dissolved natural organic material and aromatic ketones. Environ. Sci. Technol. 1995, 29 (7), 1822-1831. 2. Canonica, S.; Hellrung, B.; Wirz, J. Oxidation of phenols by triplet aromatic ketones in aqueous solution. J. Phys. Chem. A 2000, 104 (6), 1226-1232. 3. Golanoski, K. S.; Fang, S.; Del Vecchio, R.; Blough, N. V. Investigating the mechanism of phenol photooxidation by humic substances. Environ. Sci. Technol. 2012, 46 (7), 3912-3920. 4. Gerecke, A. C.; Canonica, S.; Müller, S. R.; Schärer, M.; Schwarzenbach, R. P. Quantification of dissolved natural organic matter (DOM) mediated phototransformation of phenylurea herbicides in lakes. Environ. Sci. Technol. 2001, 35 (19), 3915-3923. 5. Boreen, A. L.; Arnold, W. A.; McNeill, K. Triplet-sensitized photodegradation of sulfa drugs containing six-membered heterocyclic groups: Identification of an SO2 extrusion photoproduct. Environ. Sci. Technol. 2005, 39 (10), 3630-3638. 6. Felcyn, J. R.; Davis, J. C. C.; Tran, L. H.; Berude, J. C.; Latch, D. E. Aquatic photochemistry of isoflavone phytoestrogens: Degradation kinetics and pathways. Environ. Sci. Technol. 2012, 46 (12), 6698-6704. 7. Wenk, J.; Canonica, S. Phenolic antioxidants inhibit the triplet-induced transformation of anilines and sulfonamide antibiotics in aqueous solution. Environ. Sci. Technol. 2012, 46 (10), 5455-5462. 8. George, C.; Strekowski, R. S.; Kleffmann, J.; Stemmler, K.; Ammann, M. Photoenhanced uptake of gaseous NO2 on solid-organic compounds: a photochemical source of HONO? Faraday Discuss. 2005, 130, 195-210.

  5. Molecular Adaptation of Photoprotection: Triplet States in Light-Harvesting Proteins

    PubMed Central

    Gall, Andrew; Berera, Rudi; Alexandre, Maxime T.A.; Pascal, Andrew A.; Bordes, Luc; Mendes-Pinto, Maria M.; Andrianambinintsoa, Sandra; Stoitchkova, Katerina V.; Marin, Alessandro; Valkunas, Leonas; Horton, Peter; Kennis, John T.M.; van Grondelle, Rienk; Ruban, Alexander; Robert, Bruno

    2011-01-01

    The photosynthetic light-harvesting systems of purple bacteria and plants both utilize specific carotenoids as quenchers of the harmful (bacterio)chlorophyll triplet states via triplet-triplet energy transfer. Here, we explore how the binding of carotenoids to the different types of light-harvesting proteins found in plants and purple bacteria provides adaptation in this vital photoprotective function. We show that the creation of the carotenoid triplet states in the light-harvesting complexes may occur without detectable conformational changes, in contrast to that found for carotenoids in solution. However, in plant light-harvesting complexes, the triplet wavefunction is shared between the carotenoids and their adjacent chlorophylls. This is not observed for the antenna proteins of purple bacteria, where the triplet is virtually fully located on the carotenoid molecule. These results explain the faster triplet-triplet transfer times in plant light-harvesting complexes. We show that this molecular mechanism, which spreads the location of the triplet wavefunction through the pigments of plant light-harvesting complexes, results in the absence of any detectable chlorophyll triplet in these complexes upon excitation, and we propose that it emerged as a photoprotective adaptation during the evolution of oxygenic photosynthesis. PMID:21843485

  6. Experimental confirmation of photon-induced spin-flip transitions in helium via triplet metastable yield spectra

    SciTech Connect

    Rubensson, Jan-Erik; Moise, Angelica; Richter, Robert; Mihelic, Andrej; Bucar, Klemen; Zitnik, Matjaz

    2010-06-15

    Doubly excited states below the N=2 ionization threshold are populated by exciting helium atoms in a supersonic beam with monochromatized synchrotron radiation. The fluorescence decay of these states triggers a radiative cascade back to the ground state with large probability to populate long lived singlet and triplet helium metastable states. The yield of metastables is measured using a multichannel plate detector after the beam has passed a singlet-quenching discharge lamp. The variation of the yield observed with the lamp switched on or off is related to the triplet-singlet mixing of the doubly excited states.

  7. Stabilizing triplet excited states for ultralong organic phosphorescence

    NASA Astrophysics Data System (ADS)

    An, Zhongfu; Zheng, Chao; Tao, Ye; Chen, Runfeng; Shi, Huifang; Chen, Ting; Wang, Zhixiang; Li, Huanhuan; Deng, Renren; Liu, Xiaogang; Huang, Wei

    2015-07-01

    The control of the emission properties of synthetic organic molecules through molecular design has led to the development of high-performance optoelectronic devices with tunable emission colours, high quantum efficiencies and efficient energy/charge transfer processes. However, the task of generating excited states with long lifetimes has been met with limited success, owing to the ultrafast deactivation of the highly active excited states. Here, we present a design rule that can be used to tune the emission lifetime of a wide range of luminescent organic molecules, based on effective stabilization of triplet excited states through strong coupling in H-aggregated molecules. Our experimental data revealed that luminescence lifetimes up to 1.35 s, which are several orders of magnitude longer than those of conventional organic fluorophores, can be realized under ambient conditions. These results outline a fundamental principle to design organic molecules with extended lifetimes of excited states, providing a major step forward in expanding the scope of organic phosphorescence applications.

  8. The electronic structure of the lutein triplet state in plant light-harvesting complex II.

    PubMed

    Salvadori, Enrico; Di Valentin, Marilena; Kay, Christopher W M; Pedone, Alfonso; Barone, Vincenzo; Carbonera, Donatella

    2012-09-21

    Carotenoid molecules are essential for the life of photosynthetic organisms in that they protect the cell from the photo-oxidative damage induced by light-stress conditions. One of the photo-protective mechanisms involves triplet-triplet energy transfer from the chlorophyll molecules to the carotenoids: a process that is strongly dependent on the electronic properties of the triplet states involved. Here, we obtain a clear description of the triplet state of lutein in LHCII from higher plants for the first time by density functional theory (DFT) calculations. DFT predictions have been validated by comparison with hyperfine couplings obtained with pulsed-ENDOR spectroscopy. Knowledge of the spin density distribution, the frontier orbitals and orbital excitations forms a basis for discussing the requirements for an efficient triplet-triplet energy transfer. The results obtained for the lutein in LHCII are compared with those of the highly-substituted carotenoid peridinin in PCP from Amphidinium carterae [Di Valentin et al., Biochim. Biophys. Acta, 2008, 1777, 295-307]. The presence of substituents in the peridinin molecule does not alter significantly the triplet state electronic structure compared to lutein. Despite the unusual spectroscopic behaviour of the peridinin excited singlet state, lutein and peridinin have similar triplet state properties. In both molecules the unpaired spins are delocalized uniformly over the whole ?-conjugated system in an alternating even-odd pattern. PMID:22864767

  9. The structure of strongly additive states and Markov triplets on the CAR algebra

    E-print Network

    Anna Jencova

    2010-08-05

    We find a characterization of states satisfying equality in strong subadditivity of entropy and of Markov triplets on the CAR algebra. For even states, a more detailed structure of the density matrix is given.

  10. Interplay between singlet and triplet excited states in a conformationally locked donor-acceptor dyad.

    PubMed

    Filatov, Mikhail A; Etzold, Fabian; Gehrig, Dominik; Laquai, Frédéric; Busko, Dmitri; Landfester, Katharina; Baluschev, Stanislav

    2015-11-28

    The synthesis and photophysical characterization of a palladium(ii) porphyrin - anthracene dyad bridged via short and conformationally rigid bicyclo[2.2.2]octadiene spacer were achieved. A spectroscopic investigation of the prepared molecule in solution has been undertaken to study electronic energy transfer in excited singlet and triplet states between the anthracene and porphyrin units. By using steady-state and time-resolved photoluminescence spectroscopy it was shown that excitation of the singlet excited state of the anthracene leads to energy transfer to the lower-lying singlet state of porphyrin. Alternatively, excitation of the porphyrin followed by intersystem crossing to the triplet state leads to very fast energy transfer to the triplet state of anthracene. The rate of this energy transfer has been determined by transient absorption spectroscopy. Comparative studies of the dynamics of triplet excited states of the dyad and reference palladium octaethylporphyrin (PdOEP) have been performed. PMID:26488635

  11. Ab Initio Calculations of Singlet and Triplet Excited States of Chlorine Nitrate and Nitric Acid

    NASA Technical Reports Server (NTRS)

    Grana, Ana M.; Lee, Timothy J.; Head-Gordon, Martin; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    Ab initio calculations of vertical excitations to singlet and triplet excited states of chlorine nitrate and nitric acid are reported. The nature of the electronic transitions are examined by decomposing the difference density into the sum of detachment and attachment densities. Counterparts for the three lowest singlet excited states of nitric acid survive relatively unperturbed in chlorine nitrate, while other low-lying singlet states of chlorine nitrate appear to be directly dissociative in the ClO chromophore. These results suggest an assignment of the two main peaks in the experimental chlorine nitrate absorption spectrum. In addition, triplet vertical excitations and the lowest optimized triplet geometries of both molecules are studied.

  12. Spectroscopy of triplet states of Rb{sub 2} by femtosecond pump-probe photoionization of doped helium nanodroplets

    SciTech Connect

    Mudrich, M.; Heister, Ph.; Hippler, T.; Giese, Ch.; Stienkemeier, F.; Dulieu, O.

    2009-10-15

    The dynamics of vibrational wave packets in triplet states of rubidium dimers (Rb{sub 2}) formed on helium nanodroplets are studied using femtosecond pump-probe photoionization spectroscopy. Due to fast desorption of the excited Rb{sub 2} molecules off the droplets and due to their low internal temperature, wave-packet oscillations can be followed up to very long pump-probe delay times > or approx. 1.5 ns. In the first-excited triplet state (1){sup 3}{sigma}{sub g}{sup +}, full and fractional revivals are observed with high contrast. Fourier analysis provides high-resolution vibrational spectra which are in excellent agreement with ab initio calculations.

  13. Singlet and triplet excited state properties of natural chlorophylls and bacteriochlorophylls

    SciTech Connect

    Niedzwiedzki, Dariusz; Blankenship, R. E.

    2010-11-18

    Ten naturally occurring chlorophylls (a, b, c{sub 2}, d) and bacteriochlorophylls (a, b, c, d, e, g) were purified and studied using the optical spectroscopic techniques of both steady state and time-resolved absorption and fluorescence. The studies were carried out at room temperature in nucleophilic solvents in which the central Mg is hexacoordinated. The comprehensive studies of singlet excited state lifetimes show a clear dependency on the structural features of the macrocycle and terminal substituents. The wide-ranging studies of triplet state lifetime demonstrate the existence of an energy gap law for these molecules. The knowledge of the dynamics and the energies of the triplet state that were obtained in other studies allowed us to construct an energy gap law expression that can be used to estimate the triplet state energies of any (B)chlorophyll molecule from its triplet lifetime obtained in a liquid environment.

  14. Higher triplet state of fullerene C70 revealed by electron spin relaxation.

    PubMed

    Uvarov, Mikhail N; Behrends, Jan; Kulik, Leonid V

    2015-12-28

    Spin-lattice relaxation times T1 of photoexcited triplets (3)C70 in glassy decalin were obtained from electron spin echo inversion recovery dependences. In the range 30-100 K, the temperature dependence of T1 was fitted by the Arrhenius law with an activation energy of 172 cm(-1). This indicates that the dominant relaxation process of (3)C70 is described by an Orbach-Aminov mechanism involving the higher triplet state t2 which lies 172 cm(-1) above the lowest triplet state t1. Chemical modification of C70 fullerene not only decreases the intrinsic triplet lifetime by about ten times but also increases T1 by several orders of magnitude. The reason for this is the presence of a low-lying excited triplet state in (3)C70 and its absence in triplet C70 derivatives. The presence of the higher triplet state in C70 is in good agreement with the previous results from phosphorescence spectroscopy. PMID:26723678

  15. Valley spin-orbit interaction for the triplet and doublet 1sground states of lithium donor center in monoisotopic {sup 28}Si

    SciTech Connect

    Ezhevskii, Alexander A.; Popkov, Sergey A.; Soukhorukov, Andrey V.; Guseinov, Davud V.; Konakov, Anton A.; Abrosimov, Nikolai V.; Riemann, Helge

    2013-12-04

    Valley spin-orbit interaction for the triplet and doublet 1s-ground states of lithium donor center in monoisotopic {sup 28}Si was studied in order to determine its contribution to the electron spin relaxation rate. We observed new electron paramagnetic resonance spectra of lithium in monoisotopic silicon with g<2.000 and found the spin Hamiltonian parameters for it. Using our experimental results and taking into account spin-orbit coupling between the triplet states and the triplet and doublet states we found that the lithium donor electron spectrum and g-factors for its states strongly depend on both the internal strains in the crystal and the intervalley spin-orbit interactions.

  16. Photodissociation and radiative association of HeH+ in the metastable triplet state.

    PubMed

    Loreau, J; Vranckx, S; Desouter-Lecomte, M; Vaeck, N; Dalgarno, A

    2013-10-01

    We investigate the photodissociation of HeH(+) in the metastable triplet state as well as its formation through the inverse process, radiative association. In models of astrophysical plasmas, HeH(+) is assumed to be present only in the ground state, and the influence of the triplet state has not been explored. It may be formed by radiative association during collisions between a proton and metastable helium, which are present in significant concentrations in nebulae. The triplet state can also be formed by association of He(+) and H, although this process is less likely to occur. We compute the cross sections and rate coefficients corresponding to the photodissociation of the triplet state by UV photons from a central star using a wave packet method. We show that the photodissociation cross sections depend strongly on the initial vibrational state and that the effects of excited electronic states and nonadiabatic couplings cannot be neglected. We then calculate the cross section and rate coefficient for the radiative association of HeH(+) in the metastable triplet state. PMID:23437906

  17. Generation and quantum correlations of the triplet photon state of light

    E-print Network

    Vallette, Bruno

    Generation and quantum correlations of the triplet photon state of light Adrien Borne, Audrey Dot interest in quantum and nonlinear optics · GHZ state of light1 : - Strong correlations between photons from #12;Outline · Introduction, state of the art, motivation · Generation of triple photons · Quantum

  18. Triplet state formation in photovoltaic blends of DPP-type copolymers and PC71 BM.

    PubMed

    Ochsmann, Julian R; Chandran, Deepak; Gehrig, Dominik W; Anwar, Husna; Madathil, Pramod Kandoth; Lee, Kwang-Sup; Laquai, Frédéric

    2015-06-01

    The exciton dynamics in pristine films of two structurally related low-bandgap diketopyrrolopyrrole (DPP)-based donor-acceptor copolymers and the photophysical processes in bulk heterojunction solar cells using DPP copolymer:PC71 BM blends are investigated by broadband transient absorption (TA) pump-probe experiments covering the vis-near-infrared spectral and fs-?s dynamic range. The experiments reveal surprisingly short exciton lifetimes in the pristine poly-mer films in conjunction with fast triplet state formation. An in-depth analysis of the TA data by multivariate curve resolution analysis shows that in blends with fullerene as acceptor ultrafast exciton dissociation creates charge carriers, which then rapidly recombine on the sub-ns timescale. Furthermore, at the carrier densities created by pulsed laser excitation the charge carrier recombination leads to a substantial population of the polymer triplet state. In fact, virtually quantitative formation of triplet states is observed on the sub-ns timescale. However, the quantitative triplet formation on the sub-ns timescale is not in line with the power conversion efficiencies of devices indicating that triplet state formation is an intensity-dependent process in these blends and is reduced under solar illumination conditions, as free charge carriers can be extracted from the photoactive layer in devices. PMID:25923668

  19. Triplet excited States as a source of relevant (bio)chemical information.

    PubMed

    Jiménez, M Consuelo; Miranda, Miguel A

    2014-01-01

    The properties of triplet excited states are markedly medium-dependent, which turns this species into valuable tools for investigating the microenvironments existing in protein binding pockets. Monitoring of the triplet excited state behavior of drugs within transport proteins (serum albumins and ?1-acid glycoproteins) by laser flash photolysis constitutes a valuable source of information on the strength of interaction, conformational freedom and protection from oxygen or other external quenchers. With proteins, formation of spatially confined triplet excited states is favored over competitive processes affording ionic species. Remarkably, under aerobic atmosphere, the triplet decay of drug@protein complexes is dramatically longer than in bulk solution. This offers a convenient dynamic range for assignment of different triplet populations or for stereochemical discrimination. In this review, selected examples of the application of the laser flash photolysis technique are described, including drug distribution between the bulk solution and the protein cavities, or between two types of proteins, detection of drug-drug interactions inside proteins, and enzyme-like activity processes mediated by proteins. Finally, protein encapsulation can also modify the photoreactivity of the guest. This is illustrated by presenting an example of retarded photooxidation. PMID:25515745

  20. The role of triplet states in the emission mechanism of polymer light-emitting diodes

    E-print Network

    M. Arif; S. Mukhopadhyay; S. Ramasesha; S. Guha

    2009-03-01

    The blue emission of polyfluorene (PF) based light-emitting diodes (LEDs) is known to degrade due to a low energy green emission, which hitherto has been attributed to oxidative defects. By studying the electroluminescence from ethyl-hexyl substituted PF LEDs in the presence of oxygen and in an inert atmosphere, and by using trace quantities of paramagnetic impurities (PM) in the polymer, we show that the triplet states play a major role in the low energy emission mechanism. Our time-dependent many-body studies show that there is a large cross-section for the triplet formation in the electron-hole recombination process in presence of PM, and intersystem crossing from excited singlet to triplet states.

  1. Observation of a thermally accessible triplet state resulting from rotation around a main-group ??bond.

    PubMed

    Kostenko, Arseni; Tumanskii, Boris; Karni, Miriam; Inoue, Shigeyoshi; Ichinohe, Masaaki; Sekiguchi, Akira; Apeloig, Yitzhak

    2015-10-01

    We report the first direct spectroscopic observation by electron paramagnetic resonance (EPR) spectroscopy of a triplet diradical that is formed in a thermally induced rotation around a main-group ??bond, that is, the Si?Si double bond of tetrakis(di-tert-butylmethylsilyl)disilene (1). The highly twisted ground-state geometry of singlet 1 allows access to the perpendicular triplet diradical?2 at moderate temperatures of 350-410?K. DFT-calculated zero-field splitting (ZFS) parameters of 2 accurately reproduce the experimentally observed half-field transition. Experiment and theory suggest a thermal equilibrium between 1 and 2 with a very low singlet-triplet energy gap of only 7.3?kcal?mol(-1) . PMID:26297814

  2. Triplet-singlet conversion in ultracold Cs{sub 2} and production of ground-state molecules

    SciTech Connect

    Bouloufa, Nadia; Aymar, Mireille; Dulieu, Olivier; Pichler, Marin

    2011-02-15

    We propose a process to convert ultracold metastable Cs{sub 2} molecules in their lowest triplet state into (singlet) ground-state molecules in their lowest vibrational levels. Molecules are first pumped into an excited triplet state, and the triplet-singlet conversion is facilitated by a two-step spontaneous decay through the coupled A {sup 1{Sigma}}{sub u}{sup +}-b {sup 3{Pi}}{sub u} states. Using spectroscopic data and accurate quantum chemistry calculations for Cs{sub 2} potential curves and transition dipole moments, we show that this process competes favorably with the single-photon decay back to the lowest triplet state. In addition, we demonstrate that this conversion process represents a loss channel for vibrational cooling of metastable triplet molecules, preventing an efficient optical pumping cycle down to low vibrational levels.

  3. Formation of Triplet Positron-helium Bound State by Stripping of Positronium Atoms in Collision with Ground State Helium

    NASA Technical Reports Server (NTRS)

    Drachman, Richard J.

    2006-01-01

    Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium JOSEPH DI RlENZI, College of Notre Dame of Maryland, RICHARD J. DRACHMAN, NASA/Goddard Space Flight Center - The system consisting of a positron and a helium atom in the triplet state e(+)He(S-3)(sup e) was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He(+) have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions.

  4. Aqueous secondary organic aerosol (SOA) production from the oxidation of phenols by triplet excited state organics

    NASA Astrophysics Data System (ADS)

    Smith, J.; Yu, L.; Zhang, Q.; Anastasio, C.

    2011-12-01

    Recent literature has shown that atmospheric condensed-phase chemistry can play a significant role in the evolution of organic aerosols, including the formation of secondary organic aerosol (SOA). SOA formation from the oxidation of volatile organic compounds (VOCs) in the aqueous phase has largely focused on oxidations involving the hydroxyl radical and other oxidants, such as photochemically created triplet excited states, have not been fully investigated. Phenolic compounds are one of the primary carbon emission classes from biomass and wood combustion and have significant water solubility. Once in the aqueous phase, phenolic compounds can react with the triplet excited states of non-phenolic aromatic carbonyls (NPCs), particle-bound organics that are also emitted in large quantities from wood combustion. The oxidation of phenolic species in the condensed phase by triplet excited states can result in the production of SOA. A main goal of this study was to investigate bulk solution reaction kinetics under atmospherically relevant conditions in order to ascertain how these reactions can impact aqueous-phase SOA production. In our experiments, we studied the reactions of five phenols (phenol, guaiacol, syringol, catechol, and resorcinol) with the triplet state of 3,4-dimethoxybenzaldehyde (34-DMB) during simulated solar radiation. We have characterized the impacts of pH, ionic strength and reactant concentrations on the reaction behavior of this system. In addition, we analyzed the SOA formed using high-resolution aerosol mass spectrometry, ion chromatography, and liquid chromatography-mass spectrometry to infer the reaction mechanisms. Our evidence suggests that under atmospherically relevant conditions, triplet excited states can be the dominant oxidant of phenolics and contribute significantly to the total SOA budget.

  5. DERIVING METALLICITIES FROM THE INTEGRATED SPECTRA OF EXTRAGALACTIC GLOBULAR CLUSTERS USING THE NEAR-INFRARED CALCIUM TRIPLET

    SciTech Connect

    Foster, Caroline; Forbes, Duncan A.; Proctor, Robert N.; Spitler, Lee R.; Strader, Jay; Brodie, Jean P.

    2010-04-15

    The Ca II triplet (CaT) feature in the near-infrared has been employed as a metallicity indicator for individual stars as well as integrated light of Galactic globular clusters (GCs) and galaxies with varying degrees of success, and sometimes puzzling results. Using the DEIMOS multi-object spectrograph on Keck we obtain a sample of 144 integrated light spectra of GCs around the brightest group galaxy NGC 1407 to test whether the CaT index can be used as a metallicity indicator for extragalactic GCs. Different sets of single stellar population models make different predictions for the behavior of the CaT as a function of metallicity. In this work, the metallicities of the GCs around NGC 1407 are obtained from CaT index values using an empirical conversion. The measured CaT/metallicity distributions show unexpected features, the most remarkable being that the brightest red and blue GCs have similar CaT values despite their large difference in mean color. Suggested explanations for this behavior in the NGC 1407 GC system are (1) the CaT may be affected by a population of hot blue stars, (2) the CaT may saturate earlier than predicted by the models, and/or (3) color may not trace metallicity linearly. Until these possibilities are understood, the use of the CaT as a metallicity indicator for the integrated spectra of extragalactic GCs will remain problematic.

  6. Room temperature triplet state spectroscopy of organic semiconductors

    E-print Network

    Reineke, Sebastian

    Organic light-emitting devices and solar cells are devices that create, manipulate, and convert excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device ...

  7. Triplet versus singlet entangled states in teaching the Einstein-Podolsky-Rosen paradox

    NASA Astrophysics Data System (ADS)

    Shegelski, Mark R. A.

    2013-05-01

    The Einstein-Podolsky-Rosen paradox is considered using spin-\\frac{1}{2} singlet and triplet states prepared in the z-direction, after which measurements are made in a different direction, the x-direction, for example. An unexpected outcome and its usefulness for teaching is reported. The material will be of interest to upper-year undergraduate quantum mechanics instructors and students.

  8. Charge transfer and triplet states in OPV materials and devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Dyakonov, Vladimir

    2015-10-01

    Electron back transfer (EBT), potentially occurring after electron transfer from donor to acceptor may populate the lower lying donor or acceptor triplet state and serve as recombination channel.[1] Here we report on studies of charge transfer and triplet states in blends of highly efficient benzodithiophene PTB7 polymer in combination with the fullerene-derivative PC71BM using the spin sensitive optically detected magnetic resonance (ODMR) technique and compare the results with those obtained in P3HT (poly(3- hexylthiophene):PC61BM blends. Although PTB7:PC71BM absorbers yield much higher power conversion efficiencies in solar cells exceeding 7%, we found a significant increase of triplet exciton generation, which was absent in the P3HT based blends. We discuss this observation within the EBT scenario with the emphasis on the influence of morphology, fullerene load, HOMO/LUMO energy and presence of additives (DIO). Suppressing the EBT process by morphology and/or energetics of polymer and molecules is important to achieve the full potential of highly efficient OPV materials. [1] M. Liedtke, et al., JACS 133, 9088 (2011).

  9. Spectrum and polarization of helium doubly excited triplet states

    NASA Astrophysics Data System (ADS)

    Brooks, Robert L.; Pinnington, Eric H.

    1980-08-01

    The beam-foil spectrum of helium from 2050 to 3600 Å has been acquired at 160-keV incident ion energy using a multiple-scan, computerized system. Eleven doubly-excited-state transitions, including two not previously observed, have been assigned, and the agreement between experimental and theoretical energy levels is excellent. The Stokes parameters as a function of foil-tilt angle have been measured for the two strongest transitions (2578 and 3013 Å) from 0° to 80° in 10° increments and for two weaker transitions (2562 and 2818 Å) at 0°, 20°, 40°, and 60°. The polarization patterns are quite different from those of the helium singlets and include the first measurement of negative MI (a Stokes parameter) at 0° foil tilt for helium at this energy. The lifetime of the 2578-Å transition has been investigated in detail. The present result, 0.109+/-0.004 ns, agrees with previous measurements and yields an upper limit to the autoionization width of the 2p3p 3D levels of 6×10-6 eV.

  10. An ab initio investigation of the ground and low-lying singlet and triplet electronic states of XNO{sub 2} and XONO (X = Cl, Br, and I)

    SciTech Connect

    Peterson, Kirk A.; Francisco, Joseph S.

    2014-01-28

    A systematic ab initio treatment of the nitryl halides (XNO{sub 2}) and the cis- and trans- conformers of the halide nitrites (XONO), where X = Cl, Br, and I, have been carried out using highly correlated methods with sequences of correlation consistent basis sets. Equilibrium geometries and harmonic frequencies have been accurately calculated in all cases at the explicitly correlated CCSD(T)-F12b level of theory, including the effects of core-valence correlation for the former. Where experimental values are available for the equilibrium structures (ClNO{sub 2} and BrNO{sub 2}), the present calculations are in excellent agreement; however, the X-O distances are slightly too long by about 0.01 Å due to missing multireference effects. Accurate predictions for the iodine species are made for the first time. The vertical electronic excitation spectra have been calculated using equation-of-motion coupled cluster methods for the low-lying singlet states and multireference configuration interaction for both singlet and triplet states. The latter also included the effects of spin-orbit coupling to provide oscillator strengths for the ground state singlet to excited triplet transitions. While for ClNO{sub 2} the transitions to excited singlet states all occur at wavelengths shorter than 310 nm, there is one longer wavelength singlet transition in BrNO{sub 2} and two in the case of INO{sub 2}. The long wavelength tail in the XNO{sub 2} species is predicted to be dominated by transitions to triplet states. In addition to red-shifting from X = Cl to I, the triplet transitions also increase in oscillator strength, becoming comparable to many of the singlet transitions in the case of INO{sub 2}. Hence in particular, the latter species should be very photolabile. Similar trends are observed and reported for the halogen nitrites, many of which for the first time.

  11. Triplet states in isotopically mixed anthracene crystals: High resolution optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Port, H.; Rund, D.; Wolf, H. C.

    1981-08-01

    The triplet O,O transitions of guest and host in isotopically mixed anthracene crystals of various compositions (A- h10, 13C-monosubstituted A- h10, A- d1h9, A- d2hg in A- d10 and A- d10 in A- h10) have been investigated using high resolution laser excitation spectroscopy. The guest aggregate spectra have been studied in polarized light as a function of guest concentration up to 15%. The analyses allow us to identify the monomer, dimer and trimer lines. From the dimer splittings the dominant resonance pair interactions are dedu The comparison of different mixed crystal systems with guest levels below and above the host exciton band reveals that quasiresonance and superexchange corrections are of minor importance. The experimental resonance pair interactions are used to calculate the triplet exciton band structure of anthracen and the observed guest polarization behaviour is interpreted quantitatively by the Rashba effect. Finally, the lower Davydov component of the host is s and broadened with increasing guest concentration. The shift is discussed using a theoretical model of Lifshitz.

  12. Prediction of a neutral noble gas compound in the triplet state.

    PubMed

    Manna, Debashree; Ghosh, Ayan; Ghanty, Tapan K

    2015-05-26

    Discovery of the HArF molecule associated with H-Ar covalent bonding [Nature, 2000, 406, 874-876] has revolutionized the field of noble gas chemistry. In general, this class of noble gas compound involving conventional chemical bonds exists as closed-shell species in a singlet electronic state. For the first time, in a bid to predict neutral noble gas chemical compounds in their triplet electronic state, we have carried out a systematic investigation of xenon inserted FN and FP species by using quantum chemical calculations with density functional theory and various post-Hartree-Fock-based correlated methods, including the multireference configuration interaction technique. The FXeP and FXeN species are predicted to be stable by all the computational methods employed in the present work, such as density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2), coupled-cluster theory (CCSD(T)), and multireference configuration interaction (MRCI). For the purpose of comparison we have also included the Kr-inserted compounds of FN and FP species. Geometrical parameters, dissociation energies, transition-state barrier heights, atomic charge distributions, vibrational frequency data, and atoms-in-molecules properties clearly indicate that it is possible to experimentally realize the most stable state of FXeP and FXeN molecules, which is triplet in nature, through the matrix isolation technique under cryogenic conditions. PMID:25891838

  13. Dynamic dipole polarizabilities for the low-lying triplet states of helium

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Hui; Tang, Li-Yan; Zhang, Xian-Zhou; Shi, Ting-Yun

    2015-07-01

    The dynamic dipole polarizabilities for the four lowest triplet states (2 3S , 3 3S , 2 3P , and 3 3P ) of helium are calculated using the B -spline configuration interaction method. Present values of the static dipole polarizabilities in the length, velocity, and acceleration gauges are in good agreement with the best Hylleraas results. Also the tune-out wavelengths in the range 400 nm-4.2 ? m for the four lowest triplet states are identified, and the magic wavelengths in the range 460 nm-3.5 ? m for the 2 3S ?3 3S , 2 3S ?2 3P , and 2 3S ?3 3P transitions are determined. We show that the tune-out wavelength of 2 3S state is 413.038 28 (3 ) nm, which corroborates the value of Mitroy and Tang [Phys. Rev. A 88, 052515 (2013), 10.1103/PhysRevA.88.052515], and the magic wavelength around 1066 nm for the 2 3S ?3 3P transition can be expected for precision measurement to determine the ratio of transition matrix elements (2 3S ?2 3P ) /(3 3P ?6 3S ) .

  14. Conformational dynamics and spin-orbit interactions in a series of sterically hindered porphyrins in the lowest triplet state

    NASA Astrophysics Data System (ADS)

    Shchupak, E. E.; Ivashin, N. V.; Sagun, E. I.

    2013-07-01

    We have studied the nature and unusual photophysical properties of triplet states of a series of sterically hindered porphyrins ( meso-phenyl-substituted derivatives of octamethylporphyrin (PS-OMP)) using quantum-chemical calculations of the parameters that determine the probability of deactivation of the T 1 state and modeling the T- T absorption spectra. We show that a decrease in the lifetime of the T 1 state of PS-OMP is related with the enhancement of the channel of nonradiative deactivation ( T 1 ? S 0), which occurs (i) due to the conformational lability in the T 1 state, as a result of which the energy gap T 1- S 0 considerably decreases, and (ii) because of an increase in the matrix element of the spin-orbit interaction due to a change in the hybridization of atoms of the macrocycle as a consequence of its nonplanar distortion. The value of the vibronically induced matrix element of the spin-orbit interaction between the S 0 and T 1 states of PS-OMP depends weakly on the type of the conformation and the value and the character of distortion of the porphyrin macrocycle. The conformational lability of PS-OMP clearly manifests itself in the spectra and kinetics of the T- T absorption of these compounds at room temperature and determines the nonmonoexponential character of the phosphorescence decay kinetics in frozen matrices. Using porphin as an example, we have shown that nonplanar distortions of the macrocycle facilitate a decrease in the phosphorescence rate constant at 77 K, which is caused, on the one hand, by an increase in the energy gaps T 1- S n and S 0- T n and, on the other hand, by an increase in the wavelength of the transition T 1 ? S 0.

  15. Photoformation of Triplet Excited States and Other Oxidants in Fog Waters and Their Impact on Fog Processing of Organic Compounds

    NASA Astrophysics Data System (ADS)

    Kaur, R.; Anastasio, C.; Valsaraj, K. T.; Vempati, H. S.; Vaitilingom, M.

    2014-12-01

    Reactions in fog and cloud drops are important for a number of processes, such as formation of secondary organic aerosol (SOA), cycling of organic carbon and nitrogen, and determining the lifetimes of pollutants. The rates of these processes depend upon the steady-state concentrations of the major photooxidants, namely, hydroxyl radical (.OH), singlet molecular oxygen (1O2*) and triplet excited states of organic compounds (3C*). While there are some past measurements of .OH and 1O2* concentrations in fog and cloud drops, there are no data for the concentrations of triplet excited states. However, there is increasing evidence that triplets might be important for the processing of organics in a cloudy or foggy atmosphere. To address this question, we collected fog water samples from Davis, CA and Baton Rouge, LA, illuminated them with simulated sunlight, and measured the steady-state concentrations of .OH , 1O2* and 3C* . To understand the relative importance of these photooxidants, we also measured the photochemical loss of two added model organic compounds in the illuminated fog waters - syringol (a biomass burning phenol) and methyl jasmonate (a green leaf volatile). Our results show that triplet excited states can play a major role in oxidizing the model compounds, typically accounting for 30 - 90% of the loss of both model compounds. Given that atmospheric triplets are relatively less understood, our results highlight the importance of deeper investigation into their nature.

  16. Theoretical radiative properties between states of the triplet manifold of NH radical

    SciTech Connect

    Owono Owono, L. C.; Ben Abdallah, D.; Jaidane, N.; Ben Lakhdar, Z.

    2008-02-28

    Ab initio transition dipole moments between states of the triplet manifold of NH radical are determined at the complete active space self-consistent field, followed by the internally contracted multireference singles plus doubles configuration interaction level of theory with a modified aug-cc-pVTZ basis set that accounts for valence-Rydberg interactions. This enables the computation of various radiative characteristics such as Einstein coefficients, radiative lifetimes, and oscillator strengths. These properties concern as well valence and Rydberg states. For the valence states, only the (0, 0) band of the A {sup 3}{pi}-X {sup 3}{sigma}{sup -} transition has received some important amount of attention. Data for the other transitions are rather scarce and sometimes inexistent. The results obtained in this work show good agreement with the available experimental data in comparison to other theoretical numbers reported in the literature.

  17. Infrared vibrational spectroscopy of [Ru(bpy)2(bpm)]2+ and [Ru(bpy)3]2+ in the excited triplet state.

    PubMed

    Mukuta, Tatsuhiko; Fukazawa, Naoto; Murata, Kei; Inagaki, Akiko; Akita, Munetaka; Tanaka, Sei'ichi; Koshihara, Shin-ya; Onda, Ken

    2014-03-01

    This work involved a detailed investigation into the infrared vibrational spectra of ruthenium polypyridyl complexes, specifically heteroleptic [Ru(bpy)2(bpm)](2+) (bpy = 2,2'-bipyridine and bpm = 2,2'-bipyrimidine) and homoleptic [Ru(bpy)3](2+), in the excited triplet state. Transient spectra were acquired 500 ps after photoexcitation, corresponding to the vibrational ground state of the excited triplet state, using time-resolved infrared spectroscopy. We assigned the observed bands to specific ligands in [Ru(bpy)2(bpm)](2+) based on the results of deuterium substitution and identified the corresponding normal vibrational modes using quantum-chemical calculations. Through this process, the more complex vibrational bands of [Ru(bpy)3](2+) were assigned to normal vibrational modes. The results are in good agreement with the model in which excited electrons are localized on a single ligand. We also found that the vibrational bands of both complexes associated with the ligands on which electrons are little localized appear at approximately 1317 and 1608 cm(-1). These assignments should allow the study of the reaction dynamics of various photofunctional systems including ruthenium polypyridyl complexes. PMID:24528148

  18. The Ca II triplet in red giant spectra: [Fe/H] determinations and the role of [Ca/Fe

    NASA Astrophysics Data System (ADS)

    Da Costa, G. S.

    2016-01-01

    Measurements are presented and analysed of the strength of the Ca II triplet lines in red giants in Galactic globular and open clusters, and in a sample of red giants in the LMC disc that have significantly different [Ca/Fe] abundance ratios to the Galactic objects. The Galactic objects are used to generate a calibration between Ca II triplet line strength and [Fe/H], which is then used to estimate [Fe/H]CaT for the LMC stars. The values are then compared with the [Fe/H]spec determinations from high-dispersion spectroscopy. After allowance for a small systematic offset, the two abundance determinations are in excellent agreement. Further, as found in earlier studies, the difference is only a very weak function of the [Ca/Fe] ratio. For example, changing [Ca/Fe] from +0.3 to -0.2 causes the Ca II-based abundance to underestimate [Fe/H]spec by only ˜0.15 dex, assuming a Galactic calibration. Consequently, the Ca II triplet approach to metallicity determinations can be used without significant bias to study stellar systems that have substantially different chemical evolution histories.

  19. Singlet and Triplet State Transitions of Carotenoids in the Antenna Complexes of Higher-Plant Photosystem I

    E-print Network

    Romeo, Alessandro

    Singlet and Triplet State Transitions of Carotenoids in the Antenna Complexes of Higher-Plant complex energy equilibration is not complete at least on a fast time scale. Carotenoids play several roles number are found in higher-plant antenna complexes, while their composition is highly conserved

  20. Further evidence for dissipative energy migration via triplet states in photosynthesis. The protective mechanism of carotenoids in Rhodopseudomonas spheroides chromatophores.

    PubMed

    Renger, G; Wolff, C

    1977-04-11

    The protection action of carotenoids against irreversible photodestruction was discovered in photosynthetic bacteria by Stanieda and coworkers. In green plant material it was found by Wolff and Witt (1969) Z. Naturforsch, 24b, 1031-1037 and (1972) Proc. 2nd. Int. Congr. Photosynthesis Res. Stresa (Forti, G., Avron, M. and Melandri, A., eds.), Vol. 2, pp. 931-936, Dr. W. Junk, N. V. Publ. The Hague) that the formation of special carotenoid triplet states (via very rapid energy transfer from excited chlorophylls) and their fast radiationless decay in tau1/2 approximately 3 microns is at least one mechanism for the protective action of carotenoids to irreversible photooxidation of the chlorophylls. Hence, it is anticipated that the same mechanism might be realized also in bacteria. The present study gives evidence for such a "triplet valve" to be established also in bacteria. This conclusion was derived from the following observations: 1. The light-induced difference spectrum shows a bleaching of a carotenoid at three characteristic wavelength between 400 and 500 nm. A positive peak around 533 nm indicates the formation of a carotenoid triplet state. 2. The absorption changes can be induced by red light which excites only bacteriochlorophyll. This indicates an energy transfer from bacteriochlorophyll to carotenoids. 3. The light-induced carotenoid triplets decay radiationless in 3 microns in air-saturated aqueous suspensions of the chromatophores. 4. The carotenoid triplet formation occurs only at actinic flash intensities where the photosynthesis becomes saturated. 5. Addition of dithionite, which blocks photosynthesis, markedly increases the extent of carotenoid triplet formation. The different types of exciton migration within the photosynthetic unit are discussed, especially the routes leading to the dissipation of excess excitation energy. PMID:300630

  1. Solvent Viscosity Effect on Triplet-Triplet Pair in Triplet Fusion.

    PubMed

    Yokoyama, Kana; Wakikawa, Yusuke; Miura, Tomoaki; Fujimori, Jun-Ichi; Ito, Fuyuki; Ikoma, Tadaaki

    2015-12-31

    The effect of the solvent viscosity dependence of time-resolved magnetoluminescence (ML) on the delayed fluorescence of 9,10-diphenylanthracene (DPA) sensitized by platinum octaethylporphyrin has clarified the structure and dynamics of the triplet-triplet pair (TT), i.e., the transition state of triplet fusion. Phase inversion of the ML effect with time provides evidence for the recycle dynamics of the excited triplet state for DPA in triplet fusion. The electron spin-relaxation by random molecular rotation causes intersystem crossing among the different spin states of the triplet-triplet pair and allows the (3,5)TT to engage in triplet fusion. Therefore, slow-down of the molecular diffusion by an increase in the solvent viscosity can enhance the triplet fusion yield. However, the reduction of the ML effect observed in quite high viscosity solvents suggests that the substantially slow rotational motion decreases the triplet fusion yield due to steric factors in electron exchange from the triplet-triplet pair. PMID:26683847

  2. Fine-Tuning of ?-Substitution to Modulate the Lowest Triplet Excited States: A Bioinspired Approach to Design Phosphorescent Metalloporphyrinoids.

    PubMed

    Ke, Xian-Sheng; Zhao, Hongmei; Zou, Xiaoran; Ning, Yingying; Cheng, Xin; Su, Hongmei; Zhang, Jun-Long

    2015-08-26

    Learning nature's approach to modulate photophysical properties of NIR porphyrinoids by fine-tuning ?-substituents including the number and position, in a manner similar to naturally occurring chlorophylls, has the potential to circumvent the disadvantages of traditional "extended ?-conjugation" strategy such as stability, molecular size, solubility, and undesirable ?-? stacking. Here we show that such subtle structural changes in Pt(II) or Pd(II) cis/trans-porphodilactones (termed by cis/trans-Pt/Pd) influence photophysical properties of the lowest triplet excited states including phosphorescence, Stokes shifts, and even photosensitization ability in triplet-triplet annihilation reactions with rubrene. Prominently, the overall upconversion capability (?, ? = ?·?(UC)) of Pd or Pt trans-complex is 10(4) times higher than that of cis-analogue. Nanosecond time-resolved infrared (TR-IR) spectroscopy experiments showed larger frequency shift of ?(C?O) bands (ca. 10 cm(-1)) of cis-complexes than those of trans-complexes in the triplet excited states. These spectral features, combining with TD-DFT calculations, suggest the strong electronic coupling between the lactone moieties and the main porphyrin chromophores and thus the importance of precisely positioning ?-substituents by mimicking chlorophylls, as an alternative to "extended ?-conjugation", in designing NIR active porphyrinoids. PMID:26247480

  3. Light Absorption by Secondary Organic Aerosol Produced from Aqueous Reaction of Phenols with an Organic Excited Triplet State and Hydroxyl Radical

    NASA Astrophysics Data System (ADS)

    Smith, J.; Yu, L.; George, K.; Ruthenburg, T. C.; Dillner, A. M.; Zhang, Q.; Anastasio, C.

    2012-12-01

    Although reactions in atmospheric condensed phases can form and transform secondary organic aerosol (SOA), these reactions are not well represented in many air quality models. Previous experiments have focused on hydroxyl radical-mediated oxidation of low molecular weight precursors such as gyloxal and methylglyoxal. In our work we are examining aqueous SOA formed from phenols, which are emitted from biomass burning and formed from the oxidation of anthropogenic aromatics such as benzene and toluene. In this work we examine aqueous SOA production from oxidation of three phenols (phenol, guaiacol, syringol) and three benzene-diols (catechol, resorcinol, 1,4-hydroquinone) by hydroxyl radical (OH) and the triplet excited state of 3,4-dimethoxybenzaldehyde (DMB). Our focus is on light absorption by the reaction products, which we characterized by measuring UV-Vis spectra and calculating mass absorption coefficients. To understand the elemental and molecular composition of the SOA, we also analyzed the samples with high resolution mass spectrometry and infrared spectroscopy. Our results indicate that aqueous oxidation of phenols and benzene-diols via OH and triplet excited states efficiently produce SOA that is highly absorbing in the UV-A wavelengths, consists of both small and large molecular weight products, and is highly oxidized.

  4. Suppressed Andreev reflection and helical Andreev bound states in triplet superconductor three-dimensional topological insulator

    NASA Astrophysics Data System (ADS)

    Khezerlou, M.; Goudarzi, H.

    2015-11-01

    Effect of proximity-induced unconventional p-wave superconductivity in a three-dimensional topological insulator-based S/F/S structure on the Andreev bound states (ABSs) and Josephson supercurrent is studied. We investigate, in detail, the suppression of Andreev reflection and helical ABSs in the presence of three types of triplet superconducting gap. The magnetization of ferromagnetic section is perpendicular to the surface of junction. The influence of such features on the supercurrent flow on the surface of the topological insulator is studied. We carry out our goal by introducing a relevant form of Dirac spinors for gapless renormalized by chemical potential ? excitation states. Therefore, it enables us to consider the virtual Andreev process, simultaneously, and we propose to investigate it in a tunneling conductance junction. It is shown that the results obtained in this case are completely different from those in conventional superconductivity, as s- or d-waves, for example, the magnetization is found to decrease the gap for px and px+ipy case, whereas increase it for py order. Strongly suppressed Andreev reflection is demonstrated.

  5. ?-Conjugated Organometallic Isoindigo Oligomer and Polymer Chromophores: Singlet and Triplet Excited State Dynamics and Application in Polymer Solar Cells.

    PubMed

    Goswami, Subhadip; Gish, Melissa K; Wang, Jiliang; Winkel, Russell W; Papanikolas, John M; Schanze, Kirk S

    2015-12-01

    An isoindigo based ?-conjugated oligomer and polymer that contain cyclometalated platinum(II) "auxochrome" units were subjected to photophysical characterization, and application of the polymer in bulk heterojunction polymer solar cells with PCBM acceptor was examined. The objective of the study was to explore the effect of the heavy metal centers on the excited state properties, in particular, intersystem crossing to a triplet (exciton) state, and further how this would influence the performance of the organometallic polymer in solar cells. The materials were characterized by electrochemistry, ground state absorption, emission, and picosecond-nanosecond transient absorption spectroscopy. Electrochemical measurements indicate that the cyclometalated units have a significant impact on the HOMO energy level of the chromophores, but little effect on the LUMO, which is consistent with localization of the LUMO on the isoindigo acceptor unit. Picosecond-nanosecond transient absorption spectroscopy reveals a transient with ?100 ns lifetime that is assigned to a triplet excited state that is produced by intersystem crossing from a singlet state on a time scale of ?130 ps. This is the first time that a triplet state has been observed for isoindigo ?-conjugated chromophores. The performance of the polymer in bulk heterojunction solar cells was explored with PC61BM as an acceptor. The performance of the cells was optimum at a relatively high PCBM loading (1:6, polymer:PCBM), but the overall efficiency was relatively low with power conversion efficiency (PCE) of 0.22%. Atomic force microscopy of blend films reveals that the length scale of the phase separation decreases with increasing PCBM content, suggesting a reason for the increase in PCE with acceptor loading. Energetic considerations show that the triplet state in the polymer is too low in energy to undergo charge separation with PCBM. Further, due to the relatively low LUMO energy of the polymer, charge transfer from the singlet to PCBM is only weakly exothermic, which is believed to be the reason that the photocurrent efficiency is relatively low. PMID:26561718

  6. Photoreduction of Pt(IV) chloro complexes: substrate chlorination by a triplet excited state.

    PubMed

    Perera, Tharushi A; Masjedi, Mehdi; Sharp, Paul R

    2014-07-21

    The Pt(IV) complexes trans-Pt(PEt3)2(Cl)3(R) 2 (R = Cl, Ph, 9-phenanthryl, 2-trifluoromethylphenyl, 4-trifluoromethylphenyl, 3-perylenyl) were prepared by chlorination of the Pt(II) complexes trans-Pt(PEt3)2(R)(Cl) 1 with Cl2(g) or PhICl2. Mixed bromo-chloro complexes trans,trans-Pt(PEt3)2(Cl)2(Br)(R) (R = 9-phenanthryl, 4-trifluoromethylphenyl), trans,cis-Pt(PEt3)2(Cl)2(Br)(4-trifluoromethylphenyl), trans,trans-Pt(PEt3)2(Br)2(Cl)(R) (R = 9-phenanthryl), and trans,cis-Pt(PEt3)2(Br)2(Cl)(4-trifluoromethylphenyl) were obtained by halide exchange or by oxidative addition of Br2 to 1 or Cl2 to trans-Pt(PEt3)2(R)(Br). Except for 2 (R = Ph, 4-trifluoromethylphenyl), all of the Pt(IV) complexes are photosensitive to UV light and undergo net halogen reductive elimination to give Pt(II) products, trans-Pt(PEt3)2(R)(X) (X = Cl, Br). Chlorine trapping experiments with alkenes indicate a reductive-elimination mechanism that does not involve molecular chlorine and is sensitive to steric effects at the Pt center. DFT calculations suggest a radical pathway involving (3)LMCT excited states. Emission from a triplet is observed in glassy 2-methyltetrahydrofuran at 77 K where photoreductive elimination is markedly slowed. PMID:24971643

  7. Intramolecular photostabilization via triplet-state quenching: design principles to make organic fluorophores "self-healing".

    PubMed

    van der Velde, Jasper H M; Uusitalo, Jaakko J; Ugen, Lourens-Jan; Warszawik, Eliza M; Herrmann, Andreas; Marrink, Siewert J; Cordes, Thorben

    2015-12-12

    Covalent linkage of fluorophores and photostabilizers was recently revived as a strategy to make organic fluorophores "self-healing"via triplet-state quenching. Although Lüttke and co-workers pioneered this strategy already in the 1980s, the general design principles still remain elusive. In this contribution, we combine experiments and theory to understand what determines the photostabilization efficiency in dye-photostabilizer conjugates. Our results from single-molecule microscopy and molecular dynamics simulations of different Cy5-derivatives suggest that the distance and relative geometry between the fluorophore and photostabilizer are more important than the chemical nature of the photostabilizer, e.g. its redox potential, which is known to influence electron-transfer rates. We hypothesize that the efficiency of photostabilization scales directly with the contact rate of the fluorophore and photostabilizer. This study represents an important step in the understanding of the molecular mechanism of intramolecular photostabilization and can pave the way for further development of stable emitters for various applications. PMID:26449795

  8. Toward enabling large-scale open-shell equation-of-motion coupled cluster calculations: triplet states of ?-carotene

    SciTech Connect

    Hu, Hanshi; Bhaskaran-Nair, Kiran; Apra, Edoardo; Govind, Niranjan; Kowalski, Karol

    2014-10-02

    In this paper we discuss the application of novel parallel implementation of the coupled cluster (CC) and equation-of-motion coupled cluster methods (EOMCC) in calculations of excitation energies of triplet states in beta-carotene. Calculated excitation energies are compared with experimental data, where available. We also provide a detailed description of the new parallel algorithms for iterative CC and EOMCC models involving single and doubles excitations.

  9. Computational Modeling of the Triplet Metal-to-Ligand Charge-Transfer Excited-State Structures of Mono-Bipyridine-Ruthenium(II)

    E-print Network

    Schlegel, H. Bernhard

    of Mono-Bipyridine-Ruthenium(II) Complexes and Comparisons to their 77 K Emission Band Shapes Richard L in the lowest energy triplet metal to ligand charge-transfer (3 MLCT = T0) excited states of ruthenium

  10. Triplet state magnetic resonance and fluorescence spectroscopy of metal-substituted hemoglobins.

    PubMed

    Polm, M W; Schaafsma, T J

    1997-01-01

    Fluorescence detected magnetic resonance (FDMR) spectra detected at 596 nm of zinc-substituted hemoglobins at 4.2 K show a split D-E transition, which is not observed for zinc protoporphyrins ligated by methylimidazole in glasses. Incorporation of the zinc heme into the globin pocket is also accompanied by a blue shift of the fluorescence of 20 nm at 4.2 K. FDMR spectra recorded at 576 nm do not show the D-E splitting. The D-E splitting and the huge blue shift are not observed for the magnesium-substituted hemoglobins. Fluorescence measurements at 4.2 K and 77 K, and EPR measurements at 110 K, were carried out to obtain information about the ligation states of the zinc and magnesium protoporphyrins in glasses and in hemoglobin. The results are explained by considering ligation effects and distortion of the porphyrin plane. PMID:8994622

  11. Triplet State Absorption in Carbon Nanotubes: A TD-DFT Study

    E-print Network

    Tretiak, Sergei

    of fundamental physics phenomena. Singlet- triplet splitting in low-dimensional materials is a measure. Semiconductor or metal-like electronic features of single- walled carbon nanotubes (CNTs) result from for molecular physics, and field-specific notations. So far, extensive amount of work in nanotube science has

  12. Generation of Phosphorescent Triplet States via Photoinduced Electron Transfer: Energy and Electron Transfer Dynamics in Pt Porphyrin-Rhodamine B Dyads

    PubMed Central

    Mani, Tomoyasu; Niedzwiedzki, Dariusz M.; Vinogradov, Sergei A.

    2012-01-01

    Control over generation and dynamics of excited electronic states is fundamental to their utilization in all areas of technology. We present the first example of multichromophoric systems in which emissive triplet states are generated via a pathway involving photoinduced electron transfer (ET), as opposed to local intrachromophoric processes. In model dyads, PtP-Phn-pRhB+ (1-3, n=1-3), comprising platinum(II) meso-tetraarylporphyrin (PtP) and rhodamine B piperazine derivative (pRhB+), linked by oligo-p-phenylene bridges (Phn), upon selective excitation of pRhB+ at a frequency below that of the lowest allowed transition of PtP, room-temperature T1?S0 phosphorescence of PtP was observed. The pathway leading to the emissive PtP triplet state includes excitation of pRhB+, ET with formation of the singlet radical pair, intersystem crossing within that pair and subsequent radical recombination. Due to the close proximity of the triplet energy levels of PtP and pRhB+, reversible triplet-triplet (TT) energy transfer between these states was observed in dyads 1 and 2. As a result, the phosphorescence of PtP was extended in time by the long decay of the pRhB+ triplet. Observation of ET and TT in the same series of molecules enabled direct comparison of the distance attenuation factors ? between these two closely related processes. PMID:22400988

  13. Photon-gated photochemical hole burning by two-color sensitization of a photoreactive polymer via triplet-triplet energy transfer

    NASA Astrophysics Data System (ADS)

    Machida, Shinjiro; Horie, Kazuyuki; Yamashita, Takashi

    1992-01-01

    A new system of photon-gated photochemical hole burning is presented: zinc-tetratolyl-tetrabenzoporphine in glycidyl azide polymer matrix. The two-color irradiation with dye laser and Ar+ laser at 20 K forms holes 500 times more efficiently than the one-color irradiation with dye laser alone. No change in the area of Q-band in the absorption spectra of the guest molecules during hole formation indicates that the sensitized decomposition of azide groups via triplet-triplet energy transfer from the higher excited triplet state of the guest molecules causes the change in guest-host interaction leading to the hole formation.

  14. Kinetic and spectroscopic study of triplet state and ionic pathways in the laser-induced photoexcitation of N-ethylcarbazole in fluid solutions

    SciTech Connect

    Haggquist, G.W.; Burkhart, R.D. ); Naqvi, K.R. )

    1991-10-03

    When fluid solutions of N-ethylcarbazole (NEC) are irradiated by 308-nm pulses from an excimer laser, transient triplets and ions may be observed in the microsecond time regime. The formation of ions is favored in more polar solvents such as acetonitrile (AcN) and that of triplets in nonpolar solvents such as paraffin oil. The quantum yield of triplet formation from initial excitation is 0.23. Triplet states decay through concurrent first- and second-order channels: the second-order process, triplet-triplet annihilation, leads to formation of excited singlet states with an efficiency of 0.12. Transient carbazolyl cations and anions display double-exponential decays. To account for this behavior, a mechanism involving initial electron donation by the multiply excited chromophore to a nearby NEC molecule or solvent molecule is proposed; subsequent decay occurs primarily by germinate recombination of the resulting ion pair. The quantum yield for cation production is 0.037. Delayed fluorescence is AcN also decays by a double-exponential decay curve with rate constants, suggesting that the emission arises mainly from ion recombination.

  15. On the absorbing-state phase transition in the one-dimensional triplet creation model

    E-print Network

    Geza Odor; Ronald Dickman

    2009-08-02

    We study the lattice reaction diffusion model 3A -> 4A, A -> 0 (``triplet creation") using numerical simulations and n-site approximations. The simulation results provide evidence of a discontinuous phase transition at high diffusion rates. In this regime the order parameter appears to be a discontinuous function of the creation rate; no evidence of a stable interface between active and absorbing phases is found. Based on an effective mapping to a modified compact directed percolation process, shall nevertheless argue that the transition is continuous, despite the seemingly discontinuous phase transition suggested by studies of finite systems.

  16. Bound Triplet Pairs in the Highest Spin States of Coinage Metal Clusters.

    PubMed

    Danovich, David; Shaik, Sason

    2010-05-11

    The work discusses bonding in coinage metal clusters, (n+1)Mn (M = Cu, Ag, Au), that have maximum spin without a single electron pair. It is shown that the bonding energy per atom, De/n, exhibits a strong nonadditive behavior; it grows rapidly with the cluster size and converges to values as large as 16-19 kcal/mol for Au and Cu. A valence bond (VB) analysis shows that this no-pair ferromagnetic bonding arises from bound triplet electron pairs that spread over all the close neighbors of a given atom in the clusters. The bound triplet pair owes its stabilization to the resonance energy provided by the mixing of the local ionic configurations, (3)M(??)(-?)M(+) and M(+?3)M(??)(-), and by the various excited covalent configurations (involving pz and dz(2) atomic orbitals) into the fundamental covalent structure (3)(M??M) with a s(1)s(1) electronic configuration. The VB model shows that a weak interaction in the dimer can become a remarkably strong binding force that holds together monovalent atoms without a single electron pair. PMID:26615685

  17. Comparative ENDOR study at 34 GHz of the triplet state of the primary donor in bacterial reaction centers of Rb. sphaeroides and Bl. viridis.

    PubMed

    Marchanka, Aliaksandr; Lubitz, Wolfgang; Plato, Martin; van Gastel, Maurice

    2014-05-01

    The primary electron donor (P) in the photosynthetic bacterial reaction center of Rhodobacter sphaeroides and Blastochloris viridis consists of a dimer of bacteriochlorophyll a and b cofactors, respectively. Its photoexcited triplet state in frozen solution has been investigated by time resolved ENDOR spectroscopy at 34 GHz. The observed ENDOR spectra for (3)P865 and (3)P960 are essentially the same, indicating very similar spin density distributions. Exceptions are the ethylidene groups unique to the bacteriochlorophyll b dimer in (3)P960. Strikingly, the observed hyperfine coupling constants of the ethylidene groups are larger than in the monomer, which speaks for an asymmetrically delocalized wave function over both monomer halves in the dimer. The latter observation corroborates previous findings of the spin density in the radical cation states P 865 (•+) (Lendzian et al. in Biochim Biophys Acta 1183:139-160, 1993) and P 960 (•+) (Lendzian et al. in Chem Phys Lett 148:377-385, 1988). As compared to the bacteriochlorophyll monomer, the hyperfine coupling constants of the methyl groups 2(1) and 12(1) are reduced by at least a factor of two, and quantitative analysis of these couplings gives rise to a ratio of approximately 3:1 for the spin density on the halves PL:PM. Our findings are discussed in light of the large difference in photosynthetic activity of the two branches of cofactors present in the bacterial reaction center proteins. PMID:23184403

  18. Laser photolysis studies on the electron-transfer reaction from the photoexcited triplet state of chloroindium(III) tetraphenylporphyrin to methylviologen in methanol solutions

    SciTech Connect

    Hoshino, M.; Seki, H.; Shizuka, H.

    1985-01-31

    Laser photolysis studies were carried out for chloroindium (III) tetraphenylporphyrin, C1In/sup III/TPP, in methanol solutions. The triplet states of (In/sup III/)/sup +/TPP and methylviologen, MV/sup 2 +/, were found to form a triplet exciplex with an association constant of 6.5 x 10/sup 2/M/sup -1/. The triplet exciplex partly dissociates to the cation radical of (In/sup III/)/sup +/TPP, (In/sup III/)/sup +/TPP/sup +/), and methylviologen cation radical, MV/sup +/, followed by the back electron transfer from MV/sup +/ to ((In/sup III/)/sup +/TPP/sup +/) to regenerate MV/sup 2 +/ and (In/sup III/)/sup +/TPP. The triplet exciplex reacts with triethanolamine, TEA, presumably to produce a new triplet exciplex, /sup 3/((In/sup III/)/sup +/TPP(TEA)(MV/sup 2 +/)), in which a TEA molecule is considered to occupy the axial position. No ionic dissociation from this triplet exciplex was observed. Photolysis of the methanol solution of C1In/sup III/TPP containing 0.5 M TEA and 10-/sup 3/ M MV/sup 2 +/ gives rise to the formation of MV/sup +/ as a final product. The absorption spectroscopy study revealed that C1In/sup III/TPP in a methanol solution at 0.5 M TEA is transformed to (In/sup III/TPP(TEA)/sub 2/)/sup +/(C1/sup -/), in which two TEA molecules are located in the axial positions. On the basis of the laser photolysis study the triplet state of (In/sup III/TPP(TEA)/sub 2/)/sup +/ is confirmed to undergo efficient electron transfer toward MV/sup 2 +/, resulting in the formation of MV/sup 2 +/. 29 refs., 6 figs.

  19. Triplet states as non-radiative traps in multichromophoric entities: single molecule spectroscopy of an artificial and natural antenna system.

    PubMed

    Hofkens, J; Schroeyers, W; Loos, D; Cotlet, M; Köhn, F; Vosch, T; Maus, M; Herrmann, A; Müllen, K; Gensch, T; De Schryver, F C

    2001-09-14

    Energy transfer in antenna systems, ordered arrays of chromophores, is one of the key steps in the photosynthetic process. The photophysical processes taking place in such multichromophoric systems, even at the single molecule level, are complicated and not yet fully understood. Instead of directly studying individual antenna systems, we have chosen to focus first on systems for which the amount of chromophores and the interactions among the chromophores can be varied in a systematic way. Dendrimers with a controlled number of chromophores at the rim fulfill those requirements perfectly. A detailed photophysical study of a second-generation dendrimer, containing eight peryleneimide chromophores at the rim, was performed 'J. Am. Chem. Soc., 122 (2000) 9278'. One of the most intriguing findings was the presence of collective on/off jumps in the fluorescence intensity traces of the dendrimers. This phenomenon can be explained by assuming a simultaneous presence of both a radiative trap (energetically lowest chromophoric site) and a non-radiative trap (triplet state of one chromophore) within one individual dendrimer. It was shown that an analogue scheme could explain the collective on/off jumps in the fluorescence intensity traces of the photosynthetic pigment B-phycoerythrin (B-PE) (Porphyridium cruentum). The different values of the triplet lifetime that could be recovered for a fluorescence intensity trace of B-PE were correlated with different intensity levels in the trace, suggesting different chromophores acting as a trap as function of time. PMID:11603833

  20. Triplet states as non-radiative traps in multichromophoric entities: single molecule spectroscopy of an artificial and natural antenna system

    NASA Astrophysics Data System (ADS)

    Hofkens, Johan; Schroeyers, Wouter; Loos, Davey; Cotlet, Mircea; Köhn, Fabian; Vosch, Tom; Maus, Michael; Herrmann, A.; Müllen, K.; Gensch, Thomas; De Schryver, F. C.

    2001-09-01

    Energy transfer in antenna systems, ordered arrays of chromophores, is one of the key steps in the photosynthetic process. The photophysical processes taking place in such multichromophoric systems, even at the single molecule level, are complicated and not yet fully understood. Instead of directly studying individual antenna systems, we have chosen to focus first on systems for which the amount of chromophores and the interactions among the chromophores can be varied in a systematic way. Dendrimers with a controlled number of chromophores at the rim fulfill those requirements perfectly. A detailed photophysical study of a second-generation dendrimer, containing eight peryleneimide chromophores at the rim, was performed 'J. Am. Chem. Soc., 122 (2000) 9278'. One of the most intriguing findings was the presence of collective on/off jumps in the fluorescence intensity traces of the dendrimers. This phenomenon can be explained by assuming a simultaneous presence of both a radiative trap (energetically lowest chromophoric site) and a non-radiative trap (triplet state of one chromophore) within one individual dendrimer. It was shown that an analogue scheme could explain the collective on/off jumps in the fluorescence intensity traces of the photosynthetic pigment B-phycoerythrin (B-PE) ( Porphyridium cruentum). The different values of the triplet lifetime that could be recovered for a fluorescence intensity trace of B-PE were correlated with different intensity levels in the trace, suggesting different chromophores acting as a trap as function of time.

  1. Theory of triplet optical absorption in oligoacenes: From naphthalene to heptacene

    SciTech Connect

    Chakraborty, Himanshu Shukla, Alok

    2014-10-28

    In this paper, we present a detailed theory of the triplet states of oligoacenes containing up to seven rings, i.e., starting from naphthalene all the way up to heptacene. In particular, we present results on the optical absorption from the first triplet excited state 1{sup 3}B{sub 2u}{sup +} of these oligomers, computed using the Pariser-Parr-Pople model Hamiltonian, and a correlated electron approach employing the configuration-interaction methodology at various levels. Excitation energies of various triplets states obtained by our calculations are in good agreement with the experimental results, where available. The computed triplet spectra of oligoacenes exhibits rich structure dominated by two absorption peaks of high intensities, which are well separated in energy, and are caused by photons polarized along the conjugation direction. This prediction of ours can be tested in future experiments performed on oriented samples of oligoacenes.

  2. The photophysics of monomeric bacteriochlorophylls c and d and their derivatives: properties of the triplet state and singlet oxygen photogeneration and quenching

    NASA Technical Reports Server (NTRS)

    Krasnovsky, A. A. Jr; Cheng, P.; Blankenship, R. E.; Moore, T. A.; Gust, D.

    1993-01-01

    Measurements of pigment triplet-triplet absorption, pigment phosphorescence and photosensitized singlet oxygen luminescence were carried out on solutions containing monomeric bacteriochlorophylls (Bchl) c and d, isolated from green photosynthetic bacteria, and their magnesium-free and farnesyl-free analogs. The energies of the pigment triplet states fell in the range 1.29-1.34 eV. The triplet lifetimes in aerobic solutions were 200-250 ns; they increased to 280 +/- 70 microseconds after nitrogen purging in liquid solutions and to 0.7-2.1 ms in a solid matrix at ambient or liquid nitrogen temperatures. Rate constants for quenching of the pigment triplet state by oxygen were (2.0-2.5) x 10(9) M-1 s-1, which is close to 1/9 of the rate constant for diffusion-controlled reactions. This quenching was accompanied by singlet oxygen formation. The quantum yields for the triplet state formation and singlet oxygen production were 55-75% in air-saturated solutions. Singlet oxygen quenching by ground-state pigment molecules was observed. Quenching was the most efficient for magnesium-containing pigments, kq = (0.31-1.2) x 10(9) M-1 s-1. It is caused mainly by a physical process of singlet oxygen (1O2) deactivation. Thus, Bchl c and d and their derivatives, as well as chlorophyll and Bchl a, combine a high efficiency of singlet oxygen production with the ability to protect photochemical and photobiological systems against damage by singlet oxygen.

  3. Photophysical studies of triplet exciton processes in pure polymer films: Technical progress report for the period February 1985-July 26, 1986. [Poly (N-vinylcarbazole) (PVCA)

    SciTech Connect

    Burkhart, R.D.

    1986-01-01

    An integrated system has been constructed to conduct experiments on time resolved photoluminescence processes into the low microsecond time regime. It is specifically designed for investigations of triplet photophysical processes in polymers and it is very sensitive providing, for the first time, triplet-triplet absorption spectra of poly(N-vinylcarbazole). A primary mission for this system is the direct detection of excited triplets using triplet-triplet absorption spectroscopy. Both spectroscopic and kinetic characteristics of polymeric triplet states have been investigated with this system. Quantitative measurements have been made of molar absorptivities, triplet quantum yields and specific rate constants for both radiative and radiationless transitions for poly(4-((vinyloxy) carbonyl)-carbazole) (PFCZ) and ot its monomeric analogue (MFCZ). In addition, specific rate constants for triplet-triplet annihilation have been evaluated for several polymers and molecularly doped polymeric systems. Additional studies include computer assisted resolution of the excimeric phosphorescence of poly(N-vinylcarbazole) and the synthesis of end-capped polystyrene molecules in order to investigate intramolecular exciton transfer. Work is also under way to determine contributions from intermolecular and intramolecular triplet exciton migration in very concentrated solutions of poly(2-vinylnaphthalene). 6 refs., 3 figs.

  4. Energy landscapes of dynamic ensembles of rolling triplet repeat bulge loops: implications for DNA expansion associated with disease states.

    PubMed

    Völker, Jens; Gindikin, Vera; Klump, Horst H; Plum, G Eric; Breslauer, Kenneth J

    2012-04-01

    DNA repeat domains can form ensembles of canonical and noncanonical states, including stable and metastable DNA secondary structures. Such sequence-induced structural diversity creates complex conformational landscapes for DNA processing pathways, including those triplet expansion events that accompany replication, recombination, and/or repair. Here we demonstrate further levels of conformational complexity within repeat domains. Specifically, we show that bulge loop structures within an extended repeat domain can form dynamic ensembles containing a distribution of loop positions, thereby yielding families of positional loop isomers, which we designate as "rollamers". Our fluorescence, absorbance, and calorimetric data are consistent with loop migration/translocation between sites within the repeat domain ("rollamerization"). We demonstrate that such "rollameric" migration of bulge loops within repeat sequences can invade and disrupt previously formed base-paired domains via an isoenthalpic, entropy-driven process. We further demonstrate that destabilizing abasic lesions alter the loop distributions so as to favor "rollamers" with the lesion positioned at the duplex/loop junction, sites where the flexibility of the abasic "universal hinge" relaxes unfavorable interactions and/or facilitates topological accommodation. Another strategic siting of an abasic site induces directed loop migration toward denaturing domains, a phenomenon that merges destabilizing domains. In the aggregate, our data reveal that dynamic ensembles within repeat domains profoundly impact the overall energetics of such DNA constructs as well as the distribution of states by which they denature/renature. These static and dynamic influences within triplet repeat domains expand the conformational space available for selection and targeting by the DNA processing machinery. We propose that such dynamic ensembles and their associated impact on DNA properties influence pathways that lead to DNA expansion. PMID:22397401

  5. Triplet dynamics in fluorescent polymer light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Wallikewitz, Bodo H.; Kabra, Dinesh; Gélinas, Simon; Friend, Richard H.

    2012-01-01

    We report a study of the triplet exciton dynamics and their effect on the performance of fluorescent organic light-emitting diodes. These polymer light-emitting diodes comprise metal oxide, injection electrodes, and poly(9,9'-dioctylfluorene-co-benzothiadiazole) as the emissive material and exhibit external quantum efficiencies up to 6.5%. Transient optical absorption measurements following a short (0.5 to 50 ?s) electrical drive pulse were used to monitor triplet dynamics during device operation. Triplet generation and decay processes were modeled, and we find that triplet-triplet annihilation is the dominant triplet decay mechanism. Singlet states, generated from triplet-triplet annihilation were monitored as delayed electroluminescence after the end of the drive pulse. From the delayed electroluminescence dynamics, we determine monomolecular as well as bimolecular triplet decay rates and estimate the triplet-charge annihilation rate. Singlet states generated from bimolecular triplet-triplet annihilation contribute up to 33% of the total amount of singlets generated in these fluorescent devices. To model these results, we require that triplet states can undergo bimolecular annihilation several times. With this model, we show that singlets can reach a maximum fraction of 40% of all excitons generated by charge recombination, without violating spin statistics. Singlet states generated from triplet-triplet annihilation are one important explanation for high external quantum efficiencies found in these fluorescent devices.

  6. Is Nitrate Anion Photodissociation Mediated by Singlet-Triplet Absorption?

    PubMed

    Svoboda, Ond?ej; Slaví?ek, Petr

    2014-06-01

    Photolysis of the nitrate anion is involved in the oxidation processes in the hydrosphere, cryosphere, and stratosphere. While it is known that the nitrate photolysis in the long-wavelength region proceeds with a very low quantum yield, the mechanism of the photodissociation remains elusive. Here, we present the quantitative modeling of singlet-singlet and singlet-triplet absorption spectra in the atmospherically relevant region around 300 nm, and we argue that a spin-forbidden transition between the singlet ground state and the first triplet state contributes non-negligibly to the nitrate anion photolysis. We further propose that the nitrate anion excited into the first singlet excited state relaxes nonradiatively into its ground state. The full understanding of the nitrate anion photolysis can improve modeling of the asymmetric solvation in the atmospheric processes, e.g., photolysis on the surfaces of ice or snow. PMID:26273880

  7. Radio frequency measurements of tunnel couplings and singlet-triplet spin states in Si:P quantum dots.

    PubMed

    House, M G; Kobayashi, T; Weber, B; Hile, S J; Watson, T F; van der Heijden, J; Rogge, S; Simmons, M Y

    2015-01-01

    Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet-triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20??eV to 8?meV. We measure dot-lead tunnel rates by analysis of the reflected signal and show that they change from 100?MHz to 22?GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon. PMID:26548556

  8. Radio frequency measurements of tunnel couplings and singlet-triplet spin states in Si:P quantum dots

    NASA Astrophysics Data System (ADS)

    House, M. G.; Kobayashi, T.; Weber, B.; Hile, S. J.; Watson, T. F.; van der Heijden, J.; Rogge, S.; Simmons, M. Y.

    2015-11-01

    Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet-triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20 ?eV to 8 meV. We measure dot-lead tunnel rates by analysis of the reflected signal and show that they change from 100 MHz to 22 GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon.

  9. Radio frequency measurements of tunnel couplings and singlet–triplet spin states in Si:P quantum dots

    PubMed Central

    House, M. G.; Kobayashi, T.; Weber, B.; Hile, S. J.; Watson, T. F.; van der Heijden, J.; Rogge, S.; Simmons, M. Y.

    2015-01-01

    Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet–triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20??eV to 8?meV. We measure dot–lead tunnel rates by analysis of the reflected signal and show that they change from 100?MHz to 22?GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon. PMID:26548556

  10. A new graphical version of STROTAB: The analysis and fitting of singlet triplet spectra of asymmetric top molecules in the prolate or oblate limits

    NASA Astrophysics Data System (ADS)

    Kodet, John; Judge, Richard H.

    2007-05-01

    The original version of STROTAB has been modified to run under Microsoft Windows using the C++ programming language. The new version takes full advantage of the Microsoft Foundation Classes available within the Microsoft Visual C++ Version 6 development environment. Specifically, windows can be created that edit the input file, summarize the results of the least-squares fit, display the calculated and observed spectra, display whole or partial sections of the calculated spectra as a stick or Gaussian de-convoluted spectrum. A listing of the rotational quantum numbers in the cases (a) and (b) limits for each of the displayed lines is provided. A branch annotating routine provides a quick visual guide to the assignment of the spectrum. A new eigenvalue sorting method has been added as an option that complements the existing method based on the eigenvector coefficients. The new sorting method has eliminated some difficulties that may arise using the existing "Least Ambiguous Method". The program has been extended to handle near-oblate asymmetric tops using a type III r representation. New version summaryTitle of program: STROTAB Version number: 2 Catalogue identifier:ADCA_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADCA_v2_0 Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Reference in CPC to previous version: 93 (1996) 241-264 Catalog identifier of previous version: ADCA Authors of previous version: R.H. Judge, E.D. Womeldorf, R.A. Morris, D.E. Shimp, D.J. Clouthier, D.L. Joo, D.C. Moule Does the new version supersede the original program: Yes Computers for which the program is designed and others on which it has been tested: Pentium Xenon, Pentium Pro and Later Operating systems or monitors under which program has been tested: Windows 98, Windows 2000, Windows XP Programming language used in the new version: ANSI C, C++, Microsoft Foundation Class (MFC) No. of lines in distributed program, including test data, etc.:11 913 No. of bytes in distributed program, including test data, etc.: 2 816 652 Memory required to execute with typical data: 7 Meg No of bits in a word: 16 No of processors used: 1 Has the code been vectorized or parallelized?: No No. of bytes in distributed program, including test data, etc.: ˜3.2 MB (compressed) Distribution format: zip file Additional keywords:near oblate top, bootstrap eigenvalue sorting, graphical environment, band contour Nature of physical problem: The least-squares/band contour fitting of the singlet-triplet spectra of asymmetric tops of orthorhombic symmetry using a basis set appropriate to the symmetric top limit (prolate or oblate) of the molecule in either Hund's case (a) or case (b) coupling situations. Method of solution: The calculation of the eigenvectors and eigenvalues remains unchanged from the earlier version. An option to sort the eigenvalues of the current J by fitting them to regular progressions formed from earlier J values (bootstrap method) can be used as an option in place of the existing method based on eigenvector coefficients. Reasons for the new version: The earlier version can only handle oblate tops by diagonalizing using the prolate limit. This has turned out to be unacceptable. An improved method of sorting eigenvalues under certain conditions is also needed. A graphical interface has been added to ease the use of the program. Summary of revisions: The Hamiltonian can now be constructed in a limit appropriate the representation for of the molecule. Sorting by an alternate method is now offered. Numerous graphical features have been added. Restrictions on complexity of the problem: The rotational quantum number restrictions are J?255 and K (or P) ?127. The allowed transition frequency minus the band origin frequency must be in the range of ±10 000 cm -1. Up to five decimal places may be reported. The number of observed lines is limited by the dynamic memory and the amount of disk space available. Only molecules of symmetry D 2h, D 2 and C 2v can be accommodated in this version. Only constant

  11. Laser spectroscopy of HfO: Linkage of the triplet state manifolds

    SciTech Connect

    Kaledin, L.A.; McCord, J.E.; Heaven, M.C.

    1995-12-31

    The wavelength-resolved fluorescence excitation technique has been used to record the (0,0) band of the b{sup 3}{Pi}{sub 1} - X{sup 1}{Sigma}{sup +} electronic transition of HfO at a resolution of 0.03 cm{sup -1}. Previously, this transition has been assigned as a B{sup 1}{Pi}-X{sup 1}{Sigma}{sup +} electronic transition. The principal constants (in cm{sup -1}) obtained from recent and previous analyses are discussed. Ligand field theory (LFT) calculations were used to suggest electronic configurations for the excited states of HfO. New electronic assignments based on LFT predictions for the F and E states are indicated in parentheses.

  12. Properties of the triplet metastable states of the alkaline-earth-metal atoms

    SciTech Connect

    Mitroy, J.; Bromley, M.W.J.

    2004-11-01

    The static and dynamic properties of the alkaline-earth-metal atoms in their metastable state are computed in a configuration interaction approach with a semiempirical model potential for the core. Among the properties determined are the scalar and tensor polarizabilities, the quadrupole moment, some of the oscillator strengths, and the dispersion coefficients of the van der Waals interaction. A simple method for including the effect of the core on the dispersion parameters is described.

  13. Overview of helium-like structure measurements: A focus on the N = 2 triplet states

    SciTech Connect

    Berry, H.G.; Dunford, R.W.

    1992-01-01

    We present a comprehensive analysis of existing measurements of the 1s2s [sup 3]S[sub 1] [minus] 1s2p[sup 3]P[sub 0,1,2] transition energies in heliumlike ions for nuclear charges Z=2 to Z=92. We find agreement with the standard unified calculations of [vert bar]Drake except for the transitions from the 1s2p [sup 3]P[sub o] state. We find a deviation equal to 2.3x(Z/10)[sup 4] cm[sup [minus]1] for the most precise existing measurements.

  14. Distinct ? subunit variations of the hypothalamic GABAA receptor triplets (???) are linked to hibernating state in hamsters

    PubMed Central

    2010-01-01

    Background The structural arrangement of the ?-aminobutyric acid type A receptor (GABAAR) is known to be crucial for the maintenance of cerebral-dependent homeostatic mechanisms during the promotion of highly adaptive neurophysiological events of the permissive hibernating rodent, i.e the Syrian golden hamster. In this study, in vitro quantitative autoradiography and in situ hybridization were assessed in major hypothalamic nuclei. Reverse Transcription Reaction-Polymerase chain reaction (RT-PCR) tests were performed for specific GABAAR receptor subunit gene primers synthases of non-hibernating (NHIB) and hibernating (HIB) hamsters. Attempts were made to identify the type of ??? subunit combinations operating during the switching ON/OFF of neuronal activities in some hypothalamic nuclei of hibernators. Results Both autoradiography and molecular analysis supplied distinct expression patterns of all ? subunits considered as shown by a strong (p < 0.01) prevalence of ?1 ratio (over total ? subunits considered in the present study) in the medial preoptic area (MPOA) and arcuate nucleus (Arc) of NHIBs with respect to HIBs. At the same time ?2 subunit levels proved to be typical of periventricular nucleus (Pe) and Arc of HIB, while strong ?4 expression levels were detected during awakening state in the key circadian hypothalamic station, i.e. the suprachiasmatic nucleus (Sch; 60%). Regarding the other two subunits (? and ?), elevated ?3 and ?3 mRNAs levels mostly characterized MPOA of HIBs, while prevalently elevated expression concentrations of the same subunits were also typical of Sch, even though this time during the awakening state. In the case of Arc, notably elevated levels were obtained for ?3 and ?2 during hibernating conditions. Conclusion We conclude that different ??? subunits are operating as major elements either at the onset of torpor or during induction of the arousal state in the Syrian golden hamster. The identification of a brain regional distribution pattern of distinct GABAAR subunit combinations may prove to be very useful for highlighting GABAergic mechanisms functioning at least during the different physiological states of hibernators and this may have interesting therapeutic bearings on neurological sleeping disorders. PMID:20815943

  15. Photophysics of N-ethylcarbazole in fluid solution. Evidence for solvent dependence and triplet excimer formation

    SciTech Connect

    Haggquist, G.W.; Burkhart, R.D. )

    1993-03-18

    The photoexcitation of N-ethylcarbazole (NEC) in fluid solutions of cyclohexane, N,N-dimethylformamide (DMF), ethanol, paraffin oil, and mixtures of glycerol with either ethanol or DMF has been carried out using 308-nm pulses from a XeCl excimer laser. Emission spectra recorded at 70 [mu]s or longer after the excitation pulse depend upon the solvent. In ethanol and DMF red-shifted, structureless bands appear at these longer delay times which are attributed to delayed excimer fluorescence. No such bands are found using cyclohexane. In glycerol/ethanol or glycerol/DMF (90/10 (v/v)) monomeric delayed fluorescence is found at delay times of 70 [mu]s or less, but at delay times from 700 [mu]s to 3.8 ms a prominent band at 500 nm is observed which is attributed to emission from triplet excimers. Transient absorption spectra of NEC in cyclohexane recorded at delay times from 1 to 20 [mu]s after the excitation pulse are entirely attributable to the carbazolyl triplet state. In ethanol and DMF, however, additional bands corresponding to radical cations and anions of NEC are also found. A broad band observed near 500 nm is provisionally assigned to the triplet excimer. Kinetic decays of the absorption signals due to triplets were fit to concurrent first-order and second-order processes whereas those due to the radical anion were fit to a biexponential decay. It is proposed that delayed excimer fluorescence arises from recombination of cation dimers and radical anions and that triplet excimers are formed by recombination of geminate ion pairs to form a monomeric triplet and a ground-state partner, followed by interaction of the triplet and the same partner. The primary mechanism for ion formation is thought to involve electron transfer from multiply excited molecules to ground-state species. 34 refs., 10 figs., 1 tab.

  16. Photo-assisted intersystem crossing: The predominant triplet formation mechanism in some isolated polycyclic aromatic molecules excited with pulsed lasers

    SciTech Connect

    Johnson, Philip M.; Sears, Trevor J.

    2015-07-28

    Naphthalene, anthracene, and phenanthrene are shown to have very long-lived triplet lifetimes when the isolated molecules are excited with nanosecond pulsed lasers resonant with the lowest singlet state. For naphthalene, triplet state populations are created only during the laser pulse, excluding the possibility of normal intersystem crossing at the one photon level, and all molecules have triplet lifetimes greater than hundreds of microseconds, similar to the behavior previously reported for phenylacetylene. Although containing 7–12 thousand cm?¹ of vibrational energy, the triplet molecules have ionization thresholds appropriate to vibrationless T? states. The laser power dependences (slopes of log-log power plots) of the excited singlet and triplet populations are about 0.7 for naphthalene and about 0.5 for anthracene. Kinetic modeling of the power dependences successfully reproduces the experimental results and suggests that the triplet formation mechanism involves an enhanced spin orbit coupling caused by sigma character in states at the 2-photon level. Symmetry Adapted Cluster-Configuration Interaction calculations produced excited state absorption spectra to provide guidance for estimating kinetic rates and the sigma character present in higher electronic states. It is concluded that higher excited state populations are significant when larger molecules are excited with pulsed lasers and need to be taken into account whenever discussing the molecular photodynamics.

  17. Photo-assisted intersystem crossing: The predominant triplet formation mechanism in some isolated polycyclic aromatic molecules excited with pulsed lasers

    DOE PAGESBeta

    Johnson, Philip M.; Sears, Trevor J.

    2015-07-28

    Naphthalene, anthracene, and phenanthrene are shown to have very long-lived triplet lifetimes when the isolated molecules are excited with nanosecond pulsed lasers resonant with the lowest singlet state. For naphthalene, triplet state populations are created only during the laser pulse, excluding the possibility of normal intersystem crossing at the one photon level, and all molecules have triplet lifetimes greater than hundreds of microseconds, similar to the behavior previously reported for phenylacetylene. Although containing 7–12 thousand cm?¹ of vibrational energy, the triplet molecules have ionization thresholds appropriate to vibrationless T? states. The laser power dependences (slopes of log-log power plots) ofmore »the excited singlet and triplet populations are about 0.7 for naphthalene and about 0.5 for anthracene. Kinetic modeling of the power dependences successfully reproduces the experimental results and suggests that the triplet formation mechanism involves an enhanced spin orbit coupling caused by sigma character in states at the 2-photon level. Symmetry Adapted Cluster-Configuration Interaction calculations produced excited state absorption spectra to provide guidance for estimating kinetic rates and the sigma character present in higher electronic states. It is concluded that higher excited state populations are significant when larger molecules are excited with pulsed lasers and need to be taken into account whenever discussing the molecular photodynamics.« less

  18. Theory of Pairing Assisted Spin Polarization in Spin-Triplet Equal Spin Pairing: Origin of Extra Magnetization in Sr2RuO4 in Superconducting State

    NASA Astrophysics Data System (ADS)

    Miyake, Kazumasa

    2014-05-01

    It is shown that an extra magnetization is induced by an onset of the equal-spin-pairing of spin triplet superconductivity if the energy dependence of the density of states of quasiparticles exists in the normal state. It turns out that the effect is observable in Sr2RuO4 due to the existence of van Hove singularity in the density of states near the Fermi level, explaining the extra contribution in the Knight shift reported by Ishida et al. It is also quite non-trivial that this effect exists even without external magnetic field, which implies that the time reversal symmetry is spontaneously broken in the spin space.

  19. Neutron interferometric measurement of the scattering length difference between the triplet and singlet states of n-$^3$He

    E-print Network

    M. G. Huber; M. Arif; W. C. Chen; T. R. Gentile; D. S. Hussey; T. C. Black; D. A. Pushin; C. B. Shahi; F. E. Wietfeldt; L. Yang

    2014-09-30

    We report a determination of the n-$^3$He scattering length difference $\\Delta b^{\\prime} = b_{1}^{\\prime}-b_{0}^{\\prime} = $ ($-5.411$ $\\pm$ $0.031$ (statistical) $\\pm$ $0.039$ (systematic)) fm between the triplet and singlet states using a neutron interferometer. This revises our previous result $\\Delta b^{\\prime} = $ (-5.610 $\\pm$ $0.027$ (statistical) $\\pm$ $0.032$ (systematic) fm obtained using the same technique in 2008. This revision is due to a re-analysis of the 2008 experiment that includes a more robust treatment of the phase shift caused by magnetic field gradients near the $^3$He cell. Furthermore, we more than doubled our original data set from 2008 by acquiring six months of additional data in 2013. Both the new data set and a re-analysis of the older data are in good agreement. Scattering lengths of low Z isotopes are valued for use in few-body nuclear effective field theories, provide important tests of modern nuclear potential models and in the case of $^3$He aid in the interpretation of neutron scattering from quantum liquids. The difference $\\Delta b^{\\prime}$ was determined by measuring the relative phase shift between two incident neutron polarizations caused by the spin-dependent interaction with a polarized $^3$He target. The target $^3$He gas was sealed inside a small, flat windowed glass cell that was placed in one beam path of the interferometer. The relaxation of $^3$He polarization was monitored continuously with neutron transmission measurements. The neutron polarization and spin flipper efficiency were determined separately using $^3$He analyzers and two different polarimetry analysis methods. A summary of the measured scattering lengths for n-$^3$He with a comparison to nucleon interaction models is given.

  20. Dynamics of He2? triplet state excimer bubbles in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Eloranta, J.

    2007-02-01

    Time-dependent density functional theory calculations for bulk superfluid 4He were carried out to model dynamics around He2? excimers after optical excitation from the 3a to 3d state. The liquid dynamics occurring after a sudden change in the helium-liquid interaction results in interfacial dynamics, which can be divided into three different modes: (1) non-linear processes yielding shock and solitonic progressions, (2) fast interfacial dynamics related to thinning of the liquid-gas interface that occurs within few picoseonds and (3) slow spherical breathing motion of the liquid-gas interface with recursion times up to 110 ps. The long-range repulsive tail ( R > 12 Å) in the He-He2? interaction is found to play an important role in determining the recursion time of the solvent cavity breathing mode. As energy differences of just few wavenumbers in this region are sufficient to produce large changes in the recursion time, none of the pair potentials derived from the first principles could reproduce the experimental data [V.A. Benderskii, J. Eloranta, R. Zadoyan, V.A. Apkarian, J. Chem. Phys. 117 (2002) 1201]. Therefore it is concluded that the pump-probe experiments measure energy differences that are not possible to calculate using the current electronic structure methods. The results obtained from the density functional theory calculations are consistent with the proposed experimental scheme.

  1. 13C HYPERFINE INTERACTION IN THE TRIPLET STATE OF C60: AN ELECTRON SPIN ECHO ENVELOPE MODULATION STUDY

    E-print Network

    resonator. Typical microwave excitation pulses were 16 ns and 32 ns at a power of 1 kW. The temperature STUDY A. Grupp, J. Pfeuffer, and M. Mehring 2. Physikalisches Institut, Universität Stuttgart]. The reason for this is the high singlet to triplet intersystem crossing quantum yield of nearly 1

  2. Kinetic Monte Carlo study of triplet-triplet annihilation in organic phosphorescent emitters

    NASA Astrophysics Data System (ADS)

    van Eersel, H.; Bobbert, P. A.; Coehoorn, R.

    2015-03-01

    The triplet-triplet annihilation (TTA) rate in organic phosphorescent materials such as used in organic light-emitting diodes is determined predominantly either by the rate of single-step Förster-type triplet-triplet interactions, or by multi-step triplet diffusion. We show how kinetic Monte Carlo simulations may be used to analyze the role of both processes. Under steady state conditions, the effective triplet-triplet interaction rate coefficient, kTT, which is often regarded as a constant, is found to depend actually on the number of excitons lost upon a triplet-triplet interaction process and to show a significant higher-order dependence on the triplet volume density. Under the conditions encountered in transient photoluminescence (PL) studies, kTT is found to be effectively constant in the case of diffusion-dominated TTA. However, for the case of single-step TTA, a strongly different decay of the emission intensity is found, which also deviates from an analytic expression proposed in the literature. We discuss how the transient PL response may be used to make a distinction between both mechanisms. The simulations are applied to recently published work on the dye concentration dependence of the TTA rate in materials based on the archetypal green emitter tris[2-phenylpyridine]iridium (Ir(ppy)3).

  3. Electronic excited states and electronic spectra of biphenyl: a study using many-body wavefunction methods and density functional theories.

    PubMed

    Fukuda, Ryoichi; Ehara, Masahiro

    2013-10-28

    The low-lying electronic excited states of biphenyl were studied using the symmetry-adapted cluster-configuration interaction (SAC-CI), complete active space self-consistent field (CASSCF), complete active space perturbation theory of the second-order (CASPT2), and the time-dependent density functional theory (TDDFT). The molecular geometries in the ground and excited states were optimized using the SAC-CI and TDDFT for singlet and triplet states. The energies of vertical excitations, emissions, and adiabatic transitions were calculated. The TDDFT calculations significantly underestimated the excitation energy of the 1(1)B1 state, while the SAC-CI and CASPT2 provided essentially similar results. The present SAC-CI and CASPT2 calculations concluded that the lowest singlet state of isolated biphenyl is the 1(1)B3 state that takes a planar geometry and the second lowest state is the 1(1)B2 state with a twisted geometry. The present results were consistent with the previous experimental findings. The 1(1)B1 state that has a charge-separated biracial character in the vertical excitation relaxed into a planar quinoid structure in which bond alternations were emphasized. The other states took a benzenoid structure. The ultraviolet (UV) absorption and circular dichroism (CD) spectra below 7 eV were calculated with the SAC-CI method. The valence-Rydberg mixings were found to be significant in the second and higher series of excited states. PMID:24022338

  4. Zethrene biradicals: How pro-aromaticity is expressed in the ground electronic state and in the lowest energy singlet, triplet, and ionic states

    SciTech Connect

    Zafra, José Luis; González Cano, Rafael C.; Ruiz Delgado, M. Carmen; López Navarrete, Juan T.; Casado, Juan

    2014-02-07

    A analysis of the electronic and molecular structures of new molecular materials based on zethrene is presented with particular attention to those systems having a central benzo-quinoidal core able to generate Kekulé biradicals whose stability is provided by the aromaticity recovery in this central unit. These Kekulé biradicals display singlet ground electronic states thanks to double spin polarization and have low-energy lying triplet excited states also featured by the aromaticity gain. Pro-aromatization is also the driving force for the stabilization of the ionized species. Moreover, the low energy lying singlet excited states also display a profound biradical fingerprint allowing to singlet exciton fission. These properties are discussed in the context of the size of the zethrene core and of its substitution. The work encompasses all known long zethrenes and makes use of a variety of experimental techniques, such as Raman, UV-Vis-NIR absorption, transient absorption, in situ spectroelectrochemistry and quantum chemical calculations. This study reveals how the insertion of suitable molecular modules (i.e., quinoidal) opens the door to new intriguing molecular properties exploitable in organic electronics.

  5. Magnetic Field Effects on Triplet-Triplet Annihilation in Solutions: Modulation of Visible/NIR Luminescence

    PubMed Central

    Mani, Tomoyasu; Vinogradov, Sergei A.

    2013-01-01

    Photon upconversion based on sensitized triplet-triplet annihilation (TTA) presents interest for such areas as photovoltaics and imaging. Usually energy upconversion is observed as p-type delayed fluorescence from molecules whose triplet states are populated via energy transfer from a suitable triplet donor, followed by TTA. Magnetic field effects (MFE) on delayed fluorescence in molecular crystals are well known; however, there exist only a few examples of MFE on TTA in solutions, and all of them are limited to UV-emitting materials. Here we present MFE on TTA-mediated visible and near infrared (NIR) emission, sensitized by far-red absorbing metalloporphyrins in solutions at room temperature. In addition to visible delayed fluorescence from annihilator, we also observed NIR emission from the sensitizer, occurring as a result of triplet-triplet energy transfer back from annihilator, termed “delayed phosphorescence”. This emission also exhibits MFE, but opposite in sign to the annihilator fluorescence. PMID:24143268

  6. Improvement of photovoltaic response based on enhancement of spin-orbital coupling and triplet states in organic solar cells

    NASA Astrophysics Data System (ADS)

    Xu, Zhihua; Hu, Bin; Howe, Jane

    2008-02-01

    This article reports an improvement of photovoltaic response by dispersing phosphorescent Ir(ppy)3 molecules in an organic solar cell of poly[2-methoxy-5-(2'-ethylhexyloxy)-1 4-phenylenevinylene] (MEH-PPV) blended with surface-functionalized fullerene 1-(3-methyloxycarbonyl)propy(1-phenyl [6,6]) C61 (PCBM). The magnetic field-dependent photocurrent indicates that the dispersed Ir(ppy)3 molecules increase the spin-orbital coupling strength with the consequence of changing the singlet and triplet ratios through intersystem crossing due to the penetration of the delocalized ? electrons of MEH-PPV into the large orbital magnetic field of Ir(ppy)3 dopants. The tuning of singlet and triplet exciton ratios can lead to an enhancement of photovoltaic response due to their different contributions to the two different photocurrent generation channels: exciton dissociation and exciton-charge reaction in organic materials. In addition, the photoluminescence temperature dependence reveals that the dispersed Ir(ppy)3 reduces the recombination of dissociated charge carriers in the PCBM doped MEH-PPV. As a result, adjusting singlet and triplet ratios by introducing heavy-metal complex Ir(ppy)3 provides a mechanism to improve the photovoltaic response through controlling exciton dissociation, exciton-charge reaction, and recombination of dissociated charge carriers in organic bulk-heterojunction solar cells.

  7. Unimolecular photodissociation dynamics of ketene (CH{sub 2}CO): The singlet/triplet branching ratio and experimental observation of the vibrational level thresholds of the transition-state

    SciTech Connect

    Kim, S.K.

    1993-05-01

    The rotational distributions of CO products from the dissociation of ketene at photolysis energies 10 cm{sup {minus}1} below, 56, 110, 200, 325, 425, 1,107, 1,435, 1,720, and 2,500 cm{sup {minus}1} above the singlet threshold, are measured in a supersonic free jet of ketene. The CO(v{double_prime} = 0) rotational distributions at 56, 110, 200, 325, and 425 cm{sup {minus}1} are bimodal. The peaks at low J`s, which are due to CO from the singlet channel, show that the product rotational distribution of CO product from ketene dissociation on the singlet surface is well described by phase space theory (PST). For CO(v{double_prime} = 0) rotational distributions at higher excess energies, the singlet and triplet contributions are not clearly resolved, and the singlet/triplet branching ratios are estimated by assuming that PST accurately predicts the CO rotational distribution from the singlet channel and that the distribution from the triplet channel changes little from that at 10 cm{sup {minus}1} below the singlet threshold. At 2,500 cm{sup {minus}1} excess energy, the CO(v{double_prime} = 1) rotational distribution is obtained, and the ratio of CO(v{double_prime} = 1) to CO(v{double_prime} = 0) products for the singlet channel is close to the variational RRKM calculation, 0.038, and the separate statistical ensembles (SSE) prediction, 0.041, but much greater than the PST prediction, 0.016. Rate constants for the dissociation of ketene (CH{sub 2}CO) and deuterated ketene (CD{sub 2}CO) have been measured at the threshold for the production of the CH(D){sub 2} and CO. Sharp peaks observed in photofragment excitation (PHOFEX) spectra probing CO (v = 0, J = 2) product are identified with the C-C-O bending mode of the transition state. RRKM calculations are carried out for two limiting cases for the dynamics of K-mixing in highly vibrationally excited reactant states.

  8. Markov triplets on CCR-algebras

    E-print Network

    Anna Jencova; Denes Petz; Jozsef Pitrik

    2009-02-20

    The paper contains a detailed computation about the algebra of canonical commutation relation, the representation of the Weyl unitaries, the quasi-free states and their von Neumann entropy. The Markov triplet is defined by constant entropy increase. The Markov property of a quasi-free state is described by the representing block matrix. The proof is based on results on the statistical sufficiency in the quantum case. The relation to classical Gaussian Markov triplets is also described.

  9. Single-shot readout and relaxation of singlet and triplet states in exchange-coupled 31P electron spins in silicon.

    PubMed

    Dehollain, Juan P; Muhonen, Juha T; Tan, Kuan Y; Saraiva, Andre; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

    2014-06-13

    We present the experimental observation of a large exchange coupling J ? 300 ?eV between two (31)P electron spin qubits in silicon. The singlet and triplet states of the coupled spins are monitored in real time by a single-electron transistor, which detects ionization from tunnel-rate-dependent processes in the coupled spin system, yielding single-shot readout fidelities above 95%. The triplet to singlet relaxation time T(1) ? 4 ms at zero magnetic field agrees with the theoretical prediction for J-coupled 31P dimers in silicon. The time evolution of the two-electron state populations gives further insight into the valley-orbit eigenstates of the donor dimer, valley selection rules and relaxation rates, and the role of hyperfine interactions. These results pave the way to the realization of two-qubit quantum logic gates with spins in silicon and highlight the necessity to adopt gating schemes compatible with weak J-coupling strengths. PMID:24972221

  10. Understanding the Photoreactivity of Dissolved Organic Carbon in Natural Waters: The Role of the Triplet Excited-State of Allochthonous and Autochthonous DOC

    NASA Astrophysics Data System (ADS)

    Cottrell, B. A.; Timko, S. A.; Robinson, A. K.; Weiden, L. M.; Cooper, W.

    2012-12-01

    The photochemical reactivity of DOC in sunlit waters is a major factor for the in situ processing of DOC itself and trace contaminants in streams, lakes and the ocean. There is an increasing interest in the use of wetlands to mitigate contaminant removal. Laser flash photolysis is used to determine the reaction rate constants of dissolved organic carbon (DOC) with emerging contaminants in natural waters. DOC, produced by the decomposition of plant and microbial material, is one of the most complex naturally occurring mixtures. DOC plays a major role in the global carbon cycle, the sequestration and transport of trace chemicals and contaminants, and the biogeochemistry of natural waters. Hydrolysis, direct photolysis and reactions with singlet oxygen and the hydroxyl radical account for up to 25% of the photo reactivity of natural organic matter. The remaining 75% is attributed to reactions with the triplet-excited state of DOC (3DOC*). In this study, 1H NMR is used to characterize DOC from the Black River (NC), the San Joaquin Wetlands (Irvine, CA), and coastal seawater (Crystal Cove, CA). These sites encompass both allochthonous and autochthonous organic matter from catchment, wetlands, and marine waters. We then determine the reaction rate constants of known triplet state reactants and pharmaceuticals with the 3DOC* in the natural waters and with the DOC isolated by solid phase extraction. Studies of 3DOC* could provide a measure of DOC reactivity, essential in the design of constructed wetlands for contaminant removal.

  11. On the Photoelectron Spectra of Li4

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Arnold, James O. (Technical Monitor)

    1996-01-01

    The most stable structure for Li4(-) is found to be the rhombus. Electron detachment from this structure does not seem able to fully explain the photoelectron spectra. The computed results are consistent with those Rao, Jena, and Ray who have proposed that the experimental spectra consists of a superposition of detachment from the Li4(-) rhombus and tetrahedron, forming the singlet and triplet states of Li4, respectively.

  12. Infrared absorption spectra of various doping states in cuprate superconductors

    SciTech Connect

    Yonemitsu, K.; Bishop, A.R.; Lorenzana, J.

    1992-02-01

    Doping states in a two-dimensional three-band extended Peierls-Hubbard model was investigated within inhomogeneous Hartree-Fock and random phase approximation. They are very sensitive to small changes of interaction parameters and their distinct vibrational and optical absorption spectra can be used to identify different doping states. For electronic parameters relevant to cuprate superconductors, as intersite electron-phonon interaction strength increases, the doping state changes from a Zhang-Rice state to a covalent molecular singlet state accompanied by local quenching of the Cu magnetic moment and large local lattice distortion in an otherwise undistorted antiferromagnetic background. In a region where both intersite electron-phonon interaction and on-site electron-electron repulsion are large, we obtain new stable global phases including a bond-order-wave state and a mixed state of spin-Peierls bonds and antiferromagnetic Cu spins, as well as many metastable states. Doping in the bond-order-wave region induces separation of spin and charge. 9 refs.

  13. Infrared absorption spectra of various doping states in cuprate superconductors

    SciTech Connect

    Yonemitsu, K.; Bishop, A.R. ); Lorenzana, J. )

    1992-01-01

    Doping states in a two-dimensional three-band extended Peierls-Hubbard model was investigated within inhomogeneous Hartree-Fock and random phase approximation. They are very sensitive to small changes of interaction parameters and their distinct vibrational and optical absorption spectra can be used to identify different doping states. For electronic parameters relevant to cuprate superconductors, as intersite electron-phonon interaction strength increases, the doping state changes from a Zhang-Rice state to a covalent molecular singlet state accompanied by local quenching of the Cu magnetic moment and large local lattice distortion in an otherwise undistorted antiferromagnetic background. In a region where both intersite electron-phonon interaction and on-site electron-electron repulsion are large, we obtain new stable global phases including a bond-order-wave state and a mixed state of spin-Peierls bonds and antiferromagnetic Cu spins, as well as many metastable states. Doping in the bond-order-wave region induces separation of spin and charge. 9 refs.

  14. Synthesis and Exciton Dynamics of Triplet Sensitized Conjugated Polymers.

    PubMed

    Andernach, Rolf; Utzat, Hendrik; Dimitrov, Stoichko D; McCulloch, Iain; Heeney, Martin; Durrant, James R; Bronstein, Hugo

    2015-08-19

    We report the synthesis of a novel polythiophene-based host-guest copolymer incorporating a Pt-porphyrin complex (TTP-Pt) into the backbone for efficient singlet to triplet polymer exciton sensitization. We elucidated the exciton dynamics in thin films of the material by means of Transient Absorption Spectrosopcy (TAS) on multiple time scales and investigated the mechanism of triplet exciton formation. During sensitization, singlet exciton diffusion is followed by exciton transfer from the polymer backbone to the complex where it undergoes intersystem crossing to the triplet state of the complex. We directly monitored the triplet exciton back transfer from the Pt-porphyrin to the polymer and found that 60% of the complex triplet excitons were transferred with a time constant of 1087 ps. We propose an equilibrium between polymer and porphyrin triplet states as a result of the low triplet diffusion length in the polymer backbone and hence an increased local triplet population resulting in increased triplet-triplet annihilation. This novel system has significant implications for the design of novel materials for triplet sensitized solar cells and upconversion layers. PMID:26200595

  15. Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals.

    PubMed

    Thompson, Nicholas J; Wilson, Mark W B; Congreve, Daniel N; Brown, Patrick R; Scherer, Jennifer M; Bischof, Thomas S; Wu, Mengfei; Geva, Nadav; Welborn, Matthew; Voorhis, Troy Van; Bulovi?, Vladimir; Bawendi, Moungi G; Baldo, Marc A

    2014-11-01

    Triplet excitons are ubiquitous in organic optoelectronics, but they are often an undesirable energy sink because they are spin-forbidden from emitting light and their high binding energy hinders the generation of free electron-hole pairs. Harvesting their energy is consequently an important technological challenge. Here, we demonstrate direct excitonic energy transfer from 'dark' triplets in the organic semiconductor tetracene to colloidal PbS nanocrystals, thereby successfully harnessing molecular triplet excitons in the near infrared. Steady-state excitation spectra, supported by transient photoluminescence studies, demonstrate that the transfer efficiency is at least (90 ± 13)%. The mechanism is a Dexter hopping process consisting of the simultaneous exchange of two electrons. Triplet exciton transfer to nanocrystals is expected to be broadly applicable in solar and near-infrared light-emitting applications, where effective molecular phosphors are lacking at present. In particular, this route to 'brighten' low-energy molecular triplet excitons may permit singlet exciton fission sensitization of conventional silicon solar cells. PMID:25282507

  16. Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals

    NASA Astrophysics Data System (ADS)

    Thompson, Nicholas J.; Wilson, Mark W. B.; Congreve, Daniel N.; Brown, Patrick R.; Scherer, Jennifer M.; Bischof, Thomas S.; Wu, Mengfei; Geva, Nadav; Welborn, Matthew; Voorhis, Troy Van; Bulovi?, Vladimir; Bawendi, Moungi G.; Baldo, Marc A.

    2014-11-01

    Triplet excitons are ubiquitous in organic optoelectronics, but they are often an undesirable energy sink because they are spin-forbidden from emitting light and their high binding energy hinders the generation of free electron-hole pairs. Harvesting their energy is consequently an important technological challenge. Here, we demonstrate direct excitonic energy transfer from ‘dark’ triplets in the organic semiconductor tetracene to colloidal PbS nanocrystals, thereby successfully harnessing molecular triplet excitons in the near infrared. Steady-state excitation spectra, supported by transient photoluminescence studies, demonstrate that the transfer efficiency is at least (90 ± 13)%. The mechanism is a Dexter hopping process consisting of the simultaneous exchange of two electrons. Triplet exciton transfer to nanocrystals is expected to be broadly applicable in solar and near-infrared light-emitting applications, where effective molecular phosphors are lacking at present. In particular, this route to ‘brighten’ low-energy molecular triplet excitons may permit singlet exciton fission sensitization of conventional silicon solar cells.

  17. Assignment of IR bands of isolated and protein-bound Peridinin in its fundamental and triplet state by static FTIR, time-resolved step-scan FTIR and DFT calculations

    NASA Astrophysics Data System (ADS)

    Mezzetti, Alberto; Kish, Elizabeth; Robert, Bruno; Spezia, Riccardo

    2015-06-01

    The vibrational properties of Peridinin in its fundamental state and in the excited triplet state have been investigated by DFT calculations and static and time-resolved FTIR spectroscopy. The infrared spectrum of Peridinin in its fundamental state has been explored in the whole 2000-600 cm-1 range, and interpreted in term of molecular vibrations. In particular, new infrared bands have been identified and assigned to specific molecular vibrations. 3Peridinin molecular vibrations have also been investigated by DFT calculations. In addition, putative IR bands belonging to Peridinin and 3Peridinin have been identified in the step-scan FTIR difference spectrum of the Peridinin-Chlorophyll a-Protein from Amphidinium carterae, where light induce formation of a triplet state localized on one or more Peridinins. The exact nature of the triplet state formed in Peridinin-Chlorophyll a-Protein from dinoflagellates, in particular the possible involvement in this triplet state of 3Chlorophyll a, has been largely debated in the last few years (see Carbonera et al., 2014 [3]); time-resolved differential FTIR experiments have played a key role in this debate. Identification of IR marker bands for the main molecule (Peridinin) implicated in this photophysical process is therefore particularly important and makes this study a significant step towards the full understanding of Peridinin-Chlorophyll-a-Proteins photophysics.

  18. Quasiclassical asymptotics and coherent states for bounded discrete spectra

    SciTech Connect

    Gorska, K.; Penson, K. A.; Horzela, A.; Blasiak, P.; Duchamp, G. H. E.; Solomon, A. I.

    2010-12-15

    We consider discrete spectra of bound states for nonrelativistic motion in attractive potentials V{sub {sigma}}(x)=-|V{sub 0}| |x|{sup -}{sigma}, 0<{sigma}{<=}2. For these potentials the quasiclassical approximation for n{yields}{infinity} predicts quantized energy levels e{sub {sigma}}(n) of a bounded spectrum varying as e{sub {sigma}}(n){approx}-n{sup -}2{sigma}/(2-{sigma}). We construct collective quantum states using the set of wavefunctions of the discrete spectrum assuming this asymptotic behavior. We give examples of states that are normalizable and satisfy the resolution of unity, using explicit positive functions. These are coherent states in the sense of Klauder and their completeness is achieved via exact solutions of Hausdorff moment problems, obtained by combining Laplace and Mellin transform methods. For {sigma} in the range 0 < {sigma}{<=} 2/3 we present exact implementations of such states for the parametrization {sigma}= 2(k-l)/(3k-l) with k and l positive integers satisfying k>l.

  19. Tuneable Singlet Exciton Fission and Triplet-Triplet Annihilation in an Orthogonal Pentacene Dimer

    E-print Network

    Lukman, Steven; Musser, Andrew J.; Chen, Kai; Athanasopoulos, Stavros; Yong, Chaw K.; Zeng, Zebing; Ye, Qun; Chi, Chunyan; Hodgkiss, Justin M.; Wu, Jishan; Friend, Richard H.; Greenham, Neil C.

    2015-08-04

    We report fast and highly efficient intramolecular singlet exciton fission in a pentacene dimer, consisting of two covalently attached, nearly orthogonal pentacene units. Fission to triplet excitons from this ground state geometry occurs within 1 ps...

  20. Structural Diversity of Triplet Repeat RNAs*?

    PubMed Central

    Sobczak, Krzysztof; Michlewski, Gracjan; de Mezer, Mateusz; Kierzek, Elzbieta; Krol, Jacek; Olejniczak, Marta; Kierzek, Ryszard; Krzyzosiak, Wlodzimierz J.

    2010-01-01

    Tandem repeats of various trinucleotide motifs are present in the human transcriptome, but the functions of these regular sequences, which likely depend on the structures they form, are still poorly understood. To gain new insight into the structural and functional properties of triplet repeats in RNA, we have performed a biochemical structural analysis of the complete set of triplet repeat transcripts, each composed of a single sequence repeated 17 times. We show that these transcripts fall into four structural classes. The repeated CAA, UUG, AAG, CUU, CCU, CCA, and UAA motifs did not form any higher order structure under any analyzed conditions. The CAU, CUA, UUA, AUG, and UAG repeats are ordered according to their increasing tendency to form semistable hairpins. The repeated CGA, CGU, and all CNG motifs form fairly stable hairpins, whereas AGG and UGG repeats fold into stable G-quadruplexes. The triplet repeats that formed the most stable structures were characterized further by biophysical methods. UV-monitored structure melting revealed that CGG and CCG repeats form, respectively, the most and least stable hairpins of all CNG repeats. Circular dichroism spectra showed that the AGG and UGG repeat quadruplexes are formed by parallel RNA strands. Furthermore, we demonstrated that the different susceptibility of various triplet repeat transcripts to serum nucleases can be explained by the sequence and structural features of the tested RNAs. The results of this study provide a comprehensive structural foundation for the functional analysis of triplet repeats in transcripts. PMID:20159983

  1. Triplet absorption in carbon nanotubes: a TD-DFT study

    E-print Network

    Sergei Tretiak

    2007-02-13

    We predict properties of triplet excited states in single-walled carbon nanotubes (CNTs) using a time-dependent density-functional theory (TD-DFT). We show that the lowest triplet state energy in CNTs to be about 0.2-0.3 eV lower than the lowest singlet states. Like in $\\pi$-conjugated polymers, the lowest CNT triplets are spatially localized. These states show strong optical absorption at about 0.5-0.6 eV to the higher lying delocalized triplet states. These results demonstrate striking similarity of the electronic features between CNTs and $\\pi$-conjugated polymers and provide explicit guidelines for spectroscopic detection of CNT triplet states.

  2. Triplet-triplet energy transfer between luminescent probes bound to albumins

    NASA Astrophysics Data System (ADS)

    Mel'Nikov, A. G.; Saletskii, A. M.; Kochubey, V. I.; Pravdin, A. B.; Kurchatov, I. S.; Mel'Nikov, G. V.

    2010-08-01

    The interaction of polar and nonpolar luminescent probes with human blood serum albumins is studied by absorption and luminescence spectroscopy. It is found that the probes (polar eosin and nonpolar anthracene) can efficiently bind to proteins. The radii of the quenching spheres of energy-donor (eosin) triplet states in the presence of an acceptor (anthracene) in the process of the triplet-triplet energy transfer in proteins are determined for homogeneous and inhomogeneous distributions of acceptor molecules over the solution volume. It is shown that a decrease in the radius of the quenching sphere observed upon the addition of sodium dodecylsulfate surfactant is caused by structural changes in the protein.

  3. The Missing C1-C5 Cycloaromatization Reaction: Triplet State Antiaromaticity Relief and Self-Terminating Photorelease of Formaldehyde for Synthesis of Fulvenes from Enynes.

    PubMed

    Mohamed, Rana K; Mondal, Sayantan; Jorner, Kjell; Delgado, Thais Faria; Lobodin, Vladislav V; Ottosson, Henrik; Alabugin, Igor V

    2015-12-16

    The last missing example of the four archetypical cycloaromatizations of enediynes and enynes was discovered by combining a twisted alkene excited state with a new self-terminating path for intramolecular conversion of diradicals into closed-shell products. Photoexcitation of aromatic enynes to a twisted alkene triplet state creates a unique stereoelectronic situation, which is facilitated by the relief of excited state antiaromaticity of the benzene ring. This enables the usually unfavorable 5-endo-trig cyclization and merges it with 5-exo-dig closure. The 1,4-diradical product of the C1-C5 cyclization undergoes internal H atom transfer that is coupled with the fragmentation of an exocyclic C-C bond. This sequence provides efficient access to benzofulvenes from enynes and expands the utility of self-terminating aromatizing enyne cascades to photochemical reactions. The key feature of this self-terminating reaction is that, despite the involvement of radical species in the key cyclization step, no external radical sources or quenchers are needed to provide the products. In these cascades, both radical centers are formed transiently and converted to the closed-shell products via intramolecular H-transfer and C-C bond fragmentation. Furthermore, incorporating C-C bond cleavage into the photochemical self-terminating cyclizations of enynes opens a new way for the use of alkenes as alkyne equivalents in organic synthesis. PMID:26536479

  4. Dependence of the Efficiency of Triplet-Triplet Energy Transfer on the Distance Between the Donor and Acceptor

    NASA Astrophysics Data System (ADS)

    Ibraev, N. Kh.; Seliverstova, E. V.; Artyukhov, V. Ya.

    2015-01-01

    The triplet-triplet and singlet-singlet energy transfer is investigated both experimentally and theoretically in the anthracene - Nile red system. Quantum-chemical investigations of the special features in the formation of electronically excited states and photoprocesses in the donor-acceptor pair are performed. It is demonstrated that atypical distance dependence of the efficiency of triplet-triplet energy transfer in the Langmuir-Blodgett multilayered thin films is caused by additional quenching of donor particles due to the process of energy transfer to acceptor centers by the inductive-resonant mechanism.

  5. Excitons and excess electrons in nanometer size molecular polyoxotitanate clusters: electronic spectra, exciton dynamics, and surface states.

    PubMed

    Bao, Jianhua; Yu, Zhihao; Gundlach, Lars; Benedict, Jason B; Coppens, Philip; Chen, Hung Cheng; Miller, John R; Piotrowiak, Piotr

    2013-04-25

    The behavior of excitons and excess electrons in the confined space of a molecular polyoxotitanate cluster Ti17(?4-O)4(?3-O)16(?2-O)4(OPr(i))20 (in short Ti17) was studied using femtosecond pump-probe transient absorption, pulse radiolysis, and fluorescence spectroscopy. Due to pronounced quantum size effects, the electronic spectra of the exciton, Ti17*, and the excess electron carrying radical anion, Ti17(•-), are blue-shifted in comparison with bulk TiO2 and have maxima at 1.91 and 1.24 eV, respectively. The 0.7 eV difference in the position of the absorption maxima of Ti17* and Ti17(•-) indicates the presence of strong Coulomb interaction between the conduction band electron and the valence band hole in the ?1 nm diameter cluster. Ground state Raman spectra and the vibronic structure of the fluorescence spectrum point to the importance of the interfacial ligand modes in the stabilization and localization of the fully relaxed exciton. Four pentacoordinate Ti sites near the surface of the cluster appear to play a special role in this regard. Solvent polarity has only a minor influence on the spectral behavior of Ti17*. Exciton recombination in Ti17 is faster than in anatase nanoparticles or mesoporous films. The kinetics exhibits three components, ranging from less than 1 ps to 100 ps, which are tentatively assigned to the geminate recombination within the core of the cluster and to the decay of the surface stabilized charge transfer exciton. A persistent long-lived component with ? > 300 ps may indicate the involvement of intraband dark states, i.e., triplet excitons (3)Ti17*. PMID:23113586

  6. Hazard Analysis of Mortality Among Twins and Triplets in the United States: From 20 Weeks Gestation Through the First Year of Life 

    E-print Network

    DeSalvo, Bethany S.

    2011-08-08

    and triplet fetuses and infants occurs because they, more likely than singletons, are at the risk of suffering from the negative health effects of premature birth, low birthweight, twin-transfusion syndrome, preeclampsia and gestational diabetes. Triplet...-plus multiples are at even higher risk of these adverse outcomes that potentially may lead to disabilities later in life including ventricular hemorrhages and cerebral palsy (Polin and Frangipane 1986). Each additional fetus increases the risk of mortality...

  7. Degradation of organic pollutants in/on snow and ice by singlet molecular oxygen (¹O?*) and an organic triplet excited state.

    PubMed

    Bower, Jonathan P; Anastasio, Cort

    2014-04-01

    Singlet molecular oxygen (¹O?*) can be a significant sink for a variety of electron-rich pollutants in surface waters and atmospheric drops. We recently found that ¹O?* concentrations are enhanced by up to a factor of 10(4) on illuminated ice compared to in the equivalent liquid solution, suggesting that ¹O?* could be an important oxidant for pollutants in snow. To examine this, here we study the degradation of three model organic pollutants: furfuryl alcohol (to represent furans), tryptophan (for aromatic amino acids), and bisphenol A (for phenols). Each compound was studied in illuminated aqueous solution and ice containing Rose Bengal (RB, a sensitizer for ¹O?*) and sodium chloride (to adjust the concentration of total solutes). The RB-mediated loss of each organic compound is enhanced on illuminated ice compared to in solution, by factors of 6400 for furfuryl alcohol, 8300 for tryptophan, and 50 for bisphenol A for ice containing 0.065 mM total solutes. Rates of loss of furfuryl alcohol and tryptophan decrease at a higher total solute concentration, in qualitative agreement with predictions from freezing-point depression. In contrast, the loss of bisphenol A on ice is independent of total solute concentration. Relative to liquid tests, the enhanced loss of tryptophan on ice during control experiments made with deoxygenated solutions and solutions in D?O show that the triplet excited state of Rose Bengal may also contribute to loss of pollutants on ice. PMID:24487942

  8. Role of Intramolecular and Intermolecular Hydrogen Bonding in Both Singlet and Triplet Excited States of Aminofluorenones on Internal Conversion, Intersystem Crossing, and Twisted Intramolecular Charge Transfer

    NASA Astrophysics Data System (ADS)

    Zhao, Guang-Jiu; Han, Ke-Li

    2009-05-01

    Time-dependent density functional theory method was performed to investigate the intramolecular and intermolecular hydrogen bonding in both the singlet and triplet electronic excited states of aminofluorenones AF, MAF, and DMAF in alcoholic solutions as well as their important roles on the excited-state photophysical processes of these aminofluorenones, such as internal conversion, intersystem crossing (ISC), twisted intramolecular charge transfer (TICT), and so forth. The intramolecular hydrogen bond C?O···H-N can be formed between the carbonyl group and amino group for the isolated AF and MAF. However, no intramolecular hydrogen bond for DMAF can be formed. At the same time, the most stable conformation of DMAF is out-of-plane structure, where the two dihedral angles formed between dimethyl groups and fluorenone plane are 163.1° and 41.74°, respectively. The formation of intramolecular hydrogen bond for AF and MAF is tightly associated with the intersystem crossing of these aminofluorenones. Furthermore, the ISC process can be dominantly determined by the change of intramolecular hydrogen bond between S1 and T1 states of aminofluorenones. Since the change of hydrogen bond between S1 and T1 states of AF is stronger than that of MAF, the rate of ISC process for AF is faster than that for MAF. Moreover, the rate constant of the ISC process of DMAF is nearly close to zero because of the absence of intramolecular hydrogen bond. On the other hand, the intermolecular hydrogen bond C?O···H-O can be also formed between all aminofluorenones and alcoholic solvents. The internal conversion process from S1 to S0 state of these aminofluorenones is facilitated by the intermolecular hydrogen bond strengthening in the electronic excited state of aminofluorenones because of the decrease of energy gap between S1 and S0 states. At the same time, the change of intermolecular hydrogen bond between S1 and T1 states for AF is much stronger than that for MAF, which may also contribute to the faster ISC process for AF than that for MAF in the same solvents. The TICT process plays an important role in the deactivation of the photoexcited DMAF, since the TICT process along the twisted dihedral angle is nearly barrierless in the S1 state of DMAF. However, the TICT cannot take place for AF and MAF because of the presence of the intramolecular hydrogen bond.

  9. Far infrared spectra of solid state aliphatic amino acids in different protonation states

    NASA Astrophysics Data System (ADS)

    Trivella, Aurélien; Gaillard, Thomas; Stote, Roland H.; Hellwig, Petra

    2010-03-01

    Far infrared spectra of zwitterionic, cationic, and anionic forms of aliphatic amino acids in solid state have been studied experimentally. Measurements were done on glycine, L-alanine, L-valine, L-leucine, and L-isoleucine powder samples and film samples obtained from dried solutions prepared at pH ranging from 1 to 13. Solid state density functional theory calculations were also performed, and detailed potential energy distributions were obtained from normal mode results. A good correspondence between experimental and simulated spectra was achieved and this allowed us to propose an almost complete band assignment for the far infrared spectra of zwitterionic forms. In the 700-50 cm-1 range, three regions were identified, each corresponding to a characteristic set of normal modes. A first region between 700 and 450 cm-1 mainly contained the carboxylate bending, rocking, and wagging modes as well as the ammonium torsional mode. The 450-250 cm-1 region was representative of backbone and sidechain skeletal bending modes. At last, the low wavenumber zone, below 250 cm-1, was characteristic of carboxylate and skeletal torsional modes and of lattice modes. Assignments are also proposed for glycine cationic and anionic forms, but could not be obtained for all aliphatic amino acids due to the lack of structural data. This work is intended to provide fundamental information for the understanding of peptides vibrational properties.

  10. The Discovery of a Prolate-Oblate Shape Triplet of Spin 0+ States in the Atomic Nucleus 186PB

    NASA Astrophysics Data System (ADS)

    Andreyev, A. N.; Huyse, M.; van Duppen, P.; Weissman, L.; Ackermann, D.; Gerl, J.; He?BERGER, F. P.; Hofmann, S.; Kleinböhl, A.; Münzenberg, G.; Reshitko, S.; Schlegel, C.; Schaffner, H.; Cagarda, P.; Matos, M.; Saro, S.; Keenan, A.; Moore, C.; O'Leary, C. D.; Page, R. D.; Taylor, M.; Kettunen, H.; Leino, M.; Lavrentiev, A.; Wyss, R.; Heyde, K.

    2001-11-01

    The fundamental excitations in many-fermion systems remain one of the most exciting subjects of today's physics. In even-even atomic nuclei, pair breaking, vibrations and rotations generally form the low-lying excitation spectrum. However, for specific numbers of protons and neutrons, a subtle rearrangement of only a few nucleons among the orbitals at the Fermi surface can result in a different elementary mode: a macroscopic shape change [1,2]. We have identified for the first time in a nucleus (186Pb) three different shapes (spherical - oblate - prolate) as the lowest three states in the energy spectrum [3]. The parent 190Po nuclei were produced in the 142Nd(52Cr,4n)190Po complete fusion reaction, studied with the velocity filter SHIP [4] at the UNILAC heavy ion accelerator (GSI, Darmstadt). Nuclei of interest after separation were implanted into a position-sensitive silicon detector (PSSD), where their subsequent a decays were measured. In front of the PSSD six similar silicon detectors were mounted (Si-box), facing the PSSD, which were used to detect conversion electrons in prompt coincidence with ?-particles. A 4-fold segmented Ge Clover detector was installed behind the PSSD to record prompt ?-X and ?-? coincidences. The whole set-up has been optimized to observe fine structure in the ? decay that leads, as studied for the heavier even-even Pb nuclei [5], to the identification of low-lying 0+ band heads, which will decay predominantly by E0 conversion electron transitions to the ground state. Further details on the experimental method can be found in [3,6,7]...

  11. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    SciTech Connect

    Yu, Lu; Smith, Jeremy; Laskin, Alexander; Anastasio, Cort N.; Laskin, Julia; Zhang, Qi

    2014-01-01

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (•OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), desorption electrospray ionization mass spectrometry (DESIMS), and ion chromatography (IC). A large number of oxygenated molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O/C) ratios of phenolic aqSOA are in the range of 0.85-1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than •OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O/C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.

  12. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    DOE PAGESBeta

    Yu, L.; Smith, J.; Laskin, A.; Anastasio, C.; Laskin, J.; Zhang, Q.

    2014-12-23

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol (compound with formula C6H5OH)), guaiacol (2-methoxyphenol), and syringol (2,6-dimethoxyphenol) with two major aqueous-phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (· OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenatedmore »molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85–1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than · OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenolic compound has reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV–visible region, suggesting that aqueous-phase reactions of phenols may contribute to formation of secondary brown carbon in the atmosphere, especially in regions influenced by biomass burning.« less

  13. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    DOE PAGESBeta

    Yu, L.; Smith, J.; Laskin, A.; Anastasio, C.; Laskin, J.; Zhang, Q.

    2014-08-19

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (·OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenated molecules are identified,more »including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85–1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than ·OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.« less

  14. Spin polarization in quantum Hall state obtained by Kerr rotation spectra

    SciTech Connect

    Ito, H.; Seo, M.; Fukuoka, D.; Oto, K.; Muro, K.; Hirayama, Y.; Kumada, N.

    2011-12-23

    We developed a novel system for a high sensitive measurement of Kerr rotation spectra, and Kerr rotation spectra of quantum Hall system in AlGaAs/GaAs 17 nm quantum well were measured. Spin polarization of quantum Hall states was obtained by integrating the spectra, since Kerr rotation spectra reflect spin population of electrons. The spin polarization decreased rapidly on both sides of {nu} = 1, which is ascribed to Skyrmion effect. However, the spin polarization present a flat region around {nu} = 1 which means a quantum Hall ferromagnet is not fully spin polarized.

  15. Singlet-triplet energy splitting between 1D and 3D (1s2 2s nd), n = 3, 4, 5, and 6, Rydberg states of the beryllium atom (9Be) calculated with all-electron explicitly correlated Gaussian functions

    NASA Astrophysics Data System (ADS)

    Sharkey, Keeper L.; Bubin, Sergiy; Adamowicz, Ludwik

    2014-11-01

    Accurate variational nonrelativistic quantum-mechanical calculations are performed for the five lowest 1D and four lowest 3D states of the 9Be isotope of the beryllium atom. All-electron explicitly correlated Gaussian (ECG) functions are used in the calculations and their nonlinear parameters are optimized with the aid of the analytical energy gradient determined with respect to these parameters. The effect of the finite nuclear mass is directly included in the Hamiltonian used in the calculations. The singlet-triplet energy gaps between the corresponding 1D and 3D states, are reported.

  16. Proximity effect in ferromagnet/triplet p-wave superconductor structures

    NASA Astrophysics Data System (ADS)

    Li, Hong; Yang, Wei; Yang, Xinjian; Qin, Minghui

    2007-02-01

    The superconducting proximity effect in normal metal/insulator/ferromagnet/triplet p-wave superconductor (N/I/FP) structures is studied based on an extended Blonder Tinkham Klapwijk (BTK) theory. Three kinds of pairings for the P side are chosen: p, p, p+ip waves. The transition from the “0” to “?” state is found in the conductance spectra with increasing the thickness of F or the ferromagnetic exchange energy. The large amplitude of the normalized conductance suggests the possible coexistence of the ferromagnetism and p-wave superconductivity in a small region near the F/P interface induced by the proximity effect.

  17. Mapping Agricultural Crops with AVIRIS Spectra in Washington State

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Pavri, Betina; Roberts, Dar; Ustin, Susan

    2000-01-01

    Spectroscopy is used in the laboratory to measure the molecular components and concentrations of plant constituents to answer questions about the plant type, status, and health. Imaging spectrometers measure the upwelling spectral radiance above the Earth's surface as images. Ideally, imaging spectrometer data sets should be used to understand plant type, plant status, and health of plants in an agricultural setting. An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data set was acquired over agricultural fields near Wallula, Washington on July 23rd, 1997. AVIRIS measures upwelling radiance spectra through 224 spectral channels with contiguous 10-nm sampling from 400 to 2500 run in the solar-reflected spectrum. The spectra are measured as images of 11 by up to 800 km with 20-m spatial resolution. The spectral images measured by AVIRIS represent the integrated signal resulting from: the solar irradiance; two way transmittance and scattering of the atmosphere; the absorptions and scattering of surface materials; as well as the spectral, radiometric and spatial response functions of AVIRIS. This paper presents initial research to derive properties of the agricultural fields near Wallula from the calibrated spectral images measured by AVIRIS near the top of the atmosphere.

  18. Mapping Agricultural Crops with AVIRIS Spectra in Washington State

    NASA Technical Reports Server (NTRS)

    Green, Robert; Pavri, Betina; Roberts, Dar; Ustin, Susan

    1998-01-01

    Spectroscopy is used in the laboratory to measure the molecular components and concentrations of plant constituents to answer questions about the plant type, status, and health. Imaging spectrometers measure the upwelling spectral radiance above the Earth's surface as images. Ideally, imaging spectrometer data sets should be used to understand plant type, plant status, and health of plants in an agricultural setting. An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data set was acquired over agricultural fields near Wallula, Washington on July 23rd, 1997. AVIRIS measures upwelling radiance spectra through 224 spectral channels with contiguous 10-nm sampling from 400 to 2500 nm in the solar-reflected spectrum. The spectra are measured as images of 11 by up to 800 km with 20-m spatial resolution. The spectral images measured by AVIRIS represent the integrated signal resulting from: the solar irradiance; two way transmittance and scattering of the atmosphere; the absorptions and scattering of surface materials; as well as the spectral, radiometric and spatial response functions of AVIRIS. This paper presents initial research to derive properties of the agricultural fields near Wallula from the calibrated spectral images measured by AVIRIS near the top of the atmosphere.

  19. Electronic states and spectra of BiTe

    NASA Astrophysics Data System (ADS)

    Setzer, K. D.; Laufs, S.; Fink, E. H.

    2010-09-01

    NIR/VIS emission spectra of the bismuth telluride radical, BiTe, were measured in the 3600-20 000 cm -1 region with a Fourier-transform spectrometer. BiTe was produced by reaction of bismuth and tellurium vapors and excited by energy transfer from metastable oxygen O 2( a1? g) in a fast-flow system. The spectrum of BiTe was found to be markedly different from those of the previously studied BiO, BiS and BiSe radicals. The A24? 1/2 ? X12? 1/2 transition which forms the most prominent and extended band system in these molecules was not observed for BiTe, and the X22? 3/2 ? X12? 1/2 fine structure transition shows up with a different structure and at much lower wavenumbers than in the spectra of the lighter bismuth chalcogenides. The only common feature is the C14? -1/2 ? X12? 1/2 system which is found in the range 16 500-19 000 cm -1 similar to the three other molecules. Besides the X2 ? X1 and C1 ? X1 systems, seven other transitions show up by short ? ? = 0 sequences only. With help of the data derived from the analyses of the X2 ? X1 and C1 ? X1 systems and theoretical predictions of electronic and vibrational energies and transition probabilities of the strongest transitions of BiTe by Lingott et al. [7] the spectra were assigned to the transitions C14? -1/2 ? X22? 3/2, C14? -1/2 ? A24? 1/2, A44? 1/2 ? A24? 1/2, A44? 1/2 ? X22? 3/2, B12? 1/2 ? A24? 1/2, B12? 1/2 ? A14? 3/2, and B22? 3/2 ? X22? 3/2.

  20. Experimental Study of the Triplet Synchronization of Coupled Nonidentical Mechanical Metronomes.

    PubMed

    Jia, Ji; Song, Zhiwen; Liu, Weiqing; Kurths, Jürgen; Xiao, Jinghua

    2015-01-01

    Triplet synchrony is an interesting state when the phases and the frequencies of three coupled oscillators fulfill the conditions of a triplet locking, whereas every pair of systems remains asynchronous. Experimental observation of triplet synchrony is firstly realized in three coupled nonidentical mechanical metronomes. A more direct method based on the phase diagram is proposed to observe and determine triplet synchronization. Our results show that the stable triplet synchrony is observed in several intervals of the parameter space. Moreover, the experimental results are verified according to the theoretical model of the coupled metronomes. The outcomes are useful to understand the inner regimes of collective dynamics in coupled oscillators. PMID:26598175

  1. Experimental Study of the Triplet Synchronization of Coupled Nonidentical Mechanical Metronomes

    PubMed Central

    Jia, Ji; Song, Zhiwen; Liu, Weiqing; Kurths, Jürgen; Xiao, Jinghua

    2015-01-01

    Triplet synchrony is an interesting state when the phases and the frequencies of three coupled oscillators fulfill the conditions of a triplet locking, whereas every pair of systems remains asynchronous. Experimental observation of triplet synchrony is firstly realized in three coupled nonidentical mechanical metronomes. A more direct method based on the phase diagram is proposed to observe and determine triplet synchronization. Our results show that the stable triplet synchrony is observed in several intervals of the parameter space. Moreover, the experimental results are verified according to the theoretical model of the coupled metronomes. The outcomes are useful to understand the inner regimes of collective dynamics in coupled oscillators. PMID:26598175

  2. The influence of polymer structure on triplet luminescence

    SciTech Connect

    Burkhart, R.D.; Burrows, J.A.J.

    1987-01-01

    Triplet luminescence spectroscopy has been used to probe interactions between pendant groups of polymer chains. A styrene polymer was synthesized with naphthyl and phenylcarbonyl chromophores at the terminal positions. Information about inter- and intramolecular energy transfer was obtained from phosphorescence spectra in MTHF solutions at 77/sup 0/K. (DLC)

  3. Homomolecular non-coherent photon upconversion by triplet-triplet annihilation using a zinc porphyrin on wide bandgap semiconductors

    NASA Astrophysics Data System (ADS)

    Giri, Neeraj Kumar; Ponce, Concepcion P.; Steer, Ronald P.; Paige, Matthew F.

    2014-04-01

    Non-coherent upconversion, realized by homomolecular triplet-triplet annihilation of a zinc metalloporphyrin absorber, has been measured for the metalloporphyrin adsorbed on metal oxide films (ZrO2, TiO2 and ZrO2/TiO2 mixed oxides) in which the semiconductor conduction band energy lies between the metalloporphyrin’s upconverted and prompt S1 excited states. Upconverted emission was observed for pure and mixed metal oxide films, regardless of the relative energies of the states, indicating electron transfer from upconverted states to the semiconductor was not competitive. Upconversion was attributed to aggregation of the absorber, likely in defects on the films, leading to efficient homomolecular triplet-triplet annihilation.

  4. Nuclear magnetic resonance studies of homogeneous catalysis using parahydrogen: Analysis of nuclear singlet-triplet mixing as a diagnostic tool to characterize intermediates

    NASA Astrophysics Data System (ADS)

    Bargon, J.; Kandels, J.; Kating, P.

    1993-04-01

    The 1H-NMR polarization spectra of the products after homogeneous hydrogenations with para- or orthohydrogen (the PHIP spectra) convey significant information about the course of the reaction. Mixing of the nuclear singlet and triplet states of the two protons derived from dihydrogen during the reaction cycle has been found to modify the PHIP signal pattern of the product molecule characteristically. The intermediate coordination of the two dihydrogen protons at the catalyst is proposed to be responsible for this behavior. A parallel to the singlet-triplet mixing of electronic states according to the well-known CIDNP phenomenon is outlined. The homogeneous hydrogenation of 2,5-dihydrofuran to tetrahydrofuran using Wilkinson's catalyst serves as an example.

  5. Limits to the applicability of the rule of equality to unity of the sum of quantum yields of fluorescence and transition to the triplet state for complex organic molecules in the condensed phase (A review)

    NASA Astrophysics Data System (ADS)

    Ermolaev, V. L.; Sveshnikova, E. B.

    2015-10-01

    For different classes of molecules, we have estimated from experimental data the lower limit of the height of S 1 levels for which the rule q fl + q T = 1 ( q fl is the fluorescence quantum yield, q T is the quantum yield of formation of the triplet state) begins to be violated; i.e., direct nonradiative transition from the S 1-state to the ground state appears, the quantum yield of which exceeds measurement errors. We have found that, for compounds of different classes, this limit varies from 15000 to 21000 cm-1. It has been shown that the difference in the limit may be explained in terms of the inductive resonance theory of nonradiative transitions, which takes into account the localization of the electronic transition, its rate constant, and the overlap of the vibronic spectrum of the molecule with the vibrational spectrum of high-frequency vibrations taking into account the variation in the rate constant of the intersystem crossing transition to the triplet state.

  6. Matrix Isolation Spectroscopy and Photochemistry of Triplet 1,3-DIMETHYLPROPYNYLIDENE (MeC3Me)

    NASA Astrophysics Data System (ADS)

    Knezz, Stephanie N.; Waltz, Terese A.; Haenni, Benjamin C.; Burrmann, Nicola J.; McMahon, Robert J.

    2015-06-01

    Acetylenic carbenes and conjugated carbon chain molecules of the HCnH family are relevant to the study of combustion and chemistry in the interstellar medium (ISM). Propynylidene (HC3H) has been thoroughly studied and its structure and photochemistry determined. Here, we produce triplet diradical 1,3-dimethylpropynylidene (MeC3Me) photochemically from a precursor diazo compound in a cryogenic matrix (N2 or Ar) at 10 K, and spectroscopic analysis is carried out. The infrared, electronic absorption, and electron paramagnetic resonance spectra were examined in light of the parent (HC3H) system to ascertain the effect of alkyl substituents on delocalized carbon chains of this type. Computational analysis, EPR, and infrared analysis indicate a triplet ground state with a quasilinear structure. Infrared experiments reveal photochemical reaction to penten-3-yne upon UV irradiation. Further experimental and computational results pertaining to the structure and photochemistry will be presented. Seburg, R. A.; Patterson, E. V.; McMahon, R. J., Structure of Triplet Propynylidene (HCCCH) as Probed by IR, UV/vis, and EPR Spectroscopy of Isotopomers. Journal of the American Chemical Society 2009, 131 (26), 9442-9455.

  7. Rotational spectra of the X 2Sigma(+) states of CaH and CaD

    NASA Technical Reports Server (NTRS)

    Frum, C. I.; Oh, J. J.; Cohen, E. A.; Pickett, H. M.

    1993-01-01

    The rotational spectra of the 2Sigma(2+) ground states of calcium monohydride and monodeuteride have been recorded in absorption between 250 and 700 GHz. The gas phase free radicals have been produced in a ceramic furnace by the reaction of elemental calcium with molecular hydrogen or deuterium in the presence of an electrical discharge. The molecular constants including the rotational constant, centrifugal distortion constants, spin-rotation constants, and magnetic hyperfine interaction constants have been extracted from the spectra.

  8. Excitation spectra and wave functions of quasiparticle bound states in bilayer Rashba superconductors

    NASA Astrophysics Data System (ADS)

    Higashi, Yoichi; Nagai, Yuki; Yoshida, Tomohiro; Kato, Masaru; Yanase, Youichi

    2015-11-01

    We study the excitation spectra and the wave functions of quasiparticle bound states at a vortex and an edge in bilayer Rashba superconductors under a magnetic field. In particular, we focus on the quasiparticle states at the zero energy in the pair-density wave state in a topologically non-trivial phase. We numerically demonstrate that the quasiparticle wave functions with zero energy are localized at both the edge and the vortex core if the magnetic field exceeds the critical value.

  9. Spectra of random operators with absolutely continuous integrated density of states

    SciTech Connect

    Rio, Rafael del E-mail: delriomagia@gmail.com

    2014-04-15

    The structure of the spectrum of random operators is studied. It is shown that if the density of states measure of some subsets of the spectrum is zero, then these subsets are empty. In particular follows that absolute continuity of the integrated density of states implies singular spectra of ergodic operators is either empty or of positive measure. Our results apply to Anderson and alloy type models, perturbed Landau Hamiltonians, almost periodic potentials, and models which are not ergodic.

  10. Dimethyl ether: laboratory spectra up to 2.1 THz. Torsion-rotational spectra within the vibrational ground state

    NASA Astrophysics Data System (ADS)

    Endres, C. P.; Drouin, B. J.; Pearson, J. C.; Müller, H. S. P.; Lewen, F.; Schlemmer, S.; Giesen, T. F.

    2009-09-01

    Dimethyl ether (CH_3OCH_3) is one of the largest organic molecules detected in the interstellar medium. As an asymmetric top molecule with two methyl groups which undergo large amplitude motions and a dipole moment of ?=1.3 D, it conveys a dense spectrum throughout the terahertz region and contributes to the spectral line confusion in astronomical observations at these frequencies. In this paper, we present rotational spectra of dimethyl ether in its ground vibrational states, which have been measured in the laboratory and analyzed covering frequencies up to 2.1 THz. The analysis is based on an effective Hamiltonian for a symmetric two-top rotor and includes experimental data published so far. Frequency predictions are presented up to 2.5 THz for astronomical applications with accuracies better than 1 MHz. Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/504/635

  11. A study of the electronic states of pyrimidine by electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Linert, Ireneusz; Zubek, Mariusz

    2015-03-01

    The electron energy loss spectra were measured in pyrimidine at the constant electron residual energy varied from 15 meV to 10 eV and in the scattering angle range 0-180°. The spectra were analysed applying an iteration fitting procedure to resolve the energy loss bands corresponding to excitation of the electronic states of pyrimidine. The vertical excitation energies of the singlet states of pyrimidine and of a number of the triplet states were determined. The presently observed triplet states were tentatively assigned.

  12. Magnetic correction of RHIC triplets

    SciTech Connect

    Wei, J.; Gupta, R.; Peggs, S.

    1993-06-01

    Triplets of large bore quadrupoles will be antisymmetrically placed on either side of all six intersection points of the Relativistic Heavy Ion collider (RHIC). In RHIC collision optics, the tiplets at the two experimental detectors are intended to enable the collision beta function to be reduced to the design goal of {beta}{sup *} = 1.0 meter in both planes, in order to minimize the spot size and maximize the luminosity. This requires running with {beta}{sub max} {approx} 1400 meters in the triplet, where the beams will have their largest size, both absolutely and as a fraction of the available aperture. Hence, the ultimate performance of RHIC rests on achieving the highest possible magnetic field quality in the triplets. This paper discusses the correction of magnetic errors expected in the quadrupole bodies and ends, using both these limped correctors and also quadrupole body tuning shims.

  13. Magnetic correction of RHIC triplets

    SciTech Connect

    Wei, J.; Gupta, R.; Peggs, S.

    1993-01-01

    Triplets of large bore quadrupoles will be antisymmetrically placed on either side of all six intersection points of the Relativistic Heavy Ion collider (RHIC). In RHIC collision optics, the tiplets at the two experimental detectors are intended to enable the collision beta function to be reduced to the design goal of [beta][sup *] = 1.0 meter in both planes, in order to minimize the spot size and maximize the luminosity. This requires running with [beta][sub max] [approx] 1400 meters in the triplet, where the beams will have their largest size, both absolutely and as a fraction of the available aperture. Hence, the ultimate performance of RHIC rests on achieving the highest possible magnetic field quality in the triplets. This paper discusses the correction of magnetic errors expected in the quadrupole bodies and ends, using both these limped correctors and also quadrupole body tuning shims.

  14. Bringing light into the dark triplet space of molecular systems.

    PubMed

    Ge, Jing; Zhang, Qun; Jiang, Jun; Geng, Zhigang; Jiang, Shenlong; Fan, Kaili; Guo, Zhenkun; Hu, Jiahua; Chen, Zongwei; Chen, Yang; Wang, Xiaoping; Luo, Yi

    2015-05-21

    A molecule or a molecular system always consists of excited states of different spin multiplicities. With conventional optical excitations, only the (bright) states with the same spin multiplicity of the ground state could be directly reached. How to reveal the dynamics of excited (dark) states remains the grand challenge in the topical fields of photochemistry, photophysics, and photobiology. For a singlet-triplet coupled molecular system, the (bright) singlet dynamics can be routinely examined by conventional femtosecond pump-probe spectroscopy. However, owing to the involvement of intrinsically fast decay channels such as intramolecular vibrational redistribution and internal conversion, it is very difficult, if not impossible, to single out the (dark) triplet dynamics. Herein, we develop a novel strategy that uses an ultrafast broadband white-light continuum as a excitation light source to enhance the probability of intersystem crossing, thus facilitating the population flow from the singlet space to the triplet space. With a set of femtosecond time-reversed pump-probe experiments, we report on a proof-of-concept molecular system (i.e., the malachite green molecule) that the pure triplet dynamics can be mapped out in real time through monitoring the modulated emission that occurs solely in the triplet space. Significant differences in excited-state dynamics between the singlet and triplet spaces have been observed. This newly developed approach may provide a useful tool for examining the elusive dark-state dynamics of molecular systems and also for exploring the mechanisms underlying molecular luminescence/photonics and solar light harvesting. PMID:25916946

  15. 'Blueberry' Triplets Born in Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This microscopic image, taken at the outcrop region dubbed 'Berry Bowl' near the Mars Exploration Rover Opportunity's landing site, shows the sphere-like grains or 'blueberries' that fill Berry Bowl. Of particular interest is the blueberry triplet, which indicates that these geologic features grew in pre-existing wet sediments. Other sphere-like grains that form in the air, such as impact spherules or ejected volcanic material called lapilli, are unlikely to fuse along a line and form triplets. This image was taken by the rover's microscopic imager on the 46th martian day, or sol, of its mission.

  16. Binding energies of the ground triplet state a{sup 3}?{sub u}{sup +} of Rb{sub 2} and Cs{sub 2} in terms of the generalized Le Roy–Bernstein near-dissociation expansion

    SciTech Connect

    Sovkov, V. B.; Ivanov, V. S.

    2014-04-07

    Formulae of Le Roy–Bernstein near-dissociation theory are derived in a general isotope–invariant form, applicable to any term in the rotational expansion of a diatomic ro-vibrational term value. It is proposed to use the generalized Le Roy–Bernstein expansion to describe the binding energies (ro-vibrational term values) of the ground triplet state a{sup 3}?{sub u}{sup +} of alkali metal dimers. The parameters of this description are determined for Rb{sub 2} and Cs{sub 2} molecules. This approach gives a recipe to calculate the whole variety of the binding energies with characteristic accuracies from ?1 × 10{sup ?3} to 1 × 10{sup ?2} cm{sup ?1} using a relatively simple algebraic equation.

  17. Binding energies of the ground triplet state a^3? _u^+ of Rb2 and Cs2 in terms of the generalized Le Roy-Bernstein near-dissociation expansion

    NASA Astrophysics Data System (ADS)

    Sovkov, V. B.; Ivanov, V. S.

    2014-04-01

    Formulae of Le Roy-Bernstein near-dissociation theory are derived in a general isotope-invariant form, applicable to any term in the rotational expansion of a diatomic ro-vibrational term value. It is proposed to use the generalized Le Roy-Bernstein expansion to describe the binding energies (ro-vibrational term values) of the ground triplet state a^3? _u^+ of alkali metal dimers. The parameters of this description are determined for Rb2 and Cs2 molecules. This approach gives a recipe to calculate the whole variety of the binding energies with characteristic accuracies from ˜1 × 10-3 to 1 × 10-2 cm-1 using a relatively simple algebraic equation.

  18. Gauge and Yukawa Mediated Supersymmetry Breaking in the Triplet Seesaw Scenario

    SciTech Connect

    Joaquim, Filipe R.; Rossi, Anna

    2006-11-03

    We propose a novel supersymmetric unified scenario of the triplet seesaw mechanism where the exchange of the heavy triplets generates both neutrino masses and soft supersymmetry breaking terms. Our framework is very predictive since it relates neutrino mass parameters, lepton-flavor-violation in the slepton sector, sparticle and Higgs spectra, and electroweak symmetry breakdown. The phenomenological viability and experimental signatures in lepton flavor-violating processes are discussed.

  19. Unraveling the electronic structure, spin states, optical and vibrational spectra of malaria pigment.

    PubMed

    Ali, Md Ehesan; Oppeneer, Peter M

    2015-06-01

    A detailed knowledge of the electronic structure and magnetic and optical properties of hemozoin, the malaria pigment, is essential for the design of effective antimalarial drugs and malarial diagnosis. By employing state-of-the-art electronic structure calculations, we have performed an in-depth investigation of the malaria pigment. Specifically, molecular bond lengths and spin states of the two Fe(III) heme centers and their exchange interaction, the UV/Vis absorption spectrum, and the IR vibrational spectra were calculated and compared with available experimental data. Our density functional theory (DFT)-based calculations predict a singlet ground spin state that stems from an S=5/2 spin state on each of the Fe heme centers with a very weak antiferromagnetic exchange interaction between them. Our theoretical UV/Vis and IR spectra provide explanations for various spectroscopic studies of hemozoin and ?-hematin (a synthetic analogue of hemozoin). A good comparison of calculated and measured properties demonstrates the convincing unveiling of the electronic structure of the malaria pigment. Based on the predicted vibrational spectra, we propose a unique spectral band from the nuclear resonance vibrational spectroscopy (NRVS) results that could be used as a key fingerprint for malarial detection. PMID:25933355

  20. Identification of a triplet pair intermediate in singlet exciton fission in solution

    PubMed Central

    Stern, Hannah L.; Musser, Andrew J.; Gelinas, Simon; Parkinson, Patrick; Herz, Laura M.; Bruzek, Matthew J.; Anthony, John; Friend, Richard H.; Walker, Brian J.

    2015-01-01

    Singlet exciton fission is the spin-conserving transformation of one spin-singlet exciton into two spin-triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction Shockley–Queisser limit. Most theoretical descriptions of singlet fission invoke an intermediate state of a pair of spin-triplet excitons coupled into an overall spin-singlet configuration, but such a state has never been optically observed. In solution, we show that the dynamics of fission are diffusion limited and enable the isolation of an intermediate species. In concentrated solutions of bis(triisopropylsilylethynyl)[TIPS]—tetracene we find rapid (<100 ps) formation of excimers and a slower (?10 ns) break up of the excimer to two triplet exciton-bearing free molecules. These excimers are spectroscopically distinct from singlet and triplet excitons, yet possess both singlet and triplet characteristics, enabling identification as a triplet pair state. We find that this triplet pair state is significantly stabilized relative to free triplet excitons, and that it plays a critical role in the efficient endothermic singlet fission process. PMID:26060309

  1. The state of absorbed hydrogen in the structure of reduced copper chromite from the vibration spectra.

    PubMed

    Khassin, Alexander A; Kustova, Galina N; Jobic, Hervé; Yurieva, Tamara M; Chesalov, Yury A; Filonenko, Georgii A; Plyasova, Lyudmila M; Parmon, Valentin N

    2009-08-01

    The reduction of copper chromite, CuCr(2)O(4), is followed by means of thermogravimetric analysis. The reduced state is studied by means of FT IR spectroscopy, Raman spectroscopy and inelastic neutron scattering. The reduction of copper occurs in two stages: absorption of hydrogen at 250-400 degrees C and dehydration of the reduced state at above 450 degrees C. The measured vibrational spectra prove that a considerable amount of hydrogen is absorbed by the oxide structure with absorbed protons stabilized in OH and HOH-groups (geminal protons). Three groups of vibration bands are observed in the INS spectra, which can be assigned to stretching, bending and libration vibrations. An increase in the reduction temperature of copper chromite results in softening of the stretching and hardening of the bending vibrations, what can be related to the strengthening of hydrogen bonding. PMID:19606318

  2. Synchrotron and Compton Spectra from a Steady-state Electron Distribution

    NASA Astrophysics Data System (ADS)

    Rephaeli, Y.; Persic, M.

    2015-06-01

    Energy densities of relativistic electrons and protons in extended galactic and intracluster regions are commonly determined from spectral radio and (rarely) ?-ray measurements. The time-independent particle spectral density distributions are commonly assumed to have a power-law (PL) form over the relevant energy range. A theoretical relation between energy densities of electrons and protons is usually adopted, and energy equipartition is invoked to determine the mean magnetic field strength in the emitting region. We show that for typical conditions, in both star-forming and starburst (SB) galaxies, these estimates need to be scaled down substantially due to significant energy losses that (effectively) flatten the electron spectral density distribution, resulting in a much lower energy density than deduced when the distribution is assumed to have a PL form. The steady-state electron distribution in the nuclear regions of SB galaxies is calculated by accounting for Coulomb, bremsstrahlung, Compton, and synchrotron losses; the corresponding emission spectra of the latter two processes are calculated and compared to the respective PL spectra. We also determine the proton steady-state distribution by taking into account Coulomb and ? production losses, and briefly discuss implications of our steady-state particle spectra for estimates of proton energy densities and magnetic fields.

  3. Mass spectra of Zc and Zb exotic states as hadron molecules

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Steele, T. G.; Chen, Hua-Xing; Zhu, Shi-Lin

    2015-09-01

    We construct charmoniumlike and bottomoniumlike molecular interpolating currents with quantum numbers JP C=1+- in a systematic way, including both color singlet-singlet and color octet-octet structures. Using these interpolating currents, we calculate two-point correlation functions and perform QCD sum rule analyses to obtain mass spectra of the charmoniumlike and bottomoniumlike molecular states. Masses of the charmoniumlike q ¯ c c ¯ q molecular states for these various currents are extracted in the range 3.85-4.22 GeV, which are in good agreement with observed masses of the Zc resonances. Our numerical results suggest a possible landscape of hadronic molecule interpretations of the newly observed Zc states. Mass spectra of the bottomoniumlike q ¯b b ¯q molecular states are similarly obtained in the range 9.92-10.48 GeV, which support the interpretation of the Zb(10610 ) meson as a molecular state within theoretical uncertainties. Possible decay channels of these molecular states are also discussed.

  4. Triplet-triplet energy transfer and protection mechanisms against singlet oxygen in photosynthesis

    NASA Astrophysics Data System (ADS)

    Kihara, Shigeharu

    In photosynthesis, (bacterio)chlorophylls ((B)Chl) play a crucial role in light harvesting and electron transport. (B)Chls, however, are known to be potentially dangerous due to the formation of the triplet excited state which forms the singlet oxygen (1O2*) when exposed to the sunlight. Singlet oxygen is highly reactive and all modern organisms incorporate special protective mechanisms to minimize the oxidative damage. One of the conventional photoprotective mechanisms used by photosynthetic organisms is by the nearby carotenoids quenching the excess energy and releasing it by heat. In this dissertation, two major aspects of this process are studied. First, based on experimental data and model calculations, the oxygen content in a functioning oxygenic photosynthetic oxygen cell was determined. These organisms perform water splitting and as a result significant amount of oxygen can be formed within the organism itself. It was found, that contrary to some published estimates, the excess oxygen concentration generated within an individual cell is extremely low -- 0.025 ... 0.25 microM, i.e. about 103-104 times lower than the oxygen concentration in air saturated water. Such low concentrations imply that the first oxygenic photosynthetic cells that evolved in oxygen-free atmosphere of the Earth ~2.8 billion years ago might have invented the water splitting machinery (photosystem II) without the need for special oxygen-protective mechanisms, and the latter mechanisms could have evolved in the next 500 million years during slow rise of oxygen in the atmosphere. This result also suggests that proteins within photosynthetic membranes are not exposed to significant O2 levels and thus can be studied in vitro under the usual O2 levels. Second, the fate of triplet excited states in the Fenna Matthew Olson (FMO) pigment-protein complex is studied by means of time-resolved nanosecond spectroscopy and exciton model simulations. For the first time, the properties of several individual BChl pigments within that photosynthetic antenna complex are accessed via their triplet state dynamics. It is found that the currently used exciton model of FMO needs to be revised. It is also shown that triplet excited states can be readily transferred between the molecules. It is proposed that the triplet energy transfer between the BChl molecules can also serve as a protection mechanism. Finally, it is inferred that at least one of the BChl molecules within the FMO has a triplet state energy that is lower than that of singlet oxygen. This effectively prevents the formation of singlet oxygen and protects the complex from oxidative damage. The energy of BChl is apparently lowered by the specific protein environment, as in solution its energy is measured to be somewhat higher than the energy of singlet oxygen. Finally, the results of the triplet energy transfer within the cytochrome b6f complex are presented. This part of the work is not conclusive, and some of the problems encountered in experiments are described, as well as a new method of sample degassing developed for this type of study is presented.

  5. The singlet-triplet absorption and photodissociation of the HOCl, HOBr, and HOI molecules calculated by the MCSCF quadratic response method

    SciTech Connect

    Minaev, B.F.

    1999-09-09

    The molecular absorption spectra of hypochlorous, hypobromous, and hypoiodous acids have been studied by multiconfiguration self-consistent field (MCSCF) calculations with linear and quadratic response techniques. The complete form of the spin-orbit coupling (SOC) operator is accounted. The singlet-triplet transition to the lowest triplet state {sup 3}A{double{underscore}prime} {l{underscore}arrow} X{sup 1}A{prime} is shown to be responsible for the weak long-wavelength tail absorption and photodissociation in these molecules. The transition is polarized along the O-X bond (X = Cl, Br, I) and has an oscillator strength equal 6 x 10{sup {minus}6}, 8 x 10{sup {minus}5}, and 2 x 10{sup {minus}4} for hypochlorous, hypobromous, and hypoiodous acids, respectively. The second singlet-triplet transition {sup 3}A{prime} {l{underscore}arrow} X{sup 1}A{prime} comes to the region of the first singlet-singlet {sup 1}A{double{underscore}prime} {l{underscore}arrow} X{sup 1}A{prime} absorption and contributes significantly to the total cross-section at wavelengths {lambda} {approx} 300--320 nm (X = Cl), {lambda} {approx} 340--360 nm (X = Br), and {lambda} {approx} 400 nm (X = I). In the last case the singlet-triplet transition {sup 3}A{prime} {l{underscore}arrow} X{sup 1}A{prime} produces predominant contribution to HOI absorption in the visible region. All states are dissociative, so the singlet-triplet absorption contributes to the yield of photolysis in the important near-UV and visible region close to the intense solar actinic flux. Contributions to the removal mechanisms for atmospheric HOCl, HOBr, and HOI species are shortly discussed. The minor loss process of ozone in troposphere because of the HOI reservoir sink is getting evident on the ground of this calculations. The importance of SOC accounting for atmospheric photochemistry problems is stressed.

  6. Non-Markovian Quantum State Diffusion for temperature-dependent linear spectra of light harvesting aggregates

    SciTech Connect

    Ritschel, Gerhard; Möbius, Sebastian; Eisfeld, Alexander; Suess, Daniel; Strunz, Walter T.

    2015-01-21

    Non-Markovian Quantum State Diffusion (NMQSD) has turned out to be an efficient method to calculate excitonic properties of aggregates composed of organic chromophores, taking into account the coupling of electronic transitions to vibrational modes of the chromophores. NMQSD is an open quantum system approach that incorporates environmental degrees of freedom (the vibrations in our case) in a stochastic way. We show in this paper that for linear optical spectra (absorption, circular dichroism), no stochastics is needed, even for finite temperatures. Thus, the spectra can be obtained by propagating a single trajectory. To this end, we map a finite temperature environment to the zero temperature case using the so-called thermofield method. The resulting equations can then be solved efficiently by standard integrators.

  7. Simulation of X-ray Absorption Near Edge Spectra of Organometallic Compounds in the Ground and Optically Excited States

    E-print Network

    Mukamel, Shaul

    Simulation of X-ray Absorption Near Edge Spectra of Organometallic Compounds in the Ground spectra of Fe(II) spin crossover compound in its ground and low-lying optically excited states, motivated hemoproteins,1,2 zinc sites in proteins,3 copper and iron porphyrins,4-6 experimental7 and theoretical8 studies

  8. Magnetic chains on a triplet superconductor

    NASA Astrophysics Data System (ADS)

    Sacramento, P. D.

    2015-11-01

    The topological state of a two-dimensional triplet superconductor may be changed by an appropriate addition of magnetic impurities. A ferromagnetic magnetic chain at the surface of a superconductor with spin-orbit coupling may eliminate the edge states of a finite system giving rise to localized zero modes at the edges of the chain. The coexistence/competition between the two types of zero modes is considered. The reduction of the system to an effective 1d system gives partial information on the topological properties but the study of the two sets of zero modes requires a two-dimensional treatment. Increasing the impurity density from a magnetic chain to magnetic islands leads to a finite Chern number. At half-filling small concentrations are enough to induce chiral modes.

  9. Magnetic chains on a triplet superconductor.

    PubMed

    Sacramento, P D

    2015-11-11

    The topological state of a two-dimensional triplet superconductor may be changed by an appropriate addition of magnetic impurities. A ferromagnetic magnetic chain at the surface of a superconductor with spin-orbit coupling may eliminate the edge states of a finite system giving rise to localized zero modes at the edges of the chain. The coexistence/competition between the two types of zero modes is considered. The reduction of the system to an effective 1d system gives partial information on the topological properties but the study of the two sets of zero modes requires a two-dimensional treatment. Increasing the impurity density from a magnetic chain to magnetic islands leads to a finite Chern number. At half-filling small concentrations are enough to induce chiral modes. PMID:26459719

  10. Nearly Perfect Triplet-Triplet Energy Transfer from Wannier Excitons to Naphthalene in Organic-Inorganic Hybrid Quantum-Well Materials

    NASA Astrophysics Data System (ADS)

    Ema, K.; Inomata, M.; Kato, Y.; Kunugita, H.; Era, M.

    2008-06-01

    We report the observation of extremely efficient energy transfer (greater than 99%) in an organic-inorganic hybrid quantum-well structure consisting of perovskite-type lead bromide well layers and naphthalene-linked ammonium barrier layers. Time-resolved photoluminescence measurements confirm that the transfer is triplet-triplet Dexter-type energy transfer from Wannier excitons in the inorganic well to the triplet state of naphthalene molecules in the organic barrier. Using measurements in the 10 300 K temperature range, we also investigated the temperature dependence of the energy transfer.

  11. Analysis of PANDA Passive Containment Cooling Steady-State Tests with the Spectra Code

    SciTech Connect

    Stempniewicz, Marek M

    2000-07-15

    Results of post test simulation of the PANDA passive containment cooling (PCC) steady-state tests (S-series tests), performed at the PANDA facility at the Paul Scherrer Institute, Switzerland, are presented. The simulation has been performed using the computer code SPECTRA, a thermal-hydraulic code, designed specifically for analyzing containment behavior of nuclear power plants.Results of the present calculations are compared to the measurement data as well as the results obtained earlier with the codes MELCOR, TRAC-BF1, and TRACG. The calculated PCC efficiencies are somewhat lower than the measured values. Similar underestimation of PCC efficiencies had been obtained in the past, with the other computer codes. To explain this difference, it is postulated that condensate coming into the tubes forms a stream of liquid in one or two tubes, leaving most of the tubes unaffected. The condensate entering the water box is assumed to fall down in the form of droplets. With these assumptions, the results calculated with SPECTRA are close to the experimental data.It is concluded that the SPECTRA code is a suitable tool for analyzing containments of advanced reactors, equipped with passive containment cooling systems.

  12. Influence of the projectile charge state on electron emission spectra from a Cu(111) surface

    NASA Astrophysics Data System (ADS)

    Archubi, C. D.; Silkin, V. M.; Gravielle, M. S.

    2015-09-01

    Double differential electron emission distributions produced by grazing impact of fast dressed ions on a Cu(111) surface are investigated focusing on the effects of the electronic band structure. The process is described within the Band-Structure-Based approximation, which is a perturbative method that includes an accurate representation of the electron-surface interaction, incorporating information of the electronic band structure of the solid. Differences in the behavior of the emission spectra for He+ q, Li+ q, Be+ q and C+ q projectiles with different charge states q are explained by the combined effect of the projectile trajectory and the projectile charge distribution.

  13. Nonlinear optical spectra having characteristics of Fano interferences in coherently coupled lowest exciton biexciton states in semiconductor quantum dots

    SciTech Connect

    Gotoh, Hideki Sanada, Haruki; Yamaguchi, Hiroshi; Sogawa, Tetsuomi

    2014-10-15

    Optical nonlinear effects are examined using a two-color micro-photoluminescence (micro-PL) method in a coherently coupled exciton-biexciton system in a single quantum dot (QD). PL and photoluminescence excitation spectroscopy (PLE) are employed to measure the absorption spectra of the exciton and biexciton states. PLE for Stokes and anti-Stokes PL enables us to clarify the nonlinear optical absorption properties in the lowest exciton and biexciton states. The nonlinear absorption spectra for excitons exhibit asymmetric shapes with peak and dip structures, and provide a distinct contrast to the symmetric dip structures of conventional nonlinear spectra. Theoretical analyses with a density matrix method indicate that the nonlinear spectra are caused not by a simple coherent interaction between the exciton and biexciton states but by coupling effects among exciton, biexciton and continuum states. These results indicate that Fano quantum interference effects appear in exciton-biexciton systems at QDs and offer important insights into their physics.

  14. Photosensitization of triplet carotenoid in photosynthetic light-harvesting complex of photosystem II

    SciTech Connect

    Nechushtai, R.; Thornber, J.P.; Patterson, L.K.; Fessenden, R.W.; Levanon, H.

    1988-03-10

    A laser photolysis study, on the nanosecond time scale, has been carried out on the major light-harvesting chlorophyll-protein complex of photosystem II (LHC II..beta..). The transient triplet absorption of the isolated LHC II..beta.. has been compared to those of its constituent chromophores in dilute micellar aqueous solutions, namely, chlorophyll a, chlorophyll b, chlorophyll a + chlorophyll b, and chlorophyll a + ..beta..-carotene. The results indicate that the carotenoid in the LHC II..beta.. is photosensitized by triplet chlorophyll a and that the decay of the transient triplet absorption exhibits two transients, one in the approx. 50-ns range and the other in the approx. 10..mu..s time scales. The former transient is light-intensity dependent and is attributed to an annihilation process between two triplets of chlorophyll a, while the latter is due to the decay of the triplet carotenoid to its ground state.

  15. Nitrogen pairs, triplets, and clusters in GaAs and GaP P. R. C. Kenta)

    E-print Network

    Kent, Paul

    Nitrogen pairs, triplets, and clusters in GaAs and GaP P. R. C. Kenta) and Alex Zunger National 2001 The electronic and atomic structure of substitutional nitrogen pairs, triplets, and clusters in Ga supercells. A single nitrogen impurity creates a localized a1(N) gap state in GaP, but in GaAs, the state

  16. Competition between singlet and triplet superconductivity

    E-print Network

    Tian De Cao; Tie Bang Wang

    2009-10-04

    The competition between singlet and triplet superconductivity is examined in consideration of correlations on an extended Hubbard model. It is shown that the triplet superconductivity may not be included in the common Hubbard model since the strong correlation favors the singlet superconductivity, and thus the triplet superconductivity should be induced by the electron-phonon interaction and the ferromagnetic exchange interaction. We also present a superconducting qualification with which magnetism is unbeneficial to superconductivity.

  17. Investigating Velocity Spectra at the Hugoniot State of Shock Loaded Heterogeneous Materials

    NASA Astrophysics Data System (ADS)

    Lajeunesse, Jeff; Borg, John; Stewart, Sarah; Thadhani, Naresh

    2015-06-01

    Hugoniot states achieved in heterogeneous materials have shown oscillations in particle velocity about an averaged state for both experimental and simulated data. These oscillations arise from the scattering of the transmitted shock wave due to the presence of internal interfaces within heterogeneous materials. The goal of this work is to determine if the spectra of oscillatory behavior can be associated to characteristic length scales of the corresponding un-shocked heterogeneous material. Similarities between different types of shock-loaded materials are compared such as sand, concrete, aluminum foam, and layered composites. I would like to acknowledge the AFOSR under grant: FA9550-12-1-0128, ``Dynamic High-Pressure Behavior of Hierarchical Heterogenous Geological Granular Materials'' and the D.o.D. Supercomputing Resource Center.

  18. Experimental and theoretical study of the electronic states and spectra of SbNa

    NASA Astrophysics Data System (ADS)

    Setzer, K. D.; Fink, E. H.; Liebermann, H.-P.; Buenker, R. J.; Alekseyev, A. B.

    2015-12-01

    Gas-phase emission spectra of the hitherto unknown free radical SbNa were measured in the NIR region with a Fourier-transform spectrometer. The emissions were observed from a fast-flow system in which antimony vapor in argon or neon carrier gas was passed through a microwave discharge and mixed with sodium vapor in an observation tube. Seven transitions from five low-lying excited states A12, A21, A30+, A40-, and B2 to the X10+ and/or X21 components of the X3?- ground state have been observed and analyzed. In parallel to the experiments, relativistic configuration interaction calculations of potential energy curves, vibrational constants, bond lengths, transition moments and radiative lifetimes were carried out to aid in the analysis of the experimental data.

  19. Electronic spectra and excited state dynamics of pentafluorophenol: Effects of low-lying ??? states

    NASA Astrophysics Data System (ADS)

    Karmakar, Shreetama; Mukhopadhyay, Deb Pratim; Chakraborty, Tapas

    2015-05-01

    Multiple fluorine atom substitution effect on photophysics of an aromatic chromophore has been investigated using phenol as the reference system. It has been noticed that the discrete vibronic structure of the S1?S0 absorption system of phenol vapor is completely washed out for pentafluorophenol (PFP), and the latter also shows very large Stokes shift in the fluorescence spectrum. For excitations beyond S1 origin, the emission yield of PFP is reduced sharply with increase in excess vibronic energy. However, in a collisional environment like liquid hydrocarbon, the underlying dynamical process that drives the non-radiative decay is hindered drastically. Electronic structure theory predicts a number of low-lying dark electronic states of ??? character in the vicinity of the lowest valence ??? state of this molecule. Tentatively, we have attributed the excitation energy dependent non-radiative decay of the molecule observed only in the gas phase to an interplay between the lowest ??? and a nearby dissociative ??? state. Measurements in different liquids reveal that some of the dark excited states light up with appreciable intensity only in protic liquids like methanol and water due to hydrogen bonding between solute and solvents. Electronic structure theory methods indeed predict that for PFP-(H2O)n clusters (n = 1-11), intensities of a number of ??? states are enhanced with increase in cluster size. In contrast with emitting behavior of the molecule in the gas phase and solutions of nonpolar and polar aprotic liquids, the fluorescence is completely switched off in polar protic liquids. This behavior is a chemically significant manifestation of perfluoro effect, because a very opposite effect occurs in the case of unsubstituted phenol for which fluorescence yield undergoes a very large enhancement in protic liquids. Several dynamical mechanisms have been suggested to interpret the observed photophysical behavior.

  20. Electronic spectra and excited state dynamics of pentafluorophenol: Effects of low-lying ??(?) states.

    PubMed

    Karmakar, Shreetama; Mukhopadhyay, Deb Pratim; Chakraborty, Tapas

    2015-05-14

    Multiple fluorine atom substitution effect on photophysics of an aromatic chromophore has been investigated using phenol as the reference system. It has been noticed that the discrete vibronic structure of the S1?S0 absorption system of phenol vapor is completely washed out for pentafluorophenol (PFP), and the latter also shows very large Stokes shift in the fluorescence spectrum. For excitations beyond S1 origin, the emission yield of PFP is reduced sharply with increase in excess vibronic energy. However, in a collisional environment like liquid hydrocarbon, the underlying dynamical process that drives the non-radiative decay is hindered drastically. Electronic structure theory predicts a number of low-lying dark electronic states of ??(?) character in the vicinity of the lowest valence ??(?) state of this molecule. Tentatively, we have attributed the excitation energy dependent non-radiative decay of the molecule observed only in the gas phase to an interplay between the lowest ??(?) and a nearby dissociative ??(?) state. Measurements in different liquids reveal that some of the dark excited states light up with appreciable intensity only in protic liquids like methanol and water due to hydrogen bonding between solute and solvents. Electronic structure theory methods indeed predict that for PFP-(H2O)n clusters (n = 1-11), intensities of a number of ??(?) states are enhanced with increase in cluster size. In contrast with emitting behavior of the molecule in the gas phase and solutions of nonpolar and polar aprotic liquids, the fluorescence is completely switched off in polar protic liquids. This behavior is a chemically significant manifestation of perfluoro effect, because a very opposite effect occurs in the case of unsubstituted phenol for which fluorescence yield undergoes a very large enhancement in protic liquids. Several dynamical mechanisms have been suggested to interpret the observed photophysical behavior. PMID:25978887

  1. Infrared Spectroscopy of the Mass 31 Cation: Protonated Formaldehyde VS. The Triplet Methoxy Cation

    NASA Astrophysics Data System (ADS)

    Mosley, J. D.; Cheng, T. C.; Duncan, M. A.

    2012-06-01

    The m/z=31 cation is produced by ionization and fragmentation of methanol, ethanol, dimethyl ether, etc. Two structures have been proposed, protonated formaldehyde (^1CH_2OH^+) and the triplet methoxy cation (^3CH_3O^+). The infrared spectrum of the mass 31 cation is obtained using infrared photodissociation spectroscopy with Ar tagging. The spectrum reveals the presence of two stable isomers, protonated formaldehyde (^1CH_2OH^+) and the triplet methoxy cation (^3CH_3O^+). The triplet methoxy cation has been studied extensively and is predicted to interconvert to protonated formaldehyde through an essentially barrierless process on a timescale much faster than our experiment (>100 ?s). The presence of two structural isomers is verified by comparison of spectra from different precursors and spectra of different temperature ions from the same precursor.

  2. [Probabilistic calculations of biomolecule charge states that generate mass spectra of multiply charged ions].

    PubMed

    Raznikova, M O; Raznikov, V V

    2015-01-01

    In this work, information relating to charge states of biomolecule ions in solution obtained using the electrospray ionization mass spectrometry of different biopolymers is analyzed. The data analyses have mainly been carried out by solving an inverse problem of calculating the probabilities of retention of protons and other charge carriers by ionogenic groups of biomolecules with known primary structures. The approach is a new one and has no known to us analogues. A program titled "Decomposition" was developed and used to analyze the charge distribution of ions of native and denatured cytochrome c mass spectra. The possibility of splitting of the charge-state distribution of albumin into normal components, which likely corresponds to various conformational states of the biomolecule, has been demonstrated. The applicability criterion for using previously described method of decomposition of multidimensional charge-state distributions with two charge carriers, e.g., a proton and a sodium ion, to characterize the spatial structure of biopolymers in solution has been formulated. In contrast to known mass-spectrometric approaches, this method does not require the use of enzymatic hydrolysis or collision-induced dissociation of the biopolymers. PMID:26510600

  3. Particle diffusion and localized acceleration in inhomogeneous AGN jets - I. Steady-state spectra

    NASA Astrophysics Data System (ADS)

    Chen, Xuhui; Pohl, Martin; Böttcher, Markus

    2015-02-01

    We study the acceleration, transport, and emission of particles in relativistic jets. Localized stochastic particle acceleration, spatial diffusion, and synchrotron as well as synchrotron self-Compton (SSC) emission are considered in a leptonic model. To account for inhomogeneity, we use a 2D axisymmetric cylindrical geometry for both relativistic electrons and magnetic field. In this first phase of our work, we focus on steady-state spectra that develop from a time-dependent model. We demonstrate that small isolated acceleration region in a much larger emission volume are sufficient to accelerate particles to high energy. Diffusive escape from these small regions provides a natural explanation for the spectral form of the jet emission. The location of the acceleration regions within the jet is found to affect the cooling break of the spectrum in this diffusive model. Diffusion-caused energy-dependent inhomogeneity in the jets predicts that the SSC spectrum is harder than the synchrotron spectrum. There can also be a spectral hardening towards the high-energy section of the synchrotron spectrum, if particle escape is relatively slow. These two spectral hardening effects indicate that the jet inhomogeneity might be a natural explanation for the unexpected hard ?-ray spectra observed in some blazars.

  4. J. Phys. Chem. 1995, 99, 1199-1203 1199 Singlet and Triplet Excited State Behaviors of c60 in Nonreactive and Reactive Polymer

    E-print Network

    Sauvé, Geneviève

    in Nonreactive and Reactive Polymer Films Genevike SauvC, Nada M. DimitrijeviC,and Prashant V. Kamat* Radiation state behavior of Cm has been investigated in polystyrene (PS) and poly(9-vinylcarbazole) (PVCz) polymer of fullerenes, c60 and C70, in homogeneous and heterogeneous media (e.g., in organic cyclodex- trins,18 polymer

  5. Perturbations to the intersystem crossing of proflavin upon binding to DNA and poly d(A-IU) from triplet-delayed emission spectroscopy.

    PubMed Central

    Lee, W E; Galley, W C

    1988-01-01

    The steady-state prompt fluorescence, phosphorescence and delayed fluorescence spectra and triplet lifetimes of free proflavin and proflavin bound to native DNA and alternating poly d(A-IU) were obtained as a function of temperature in a buffer-glycerol solvent. The intensity of the proflavin E-type delayed fluorescence (DF) relative to both the phosphorescence (Ph) and the prompt fluorescence (F) was observed to increase with temperature, and plots of both ln (DF/Ph) and ln (DF/(F.tau T] as a function of 1/T were linear over a wide range of temperatures. Although the activation energies for the thermal repopulation of the proflavin excited singlet state from the triplet obtained from the slopes of these plots were essentially unchanged on binding, perturbations to the S1----T1 intersystem crossing rate constants extracted from the intercepts at infinite temperature were observed. The marked enhancement of the intersystem crossing that occurs with binding to the iodinated polynucleotide reflects an external heavy atom perturbation upon the intercalated dye which also induces a shortening in the triplet lifetime. With proflavin bound to DNA an enhancement to the S1----T1 intersystem crossing, though lesser in magnitude than for poly d(A-IU), is observed but with no change to the triplet lifetime. The well-studied fluorescence quenching of DNA-bound proflavin is a result of this increase in the intersystem crossing. It is proposed that these non-heavy atom enhancements in the intersystem crossing are due to distortions of the molecular plane of the bound proflavin molecule. In total these analyses provide a complete description of the excited state processes of the proflavin molecule and their variations with temperature. PMID:3224148

  6. Excited-state Raman spectroscopy with and without actinic excitation: S{sub 1} Raman spectra of trans-azobenzene

    SciTech Connect

    Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.

    2014-05-14

    We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S{sub 1} and S{sub 0} spectra of trans-azobenzene in n-hexane. The S{sub 1} spectra were also measured conventionally, upon n?* (S{sub 0} ? S{sub 1}) actinic excitation. The results are discussed and compared to earlier reports.

  7. Doublet-Triplet Fermionic Dark Matter

    E-print Network

    Athanasios Dedes; Dimitrios Karamitros

    2015-06-23

    We extend the Standard Model (SM) by adding a pair of fermionic SU(2)-doublets with opposite hypercharge and a fermionic SU(2)-triplet with zero hypercharge. We impose a discrete Z_2-symmetry that distinguishes the SM fermions from the new ones. Then, gauge invariance allows for two renormalizable Yukawa couplings between the new fermions and the SM Higgs field, as well as for direct masses for the doublet (M_D) and the triplet (M_T). After electroweak symmetry breaking, this model contains, in addition to SM particles, two charged Dirac fermions and a set of three neutral Majorana fermions, the lightest of which contributes to Dark Matter (DM). We consider a case where the lightest neutral fermion is an equal admixture of the two doublets with mass M_D close to the Z-boson mass. This state remains stable under radiative corrections thanks to a custodial SU(2)-symmetry and is consistent with the experimental data from oblique electroweak corrections. Moreover, the amplitudes relevant to spin-dependent or independent nucleus-DM particle scattering cross section both vanish at tree level. They arise at one loop at a level that may be observed in near future DM direct detection experiments. For Yukawa couplings comparable to the top-quark, the DM particle relic abundance is consistent with observation, not relying on co-annihilation or resonant effects and has a mass at the electroweak scale. Furthermore, the heavier fermions decay to the DM particle and to electroweak gauge bosons making this model easily testable at the LHC. In the regime of interest, the charged fermions suppress the Higgs decays to diphoton by 45-75 % relative to SM prediction.

  8. Spectroscopic study on deuterated benzenes. I. Microwave spectra and molecular structure in the ground state.

    PubMed

    Kunishige, Sachi; Katori, Toshiharu; Baba, Masaaki; Nakajima, Masakazu; Endo, Yasuki

    2015-12-28

    We observed microwave absorption spectra of some deuterated benzenes and accurately determined the rotational constants of all H/D isotopomers in the ground vibrational state. Using synthetic analysis assuming that all bond angles are 120°, the mean bond lengths were obtained to be r0(C-C) = 1.3971 Å and r0(C-H) = r0(C-D) = 1.0805 Å. It has been concluded that the effect of deuterium substitution on the molecular structure is negligibly small and that the mean bond lengths of C-H and C-D are identical unlike small aliphatic hydrocarbons, in which r0(C-D) is about 5 mÅ shorter than r0(C-H). It is considered that anharmonicity is very small in the C-H stretching vibration of aromatic hydrocarbons. PMID:26723666

  9. Definition and determination of the triplet-triplet energy transfer reaction coordinate

    SciTech Connect

    Zapata, Felipe; Marazzi, Marco; Castaño, Obis; Frutos, Luis Manuel; Acuña, A. Ulises

    2014-01-21

    A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail.

  10. Prenatally diagnosed monochorionic diamniotic triplet pregnancy.

    PubMed

    Yonetani, Naoto; Ishii, Keisuke; Mabuchi, Aki; Sasahara, Jun; Hayashi, Shusaku; Mitsuda, Nobuaki

    2015-08-01

    We present an extremely rare case of monochorionic diamniotic (MD) triplet pregnancy diagnosed via ultrasonography at the end of the first trimester that resulted in delivery of three healthy newborns. Ultrasonography for a 34-year-old woman at 12 weeks of gestation showed three fetuses and one placenta with a T-sign at the initial segment of the dividing membrane. Color Doppler examination revealed umbilical cord entanglement between two fetuses in one sac in addition to another sac containing one fetus. Therefore, this was diagnosed as MD triplet pregnancy. The triplets were delivered by cesarean section at 35 weeks of gestation and were healthy without neurological morbidities at the age of 28 days. Histopathological examination also revealed an MD triplet placenta. The possibility of MD triplet pregnancy should be recognized, although it is rare. PMID:25832331

  11. Polaron pair mediated triplet generation in polymer/fullerene blends

    PubMed Central

    Dimitrov, Stoichko D.; Wheeler, Scot; Niedzialek, Dorota; Schroeder, Bob C.; Utzat, Hendrik; Frost, Jarvist M.; Yao, Jizhong; Gillett, Alexander; Tuladhar, Pabitra S.; McCulloch, Iain; Nelson, Jenny; Durrant, James R.

    2015-01-01

    Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields. PMID:25735188

  12. Polaron pair mediated triplet generation in polymer/fullerene blends.

    PubMed

    Dimitrov, Stoichko D; Wheeler, Scot; Niedzialek, Dorota; Schroeder, Bob C; Utzat, Hendrik; Frost, Jarvist M; Yao, Jizhong; Gillett, Alexander; Tuladhar, Pabitra S; McCulloch, Iain; Nelson, Jenny; Durrant, James R

    2015-01-01

    Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields. PMID:25735188

  13. Perturbations in the Spectra of High Rydberg States: Channel Interactions, Stark and Zeeman Effects

    NASA Astrophysics Data System (ADS)

    Haase, Christa; Schäfer, Martin; Hogan, Stephen D.; Merkt, Frédéric

    2011-06-01

    Rydberg states of principal quantum number n?50 have been prepared by irradiation of an atomic beam of xenon with vacuum ultraviolet (VUV) radiation. Narrowband submillimeter-wave (THz) radiation was then used to record spectra of transitions from these Rydberg states to higher or lower-lying Rydberg states. The transitions were detected by selective field ionization and recording either the electrons or the ions, the latter offering the advantage of mass selection. Rydberg states of high principal quantum number are extremely sensitive to their environment, which can be exploited to characterize the experimental conditions under which the spectroscopic measurements are carried out. The high resolution achieved in the experiments (better than 100 kHz) enabled the study of the spectral lineshapes and line positions in dependence of weak electric (down to below 100?V/cm) and magnetic fields (down to a few ?T), and of the density of Rydberg atoms and ions generated in the experimental volume. The experiments rely on the use of a pulsed, broadly tunable, laser-based source of THz radiation for survey scans, and of a phase- and frequency-stabilized submillimeter-wave backward-wave oscillator-based radiation source for precision measurements. To illustrate the use of these sources, we present the results of the spectroscopic investigations of the hyperfine structure of 129Xe Rydberg states in spectral regions where s-d interactions are expected to play a role. F. Merkt and A. Osterwalder Int. Rev. Phys. Chem. 21, 385, (2002). J. Liu and F. Merkt Appl. Phys. Lett. 93, 131105, (2008). M. Schäfer, M. Andrist, H. Schmutz, F. Lewen, G. Winnewisser and F. Merkt J. Phys. B: At. Mol. Opt. Phys. 39, 831, (2006).

  14. Walking Down the Chalcogenic Group of the Periodic Table: From Singlet to Triplet Organic Emitters.

    PubMed

    Kremer, Adrian; Aurisicchio, Claudia; De Leo, Federica; Ventura, Barbara; Wouters, Johan; Armaroli, Nicola; Barbieri, Andrea; Bonifazi, Davide

    2015-10-19

    The synthesis, X-ray crystal structures, ground- and excited-state UV/Vis absorption spectra, and luminescence properties of chalcogen-doped organic emitters equipped on both extremities with benzoxa-, benzothia-, benzoselena- and benzotellurazole (1X and 2X ) moieties have been reported for the first time. The insertion of the four different chalcogen atoms within the same molecular skeleton enables the investigation of only the chalcogenic effect on the organisation and photophysical properties of the material. Detailed crystal-structure analyses provide evidence of similar packing for 2O -2Se , in which the benzoazoles are engaged in ?-? stacking and, for the heavier atoms, in secondary X???X and X???N bonding interactions. Detailed computational analysis shows that the arrangement is essentially governed by the interplay of van der Waals and secondary bonding interactions. Progressive quenching of the fluorescence and concomitant onset of phosphorescence features with gradually shorter lifetimes are detected as the atomic weight of the chalcogen heteroatom increases, with the tellurium-doped derivatives exhibiting only emission from the lowest triplet excited state. Notably, the phosphorescence spectra of the selenium and tellurium derivatives can be recorded even at room temperature; this is a very rare finding for fully organic emitters. PMID:26471446

  15. Singlet and triplet instability theorems

    NASA Astrophysics Data System (ADS)

    Yamada, Tomonori; Hirata, So

    2015-09-01

    A useful definition of orbital degeneracy—form-degeneracy—is introduced, which is distinct from the usual energy-degeneracy: Two canonical spatial orbitals are form-degenerate when the energy expectation value in the restricted Hartree-Fock (RHF) wave function is unaltered upon a two-electron excitation from one of these orbitals to the other. Form-degenerate orbitals tend to have isomorphic electron densities and occur in the highest-occupied and lowest-unoccupied molecular orbitals (HOMOs and LUMOs) of strongly correlated systems. Here, we present a mathematical proof of the existence of a triplet instability in a real or complex RHF wave function of a finite system in the space of real or complex unrestricted Hartree-Fock wave functions when HOMO and LUMO are energy- or form-degenerate. We also show that a singlet instability always exists in a real RHF wave function of a finite system in the space of complex RHF wave functions, when HOMO and LUMO are form-degenerate, but have nonidentical electron densities, or are energy-degenerate. These theorems provide Hartree-Fock-theory-based explanations of Hund's rule, a singlet instability in Jahn-Teller systems, biradicaloid electronic structures, and a triplet instability during some covalent bond breaking. They also suggest (but not guarantee) the spontaneous formation of a spin density wave (SDW) in a metallic solid. The stability theory underlying these theorems extended to a continuous orbital-energy spectrum proves the existence of an oscillating (nonspiral) SDW instability in one- and three-dimensional homogeneous electron gases, but only at low densities or for strong interactions.

  16. Triplet Pairing in Neutron Matter

    E-print Network

    V. V. Khodel; V. A. Khodel; J. W. Clark

    2000-01-05

    The separation method developed earlier by us [Nucl. Phys. {\\bf A598} 390 (1996)] to calculate and analyze solutions of the BCS gap equation for $^1$S$_0$ pairing is extended and applied to $^3$P$_2$--$^3$F$_2$ pairing in pure neutron matter. The pairing matrix elements are written as a separable part plus a remainder that vanishes when either momentum variable is on the Fermi surface. This decomposition effects a separation of the problem of determining the dependence of the gap components in a spin-angle representation on the magnitude of the momentum (described by a set of functions independent of magnetic quantum number) from the problem of determining the dependence of the gap on angle or magnetic projection. The former problem is solved through a set of nonsingular, quasilinear integral equations, providing inputs for solution of the latter problem through a coupled system of algebraic equations for a set of numerical coefficients. An incisive criterion is given for finding the upper critical density for closure of the triplet gap. The separation method and its development for triplet pairing exploit the existence of a small parameter, given by a gap-amplitude measure divided by the Fermi energy. The revised BCS equations admit analysis revealing universal properties of the full set of solutions for $^3$P$_2$ pairing in the absence of tensor coupling, referring especially to the energy degeneracy and energetic order of these solutions. The angle-average approximation introduced by Baldo et al. is illuminated in terms of the separation-transformed BCS problem and the small parameter expansion...

  17. The fate of the triplet excitations in the Fenna-Matthews-Olson complex.

    PubMed

    Kihara, Shigeharu; Hartzler, Daniel A; Orf, Gregory S; Blankenship, Robert E; Savikhin, Sergei

    2015-05-01

    The fate of triplet excited states in the Fenna-Matthew-Olson (FMO) pigment-protein complex is studied by means of time-resolved nanosecond spectroscopy and exciton model simulations. Experiments reveal microsecond triplet excited-state energy transfer between the bacteriochlorophyll (BChl) pigments, but show no evidence of triplet energy transfer to molecular oxygen, which is known to produce highly reactive singlet oxygen and is the leading cause of photo damage in photosynthetic proteins. The FMO complex is exceptionally photo stable despite the fact it contains no carotenoids, which could effectively quench triplet excited states of (bacterio)chlorophylls and are usually found within pigment-protein complexes. It is inferred that the triplet excitation is transferred to the lowest energy pigment, BChl 3, within the FMO complex, whose triplet state energy is shifted by pigment-protein interactions below that of the singlet oxygen excitation. Thus, the energy transfer to molecular oxygen is blocked and the FMO does not need carotenoids for photo protection. PMID:25856694

  18. Impedance spectra classification for determining the state of charge on a lithium iron phosphate cell using a support vector machine

    NASA Astrophysics Data System (ADS)

    Jansen, P.; Vergossen, D.; Renner, D.; John, W.; Götze, J.

    2015-11-01

    An alternative method for determining the state of charge (SOC) on lithium iron phosphate cells by impedance spectra classification is given. Methods based on the electric equivalent circuit diagram (ECD), such as the Kalman Filter, the extended Kalman Filter and the state space observer, for instance, have reached their limits for this cell chemistry. The new method resigns on the open circuit voltage curve and the parameters for the electric ECD. Impedance spectra classification is implemented by a Support Vector Machine (SVM). The classes for the SVM-algorithm are represented by all the impedance spectra that correspond to the SOC (the SOC classes) for defined temperature and aging states. A divide and conquer based search algorithm on a binary search tree makes it possible to grade measured impedances using the SVM method. Statistical analysis is used to verify the concept by grading every single impedance from each impedance spectrum corresponding to the SOC by class with different magnitudes of charged error.

  19. Photochromic dibenzobarrlenes: long-lived triplet biradical intermediates.

    PubMed

    Sajimon, Meledathu C; Ramaiah, Danaboyina; Suresh, Cherumuttathu H; Adam, Waldemar; Lewis, Frederick D; George, Manapurathu V

    2007-08-01

    Upon exposure to UV light, the disubstituted dibenzobarrelene derivative 1a turns green in the solid phase and reverts back to its original pale-yellow color within several hours in the dark. The lifetime of the colored species in degassed benzene at room temperature is 37 +/- 2 s (Ea for decoloration is 14.5 +/- 0.7 kcal mol-1 and log A is 8.92 +/- 0.5 s-1) and highly sensitive to molecular oxygen; the Stern-Volmer quenching constant is 6.9 +/- 0.2 x 108 M-1 s-1. Similarly, the disubstituted dibenzobarrelenes 1b and 1c exhibited pink coloration when exposed to UV light in the solid phase. On the basis of combined experimental and theoretical evidence, it is proposed that upon photoexcitation the excited singlet state of 1a undergoes rapid intersystem crossing to its triplet state, followed by intramolecular delta-H abstraction, to yield the triplet biradical intermediate (3)2. Upon prolonged irradiation, 2 undergoes cyclization to the alcohol 3, which affords the enone 4 as the final photoproduct. The delta-H abstraction on the triplet-state potential energy surface, calculated at the B3LYP/6-31G* level of density functional theory (DFT), has an activation energy of 18.5 kcal/mol. Further, the absorption spectrum of the triplet biradical (3)2, obtained from time-dependent DFT calculations, displays an intense absorption maximum at 670 nm, which is in good agreement with the observed absorption peak at 700 nm. The molecular-orbital analysis of the triplet diradical (3)2 suggests that its long-wavelength absorption involves the transition of the unpaired electron from the comparatively localized benzyl-type HOMO to the extensively conjugated benzoyl-type LUMO. The present experimental and theoretical results strongly support the intervention of a long-lived triplet biradical (3)2 in the photochromism of appropriately substituted dibenzobarrelenes. PMID:17625852

  20. Analysis of source spectra, attenuation, and site effects from central and eastern United States earthquakes

    SciTech Connect

    Lindley, G.

    1998-02-01

    This report describes the results from three studies of source spectra, attenuation, and site effects of central and eastern United States earthquakes. In the first study source parameter estimates taken from 27 previous studies were combined to test the assumption that the earthquake stress drop is roughly a constant, independent of earthquake size. 200 estimates of stress drop and seismic moment from eastern North American earthquakes were combined. It was found that the estimated stress drop from the 27 studies increases approximately as the square-root of the seismic moment, from about 3 bars at 10{sup 20} dyne-cm to 690 bars at 10{sup 25} dyne-cm. These results do not support the assumption of a constant stress drop when estimating ground motion parameters from eastern North American earthquakes. In the second study, broadband seismograms recorded by the United States National Seismograph Network and cooperating stations have been analysed to determine Q{sub Lg} as a function of frequency in five regions: the northeastern US, southeastern US, central US, northern Basin and Range, and California and western Nevada. In the third study, using spectral analysis, estimates have been made for the anelastic attenuation of four regional phases, and estimates have been made for the source parameters of 27 earthquakes, including the M{sub b} 5.6, 14 April, 1995, West Texas earthquake.

  1. (??1) ? (??1), (??1) emission spectra of chlorofluorobenzene cations in the gaseous phase and their lifetimes in the (0o) states

    USGS Publications Warehouse

    Maier, John Paul; Marthaler, O.; Mohraz, Manijeh; Shiley, R.H.

    1980-01-01

    The radiative decay of seventeen electronically excited chlorofluorobenzene cations in the gaseous phase has been detected. The reported emission spectra, which have been obtained using low energy electron beam excitation, are assigned to the B(??-1 ??? X(??-1 electronic transitions of these cations on the basis of their Ne(I) photoelectron spectra. In another sixteen chloroflourobenzene cations, the B ??? X radiative decay could not be detected, from which is inferred that the B states are now associated with Cl 3p(??-1 ionisation processes. The lifetimes of the studied cations in the lowest vibrational levels of the B(??-1 state have been measured. ?? 1980.

  2. Higgs triplets and limits from precision measurements

    SciTech Connect

    Chen, Mu-Chun; Dawson, Sally; Krupovnickas, Tadas; /Brookhaven

    2006-04-01

    In this letter, they present the results on a global fit to precision electroweak data in a Higgs triplet model. In models with a triplet Higgs boson, a consistent renormalization scheme differs from that of the Standard Model and the global fit shows that a light Higgs boson with mass of 100-200 GeV is preferred. Triplet Higgs bosons arise in many extensions of the Standard Model, including the left-right model and the Little Higgs models. The result demonstrates the importance of the scalar loops when there is a large mass splitting between the heavy scalars. It also indicates the significance of the global fit.

  3. The Calcium Triplet metallicity calibration for galactic bulge stars

    E-print Network

    Vasquez, S; Hill, V; Gonzalez, O A; Saviane, I; Rejkuba, M; Battaglia, G

    2015-01-01

    We present a new calibration of the Calcium II Triplet equivalent widths versus [Fe/H], constructed upon K giant stars in the Galactic bulge. This calibration will be used to derive iron abundances for the targets of the GIBS survey, and in general it is especially suited for solar and supersolar metallicity giants, typical of external massive galaxies. About 150 bulge K giants were observed with the GIRAFFE spectrograph at VLT, both at resolution R~20,000 and at R~6,000. In the first case, the spectra allowed us to perform direct determination of Fe abundances from several unblended Fe lines, deriving what we call here high resolution [Fe/H] measurements. The low resolution spectra allowed us to measure equivalent widths of the two strongest lines of the near infrared Calcium II triplet at 8542 and 8662 A. By comparing the two measurements we derived a relation between Calcium equivalent widths and [Fe/H] that is linear over the metallicity range probed here, -1<[Fe/H]<+0.7. By adding a small second or...

  4. The biomolecule of 5-bromocytosine: FT-IR and FT-Raman spectra and DFT calculations. Identification of the tautomers in the isolated state and simulation the spectra in the solid state.

    PubMed

    Alcolea Palafox, M; Rastogi, V K; Kumar, Satendra; Joe, Hubert

    2013-07-01

    An accurate assignment of the IR spectrum in Ar matrix of 5-bromocytosine and of the IR and Raman spectra in the solid state was carried out. For this purpose Density functional calculations (DFTs) were performed to clarify wavenumber assignments of the experimental observed bands. The calculated values were scaled using scaling equations and they were compared with IR and Raman experimental data. Good reproduction of the experimental wavenumbers is obtained and the% error is very small in the majority of cases. In the isolated state all the tautomer forms of 5-bromocytosine were determined and optimized. The wavenumbers corresponding to C1 and C2b tautomers were identified and assigned in the IR experimental spectrum reported in Ar matrix. Our study confirms the existence of at least two tautomers, the amino-oxo and the amino-hydroxy in the isolated state. In the solid state the FT-IR and FT-Raman spectra of 5-bromocytosine in the powder form were recorded in the region 400-4000 cm(-1) and 50-3500 cm(-1), respectively. The unit cell found in the crystal was simulated as a tetramer form in three tautomers. Thus, it has been possible to assign all the 33 normal modes of vibration. The study indicates that the features, that are the characteristic of the vibrational spectra of cytosine, are retained by the spectra of 5-bromocytosine and it exists in the solid phase in the amino-oxo form. PMID:23608134

  5. NMR crystallography: The effect of deuteration on high resolution 13 state NMR spectra of a 7-TM protein

    E-print Network

    Watts, Anthony

    NMR crystallography: The effect of deuteration on high resolution 13 C solid state NMR spectra, and indirect, 9­17 ppm, dimensions). The measured 13 C NMR line-widths observed for both protonated. Introduction Perdeuteration has been used routinely in solution NMR for 13 C, 15 N labeled protein assignment

  6. Saddle-node states in the spectra of HCO and DCO: a periodic orbit classication of vibrational levels

    E-print Network

    Farantos, Stavros C.

    Saddle-node states in the spectra of HCO and DCO: a periodic orbit classi®cation of vibrational isotopomer DCO are analyzed in terms of periodic orbits (POs) and continuation/bifurcation diagrams. Both by counting the nodes along the three coordinate axes; therefore, many of the assignments given in Table 1

  7. TRIO (Triplet Ionospheric Observatory) Mission

    NASA Astrophysics Data System (ADS)

    Lee, D.; Seon, J.; Jin, H.; Kim, K.; Lee, J.; Jang, M.; Pak, S.; Kim, K.; Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Roelof, E. C.; Horbury, T. S.

    2009-12-01

    Triplets of identical cubesats will be built to carry out the following scientific objectives: i) multi-observations of ionospheric ENA (Energetic Neutral Atom) imaging, ii) ionospheric signature of suprathermal electrons and ions associated with auroral acceleration as well as electron microbursts, and iii) complementary measurements of magnetic fields for particle data. Each satellite, a cubesat for ion, neutral, electron, and magnetic fields (CINEMA), is equipped with a suprathermal electron, ion, neutral (STEIN) instrument and a 3-axis magnetometer of magnetoresistive sensors. TRIO is developed by three institutes: i) two CINEMA by Kyung Hee University (KHU) under the WCU program, ii) one CINEMA by UC Berkeley under the NSF support, and iii) three magnetometers by Imperial College, respectively. Multi-spacecraft observations in the STEIN instruments will provide i) stereo ENA imaging with a wide angle in local times, which are sensitive to the evolution of ring current phase space distributions, ii) suprathermal electron measurements with narrow spacings, which reveal the differential signature of accelerated electrons driven by Alfven waves and/or double layer formation in the ionosphere between the acceleration region and the aurora, and iii) suprathermal ion precipitation when the storm-time ring current appears. In addition, multi-spacecraft magnetic field measurements in low earth orbits will allow the tracking of the phase fronts of ULF waves, FTEs, and quasi-periodic reconnection events between ground-based magnetometer data and upstream satellite data.

  8. Controlling a Singlet-Triplet Spin Qubit

    NASA Astrophysics Data System (ADS)

    Petta, Jason

    2006-03-01

    An attractive candidate for a solid-state quantum bit is based on semiconductor quantum dots, which allow controlled coupling of one or more electrons, using rapidly switchable voltages applied to electrostatic gates [1]. Due to tight confinement and the high degree of isolation from the environment, spin relaxation times in quantum dots can approach millisecond timescales [2]. In this talk I will describe how fast electrical control of the exchange interaction can be used to coherently manipulate two-electron spin states [3]. By separating a spin singlet state on-chip, we measure an ensemble averaged spin dephasing time T2^* of 10 ns, limited by the contact hyperfine interaction with the GaAs host nuclei. We develop quantum control techniques based on the exchange interaction to correct for hyperfine dephasing. Coherent spin state rotations are achieved, including spin SWAP. By using a spin-echo pulse sequence based on the exchange interaction we extend the spin coherence time, T2 beyond 1.2 microseconds. The quantum control techniques demonstrated here are general and may be used to manipulate singlet-triplet spin qubits in carbon nanotubes, electrons on helium, and semiconducting nanowires. In collaboration with A. C. Johnson, J. M. Taylor, E. A. Laird, A. Yacoby, M. D. Lukin, C. M. Marcus, M. P. Hanson, A. C. Gossard. [1] J. R. Petta, A. C. Johnson, A. Yacoby, C. M. Marcus, A. C. Gossard, M. P. Hanson, Phys. Rev. B 72, R161301 (2005). [2] A. C. Johnson, J. R. Petta, J. M. Taylor, A. Yacoby, M. D. Lukin, C. M. Marcus, M. P. Hanson, A. C. Gossard, Nature 435, 925 (2005). [3] J. R. Petta, A. C. Johnson, J. M. Taylor, E. A. Laird, A. Yacoby, M. D. Lukin, C. M. Marcus, M. P. Hanson, A. C. Gossard, Science 309, 2180 (2005).

  9. Triplet-triplet energy transfer in fucoxanthin-chlorophyll protein from diatom Cyclotella meneghiniana: insights into the structure of the complex.

    PubMed

    Di Valentin, Marilena; Meneghin, Elena; Orian, Laura; Polimeno, Antonino; Büchel, Claudia; Salvadori, Enrico; Kay, Christopher W M; Carbonera, Donatella

    2013-10-01

    Although the major light harvesting complexes of diatoms, called FCPs (fucoxanthin chlorophyll a/c binding proteins), are related to the cab proteins of higher plants, the structures of these light harvesting protein complexes are much less characterized. Here, a structural/functional model for the "core" of FCP, based on the sequence homology with LHCII, in which two fucoxanthins replace the central luteins and act as quenchers of the Chl a triplet states, is proposed. Combining the information obtained by time-resolved EPR spectroscopy on the triplet states populated under illumination, with quantum mechanical calculations, we discuss the chlorophyll triplet quenching in terms of the geometry of the chlorophyll-carotenoid pairs participating to the process. The results show that local structural rearrangements occur in FCP, with respect to LHCII, in the photoprotective site. PMID:23856166

  10. The contribution of triplet-triplet annihilation to the lifetime and efficiency of fluorescent polymer organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    King, S. M.; Cass, M.; Pintani, M.; Coward, C.; Dias, F. B.; Monkman, A. P.; Roberts, M.

    2011-04-01

    We demonstrate that the fast initial decay of a prototypical fluorescent polymer based organic light emitting diode device is related to the contribution that triplet-triplet annihilation makes to the device efficiency. We show that, during typical operating conditions, approximately 20% of the device efficiency originates from the production of singlet excitons by triplet-triplet annihilation. During prolonged device operation, the triplet excitons are quenched much more easily than the emissive singlets; thus, the contribution to the efficiency from triplet-triplet annihilation is lost during the early stages of the device lifetest. The fast initial decay of the device luminance can be removed by incorporating a triplet quenching additive into the active layer to remove any effect of triplet-triplet annihilation; this yields an increase in the device lifetime of greater than 3× and an even more significant improvement in the initial luminance decay.

  11. Intramolecular charge transfer of push-pull pyridinium salts in the triplet manifold.

    PubMed

    Carlotti, Benedetta; Consiglio, Giuseppe; Elisei, Fausto; Fortuna, Cosimo G; Mazzucato, Ugo; Spalletti, Anna

    2014-09-11

    The solvent effect on the triplet state properties of the iodides of three trans (E) isomers of 2-D-vinyl-1-methylpyridinium, where D is a donor group (4-(dimethylamino)phenyl, 3,4,5-trimethoxyphenyl, and 1-pyrenyl), was studied by nanosecond transient absorption techniques. The results obtained allowed us to complete a previous study on the negative solvatochromism and the role of the solvent-controlled intramolecular charge transfer (ICT) relaxation pathways in the excited singlet state, carried out by ultrafast absorption techniques and DFT calculations (J. Phys. Chem. A 2014, 118, 3580-3592 ). The solvent effect on the intersystem crossing to the triplet manifold gave information on the competition of the relaxation processes in the singlet and triplet states and the extent and mechanism of the photoreactive deactivation, particularly operative for the pyrenyl derivative. For the latter the results showed that the ICT process also occurs in the triplet manifold. In fact, the formation of two triplet states with different nature and affected differently by oxygen was observed for the pyrenyl derivative in water and assigned to the (3)LE* and (3)ICT* states. The related structure and solvent effects on the trans ? cis photoisomerization are briefly discussed. PMID:25146975

  12. Photochemical studies of alkylammonium molybdates. Part 12. O?Mo charge-transfer triplet-states-initiated self-assembly to {Mo154} ring- and tube-molybdenum-blues

    NASA Astrophysics Data System (ADS)

    Yamase, T.; Prokop, P.; Arai, Y.

    2003-08-01

    The chemically induced dynamic electron-spin-polarization technique is employed in order to investigate the primary steps of the photoredox reaction between polyoxomolybdates and alkylammonium cations as both proton and electron-donors in solutions. An observation of emissive electron-spin-polarization signals of alkylamino radical cations for the photoredox reaction between polyoxomolybdates and alkylammonium cations in solutions reveals that the O?Mo ligand-to-metal charge-transfer triplet states are involved in the transfers of both proton and electron from alkylammonium cation to polyoxomolybdate anions. Prolonged photolysis of aqueous solutions containing [Mo36O112(H2O)16]8-, [iPrNH3]+, and LaCl3 at pH 1.0 leads to formation of two kinds of {Mo154} molybdenum-blues, [Mo28VMo126VIO462H28(H2O)70]·156.5H2O (1) and [iPrNH3]8 [Mo28VMo126VIO458H12(H2O)66]·127H2O (2), which were X-ray crystallographically characterized. The former exhibits the intact car-tire-shaped {Mo154} ring structure (with thickness of about 1.1 nm and with outer- and inner-rings of approximately 3.5- and 2.3-nm diameters, respectively) derived formally from the dehydrated cyclic heptamerization of four-electron reduced building blocks of {Mo22} (?[Mo4VMo18VIO70H12(H2O)10]) with overall symmetry of D7d. The anion for the latter, [Mo28VMo126VIO458H12(H2O)66]8- (2a), exhibits a nanotube structure of {Mo154} rings, each inner ring of which contains a bis(?-oxo)-linkaged [MoO2(?-O)(?-H2O)MoO2]2+ unit replacing one of seven [Mo(H2O)O2(?-O)Mo(H2O)O2]2+linker units. The neighboring {Mo154} rings are connected by six Mo-O-Mo bridge between inner-rings consisting of 7 head- and 14 linkers-MoO6 octahedra for each.

  13. Wavelength shifts in solid-state circular dichroism spectra: a possible explanation.

    PubMed

    Castiglioni, Ettore; Abbate, Sergio; Longhi, Giovanna; Gangemi, Roberto

    2007-06-01

    We have devised an artificial sampling approach generating "absorption flattening" (AF) on the UV-Vis spectrum of a solution of a chiral compound: Tris (ethylendiamine)cobalt(III) chloride (Lambda-Co(en)(3)Cl(3)). We have observed a concomitant red shift of the CD maxima. Related CD and absorption spectra have been calculated from spectra recorded on diluted homogeneous solutions, thus monitoring the effect of AF on both types of data. Experimental data are in good agreement with calculated spectra. Simulations with suitable bandshapes show that the red shift of the CD spectrum is due to AF. On the basis of these results, we conclude that AF is an important cause of distortions in CD spectra for inhomogeneous samples. Plans to compensate or at least to take into account this effect are presented. PMID:17437265

  14. The structure definition of complementary pairs Ade-Ura in different phase states using IR spectra

    NASA Astrophysics Data System (ADS)

    Ten, G. N.; Glukhova, O. E.; Semagina, A. M.; Slepchenkov, M. M.; Baranov, V. I.

    2015-03-01

    The parameters of hydrogen bridges and oscillation spectra of complementary pairs of adenine-uracil formed by Watson- Crick and Hugstin and two reverse to them structures are calculated. Performed analysis shows that due to the characteristic oscillations of the IR spectra in the area of 1600-1800 and 2900-3500 cm-1 it is possible to identify uniquely each of the four pairs in the gas phase and aqueous solution.

  15. Scalar triplet flavored leptogenesis: a systematic approach

    SciTech Connect

    Sierra, D. Aristizabal; Dhen, Mikaël; Hambye, Thomas E-mail: mikadhen@ulb.ac.be

    2014-08-01

    Type-II seesaw is a simple scenario in which Majorana neutrino masses are generated by the exchange of a heavy scalar electroweak triplet. When endowed with additional heavy fields, such as right-handed neutrinos or extra triplets, it also provides a compelling framework for baryogenesis via leptogenesis. We derive in this context the full network of Boltzmann equations for studying leptogenesis in the flavored regime. To this end we determine the relations which hold among the chemical potentials of the various particle species in the thermal bath. This takes into account the standard model Yukawa interactions of both leptons and quarks as well as sphaleron processes which, depending on the temperature, may be classified as faster or slower than the Universe Hubble expansion. We find that when leptogenesis is enabled by the presence of an extra triplet, lepton flavor effects allow the production of the B-L asymmetry through lepton number conserving CP asymmetries. This scenario becomes dominant as soon as the triplets couple more to leptons than to standard model scalar doublets. In this case, the way the B-L asymmetry is created through flavor effects is novel: instead of invoking the effect of L-violating inverse decays faster than the Hubble rate, it involves the effect of L-violating decays slower than the Hubble rate. We also analyze the more general situation where lepton number violating CP asymmetries are present and actively participate in the generation of the B-L asymmetry, pointing out that as long as L-violating triplet decays are still in thermal equilibrium when the triplet gauge scattering processes decouple, flavor effects can be striking, allowing to avoid all washout suppression effects from seesaw interactions. In this case the amount of B-L asymmetry produced is limited only by a universal gauge suppression effect, which nevertheless goes away for large triplet decay rates.

  16. Singlet-triplet annihilation in single LHCII complexes.

    PubMed

    Gruber, J Michael; Chmeliov, Jevgenij; Krüger, Tjaart P J; Valkunas, Leonas; van Grondelle, Rienk

    2015-08-14

    In light harvesting complex II (LHCII) of higher plants and green algae, carotenoids (Cars) have an important function to quench chlorophyll (Chl) triplet states and therefore avoid the production of harmful singlet oxygen. The resulting Car triplet states lead to a non-linear self-quenching mechanism called singlet-triplet (S-T) annihilation that strongly depends on the excitation density. In this work we investigated the fluorescence decay kinetics of single immobilized LHCIIs at room temperature and found a two-exponential decay with a slow (3.5 ns) and a fast (35 ps) component. The relative amplitude fraction of the fast component increases with increasing excitation intensity, and the resulting decrease in the fluorescence quantum yield suggests annihilation effects. Modulation of the excitation pattern by means of an acousto-optic modulator (AOM) furthermore allowed us to resolve the time-dependent accumulation and decay rate (?7 ?s) of the quenching species. Inspired by singlet-singlet (S-S) annihilation studies, we developed a stochastic model and then successfully applied it to describe and explain all the experimentally observed steady-state and time-dependent kinetics. That allowed us to distinctively identify the quenching mechanism as S-T annihilation. Quantitative fitting resulted in a conclusive set of parameters validating our interpretation of the experimental results. The obtained stochastic model can be generalized to describe S-T annihilation in small molecular aggregates where the equilibration time of excitations is much faster than the annihilation-free singlet excited state lifetime. PMID:26156159

  17. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Zhang, Chunfeng; Zhang, Bo; Liu, Yunlong; Wang, Xiaoyong; Xiao, Min

    2015-10-01

    Singlet fission can potentially break the Shockley-Queisser efficiency limit in single-junction solar cells by splitting one photoexcited singlet exciton (S1) into two triplets (2T1) in organic semiconductors. A dark multiexciton state has been proposed as the intermediate connecting S1 to 2T1. However, the exact nature of this multiexciton state, especially how the doubly excited triplets interact, remains elusive. Here we report a quantitative study on the magnetic dipolar interaction between singlet-fission-induced correlated triplets in tetracene crystals by monitoring quantum beats relevant to the multiexciton sublevels at room temperature. The resonances of multiexciton sublevels approached by tuning an external magnetic field are observed to be avoided, which agrees well with the theoretical predictions considering a magnetic dipolar interaction of ~0.008 GHz. Our work quantifies the magnetic dipolar interaction in certain organic materials and marks an important step towards understanding the underlying physics of the multiexciton state in singlet fission.

  18. Renormalizing Chiral Nuclear Forces: Triplet Channels

    E-print Network

    Bingwei Long; Chieh-Jen Yang

    2012-03-14

    We discuss the subleading contact interactions, or counterterms, of the triplet channels of nucleon-nucleon scattering in the framework of chiral effective field theory, with S and P waves as the examples. The triplet channels are special in that they allow the singular attraction of one-pion exchange to modify Weinberg's original power counting (WPC) scheme. With renormalization group invariance as the constraint, our power counting for the triplet channels can be summarized as a modified version of naive dimensional analysis in which, when compared with WPC, all of the counterterms in a given partial wave (leading or subleading) are enhanced by the same amount. More specifically, this means that WPC needs no modification in 3S1-3D1 and 3P1, whereas a two-order enhancement is necessary in both 3P0 and 3P2 - 3F2.

  19. Ultrabright fluorescent OLEDS using triplet sinks

    DOEpatents

    Zhang, Yifan; Forrest, Stephen R; Thompson, Mark

    2013-06-04

    A first device is provided. The first device further comprises an organic light emitting device. The organic light emitting device further comprises an anode, a cathode, and an emissive layer disposed between the anode and the cathode. The emissive layer further comprises an organic host compound, an organic emitting compound capable of fluorescent emission at room temperature, and an organic dopant compound. The triplet energy of the dopant compound is lower than the triplet energy of the host compound. The dopant compound does not strongly absorb the fluorescent emission of the emitting compound.

  20. Ground state charmed meson spectra for N_f=2+1+1

    E-print Network

    Rae, T D

    2015-01-01

    We present a preliminary study of the charmed meson spectra using the electrically neutral subset of the new Budapest-Marseille-Wuppertal N_f=2+1+1 gauge configurations that utilise the 3-HEX smeared clover action. The analysis is performed with a focus on the hyperfine splitting.

  1. Ground state charmed meson spectra for N_f=2+1+1

    E-print Network

    T. D. Rae; S. Durr

    2015-09-08

    We present a preliminary study of the charmed meson spectra using the electrically neutral subset of the new Budapest-Marseille-Wuppertal N_f=2+1+1 gauge configurations that utilise the 3-HEX smeared clover action. The analysis is performed with a focus on the hyperfine splitting.

  2. FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

    E-print Network

    Le Roy, Robert J.

    , Jenning Y. Seto, Tsuyoshi Hirao, Peter F. Bernath, and Robert J. Le Roy Guelph­Waterloo Centre allows for the presence of atomic mass-dependent Born­ Oppenheimer breakdown terms, and (ii) a "direct for Born­Oppenheimer breakdown terms. II. EXPERIMENTAL The high-resolution infrared emission spectra of Ge

  3. Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states

    NASA Astrophysics Data System (ADS)

    Pinjari, Rahul V.; Delcey, Mickaël G.; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

    2014-09-01

    The metal L-edge (2p ? 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d5) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6]3- with ligand donor bonding, and low-spin [Fe(CN)6]3- that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

  4. Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states

    SciTech Connect

    Pinjari, Rahul V.; Delcey, Mickaël G.; Guo, Meiyuan; Lundberg, Marcus; Odelius, Michael

    2014-09-28

    The metal L-edge (2p ? 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d{sup 5}) model systems with well-known electronic structure, viz., atomic Fe{sup 3+}, high-spin [FeCl{sub 6}]{sup 3?} with ligand donor bonding, and low-spin [Fe(CN){sub 6}]{sup 3?} that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

  5. Calcium triplet metallicity calibration for stars in the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Vásquez, S.; Zoccali, M.; Hill, V.; Gonzalez, O. A.; Saviane, I.; Rejkuba, M.; Battaglia, G.

    2015-08-01

    Aims: We present a new calibration of the calcium II triplet equivalent widths versus [Fe/H], constructed upon K giant stars in the Galactic bulge. This calibration will be used to derive iron abundances for the targets of the GIBS survey, and is in general especially well suited for solar and supersolar metallicity giants, which are typical of external massive galaxies. Methods: About 150 bulge K giants were observed with the GIRAFFE spectrograph at the VLT with a resolution of R ~ 20 000 and at R ~ 6000. In the first case, the spectra allowed us to directly determine the Fe abundances from several unblended Fe lines, deriving what we call here high-resolution [Fe/H] measurements. The low-resolution spectra allowed us to measure equivalent widths of the two strongest lines of the near-infrared calcium II triplet at 8542 and 8662 Å. Results: By comparing the two measurements, we derived a relation between calcium equivalent widths and [Fe/H] that is linear over the metallicity range probed here, - 1 < [Fe/H] < +0.7. By adding a small second-order correction based on literature globular cluster data, we derived the unique calibration equation [Fe/H] CaT = -3.150 + 0.432W' + 0.006W'2, with an rms dispersion of 0.197 dex, valid across the whole metallicity range -2.3 < [Fe/H] < +0.7. Based on observations taken with ESO telescopes at the La Silla Paranal Observatory under programme ID 385.B-0735(B).Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A121

  6. Triplet annihilation exceeding spin statistical limit in highly efficient fluorescent organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kondakov, D. Y.; Pawlik, T. D.; Hatwar, T. K.; Spindler, J. P.

    2009-12-01

    We have demonstrated that the exemplary red fluorescent organic light-emitting diodes (OLEDs) gain as much as half of their electroluminescence from annihilation of triplet states generated by recombining charge carriers. The magnitude of triplet-triplet annihilation (TTA) contribution in combination with the remarkably high total efficiencies [>11% external quantum efficiency (EQE)] indicates that the absolute amount of electroluminescence attributable to TTA substantially exceeds the limit imposed by spin statistics, which was independently confirmed by studying magnetic field effects on delayed luminescence. We determined the value of 1.3 for the ratio of the rate constants of singlet and triplet channels of annihilation, which is indeed substantially higher than the value of 0.33 expected for a purely statistical annihilation process. It is, however, in an excellent quantitative agreement with the extent of the experimental contribution of delayed luminescence to steady-state electroluminescence. The nonstatistical branching ratio of the two annihilation channels is attributed to the favorable relationship between the energies of the excited singlet and triplet states of rubrene—emissive layer host. We surmise that, with the appropriate emissive layer materials, the fluorescent OLED devices are capable of using a considerably larger fraction of triplet states than was previously believed. In principle, the upper limit for the singlet excited state yield in the TTA process is 0.5, which makes the maximum internal quantum efficiency of fluorescent OLEDs to be 25%+0.5×75%=62.5%. The estimates of maximum EQE of the fluorescent OLEDs should be revised to at least 0.2×62.5%=12.5% and, likely, even higher to account for optical outcoupling exceeding 0.2.

  7. Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene

    PubMed Central

    Pharr, Caroline R.; Kopff, Laura A.; Bennett, Brian; Reid, Scott A.; McMahon, Robert J.

    2014-01-01

    Photolysis (? > 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N2 at 10 K, yields triplet 3-thienylcarbene (13) and ?-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cm?1, |E/hc| = 0.0554 cm?1; |D/hc| = 0.579 cm?1, |E/hc| = 0.0315 cm?1). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding ? orbital between sulfur and the neighboring carbon—an interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (?max = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C5H4S or C5H4O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively). PMID:22463599

  8. Collision-induced light scattering spectra and ground state potential of gaseous xenon

    NASA Astrophysics Data System (ADS)

    Abdel Kader, Mohamed Sayed

    2008-09-01

    Polarized and depolarized collision-induced light scattering spectra of xenon gas at room temperature 295 K with the pressure second virial coefficients, viscosity and thermal conductivity have been used for deriving the empirical models of the pair-polarizability trace and anisotropy and the interaction potential. Theoretical zeroth and second moments of the binary spectra using various models for the pair polarizabilities and interatomic potential are compared with the experimental values performed by Frommhold's group. In addition, vibrational energy levels, self diffusion coefficients and second virial dielectric constants calculated for these models are compared with experimental ones. The results show that these models are the most accurate models reported to date for this system.

  9. One Interesting Family of Diophantine Triplets

    ERIC Educational Resources Information Center

    Deshpande, M. N.

    2002-01-01

    In this note properties of two sequences generated by the recurrence relation G[subscript n] +2 = 4 G[subscript n] +1 - G[subscript n], are studied. It is shown that one of the sequences leads to a family of diophantine triplets. Some interesting properties of these sequences are also established.

  10. J. Phys. Chem. 1990, 94, 6963-6969 6963 Singlet-Triplet Energy Gaps in Chlorine-Substituted Methylenes and Silylenest

    E-print Network

    Goddard III, William A.

    J. Phys. Chem. 1990, 94, 6963-6969 6963 Singlet-Triplet Energy Gaps in Chlorine: August 11. 1989; In Final Form: March 12, 1990) The singlet-triplet splittingsof chlorine-consistentconfiguration interaction (DCCI) method. All chlorine-substituted methylenes and silylenes have singlet ground states

  11. How disorder controls the kinetics of triplet charge recombination in semiconducting organic polymer photovoltaics.

    PubMed

    Bittner, Eric R; Lankevich, Vladimir; Gélinas, Simon; Rao, Akshay; Ginger, David A; Friend, Richard H

    2014-10-14

    Recent experiments by Rao et al. (Nature, 2013, 500, 435-439) indicate that recombination of triplet charge-separated states is suppressed in organic polymer-fullerene based bulk-heterojunction (BHJ) photovoltaic cells exhibiting a high degree of crystallinity in the fullerene phase relative to systems with more disorder. In this paper, we use a series of Frenkel-exciton lattice models to rationalize these results in terms of wave-function localization, interface geometry, and density of states. In one-dimensional co-linear and co-facial models of the interface, increasing local energetic disorder in one phase localizes the interfacial triplet charge-transfer ((3)CT) states and increases the rate at which these states relax to form lower-energy triplet excitons. In two dimensional BHJ models, energetic disorder within the fullerene phase plays little role in further localizing states pinned to the interface. However, inhomogeneous broadening introduces strong coupling between the interfacial (3)CT and nearby fullerene triplet excitons and can enhance the decay of these states in systems with higher degrees of energetic disorder. PMID:24922118

  12. Spectral Assignments and Analysis of the Ground State of Nitromethane in High-Resolution FTIR Synchrotron Spectra

    NASA Astrophysics Data System (ADS)

    Twagirayezu, Sylvestre; Billinghurst, Brant E.; May, Tim E.; Dawadi, Mahesh B.; Perry, David S.

    2014-06-01

    The Fourier Transform infrared spectra of CH3NO2, have been recorded, in the 400-950 wn spectral region, at a resolution of 0.00096 wn, using the Far-Infrared Beamline at Canadian Light Source. The observed spectra contain four fundamental vibrations: the NO2 in-plane rock (475.2 wn), the NO2 out-of-plane rock (604.9 wn), the NO2 symmetric bend (657.1 wn), and the CN-stretch (917.2 wn). For the lowest torsional state of CN-stretch and NO2 in-plane rock, transitions involving quantum numbers, " = 0; " {? 50} and {_a}" {? 10}, have been assigned with the aid of an automated ground state combination difference program together with a traditional Loomis Wood approach Ground state combination differences derived from more than 2100 infrared transitions have been fit with the six-fold torsion-rotation program developed by Ilyushin et al. Additional sextic and octic centrifugal distortion parameters are derived for the ground vibrational state. C. F. Neese., An Interactive Loomis-Wood Package, V2.0, {56th},OSU Interanational Symposium on Molecular Spectroscopy (2001). V. V. Ilyushin, Z. Kisiel, L. Pszczolkowski, H. Mader, and J. T. Hougen, J. Mol. Spectrosc., 259, 26, (2010).

  13. Improved Cell Typing by Charge-State Deconvolution of matrix-assisted laser desorption/ionization Mass Spectra

    SciTech Connect

    Wilkes, Jon G.; Buzantu, Dan A.; Dare, Diane J.; Dragan, Yvonne P.; Chiarelli, M. Paul; Holland, Ricky D.; Beaudoin, Michael; Heinze, Thomas M.; Nayak, Rajesh; Shvartsburg, Alexandre A.

    2006-05-30

    Robust, specific, and rapid identification of toxic strains of bacteria and viruses, to guide the mitigation of their adverse health effects and optimum implementation of other response actions, remains a major analytical challenge. This need has driven the development of methods for classification of microorganisms using mass spectrometry, particularly matrix-assisted laser desorption ionization MS (MALDI) that allows high throughput analyses with minimum sample preparation. We describe a novel approach to cell typing based on pattern recognition of MALDI spectra, which involves charge-state deconvolution in conjunction with a new correlation analysis procedure. The method is applicable to both prokaryotic and eukaryotic cells. Charge-state deconvolution improves the quantitative reproducibility of spectra because multiply-charged ions resulting from the same biomarker attaching a different number of protons are recognized and their abundances are combined. This allows a clearer distinction of bacterial strains or of cancerous and normal liver cells. Improved class distinction provided by charge-state deconvolution was demonstrated by cluster spacing on canonical variate score charts and by correlation analyses. Deconvolution may enhance detection of early disease state or therapy progress markers in various tissues analyzed by MALDI.

  14. Calculation of absorption spectra involving multiple excited states: Approximate methods based on the mixed quantum classical Liouville equation

    SciTech Connect

    Bai, Shuming; Xie, Weiwei; Zhu, Lili; Shi, Qiang

    2014-02-28

    We investigate the calculation of absorption spectra based on the mixed quantum classical Liouville equation (MQCL) methods. It has been shown previously that, for a single excited state, the averaged classical dynamics approach to calculate the linear and nonlinear spectroscopy can be derived using the MQCL formalism. This work focuses on problems involving multiple coupled excited state surfaces, such as in molecular aggregates and in the cases of coupled electronic states. A new equation of motion to calculate the dipole-dipole correlation functions within the MQCL formalism is first presented. Two approximate methods are then proposed to solve the resulted equations of motion. The first approximation results in a mean field approach, where the nuclear dynamics is governed by averaged forces depending on the instantaneous electronic states. A modification to the mean field approach based on first order moment expansion is also proposed. Numerical examples including calculation of the absorption spectra of Frenkel exciton models of molecular aggregates, and the pyrazine molecule are presented.

  15. Electronic structure of some adenosine receptor antagonists. III. Quantitative investigation of the electronic absorption spectra of alkyl xanthines

    NASA Astrophysics Data System (ADS)

    Moustafa, H.; Shalaby, Samia H.; El-sawy, K. M.; Hilal, Rifaat

    2002-07-01

    Quantitative and comparative investigation of the electronic absorption spectra of theophylline, caffeine and their derivatives is reported. The spectra of theophylline, caffeine and theobromine were compared to establish the predominant tautomeric species in solution. This comparison, analysis of solvent effects and assignments of the observed transitions via MO computations indicate the exits of only one tautomeric species in solution that is the N7 form. A low-lying triplet state was identified which corresponds to a HOMO-LUMO transition. This relatively long-lived T 1 state is always less polar than the ground state and may very well underlie the photochemical reactivity of alkyl xanthines. Substituents of different electron donating or withdrawing strengths and solvent effects are investigated and analyzed. The present analysis is facilitated via computer deconvolution of the observed spectra and MO computation.

  16. Sensitized non-coherent photon upconversion by intramolecular triplet-triplet annihilation in a diphenylanthracene pendant polymer

    NASA Astrophysics Data System (ADS)

    Tilley, Andrew J.; Robotham, Benjamin E.; Steer, Ronald P.; Ghiggino, Kenneth P.

    2015-01-01

    Non-coherent photon upconversion by rapid intramolecular triplet-triplet annihilation has been observed following nanosecond laser excitation of Ru(dmb)3 and sequential two-fold triplet energy sensitization of a polymer containing 30 pendant diphenylanthracene groups. A global kinetic analysis of the system has been performed; the intramolecular annihilation step occurs on a sub-nanosecond time scale.

  17. Vibrational overtone spectra of N-H stretches and intramolecular dynamics on the ground and electronically excited states of methylamine

    SciTech Connect

    Marom, Ran; Zecharia, Uzi; Rosenwaks, Salman; Bar, Ilana

    2008-04-21

    The vibrational pattern and energy flow in the N-H stretch manifolds and the dissociation dynamics of methylamine (CH{sub 3}NH{sub 2}) were investigated via vibrationally mediated photodissociation. Action spectra and Doppler profiles, reflecting the yield of the ensuing H photofragments, versus near infrared/visible vibrational excitation and UV excitation, respectively, were measured. The jet-cooled action spectra and the simultaneously measured room temperature photoacoustic spectra of the first to third N-H stretching overtones exhibit broad features, somewhat narrower in the former, consisting of barely recognized multiple bands. Two phases of fitting of the spectroscopic data were performed. In the first phase, the raw data were analyzed to obtain band positions, types, intensities, and transition linewidths. In the second, the information derived from the first phase was then used as data in a fit to joint local mode/normal mode (LM/NM) and NM Hamiltonian parameters. The derived parameters predicted well band positions and allowed band assignment. The LM/NM Hamiltonian and the extracted Lorentzian linewidths enabled the determination of the initial pathways for energy redistribution and the overall temporal behavior of the N-H stretch and doorway states, as a result of Fermi couplings and interactions with bath states. The results indicate a nonstatistical energy flow in the V=2 manifold region, pointing to the dependence of the coupling on specific low order resonances rather than on the total density of bath states. The Doppler profiles suggest lower average translational energies for the released H photofragments, in particular, for V=3 and 4 as compared to V=1 and 2, implying a change in the mechanism for bond cleavage.

  18. Toward Singlet-Triplet Bistable Nonalternant Kekulé Hydrocarbons: Azulene-to-Naphthalene Rearrangement.

    PubMed

    Das, Soumyajit; Wu, Jishan

    2015-12-01

    Recent developments of open-shell singlet diradicaloids motivated the search for stable singlet-triplet bistable nonalternant polycyclic hydrocarbons. During the synthesis of this type of molecule, such as the dibenzo-cyclohepta[def]fluorene 3, an unexpected azulene-to-naphthalene rearrangement was observed at room temperature, which resulted in new nonalternant hydrocarbons 8a/8b with a closed-shell singlet ground state. These studies provided insight into the unique chemistry of azulene and challenges for the synthesis of singlet-triplet bistable polycyclic hydrocarbons. PMID:26569547

  19. Singlet-Triplet Excitations in the Unconventional Spin-Peierls TiOBr Compound

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gaulin, B. D.; Adams, C. P.; Granroth, G. E.; Kolesnikov, A. I.; Sherline, T. E.; Chou, F. C.

    2011-03-01

    We have performed time-of-flight neutron scattering measurements on powder samples of the unconventional spin-Peierls compound TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the Spallation Neutron Source at Oak Ridge National Laboratory. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate spin-Peierls phases, which we associate with n=1 and n=2 triplet excitations out of the singlet ground state. These results represent the first direct measurement of the singlet-triplet energy gap in TiOBr, which has a value of Eg=21.2±1.0meV.

  20. Singlet-to-Triplet Excitations in the Unconventional Spin-Peierls System TiOBr

    SciTech Connect

    Clancy, James P; Gaulin, Bruce D.; Adams, Carl P; Granroth, Garrett E; Kolesnikov, Alexander I; Sherline, Todd E; Chou, F. C.

    2011-01-01

    We have performed time-of-flight neutron scattering measurements on powder samples of the unconventional spin-Peierls compound TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the SNS. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate spin-Peierls phases, which we associate with n = 1 and n = 2 triplet excitations out of the singlet ground state. These measurements represent the first direct measure of the singlet-triplet energy gap in TiOBr, which is found to have a value of Eg 21 meV.

  1. 1H NMR z-spectra of acetate methyl in stretched hydrogels: Quantum-mechanical description and Markov chain Monte Carlo relaxation-parameter estimation

    NASA Astrophysics Data System (ADS)

    Shishmarev, Dmitry; Chapman, Bogdan E.; Naumann, Christoph; Mamone, Salvatore; Kuchel, Philip W.

    2015-01-01

    The 1H NMR signal of the methyl group of sodium acetate is shown to be a triplet in the anisotropic environment of stretched gelatin gel. The multiplet structure of the signal is due to the intra-methyl residual dipolar couplings. The relaxation properties of the spin system were probed by recording steady-state irradiation envelopes ('z-spectra'). A quantum-mechanical model based on irreducible spherical tensors formed by the three magnetically equivalent spins of the methyl group was used to simulate and fit experimental z-spectra. The multiple parameter values of the relaxation model were estimated by using a Bayesian-based Markov chain Monte Carlo algorithm.

  2. EMITTING ELECTRONS SPECTRA AND ACCELERATION PROCESSES IN THE JET OF Mrk 421: FROM THE LOW STATE TO THE GIANT FLARE STATE

    SciTech Connect

    Yan Dahai; Zhang Li; Fan Zhonghui; Zeng Houdun; Yuan Qiang

    2013-03-10

    We investigate the electron energy distributions (EEDs) and the acceleration processes in the jet of Mrk 421 through fitting the spectral energy distributions (SEDs) in different active states in the frame of a one-zone synchrotron self-Compton model. After assuming two possible EEDs formed in different acceleration models: the shock-accelerated power law with exponential cut-off (PLC) EED and the stochastic-turbulence-accelerated log-parabolic (LP) EED, we fit the observed SEDs of Mrk 421 in both low and giant flare states using the Markov Chain Monte Carlo method which constrains the model parameters in a more efficient way. The results from our calculations indicate that (1) the PLC and LP models give comparably good fits for the SED in the low state, but the variations of model parameters from low state to flaring can be reasonably explained only in the case of the PLC in the low state; and (2) the LP model gives better fits compared to the PLC model for the SED in the flare state, and the intra-day/night variability observed at GeV-TeV bands can be accommodated only in the LP model. The giant flare may be attributed to the stochastic turbulence re-acceleration of the shock-accelerated electrons in the low state. Therefore, we may conclude that shock acceleration is dominant in the low state, while stochastic turbulence acceleration is dominant in the flare state. Moreover, our result shows that the extrapolated TeV spectra from the best-fit SEDs from optical through GeV with the two EEDs are different. It should be considered with caution when such extrapolated TeV spectra are used to constrain extragalactic background light models.

  3. Triplet Superconductivity in the One-Dimensional Hubbard Model with Modulated Kinetic Hopping at Weak Coupling

    NASA Astrophysics Data System (ADS)

    Ding, Hanqin; Zhang, Jun

    2015-12-01

    We construct a theoretical model for one-dimensional interacting electrons by modulating electronic kinetic hopping in the weak-coupling regime. The use of bosonization and renormalization group analysis allows us to obtain the phase diagram. The induced three-body attraction gives rise to a triplet superconducting phase in the ground state.

  4. Delayed interval delivery in a triplet gestation

    PubMed Central

    Wooldridge, Rachel J; Oliver, Emily A; Singh, Tulika

    2012-01-01

    A 27-year-old Ghanaian primigravida with a known triamniotic trichorionic triplet pregnancy presented at 17?weeks gestation following a miscarriage of one triplet at home. Examination and investigation revealed no signs of imminent delivery or infection. After careful counselling with regard to prognosis and options available for management, the couple opted for intervention including rescue cerclage. The patient received antibiotic prophylaxis for five?days and daily progesterone suppositories until delivery. An ultrasound scan was performed every three?weeks to monitor fetal growth and cervical length. At 24?weeks corticosteroids for fetal lung maturity were given. At 31?weeks gestation she experienced spontaneous rupture of membranes followed by active labour and forceps delivery. There were no maternal complications. Both babies were born in a good condition, but required ventilatory support for 72?h. PMID:23188854

  5. Delayed interval delivery in a triplet gestation.

    PubMed

    Wooldridge, Rachel J; Oliver, Emily A; Singh, Tulika

    2012-01-01

    A 27-year-old Ghanaian primigravida with a known triamniotic trichorionic triplet pregnancy presented at 17 weeks gestation following a miscarriage of one triplet at home. Examination and investigation revealed no signs of imminent delivery or infection. After careful counselling with regard to prognosis and options available for management, the couple opted for intervention including rescue cerclage. The patient received antibiotic prophylaxis for five days and daily progesterone suppositories until delivery. An ultrasound scan was performed every three weeks to monitor fetal growth and cervical length. At 24 weeks corticosteroids for fetal lung maturity were given. At 31 weeks gestation she experienced spontaneous rupture of membranes followed by active labour and forceps delivery. There were no maternal complications. Both babies were born in a good condition, but required ventilatory support for 72 h. PMID:23188854

  6. EASY-GOING deconvolution: Combining accurate simulation and evolutionary algorithms for fast deconvolution of solid-state quadrupolar NMR spectra

    NASA Astrophysics Data System (ADS)

    Grimminck, Dennis L. A. G.; Polman, Ben J. W.; Kentgens, Arno P. M.; Leo Meerts, W.

    2011-08-01

    A fast and accurate fit program is presented for deconvolution of one-dimensional solid-state quadrupolar NMR spectra of powdered materials. Computational costs of the synthesis of theoretical spectra are reduced by the use of libraries containing simulated time/frequency domain data. These libraries are calculated once and with the use of second-party simulation software readily available in the NMR community, to ensure a maximum flexibility and accuracy with respect to experimental conditions. EASY-GOING deconvolution ( EGdeconv) is equipped with evolutionary algorithms that provide robust many-parameter fitting and offers efficient parallellised computing. The program supports quantification of relative chemical site abundances and (dis)order in the solid-state by incorporation of (extended) Czjzek and order parameter models. To illustrate EGdeconv's current capabilities, we provide three case studies. Given the program's simple concept it allows a straightforward extension to include other NMR interactions. The program is available as is for 64-bit Linux operating systems.

  7. Electronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study.

    PubMed

    Arulmozhiraja, Sundaram; Coote, Michelle L; Hasegawa, Jun-Ya

    2015-11-28

    Electronic structures of azaindole were studied using symmetry-adapted cluster configuration interaction theory utilizing Dunning's cc-pVTZ basis set augmented with appropriate Rydberg spd functions on carbon and nitrogen atoms. The results obtained in the present study show good agreement with the available experimental values. Importantly, and contrary to previous theoretical studies, the excitation energy calculated for the important n-?(?) state agrees well with the experimental value. A recent study by Pratt and co-workers concluded that significant mixing of ?-?(?) and n-?(?) states leads to major change in the magnitude and direction of the dipole moment of the upper state vibrational level in the 0,0 + 280 cm(-1) band in the S1?S0 transition when compared to that of the zero-point level of the S1 state. The present study, however, shows that all the four lowest lying excited states, (1)Lb ?-?(?), (1)La ?-?(?), n-?(?), and ?-?(?), cross each other in one way or another, and hence, significant state mixing between them is likely. The upper state vibrational level in the 0,0 + 280 cm(-1) band in the S1?S0 transition benefits from this four-state mixing and this can explain the change in magnitude and direction of the dipole moment of the S1 excited vibrational level. This multistate mixing, and especially the involvement of ?-?(?) state in mixing, could also provide a route for hydrogen atom detachment reactions. The electronic spectra of benzimidazole, a closely related system, were also investigated in the present study. PMID:26627956

  8. Electronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study

    NASA Astrophysics Data System (ADS)

    Arulmozhiraja, Sundaram; Coote, Michelle L.; Hasegawa, Jun-ya

    2015-11-01

    Electronic structures of azaindole were studied using symmetry-adapted cluster configuration interaction theory utilizing Dunning's cc-pVTZ basis set augmented with appropriate Rydberg spd functions on carbon and nitrogen atoms. The results obtained in the present study show good agreement with the available experimental values. Importantly, and contrary to previous theoretical studies, the excitation energy calculated for the important n-?? state agrees well with the experimental value. A recent study by Pratt and co-workers concluded that significant mixing of ?-?? and n-?? states leads to major change in the magnitude and direction of the dipole moment of the upper state vibrational level in the 0,0 + 280 cm-1 band in the S1?S0 transition when compared to that of the zero-point level of the S1 state. The present study, however, shows that all the four lowest lying excited states, 1Lb ?-??, 1La ?-??, n-??, and ?-??, cross each other in one way or another, and hence, significant state mixing between them is likely. The upper state vibrational level in the 0,0 + 280 cm-1 band in the S1?S0 transition benefits from this four-state mixing and this can explain the change in magnitude and direction of the dipole moment of the S1 excited vibrational level. This multistate mixing, and especially the involvement of ?-?? state in mixing, could also provide a route for hydrogen atom detachment reactions. The electronic spectra of benzimidazole, a closely related system, were also investigated in the present study.

  9. Twin and Triplet Drugs in Opioid Research

    NASA Astrophysics Data System (ADS)

    Fujii, Hideaki

    Twin and triplet drugs are defined as compounds that contain respectively two and three pharmacophore components exerting pharmacological effects in a molecule. The twin drug bearing the same pharmacophores is a "symmetrical twin drug", whereas that possessing different pharmacophores is a "nonsymmetrical twin drug." In general, the symmetrical twin drug is expected to produce more potent and/or selective pharmacological effects, whereas the nonsymmetrical twin drug is anticipated to show both pharmacological activities stemming from the individual pharmacophores (dual action). On the other hand, nonsymmetrical triplet drugs, which have two of the same pharmacophores and one different moiety, are expected to elicit both increased pharmacological action and dual action. The two identical portions could bind the same receptor sites simultaneously while the third portion could bind a different receptor site or enzyme. This review will mainly focus on the twin and triplet drugs with an evaluation of their in vivo pharmacological effects, and will also include a description of their pharmacology and synthesis.

  10. Nucleon, Delta and Omega excited state spectra at three pion mass values

    E-print Network

    John Bulava; Robert G. Edwards; Bálint Joó; David G. Richards; Eric Engelson; Huey-Wen Lin; Colin Morningstar; Stephen J. Wallace

    2010-11-05

    The energies of the excited states of the Nucleon, Delta and Omega are computed in lattice QCD, using two light quarks and one strange quark on anisotropic lattices. The calculations are performed at three values of the pion mass: 392(4), 438(3) and 521(3) MeV. We employ the variational method with a basis of about ten interpolating operators enabling six energies to be distinguished clearly in each irreducible representation of the octahedral group. We compare our calculations of nucleon excited states with the low-lying experimental spectrum. There is reasonable agreement for the pattern of states.

  11. Nucleon, Delta and Omega excited state spectra at three pion mass values

    SciTech Connect

    John Bulava, Robert G. Edwards, Balint Joo, David G. Richards, Eric Engelson, Huey-Wen Lin, Colin Morningstar, Stephen J. Wallace

    2010-06-01

    The energies of the excited states of the Nucleon, Delta and Omega are computed in lattice QCD, using two light quarks and one strange quark on anisotropic lattices. The calculations are performed at three values of the pion mass: 392(4), 438(3) and 521(3) MeV. We employ the variational method with a basis of about ten interpolating operators enabling six energies to be distinguished clearly in each irreducible representation of the octahedral group. We compare our calculations of nucleon excited states with the low-lying experimental spectrum. There is reasonable agreement for the pattern of states.

  12. Electronic spectra and excited-state dynamics of 4-fluoro-N,N-dimethylaniline

    NASA Astrophysics Data System (ADS)

    Fujiwara, Takashige; Reichardt, Christian; Aaron Vogt, R.; Crespo-Hernández, Carlos E.; Zgierski, Marek Z.; Lim, Edward C.

    2013-10-01

    Concerted ultrafast time-resolved spectroscopic experiments and ab initio computational (TDDFT) studies of the electronic transitions of 4-fluoro-N,N-dimethylaniline (FDMA) have been performed to investigate the mechanism of photo-induced intramolecular charge transfer (ICT). The compound FDMA shows dual fluorescence from a ??? state and a closely-lying twisted intramolecular charge transfer (TICT) state in both n-hexane and acetonitrile. The very similar lifetimes observed for the two emission bands indicate that the ??? and the TICT states are effectively in thermal equilibrium at room temperature.

  13. Density of states and tunneling spectra in two-dimensional d-wave superconductors

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Schulz, H. J.

    1992-04-01

    The quasiparticle density of states is discussed in the framework of d-wave superconductivity, and the corresponding superconductor-insulator-superconductor tunneling conductivity ?(V) is obtained. We find a quadratic increase of ?(V) at low voltage and two maxima at higher voltage. These features are in qualitative agreement with recent experimental findings of Forro et al. An s-wave state also gives rise to a double-peak structure, but no quadratic low-voltage behavior is found.

  14. Composite spectra: XX. 45 Cancri. Two stars with very similar masses but quite different evolutionary states

    NASA Astrophysics Data System (ADS)

    Griffin, R. E. M.; Griffin, R. F.

    2015-02-01

    From accurate radial-velocity measurements covering 11 circuits of the orbit of the composite-spectrum binary 45 Cnc, together with high-resolution spectroscopy spanning nearly 3 circuits, we have (i) isolated cleanly the spectrum of the early-type secondary, (ii) classified the component spectra as G8 III and A3 III, (iii) derived the first double-lined orbit for the system and a mass ratio (M_1/M_2) of 1.035 ± 0.01, and (iv) extracted physical parameters for the component stars, deriving the masses and (log) luminosities of the G star and A star as 3.11 and 3.00 M?} R?, and 2.34 and 2.28 L?, respectively, with corresponding uncertainties of ±0.10 M? R? and ±0.09 L?. Since the mass ratio is close to unity, we argue that the more evolved component is unlikely to have been a red giant long enough to have made multiple ascents of the RGB, an argument that is supported somewhat by the rather high eccentricity of the orbit (e = 0.46) and the evolutionary time-scales of the two components, but chiefly by the presence of significant Li I in the spectrum of the cool giant.

  15. Triplet-triplet annihilation upconversion followed by FRET for the red light activation of a photodissociative ruthenium complex in liposomes.

    PubMed

    Askes, Sven H C; Kloz, Miroslav; Bruylants, Gilles; Kennis, John T M; Bonnet, Sylvestre

    2015-10-14

    Upconversion is a promising way to trigger high-energy photochemistry with low-energy photons. However, combining upconversion schemes with non-radiative energy transfer is challenging because bringing several photochemically active components in close proximity results in complex multi-component systems where quenching processes may deactivate the whole assembly. In this work, PEGylated liposomes were prepared that contained three photoactive components: a porphyrin dye absorbing red light, a perylene moiety emitting in the blue, and a light-activatable ruthenium prodrug sensitive to blue light. Time-dependent spectroscopic studies demonstrate that singlet perylene excited states are non-radiatively transferred to the nearby ruthenium complex by Förster resonance energy transfer (FRET). Under red-light irradiation of the three-component membranes, triplet-triplet annihilation upconversion (TTA-UC) occurs followed by FRET, which results in a more efficient activation of the ruthenium prodrug compared to a physical mixture of two-component upconverting liposomes and liposomes containing only the ruthenium complex. This work represents a rare example where TTA-UC and Förster resonance energy transfer are combined to achieve prodrug activation in the phototherapeutic window. PMID:26420663

  16. Coherent transient in dressed-state and transient spectra of Autler-Townes doublet

    SciTech Connect

    Zhang Lianshui; Feng Xiaomin; Fu Guangsheng; Li Xiaowei; Han Li; Manson, Neil B.; Wei Changjiang

    2004-12-01

    In this paper we present a theoretical study of the time-dependent probe response in the presence of a strong pump field in a three-level pump-probe configuration. Two situations are investigated: a cw pump with a pulsed probe field and a pulsed pump with a cw probe field. The results are explained as dressed-state nutation and nutation by dynamic Stark switching. Dressed-state quantum beats are also an important feature for both situations. Furthermore, when a 90 deg. phase shift after a {pi}/2 period is introduced in the pulsed probe field, there is a spin locking in the dressed-state transition. Our results give a satisfactory theoretical account of a previous experimental observation [Wei et al., Phys. Rev. Lett. 74, 1083 (1995)].

  17. Quasiparticle energies, excitons, and optical spectra of few-layer black phosphorus

    NASA Astrophysics Data System (ADS)

    Tran, Vy; Fei, Ruixiang; Yang, Li

    2015-12-01

    We report first-principles GW–Bethe–Salpeter-equation (BSE) studies of excited-state properties of few-layer black phosphorus (BP) (phosphorene). With improved GW computational methods, we obtained converged quasiparticle band gaps and optical absorption spectra by the single-shot (G0W0) procedure. Moreover, we reveal fine structures of anisotropic excitons, including the series of one-dimensional like wave functions, spin singlet–triplet splitting, and electron–hole binding energy spectra by solving BSE. An effective-mass model is employed to describe these electron–hole pairs, shedding light on estimating the exciton binding energy of anisotropic two-dimensional semiconductors without expensive ab initio simulations. Finally, the anisotropic optical response of BP is explained by using optical selection rules based on the projected single-particle density of states at band edges.

  18. Rydberg-Blockade Effects in Autler-Townes Spectra of Ultracold Strontium

    E-print Network

    B. J. DeSalvo; J. A. Aman; C. Gaul; T. Pohl; S. Yoshida; J. Burgdörfer; K. R. A. Hazzard; F. B. Dunning; T. C. Killian

    2015-10-27

    We present a combined experimental and theoretical study of the effects of Rydberg interactions on Autler-Townes spectra of ultracold gases of atomic strontium. Realizing two-photon Rydberg excitation via a long-lived triplet state allows us to probe the thus far unexplored regime where Rydberg state decay presents the dominant decoherence mechanism. The effects of Rydberg interactions are observed in shifts, asymmetries, and broadening of the measured atom-loss spectra. The experiment is analyzed within a one-body density matrix approach, accounting for interaction-induced level shifts and dephasing through nonlinear terms that approximately incorporate correlations due to the Rydberg blockade. This description yields good agreement with our experimental observations for short excitation times. For longer excitation times, the loss spectrum is altered qualitatively, suggesting additional dephasing mechanisms beyond the standard blockade mechanism based on pure van der Waals interactions.

  19. Rydberg-Blockade Effects in Autler-Townes Spectra of Ultracold Strontium

    E-print Network

    DeSalvo, B J; Gaul, C; Pohl, T; Yoshida, S; Burgdörfer, J; Hazzard, K R A; Dunning, F B; Killian, T C

    2015-01-01

    We present a combined experimental and theoretical study of the effects of Rydberg interactions on Autler-Townes spectra of ultracold gases of atomic strontium. Realizing two-photon Rydberg excitation via a long-lived triplet state allows us to probe the thus far unexplored regime where Rydberg state decay presents the dominant decoherence mechanism. The effects of Rydberg interactions are observed in shifts, asymmetries, and broadening of the measured atom-loss spectra. The experiment is analyzed within a one-body density matrix approach, accounting for interaction-induced level shifts and dephasing through nonlinear terms that approximately incorporate correlations due to the Rydberg blockade. This description yields good agreement with our experimental observations for short excitation times. For longer excitation times, the loss spectrum is altered qualitatively, suggesting additional dephasing mechanisms beyond the standard blockade mechanism based on pure van der Waals interactions.

  20. Exchange interaction between the triplet exciton and the localized spin in copper-phthalocyanine.

    PubMed

    Wu, Wei

    2014-06-14

    Triplet excitonic state in the organic molecule may arise from a singlet excitation and the following inter-system crossing. Especially for a spin-bearing molecule, an exchange interaction between the triplet exciton and the original spin on the molecule can be expected. In this paper, such exchange interaction in copper-phthalocyanine (CuPc, spin-½) was investigated from first-principles by using density-functional theory within a variety of approximations to the exchange correlation, ranging from local-density approximation to long-range corrected hybrid-exchange functional. The magnitude of the computed exchange interaction is in the order of meV with the minimum value (1.5 meV, ferromagnetic) given by the long-range corrected hybrid-exchange functional CAM-B3LYP. This exchange interaction can therefore give rise to a spin coherence with an oscillation period in the order of picoseconds, which is much shorter than the triplet lifetime in CuPc (typically tens of nanoseconds). This implies that it might be possible to manipulate the localized spin on Cu experimentally using optical excitation and inter-system crossing well before the triplet state disappears. PMID:24929382

  1. Enhancement of Vibronic and Ground-State Vibrational Coherences in 2D Spectra of Photosynthetic Complexes

    PubMed Central

    Chenu, Aurélia; Christensson, Niklas; Kauffmann, Harald F.; Man?al, Tomáš

    2013-01-01

    A vibronic-exciton model is applied to investigate the recently proposed mechanism of enhancement of coherent oscillations due to mixing of electronic and nuclear degrees of freedom. We study a dimer system to elucidate the role of resonance coupling, site energies, vibrational frequency and energy disorder in the enhancement of vibronic-exciton and ground-state vibrational coherences, and to identify regimes where this enhancement is significant. For a heterodimer representing two coupled bachteriochloropylls of the FMO complex, long-lived vibronic coherences are found to be generated only when the frequency of the mode is in the vicinity of the electronic energy difference. Although the vibronic-exciton coherences exhibit a larger initial amplitude compared to the ground-state vibrational coherences, we conclude that, due to the dephasing of the former, both type of coherences have a similar magnitude at longer population time. PMID:23778355

  2. Final-State Projection Method in Charge-Transfer Multiplet Calculations: An Analysis of Ti L-Edge Absorption Spectra.

    PubMed

    Kroll, Thomas; Solomon, Edward I; de Groot, Frank M F

    2015-10-29

    A projection method to determine the final-state configuration character of all peaks in a charge transfer multiplet calculation of a 2p X-ray absorption spectrum is presented using a d(0) system as an example. The projection method is used to identify the most important influences on spectral shape and to map out the configuration weights. The spectral shape of a 2p X-ray absorption or L2,3-edge spectrum is largely determined by the ratio of the 2p core-hole interactions relative to the 2p3d atomic multiplet interaction. This leads to a nontrivial spectral assignment, which makes a detailed theoretical description of experimental spectra valuable for the analysis of bonding. PMID:26226507

  3. Correlations between metal spin states and vibrational spectra of a trinuclear Fe(II) complex exhibiting spin crossover

    NASA Astrophysics Data System (ADS)

    Gerasimova, Tatiana P.; Katsyuba, Sergey A.; Lavrenova, Ludmila G.; Pelmenschikov, Vladimir; Kaupp, Martin

    2015-12-01

    Combined IR spectroscopic/quantum-chemical analysis of a 4-propyl-1,2,4-triazole trinuclear Fe(II) complex capable of reversible thermal spin crossover has revealed mid-IR bands of the ligand sensitive to the Fe(II) spin state. The character of the correlations found between the intensity and peak position of the triazole bands and the spin state of the metal center depends neither on the identity of the metal nor on the nuclearity of the complex. The found spectral correlations therefore allow analysis of various similar complexes. This is illustrated by the example of experimental IR spectra reported earlier for Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with triazole ligands. Quantum-chemical IR spectral simulations further suggest that certain ligand bands vary between the states with the same total molecular spin, but different distribution of the spin density between the metal centers. However these variations are too subtle to discriminate between the spin transitions of the central and peripheral Fe(II) ions. The experimentally revealed mid-IR markers are therefore conclusive only for the total molecular spin.

  4. Dressing effects in the attosecond transient absorption spectra of doubly excited states in helium

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Jiménez-Galán, Á.; Marante, C.; Ott, C.; Pfeifer, T.; Martín, F.

    2015-06-01

    Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum (ATAS) of helium dressed by a few-cycle visible pulse [C. Ott et al., Nature (London) 516, 374 (2014), 10.1038/nature14026] provide evidence of the inversion of Fano profiles. With the support of accurate ab initio calculations that reproduce the results of the latter experiment, here we investigate the new physics that arise from ATAS when the laser intensity is increased. In particular, we show that (i) previously unnoticed signatures of the dark 2 p21S doubly excited state are observed in the experimental spectrum, (ii) inversion of Fano profiles is predicted to be periodic in the laser intensity, and (iii) the ac Stark shift of the higher terms in the s p2,n + autoionizing series exceeds the ponderomotive energy, which is the result of a genuine two-electron contribution to the polarization of the excited atom.

  5. Consistency of the triplet seesaw model revisited

    NASA Astrophysics Data System (ADS)

    Bonilla, Cesar; Fonseca, Renato M.; Valle, J. W. F.

    2015-10-01

    Adding a scalar triplet to the Standard Model is one of the simplest ways of giving mass to neutrinos, providing at the same time a mechanism to stabilize the theory's vacuum. In this paper, we revisit these aspects of the type-II seesaw model pointing out that the bounded-from-below conditions for the scalar potential in use in the literature are not correct. We discuss some scenarios where the correction can be significant and sketch the typical scalar boson profile expected by consistency.

  6. Triplet Repeats Replication by 2D-GE 17 ANALYSIS OF TRIPLET REPEAT DNAS AND RNAS

    E-print Network

    Mirkin, Sergei

    repeats in vivo. We analyzed the effects of triplet repeats on replication of bacterial or yeast plasmids electrophoresis; replication fork; replication attenuation; bacterial plasmid; yeast plasmid. 1. Introduction replication fork replicates the whole bacterial plasmid, whereas the yeast plasmid is replicated by two forks

  7. Ruthenium complexes in different oxidation states: synthesis, crystal structure, spectra and redox properties.

    PubMed

    Jab?o?ska-Wawrzycka, Agnieszka; Rogala, Patrycja; Micha?kiewicz, S?awomir; Hodorowicz, Maciej; Barszcz, Barbara

    2013-05-01

    The reactions of a mother solution of RuCl(3) with benzimidazole derivatives 2-(2'-pyridyl)benzimidazole (2,2'-PyBIm, L(1)) and 2-hydroxymethylbenzimidazole (2-CH(2)OHBIm, L(2)) yielded three novel ruthenium complexes: (H(2)L(1))(2)[Ru(III)Cl(4)(CH(3)CN)(2)](2)[Ru(IV)Cl(4)(CH(3)CN)(2)]·2Cl·6H(2)O (1), mer-[Ru(III)Cl(3)L(1)(CH(3)CN)]·L(1)·3H(2)O (2), and (HL(2))(4)[Ru(IV)Cl(6)]·2Cl·4H(2)O (3). The isolated compounds were characterised by elemental analyses, UV-Vis and IR spectroscopy, and magnetic measurements. The nature of the ligands bound to the metal ions of these compounds and the experimental conditions significantly influenced the ruthenium complexes in different oxidation states. The N,N-donor ligand bound to the metal centre is a recognised stabiliser of the +III state of ruthenium, whereas the lack of ligand coordination promotes the formation of a mixed (Ru(III)/Ru(IV)) complex. In the case of complex 3, the absence of a N,O-donor ligand in the coordinate sphere facilitates the formation of the compound in a higher oxidation state. X-ray single crystal analyses revealed an octahedral geometry in each of the complexes. The crystal structure of ruthenium complexes is formed by a network of intermolecular classical and unconventional (C-H···?) hydrogen bonds. The most interesting feature of the supramolecular architecture of complexes is the existence of a very rare Cl(-)···? interaction and ?···? stacking, which also contribute to structural stabilisation. Ruthenium compounds 2 and 3 behave as paramagnets with an octahedral geometry, corresponding to the presence of one or two unpaired electrons, respectively. The cyclic voltammetric data of complex 2 show three one-electron redox processes. The first redox couple is reversible, whereas the two other couples have a quasi-reversible nature. In the case of complex 3, two redox couples are reversible and the electrode processes are connected with exchange of one electron. PMID:23381742

  8. Determination of the Effective Ground State Potential Energy Function of Ozone from High-Resolution Infrared Spectra.

    PubMed

    Tyuterev; Tashkun; Jensen; Barbe; Cours

    1999-11-01

    The effective ground state potential energy function of the ozone molecule near the C(2v) equilibrium configuration was obtained in a least-squares fit to the largest sample of experimental, high-resolution vibration-rotation data used for this purpose so far. The fitting is based on variational calculations carried out with the extended Morse Oscillator Rigid Bender Internal Dynamics model. The potential function is expanded in Morse-type functions of the stretching variables and in cosine of the bending angle. The present calculation produces results in significantly better agreement with experiment than previous determinations of the potential energy surface, and the energies predicted with the new surface are sufficiently accurate to be useful for the assignment of new high-resolution spectra. The rms (root-mean-square) deviation of the fit of rovibrational data up to J = 5 is 0.02 cm(-1). For the set of all 60 band centers of the (16)O(3) molecule included in the Atlas of Ozone Line Parameters, the rms deviation is 0.025 cm(-1), and for all band centers determined so far from high-resolution spectra, including those recently observed and assigned in Reims corresponding to highly excited stretching and bending vibrations (v(1) + v(2) + v(3) = 6), the rms deviation is 0.1 cm(-1). The "dark states" that produce resonance perturbations in the observed bands are described with experimental accuracy up to the (v(1)v(2)v(3)) = (080) state. Extrapolation tests demonstrate the predictive power of the potential function obtained: rotational extrapolation up to J = 10 for the 11 lowest vibrational states results in an rms deviation of 0.06cm(-1). Also, vibrational energies measured by low-resolution Raman spectroscopy (which were not included in the input data for the fit) are calculated within the experimental accuracy (rms = 1.6 cm(-1)) of the experimental values up to the dissociation limit. The statistical analysis suggests that the accuracy of the equilibrium geometry and force constants of the molecule is considerably improved relative to previous determinations. The long-range behavior of the fitted potential at the dissociation limit O(3) --> O(2) + O shows very good agreement with experimental data. The new potential energy surface was used to predict the band centers of the isotopomers (17)O(3) and (18)O(3). Copyright 1999 Academic Press. PMID:10527781

  9. Synchrotron and Compton Spectra from a Steady-State Electron Distribution

    E-print Network

    Rephaeli, Yoel

    2015-01-01

    Energy densities of relativistic electrons and protons in extended galactic and intracluster regions are commonly determined from spectral radio and (rarely) $\\gamma$-ray measurements. The time-independent particle spectral density distributions are commonly assumed to have a power-law (PL) form over the relevant energy range. A theoretical relation between energy densities of electrons and protons is usually adopted, and energy equipartition is invoked to determine the mean magnetic field strength in the emitting region. We show that for typical conditions, in both star-forming and starburst galaxies, these estimates need to be scaled down substantially due to significant energy losses that (effectively) flatten the electron spectral density distribution, resulting in a much lower energy density than deduced when the distribution is assumed to have a PL form. The steady-state electron distribution in the nuclear regions of starburst galaxies is calculated by accounting for Coulomb, bremsstrahlung, Compton, a...

  10. Lowest vibrational states of acrylonitrile from microwave and synchrotron radiation spectra

    NASA Astrophysics Data System (ADS)

    Kisiel, Zbigniew; Martin-Drumel, Marie-Aline; Pirali, Olivier

    2015-09-01

    The high resolution Fourier-transform spectrum of acrylonitrile covering the 40-700 cm-1 spectral region was recorded at the AILES infrared beamline of the SOLEIL synchrotron. The spectrum allowed assignment of vibration-rotation transitions in four different fundamental bands, five hot bands, one overtone band, as well as of some pure rotational transitions. The new infrared data and previous measurements made with microwave techniques have been combined into a single global fit encompassing over 31 000 measured transitions. Precise vibrational term values have been determined for the eight lowest excited vibrational states, including ?11 = 228.299930(4), ?15 = 332.678207(4), ?10 = 560.716701(5), and ?14 = 681.793862 (13) cm-1. The new values are compared with those obtained previously entirely on the basis of rotational perturbations. Several anharmonicity coefficients are determined and compared with ab initio anharmonic force field calculations. The assignment of the ?10 mode is also clarified.

  11. Hindered and modulated rotational states and spectra of adsorbed diatomic molecules

    SciTech Connect

    Shih, Y.T.; Chuu, D.S.; Mei, W.N.

    1996-10-01

    Both vertical and horizontal adsorption configurations of a diatomic molecule were modeled as the rigid rotor with which the spatial motion was confined by a finite conical well. In addition to the polar hindering potential, a sinusoidal azimuthal modulation, which bears the local symmetry of the adsorption site, was incorporated. Eigenfunctions for different models were expressed analytically in terms of the hypergeometric functions, and eigenvalues were solved numerically. We found that the rotational energy levels exhibit oscillatory behavior when plotted as functions of the hindrance angle. This particular phenomenon was interpreted as the occurrence of resonance transmission of the rotor wave function at certain hindrance condition. We also found that the rotational levels were grouped into bands when the azimuthal modulation strength was increased. The solutions were used to calculate the rotational-state distribution of desorbed molecules, and agreement with the previous experiment was obtained. {copyright} {ital 1996 The American Physical Society.}

  12. Exchange-only optimized effective potential calculation of excited state spectra for He and Be atoms.

    SciTech Connect

    Desjarlais, Michael Paul; Muller, Richard Partain

    2006-02-01

    The optimized effective potential (OEP) method allows orbital-dependent functionals to be used in density functional theory (DFT), which, in particular, allows exact exchange formulations of the exchange energy to be used in DFT calculations. Because the exact exchange is inherently self-interaction correcting, the resulting OEP calculations have been found to yield superior band-gaps for condensed-phase systems. Here we apply these methods to the isolated atoms He and Be, and compare to high quality experiments and calculations to demonstrate that the orbital energies accurately reproduce the excited state spectrum for these species. These results suggest that coupling the exchange-only OEP calculations with proper (orbital-dependent or other) correlation functions might allow quantitative accuracy from DFT calculations.

  13. Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs

    NASA Astrophysics Data System (ADS)

    Furukawa, Taro; Nakanotani, Hajime; Inoue, Munetomo; Adachi, Chihaya

    2015-02-01

    Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a ``one-way'' rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved.

  14. Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs.

    PubMed

    Furukawa, Taro; Nakanotani, Hajime; Inoue, Munetomo; Adachi, Chihaya

    2015-01-01

    Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a "one-way" rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved. PMID:25673259

  15. Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs

    PubMed Central

    Furukawa, Taro; Nakanotani, Hajime; Inoue, Munetomo; Adachi, Chihaya

    2015-01-01

    Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a “one-way” rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved. PMID:25673259

  16. Triplet energy transfer in conjugated polymers. II. A polaron theory description addressing the influence of disorder

    NASA Astrophysics Data System (ADS)

    Fishchuk, Ivan I.; Kadashchuk, Andrey; Sudha Devi, Lekshmi; Heremans, Paul; Bässler, Heinz; Köhler, Anna

    2008-07-01

    Motivated by experiments monitoring motion of triplet excitations in a conjugated polymer containing Pt-atoms in the main chain (see Paper I), a theoretical formalism for electronic transport has been developed. It considers the interplay between polaronic distortion of the excited chain elements and disorder treated in terms of effective-medium theory. The essential parameters are the electronic coupling J , the polaronic binding energy ? that determines the activation energy of polaron motion Ea , and the variance ? of the density of states distribution controlling the incoherent hopping motion. It turns out that for the weak electronic coupling associated with triplet motion ( J a few meV), the transfer is nonadiabatic. For a critical ratio of ?/Ea<0.3 , Marcus-type multiphonon transport prevails above a certain transition temperature. At lower temperatures, transport is disorder controlled consistent with the Miller-Abrahams formalism. Theoretical results are consistent with triplet transport in the Pt-polymer. Implications for charge and triplet motion in random organic semiconductors in general are discussed.

  17. Non-linear advanced control of the LHC inner triplet heat exchanger test unit

    NASA Astrophysics Data System (ADS)

    Viñuela, E. Blanco; Cubillos, J. Casas; de Prada Moraga, C.; Cristea, S.

    2002-05-01

    The future Large Hadron Collider (LHC) at CERN will include eight interaction region final focus magnet systems, the so-called "Inner Triplet," one on each side of the four beam collision points. The Inner Triplets will be cooled in a static bath of pressurized He II nominally at 1.9 K. This temperature is a control parameter and has very severe constraints in order to avoid the transition from the superconducting to normal resistive state. The main difference in these special zones with respect to a regular LHC cell is higher dynamic heat load unevenly distributed which modifies largely the process characteristics and hence the controller performance. Several control strategies have already been tested at CERN in a pilot plant (LHC String Test) which reproduced a LHC half-cell. In order to validate a common control structure along the whole LHC ring, a Nonlinear Model Predictive Control (NMPC) has been developed and implemented in the Inner Triplet Heat Exchanger Unit (IT-HXTU) at CERN. Automation of the Inner Triplet setup and the advanced control techniques deployed based on the Model Based Predictive Control (MBPC) principle are presented.

  18. Higgs Triplet Model with Classically Conformal Invariance

    E-print Network

    Okada, Hiroshi; Yagyu, Kei

    2015-01-01

    We discuss an extension of the minimal Higgs triplet model with a classically conformal invariance and with a gauged $U(1)_{B-L}$ symmetry. In our scenario, tiny masses of neutrinos are generated by a hybrid contribution from the type-I and type-II seesaw mechanisms. The shape of the Higgs potential at low energies is determined by solving one-loop renormalization group equations for all the scalar quartic couplings with a set of initial values of parameters at the Planck scale. We find a successful set of the parameters in which the $U(1)_{B-L}$ symmetry is radiatively broken via the Coleman-Weinberg mechanism at the ${\\cal O}$(10) TeV scale, and the electroweak symmetry breaking is also triggered by the $U(1)_{B-L}$ breaking. Under this configuration, we can predict various low energy observables such as the mass spectrum of extra Higgs bosons, and the mixing angles. Furthermore, using these predicted mass parameters, we obtain upper limits on Yukawa couplings among an isospin triplet Higgs field and lepton...

  19. Higgs Triplet Model with Classically Conformal Invariance

    E-print Network

    Hiroshi Okada; Yuta Orikasa; Kei Yagyu

    2015-10-13

    We discuss an extension of the minimal Higgs triplet model with a classically conformal invariance and with a gauged $U(1)_{B-L}$ symmetry. In our scenario, tiny masses of neutrinos are generated by a hybrid contribution from the type-I and type-II seesaw mechanisms. The shape of the Higgs potential at low energies is determined by solving one-loop renormalization group equations for all the scalar quartic couplings with a set of initial values of parameters at the Planck scale. We find a successful set of the parameters in which the $U(1)_{B-L}$ symmetry is radiatively broken via the Coleman-Weinberg mechanism at the ${\\cal O}$(10) TeV scale, and the electroweak symmetry breaking is also triggered by the $U(1)_{B-L}$ breaking. Under this configuration, we can predict various low energy observables such as the mass spectrum of extra Higgs bosons, and the mixing angles. Furthermore, using these predicted mass parameters, we obtain upper limits on Yukawa couplings among an isospin triplet Higgs field and lepton doublets from lepton flavor violation data.

  20. Reaction of Triplet Phenylnitrene with Molecular Oxygen.

    PubMed

    Mieres-Pérez, Joel; Mendez-Vega, Enrique; Velappan, Kavitha; Sander, Wolfram

    2015-12-18

    Triplet carbenes react with molecular oxygen with rates that approach diffusion control to carbonyl O-oxides, whereas triplet nitrenes react much slower. For investigating the reaction of phenylnitrene with O2, the nitrene was generated by flash vacuum thermolysis (FVT) of phenylazide and subsequently isolated in O2-doped matrices. FVT of the azide produces the nitrene in high yield and with only minor contaminations of the rearranged products that are frequently observed if the nitrene is produced by photolysis. The phenylnitrene was isolated in solid Ar, Xe, mixtures of these rare gases with O2, and even in pure solid O2. At temperatures between 30 and 35 K an extremely slow thermal reaction between the nitrene and O2 was observed, whereas at higher temperatures, solid Ar and O2 rapidly evaporate. Only O2-doped Xe matrices allowed us to anneal at temperatures above 40 K, and at these temperatures, the nitrene reacts with O2 to produce nitroso O-oxide mainly in its syn conformation. Upon visible light irradiation (450 nm), the nitroso oxide rapidly rearranges to nitrobenzene. PMID:26524191

  1. Rotationally resolved photoelectron spectra in resonance enhanced multiphoton ionization of HCl via the F 1?2 Rydberg state

    NASA Astrophysics Data System (ADS)

    Wang, Kwanghsi; McKoy, V.

    1991-12-01

    Results of studies of rotational ion distributions in the X 2?3/2 and X 2?1/2 spin-orbit states of HCl+ resulting from (2+1') resonance enhanced multiphoton ionization (REMPI) via the S(0) branch of the F 1?2 Rydberg state are reported and compared with measured threshold-field-ionization zero-kinetic-energy spectra reported recently [K. S. Haber, Y. Jiang, G. Bryant, H. Lefebvre-Brion, and E. R. Grant, Phys. Rev. A (in press)]. These results show comparable intensities for J+=3/2 of the X 2?3/2 ion and J+=1/2 of the X 2?1/2 ion. Both transitions require an angular momentum change of ?N=-1 upon photoionization. To provide further insight into the near-threshold dynamics of this process, we also show rotationally resolved photoelectron angular distributions, alignment of the ion rotational levels, and rotational distributions for the parity components of the ion rotational levels. About 18% population is predicted to occur in the (+) parity component, which would arise from odd partial-wave contributions to the photoelectron matrix element. This behavior is similar to that in (2+1) REMPI via the S(2) branch of the F 1?2 state of HBr and was shown to arise from significant l mixing in the electronic continuum due to the nonspherical molecular ion potential. Rotational ion distributions resulting from (2+1) REMPI via the S(10) branch of the F 1?2 state are also shown.

  2. A versatile detector system to measure the change states, mass compositions and energy spectra of interplanetary and magnetosphere ions

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1977-01-01

    An instrument is described for measuring the mass and charge state composition as well as the energy spectra and angular distributions of 0.5 to 350 kev/charge ions in interplanetary space and in magnetospheres of planets such as Jupiter and earth. Electrostatic deflection combined with a time-of-flight and energy measurement allows three-parameter analysis of output signals from which the mass, charge states, and energy are determined. Post-acceleration by 30 kV extends the energy range of the detector system into the solar wind and magnetosphere plasma regime. Isotopes of H and He are easily resolved as are individual elements up to Ne and the dominant elements up to and including Fe. This instrument has an extremely large dynamic range in intensity and is sensitive to rare elements even in the presence of high intensity radiation, and is adapted for interplanetary, deep-space, and out-of-the-ecliptic missions, as well as for flights on spacecraft orbiting Jupiter and earth.

  3. Triplet excimer formation of triphenylamine and related chromophores in polystyrene films

    SciTech Connect

    Burkhart, R.D.; Jhon, Namin )

    1991-09-19

    The phosphorescence of triphenylamine (TPA) and of the (N,N-diphenylamino) phenylmethyl ester of 2-methylpropanoic acid (DAPM) was investigated in polystyrene films at temperatures from 20 to 230 k. Their phosphorescence spectra at low temperatures are similar to those recorded in rigid glassy solvents at 77 K, but as the temperature is raised, a new phosphorescence band at 470 mn grows in and the low-temperature band gradually disappears. The new emission is due to an excimeric triplet since it is similar to one found earlier from the polymeric analogue of DAPM and is also similar to the totally excimeric phosphorescence of crystalline TPA at 77K. Rates of excimer formation and dissociation were determined as a function of temperature as were the corresponding activation energies. Triplet exciton migration is not the rate-limiting step in excimer formation. The activation energies for dissociation of the triplet excimers were found to depend upon the concentration of the amine. For DAPM the evidence suggests that excimers formed in dilute samples are in a strained configuration which relaxes slowly compared to the excimer lifetime.

  4. How to calculate linear absorption spectra with lifetime broadening using fewest switches surface hopping trajectories: A simple generalization of ground-state Kubo theory

    SciTech Connect

    Petit, Andrew S.; Subotnik, Joseph E.

    2014-07-07

    In this paper, we develop a surface hopping approach for calculating linear absorption spectra using ensembles of classical trajectories propagated on both the ground and excited potential energy surfaces. We demonstrate that our method allows the dipole-dipole correlation function to be determined exactly for the model problem of two shifted, uncoupled harmonic potentials with the same harmonic frequency. For systems where nonadiabatic dynamics and electronic relaxation are present, preliminary results show that our method produces spectra in better agreement with the results of exact quantum dynamics calculations than spectra obtained using the standard ground-state Kubo formalism. As such, our proposed surface hopping approach should find immediate use for modeling condensed phase spectra, especially for expensive calculations using ab initio potential energy surfaces.

  5. Triplet-exciton fine structure of anthracene: high-resolution optical measurements

    NASA Astrophysics Data System (ADS)

    Port, H.; Rund, D.

    1980-01-01

    The optical transitions to the magnetic sublevels of the lowest triplet exciton Davydov component in anthracene are spectrally resolved in photoexcitation at 1.8 K. This allows, for the first time, the direct analysis of the properties of the individual magnetic substates in zero-field and in low magnetic fields. From polarized excitation spectra the ordering of the zero-field spin sublevels and the associated absolute signs of the zero-field splitting parameters are determined. The zerofield intensities are compared with the predictions of spin-orbit coupling theory.

  6. Integrin triplets of marine sponges in human brain receptor heteromers.

    PubMed

    Tarakanov, Alexander O; Fuxe, Kjell G; Borroto-Escuela, Dasiel O

    2012-09-01

    Based on our theory, we have discovered main triplets of amino acid residues in cell-adhesion receptors of marine sponges, which appear also as homologies in several receptor heteromers of human brain. The obtained results strengthen our hypothesis that these triplets may "guide-and-clasp" receptor-receptor interactions. PMID:22573093

  7. Theoretical Rationalization of the Singlet-Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character.

    PubMed

    Moral, M; Muccioli, L; Son, W-J; Olivier, Y; Sancho-García, J C

    2015-01-13

    New materials for OLED applications with low singlet-triplet energy splitting have been recently synthesized in order to allow for the conversion of triplet into singlet excitons (emitting light) via a Thermally Activated Delayed Fluorescence (TADF) process, which involves excited-states with a non-negligible amount of Charge-Transfer (CT). The accurate modeling of these states with Time-Dependent Density Functional Theory (TD-DFT), the most used method so far because of the favorable trade-off between accuracy and computational cost, is however particularly challenging. We carefully address this issue here by considering materials with small (high) singlet-triplet gap acting as emitter (host) in OLEDs and by comparing the accuracy of TD-DFT and the corresponding Tamm-Dancoff Approximation (TDA), which is found to greatly reduce error bars with respect to experiments thanks to better estimates for the lowest singlet-triplet transition. Finally, we quantitatively correlate the singlet-triplet splitting values with the extent of CT, using for it a simple metric extracted from calculations with double-hybrid functionals, that might be applied in further molecular engineering studies. PMID:26574215

  8. Triplet leptogenesis in left-right symmetric seesaw models

    SciTech Connect

    Haellgren, Tomas; Konstandin, Thomas; Ohlsson, Tommy E-mail: konstand@kth.se E-mail: tommy@theophys.kth.se

    2008-01-15

    We discuss scalar triplet leptogenesis in a specific left-right symmetric seesaw model. We show that the Majorana phases that are present in the model can be effectively used to saturate the existing upper limit on the CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and analyze the viability of triplet leptogenesis. It is known for this kind of scenario that the efficiency of leptogenesis is maximal if there exists a hierarchy between the branching ratios of the triplet decays into leptons and Higgs particles. We show that triplet leptogenesis typically favors branching ratios with not too strong hierarchies, since maximal efficiency can only be obtained at the expense of suppressed CP-asymmetries.

  9. Far infrared spectra of solid state L-serine, L-threonine, L-cysteine, and L-methionine in different protonation states.

    PubMed

    Gaillard, Thomas; Trivella, Aurélien; Stote, Roland H; Hellwig, Petra

    2015-11-01

    In this study, experimental far infrared measurements of L-serine, L-threonine, L-cysteine, and L-methionine are presented showing the spectra for the 1.0-13.0 pH range. In parallel, solid state DFT calculations were performed on the amino acid zwitterions in the crystalline form. We focused on the lowest frequency far infrared normal modes, which required the most precision and convergence of the calculations. Analysis of the computational results, which included the potential energy distribution of the vibrational modes, permitted a detailed and almost complete assignment of the experimental spectrum. In addition to characteristic signals of the two main acid-base couples, CO2H/CO2(-) and NH3(+)/NH2, specific side chain contributions for these amino acids, including CCO and CCS vibrational modes were analyzed. This study is in line with the growing application of FIR measurements to biomolecules. PMID:26056980

  10. Triplet-triplet annihilation photon-upconversion: towards solar energy applications.

    PubMed

    Gray, Victor; Dzebo, Damir; Abrahamsson, Maria; Albinsson, Bo; Moth-Poulsen, Kasper

    2014-06-14

    Solar power production and solar energy storage are important research areas for development of technologies that can facilitate a transition to a future society independent of fossil fuel based energy sources. Devices for direct conversion of solar photons suffer from poor efficiencies due to spectrum losses, which are caused by energy mismatch between the optical absorption of the devices and the broadband irradiation provided by the sun. In this context, photon-upconversion technologies are becoming increasingly interesting since they might offer an efficient way of converting low energy solar energy photons into higher energy photons, ideal for solar power production and solar energy storage. This perspective discusses recent progress in triplet-triplet annihilation (TTA) photon-upconversion systems and devices for solar energy applications. Furthermore, challenges with evaluation of the efficiency of TTA-photon-upconversion systems are discussed and a general approach for evaluation and comparison of existing systems is suggested. PMID:24733519

  11. Dephasing-enabled triplet Andreev conductance

    NASA Astrophysics Data System (ADS)

    Béri, B.

    2009-06-01

    We study the conductance of normal-superconducting quantum dots with strong spin-orbit scattering coupled to a source reservoir using a single-mode spin-filtering quantum-point contact. The choice of the system is guided by the aim to study triplet Andreev reflection without relying on half-metallic materials with specific interface properties. Focusing on the zero-temperature, zero-bias regime, we show how dephasing due to the presence of a voltage probe enables the conductance, which vanishes in the quantum limit, to take nonzero values. Concentrating on chaotic quantum dots, we obtain the full distribution of the conductance as a function of the dephasing rate. As dephasing gradually lifts the conductance from zero, the dependence of the conductance fluctuations on the dephasing rate is nonmonotonic. This is in contrast to chaotic quantum dots in usual transport situations, where dephasing monotonically suppresses the conductance fluctuations.

  12. Photodissociation dynamics of the reaction H2CO-->H+HCO via the singlet (S0) and triplet (T1) surfaces

    NASA Astrophysics Data System (ADS)

    Yin, Hong-Ming; Rowling, Steven J.; Büll, Alexander; Kable, Scott H.

    2007-08-01

    We have explored the photodissociation dynamics of the reaction H2CO+h??H+HCO in the range of 810-2600cm-1 above the reaction threshold. Supersonically cooled formaldehyde was excited into selected JKa,Kc rotational states of six vibrational levels (1141, 51, 2261, 2243, 2341, and 2441) in the Ã(A21) state. The laser induced fluorescence spectra of the nascent HCO fragment provided detailed product state distributions. When formaldehyde was excited into the low-lying levels 1141, 51, and 2261, at Eavail<1120cm-1, the product state distribution can be modeled qualitatively by phase space theory. These dynamics are interpreted as arising from a reaction path on the barrierless S0 surface. When the initial states 2243 and 2341 were excited (Eavail=1120-1500cm-1), a second type of product state distribution appeared. This second distribution peaked sharply at low N, Ka and was severely truncated in comparison with those obtained from the lower lying states. At the even higher energy of 2441 (Eavail?2600cm-1) the sharply peaked distribution appears to be dominant. We attribute this change in dynamics to the opening up of the triplet channel to produce HCO. The theoretical height of the barrier on the T1 surface lies between 1700 and 2100cm-1 and so we consider the triplet reaction to proceed via tunneling at the intermediate energies and proceed over the barrier at the higher energies. Considerable population was observed in the excited (0,0,1) state for all initial H2CO states that lie above the appearance energy. Rotational populations in the (0,0,1) state dropped more rapidly with (N,Ka) than did the equivalent populations in (0,0,0). This indicates that, although individual rotational states are highly populated in (0,0,1), the total v3=1 population might not be so large. Specific population was also measured in the almost isoenergetic Kc and J states. No consistent population preference was found for either asymmetry or spin-rotation component.

  13. Resonator-assisted entangling gate for singlet-triplet spin qubits in nanowire double quantum dots

    E-print Network

    Peng Xue; Yun-Feng Xiao

    2010-05-17

    We propose a resonator-assisted entangling gate for spin qubits with high fidelity. Each spin qubit corresponds to two electrons in a nanowire double quantum dot, with the singlet and one of the triplets as the logical qubit states. The gate is effected by virtual charge dipole transitions. We include noise in our model to show feasibility of the scheme under current experimental conditions.

  14. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals.

    PubMed

    Wang, Rui; Zhang, Chunfeng; Zhang, Bo; Liu, Yunlong; Wang, Xiaoyong; Xiao, Min

    2015-01-01

    Singlet fission can potentially break the Shockley-Queisser efficiency limit in single-junction solar cells by splitting one photoexcited singlet exciton (S1) into two triplets (2T1) in organic semiconductors. A dark multiexciton state has been proposed as the intermediate connecting S1 to 2T1. However, the exact nature of this multiexciton state, especially how the doubly excited triplets interact, remains elusive. Here we report a quantitative study on the magnetic dipolar interaction between singlet-fission-induced correlated triplets in tetracene crystals by monitoring quantum beats relevant to the multiexciton sublevels at room temperature. The resonances of multiexciton sublevels approached by tuning an external magnetic field are observed to be avoided, which agrees well with the theoretical predictions considering a magnetic dipolar interaction of ?0.008?GHz. Our work quantifies the magnetic dipolar interaction in certain organic materials and marks an important step towards understanding the underlying physics of the multiexciton state in singlet fission. PMID:26456368

  15. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals

    PubMed Central

    Wang, Rui; Zhang, Chunfeng; Zhang, Bo; Liu, Yunlong; Wang, Xiaoyong; Xiao, Min

    2015-01-01

    Singlet fission can potentially break the Shockley–Queisser efficiency limit in single-junction solar cells by splitting one photoexcited singlet exciton (S1) into two triplets (2T1) in organic semiconductors. A dark multiexciton state has been proposed as the intermediate connecting S1 to 2T1. However, the exact nature of this multiexciton state, especially how the doubly excited triplets interact, remains elusive. Here we report a quantitative study on the magnetic dipolar interaction between singlet-fission-induced correlated triplets in tetracene crystals by monitoring quantum beats relevant to the multiexciton sublevels at room temperature. The resonances of multiexciton sublevels approached by tuning an external magnetic field are observed to be avoided, which agrees well with the theoretical predictions considering a magnetic dipolar interaction of ?0.008?GHz. Our work quantifies the magnetic dipolar interaction in certain organic materials and marks an important step towards understanding the underlying physics of the multiexciton state in singlet fission. PMID:26456368

  16. Coherent Singlet-Triplet Oscillations in a Silicon-based Double Quantum Dot

    NASA Astrophysics Data System (ADS)

    Maune, Brett; Borselli, Matthew; Huang, Biqin; Ladd, Thaddeus; Deelman, Peter; Holabird, Kevin; Kiselev, Andrey; Alvarado-Rodriguez, Ivan; Ross, Richard; Schmitz, Adele; Sokolich, Marko; Watson, Christopher; Gyure, Mark; Hunter, Andrew

    2012-02-01

    We have performed coherent spin manipulation of a singlet-triplet qubit in a Si/SiGe double quantum-dot device fabricated in an undoped heterostructure. A charge stability diagram showed that the (0,0) charge state was reached and Pauli spin blockade was detected at the (1,1)-(0,2) anticrossing. A singlet-triplet splitting of ˜140 ?eV in the (0,2) charge state provided a read-out window sufficiently wide for singlet-triplet discrimination. We used the S/T- spin funnel, Rabi oscillation, and T2* pulsing experiments to measure (1,1) exchange energies spanning ˜0.6-700 neV over a large detuning range and measured a T2* of 360 ns, consistent with theoretical expectations for our device. Sponsored by the United States Department of Defense. Approved for Public Release, Distribution Unlimited. The views expressed are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government.

  17. Third-order spontaneous parametric down-conversion in thin optical fibers as a photon-triplet source

    SciTech Connect

    Corona, Maria; Garay-Palmett, Karina; U'Ren, Alfred B.

    2011-09-15

    We study the third-order spontaneous parametric down-conversion (TOSPDC) process, as a means to generate entangled photon triplets. Specifically, we consider thin optical fibers as the nonlinear medium to be used as the basis for TOSPDC in configurations where phase matching is attained through the use of more than one fiber transverse modes. Our analysis in this paper, which follows from our earlier paper [Opt. Lett. 36, 190-192 (2011)], aims to supply experimentalists with the details required in order to design a TOSPDC photon-triplet source. Specifically, our analysis focuses on the photon triplet state, on the rate of emission, and on the TOSPDC phase-matching characteristics for the cases of frequency-degenerate and frequency nondegenerate TOSPDC.

  18. Theory of Triplet Excitation Transfer in the Donor-Oxygen-Acceptor System: Application to Cytochrome b6f.

    PubMed

    Petrov, Elmar G; Robert, Bruno; Lin, Sheng Hsien; Valkunas, Leonas

    2015-10-20

    Theoretical consideration is presented of the triplet excitation dynamics in donor-acceptor systems in conditions where the transfer is mediated by an oxygen molecule. It is demonstrated that oxygen may be involved in both real and virtual intramolecular triplet-singlet conversions in the course of the process under consideration. Expressions describing a superexchange donor-acceptor coupling owing to a participation of the bridging twofold degenerate oxygen's virtual singlet state are derived and the transfer kinetics including the sequential (hopping) and coherent (distant) routes are analyzed. Applicability of this theoretical description to the pigment-protein complex cytochrome b6f, by considering the triplet excitation transfer from the chlorophyll a molecule to distant ?-carotene, is discussed. PMID:26488665

  19. Fluorescence excitation and ultraviolet absorption spectra and theoretical calculations for benzocyclobutane: Vibrations and structure of its excited S{sub 1}(?,?{sup *}) electronic state

    SciTech Connect

    Shin, Hee Won; Ocola, Esther J.; Laane, Jaan; Kim, Sunghwan

    2014-01-21

    The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S{sub 1}(?,?{sup *}) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S{sub 0} and S{sub 1}(?,?{sup *}) electronic states. In each case the decreased ? bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S{sub 0} and S{sub 1}(?,?{sup *}) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S{sub 1}(?,?{sup *}) excited state.

  20. Variational analysis of mass spectra and decay constants for ground state pseudoscalar and vector mesons in the light-front quark model

    NASA Astrophysics Data System (ADS)

    Choi, Ho-Meoyng; Ji, Chueng-Ryong; Li, Ziyue; Ryu, Hui-Young

    2015-11-01

    Using the variational principle, we compute mass spectra and decay constants of ground state pseudoscalar and vector mesons in the light-front quark model (LFQM) with the QCD-motivated effective Hamiltonian including the hyperfine interaction. By smearing out the Dirac ? function in the hyperfine interaction, we avoid the issue of negative infinity in applying the variational principle to the computation of meson mass spectra and provide analytic expressions for the meson mass spectra. Our analysis with the smeared hyperfine interaction indicates that the interaction for the heavy meson sector including the bottom and charm quarks gets more point-like. We also consider the flavor mixing effect in our analysis and determine the mixing angles from the mass spectra of (? ,? ) and (? ,?') . Our variational analysis with the trial wave function including the two lowest order harmonic oscillator basis functions appears to improve the agreement with the data of meson decay constants and the heavy meson mass spectra over the previous computation handling the hyperfine interaction as perturbation.

  1. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals

    E-print Network

    Wang, Rui; Zhang, Bo; Liu, Yunlong; Wang, Xiaoyong; Xiao, Min

    2015-01-01

    Singlet fission (SF) can potentially break the Shockley-Queisser efficiency limit in single-junction solar cells by splitting one photo-excited singlet exciton (S1) into two triplets (2T1) in organic semiconductors. A dark multi-exciton (ME) state has been proposed as the intermediate connecting S1 to 2T1. However, the exact nature of this ME state, especially how the doubly-excited triplets interact, remains elusive. Here, we report a quantitative study on the magnetic dipolar interaction between SF-induced correlated triplets in tetracene crystals by monitoring quantum beats relevant to the ME sublevels at room temperature. The resonances of ME sublevels approached by tuning an external magnetic field are observed to be avoided, which agrees well with the theoretical predictions considering a magnetic dipolar interaction of ~ 0.008 GHz. Our work paves a way to quantify the magnetic dipolar interaction in organic materials and marks an important step towards understanding the underlying physics of the ME sta...

  2. Triplet superconductivity in 3D Dirac semi-metal due to exchange interaction.

    PubMed

    Rosenstein, Baruch; Shapiro, B Ya; Li, Dingping; Shapiro, I

    2015-01-21

    Conventional phonon-electron interaction induces either triplet or one of two (degenerate) singlet pairing states in time reversal and inversion invariant 3D Dirac semi-metal. Investigation of the order parameters and energies of these states at zero temperature in a wide range of values of chemical potential ?, the effective electron-electron coupling constant ? and Debye energy TD demonstrates that when the exchange interaction is neglected the singlet always prevails, however, in significant portions of the (?, ?, TD) parameter space the energy difference is very small. This means that interactions that are small, but discriminate between the spin singlet and the spin triplet, are important in order to determine the nature of the superconducting order there. The best candidate for such an interaction in the materials under consideration is the exchange (the Stoner term) characterized by constant ?ex. We show that at values of ?ex, much smaller than ones creating Stoner instability to ferromagnetism ?ex ? 1, the triplet pairing becomes energetically favored over the singlet ones. The 3D quantum critical point at ? = 0 is considered in detail. This can be realized experimentally in optically trapped cold atom systems. PMID:25501668

  3. Triplet energy management between two signaling units through cooperative rigid scaffolds.

    PubMed

    Miro, Paula; Vayá, Ignacio; Sastre, Germán; Jiménez, M Consuelo; Marin, M Luisa; Miranda, Miguel A

    2015-12-24

    Through-bond triplet exciplex formation in donor-acceptor systems linked through a rigid bile acid scaffold has been demonstrated on the basis of kinetic evidence upon population of the triplet acceptors (naphthalene, or biphenyl) by through-bond triplet-triplet energy transfer from benzophenone. PMID:26561577

  4. Left-right symmetric model with SU(2)-triplet fermions

    SciTech Connect

    Gu Peihong

    2011-11-01

    We consider an SU(3){sub c} x SU(2){sub L} x SU(2){sub R} x U(1){sub B-L} left-right symmetric model with three Higgs scalars including an SU(2){sub L} doublet, an SU(2){sub R} doublet and an SU(2){sub L} x SU(2){sub R} bidoublet. In addition to usual SU(2)-doublet fermions, our model contains SU(2)-triplet fermions with Majorana masses. The neutral components of the left-handed triplets can contribute a canonical seesaw while the neutral components of the right-handed triplets associated with the right-handed neutrinos can contribute a double/inverse-type seesaw. Our model can be embedded into an SO(10) grand unification theory where the triplets belong to the 45=(1,3,1,0)+(1,1,3,0)+... representations.

  5. Galaxy triplets in SDSS-DR7: I. Catalogue

    E-print Network

    O'Mill, Ana Laura; Lambas, Diego García; Valotto, Carlos; Sodré, Laerte

    2011-01-01

    We present a new catalogue of galaxy triplets derived from the Sloan Digital Sky Survey Data Release 7. The identification of systems was performed considering galaxies brighter than M_r=-20.5 and imposing constraints over the projected distances, radial velocity differences of neighbouring galaxies and isolation. To improve the identification of triplets we employed a data pixelization scheme, which allows to handle large amounts of data as in the SDSS photometric survey. Using spectroscopic and photometric data in the redshift range 0.01triplet candidates. We have used a mock catalogue to analyse the completeness and contamination of our methods. The results show a high level of completeness (~80%) and low contamination (~5%). By using photometric and spectroscopic data we have also addressed the effects of fiber collisions in the spectroscopic sample. We have defined an isolation criterion considering the distance of the triplet brightest galaxy to closest neighbour cluster, to...

  6. Correlated Pair States Formed by Singlet Fission and Exciton-Exciton Annihilation.

    PubMed

    Scholes, Gregory D

    2015-12-24

    Singlet fission to form a pair of triplet excitations on two neighboring molecules and the reverse process, triplet-triplet annihilation to upconvert excitation, have been extensively studied. Comparatively little work has sought to examine the properties of the intermediate state in both of these processes-the bimolecular pair state. Here, the eigenstates constituting the manifold of 16 bimolecular pair excitations and their relative energies in the weak-coupling regime are reported. The lowest-energy states obtained from the branching diagram method are the triplet pairs with overall singlet spin |X1? ? (1)[TT] and quintet spin |Q? ? (5)[TT]. It is shown that triplet pair states can be separated by a triplet-triplet energy-transfer mechanism to give a separated, yet entangled triplet pair (1)[T···T]. Independent triplets are produced by decoherence of the separated triplet pair. Recombination of independent triplets by exciton-exciton annihilation to form the correlated triplet pair (i.e., nongeminate recombination) happens with 1/3 of the rate of either triplet migration or recombination of the separated correlated triplet pair (geminate recombination). PMID:26595530

  7. Epigenetics and Triplet-Repeat Neurological Diseases

    PubMed Central

    Nageshwaran, Sathiji; Festenstein, Richard

    2015-01-01

    The term “junk DNA” has been reconsidered following the delineation of the functional significance of repetitive DNA regions. Typically associated with centromeres and telomeres, DNA repeats are found in nearly all organisms throughout their genomes. Repetitive regions are frequently heterochromatinized resulting in silencing of intrinsic and nearby genes. However, this is not a uniform rule, with several genes known to require such an environment to permit transcription. Repetitive regions frequently exist as dinucleotide, trinucleotide, and tetranucleotide repeats. The association between repetitive regions and disease was emphasized following the discovery of abnormal trinucleotide repeats underlying spinal and bulbar muscular atrophy (Kennedy’s disease) and fragile X syndrome of mental retardation (FRAXA) in 1991. In this review, we provide a brief overview of epigenetic mechanisms and then focus on several diseases caused by DNA triplet-repeat expansions, which exhibit diverse epigenetic effects. It is clear that the emerging field of epigenetics is already generating novel potential therapeutic avenues for this group of largely incurable diseases.

  8. Dark Matter in the Higgs Triplet Model

    E-print Network

    Sahar Bahrami; Mariana Frank

    2015-09-15

    The inability to predict neutrino masses and the existence of the dark matter are two essential shortcomings of the Standard Model. The Higgs Triplet Model provides an elegant resolution of neutrino masses via the seesaw mechanism. We show here that introducing vectorlike leptons in the model also provides a resolution to the problem of dark matter. We investigate constraints, including the invisible decay width of the Higgs boson and the electroweak precision variables, and impose restrictions on model parameters. We analyze the effect of the relic density constraint on the mass and Yukawa coupling of dark matter. We also calculate the cross sections for indirect and direct dark matter detection and show our model predictions for the neutrino and muon fluxes from the Sun, and the restrictions they impose on the parameter space. With the addition of vectorlike leptons, the model is completely consistent with dark matter constraints, in addition to improving electroweak precision and doubly charged mass restrictions, which are rendered consistent with present experimental data.

  9. VIBRATION STUDIES ON A SUPERCONDUCTING RHIC INTERACTION REGION QUADRUPOLE TRIPLET.

    SciTech Connect

    MONTAG,C.GANETIS,G.JIA,L.LOUIE,W.

    2003-05-12

    Mechanical vibrations of the superconducting interaction region triplets have been identified as source of horizontal beam jitter around 10 Hz in the Relativistic Heavy Ion Collider (RHIC). Therefore, cold masses inside one triplet cryostat have been equipped with accelerometers to further investigate the phenomenon. Additionally, helium pressure transducers have been installed to determine helium pressure oscillations as a possible primary vibration source. Recent results will be reported.

  10. Signature of proximity-induced px + ipy triplet pairing in the doped topological insulator Bi2Se3 by the s-wave superconductor NbN

    NASA Astrophysics Data System (ADS)

    Koren, Gad; Kirzhner, Tal; Kalcheim, Yoav; Millo, Oded

    2013-09-01

    In the search for Majorana fermions in proximity-induced topological superconducting junctions, we happened to find a signature of same-spin triplet superconductivity which appears to dominate these elusive elementary excitations. Thin-film junctions and bilayers of the doped topological insulator \\text{Bi}_2\\text{Se}_3 and the s-wave superconductor NbN exhibit conductance spectra with coexisting prominent zero-bias and coherence peaks. Various tunneling models with different pair potentials have failed to fit our data, except for the triplet p_x+ip_y pair potential, which breaks time-reversal symmetry, that yielded reasonably good fits. This provides supporting evidence for proximity-induced triplet superconductivity in the \\text{Bi}_2\\text{Se}_3 layer near the interface with the NbN film.

  11. A re-interpretation of the UV-photoelectron spectra of dewar benzene, norbornadiene and barrelene by ab initio configuration interaction calculations

    NASA Astrophysics Data System (ADS)

    Palmer, Michael H.

    1987-10-01

    Ab initio configuration interaction calculations of the ground and cationic states of Dewar benzene, norbornadiene and barrelene have enabled a firm assignment of the uv-photoelectron spectra in the range 8-16 eV to be made. Many of the states are of Koopman's one-electron process type, and the order of states is close to that of the SCF double zeta ground state calculations. A number of shake-up doublet states were computed, and for barrelene at least, these appear from about 12 eV onwards; the lowest lying triplet and singlet states for barrelene were computed at 3.82 and 6.04 eV, respectively, and most of the low-lying shake-up states are related to this HOMO—LUMO pair of transitions.

  12. Triplet energy differences and the low lying structure of 62Ga

    NASA Astrophysics Data System (ADS)

    Henry, T. W.; Bentley, M. A.; Clark, R. M.; Davies, P. J.; Bader, V. M.; Baugher, T.; Bazin, D.; Beausang, C. W.; Berryman, J. S.; Bruce, A. M.; Campbell, C. M.; Crawford, H. L.; Cromaz, M.; Fallon, P.; Gade, A.; Henderson, J.; Iwasaki, H.; Jenkins, D. G.; Lee, I. Y.; Lemasson, A.; Lenzi, S. M.; Macchiavelli, A. O.; Napoli, D. R.; Nichols, A. J.; Paschalis, S.; Petri, M.; Recchia, F.; Rissanen, J.; Simpson, E. C.; Stroberg, S. R.; Wadsworth, R.; Weisshaar, D.; Wiens, A.; Walz, C.

    2015-08-01

    Background: Triplet energy differences (TED) can be studied to yield information on isospin-non-conserving interactions in nuclei. Purpose: The systematic behavior of triplet energy differences (TED) of T =1 , J?=2+ states is examined. The A =62 isobar is identified as having a TED value that deviates significantly from an otherwise very consistent trend. This deviation can be attributed to the tentative assignments of the pertinent states in 62Ga and 62Ge . Methods: An in-beam ? -ray spectroscopy experiment was performed to identify excited states in 62Ga using Gamma-Ray Energy Tracking In-Beam Nuclear Array with the S800 spectrometer at NSCL using a two-nucleon knockout approach. Cross-section calculations for the knockout process and shell-model calculations have been performed to interpret the population and decay properties observed. Results: Using the systematics as a guide, a candidate for the transition from the T =1 , 2+ state is identified. However, previous work has identified similar states with different J? assignments. Cross-section calculations indicate that the relevant T =1 , 2+ state should be one of the states directly populated in this reaction. Conclusions: As spins and parities were not measurable, it is concluded that an unambiguous identification of the first T =1 , 2+ state is required to reconcile our understanding of TED systematics.

  13. Theoretical Analysis of the Triplet Excited State of the [Pt2(H2P2O5)4]4-Ion and Comparison with Time-Resolved X-ray

    E-print Network

    Coppens, Philip

    Coppens* Contribution from the Department of Chemistry, State UniVersity of New York at Buffalo, Buffalo, New York 14260-3000 Received July 25, 2002 ; E-mail: coppens@acsu.buffalo.edu Abstract: A full a lifetime of 9-10 µs in water and acetonitrile solutions, and a high quantum yield (r ) 0

  14. On the origin of the triplet puzzle of homologies in receptor heteromers: immunoglobulin triplets in different types of receptors.

    PubMed

    Tarakanov, Alexander O; Fuxe, Kjell G; Borroto-Escuela, Dasiel O

    2012-03-01

    Based on our theory, we have discovered main triplets of amino acid residues in the GABAB1 receptor and several other neural receptors which seem to come from immunoglobulin chains and appear also as homologies in receptor heteromers. The obtained results strengthen our hypothesis that these triplets may "guide-and-clasp" receptor-receptor interactions playing a role, e.g., in neuroinflammation disorders. PMID:21932037

  15. Efficient Triplet-Triplet Annihilation-Based Upconversion for Nanoparticle Phototargeting.

    PubMed

    Wang, Weiping; Liu, Qian; Zhan, Changyou; Barhoumi, Aoune; Yang, Tianshe; Wylie, Ryan G; Armstrong, Patrick A; Kohane, Daniel S

    2015-10-14

    High-efficiency upconverted light would be a desirable stimulus for triggered drug delivery. Here we present a general strategy to achieve photoreactions based on triplet-triplet annihilation upconversion (TTA-UC) and Förster resonance energy transfer (FRET). We designed PLA-PEG micellar nanoparticles containing in their cores hydrophobic photosensitizer and annihilator molecules which, when stimulated with green light, would undergo TTA-UC. The upconverted energy was then transferred by FRET to a hydrophobic photocleavable group (DEACM), also in the core. The DEACM was bonded to (and thus inactivated) the cell-binding peptide cyclo-(RGDfK), which was bound to the PLA-PEG chain. Cleavage of DEACM by FRET reactivated the PLA-PEG-bound peptide and allowed it to move from the particle core to the surface. TTA-UC followed by FRET allowed photocontrolled binding of cell adhesion with green light LED irradiation at low irradiance for short periods. These are attractive properties in phototriggered systems. PMID:26158690

  16. Broadband up-conversion at subsolar irradiance: triplet-triplet annihilation boosted by fluorescent semiconductor nanocrystals.

    PubMed

    Monguzzi, A; Braga, D; Gandini, M; Holmberg, V C; Kim, D K; Sahu, A; Norris, D J; Meinardi, F

    2014-11-12

    Conventional solar cells exhibit limited efficiencies in part due to their inability to absorb the entire solar spectrum. Sub-band-gap photons are typically lost but could be captured if a material that performs up-conversion, which shifts photon energies higher, is coupled to the device. Recently, molecular chromophores that undergo triplet-triplet annihilation (TTA) have shown promise for efficient up-conversion at low irradiance, suitable for some types of solar cells. However, the molecular systems that have shown the highest up-conversion efficiency to date are ill suited to broadband light harvesting, reducing their applicability. Here we overcome this limitation by combining an organic TTA system with highly fluorescent CdSe semiconductor nanocrystals. Because of their broadband absorption and spectrally narrow, size-tunable fluorescence, the nanocrystals absorb the radiation lost by the TTA chromophores, returning this energy to the up-converter. The resulting nanocrystal-boosted system shows a doubled light-harvesting ability, which allows a green-to-blue conversion efficiency of ?12.5% under 0.5 suns of incoherent excitation. This record efficiency at subsolar irradiance demonstrates that boosting the TTA by light-emitting nanocrystals can potentially provide a general route for up-conversion for different photovoltaic and photocatalytic applications. PMID:25322197

  17. Effect of stacking and redox state on optical absorption spectra of melanins -- comparison of theoretical and experimental results.

    PubMed

    Stark, Klaus B; Gallas, James M; Zajac, Gerry W; Golab, Joseph T; Gidanian, Shirley; McIntire, Theresa; Farmer, Patrick J

    2005-02-10

    In this work the effect of aggregation and oxidation on the optical absorption of eumelanin oligomeric sheets is investigated by applying quantum mechanics and atomistic simulation studies to a simplified eumelanin structural model that includes 1-3 sheets of hexameric oligomer sheets. The oligomeric hypothesis is supported by AFM characterizations of synthetic eumelanins, formed by auto-oxidation or electrochemical oxidation of dihydroxyindole (DHI). Comparison of calculated absorption spectra to experimental spectra demonstrates a red shift in absorption with oxidation and stacking of the eumelanin and validates the theoretical results. PMID:16851181

  18. Transport of triplet excitons along continuous 100 nm polyfluorene chains

    SciTech Connect

    Xi, Liang; Bird, Matthew; Mauro, Gina; Asaoka, Sadayuki; Cook, Andrew R.; Chen, Hung -Cheng; Miller, John R.

    2014-12-03

    Triplet excitons created in poly-2,7-(9,9-dihexyl)fluorene (pF) chains with end trap groups in solution are efficiently transported to and captured by the end groups. The triplets explore the entire lengths of the chains, even for ~100 nm long chains enabling determination of the completeness of end capping. The results show that the chains continuous: they may contain transient barriers or traps, such as those from fluctuations of dihedral angles, but are free of major defects that stop motion of the triplets. Quantitative determinations are aided by the addition of a strong electron donor, TMPD, which removes absorption bands of the end-trapped triplets. For chains having at least one end trap, triplet capture is quantitative on the 1 µs timescale imposed by the use of the donor. Fractions of chains having no end traps were 0.15 for pF samples with anthraquinone (AQ) end traps and 0.063 with naphthylimide (NI) end traps. These determinations agreed with measurements by NMR for short (<40 polymer repeat units (PRU)) chains, where NMR determinations are accurate. The results find no evidence for traps or barriers to transport of triplets, and places limits on the possible presence of defects as impenetrable barriers to less than one per 300 PRU. The present results present a paradigm different from the current consensus, derived from observations of singlet excitons, that conjugated chains are divided into “segments,” perhaps by some kind of defects. For the present pF chains, the segmentation either does not apply to triplet excitons or is transient so that the defects are healed or surmounted in times much shorter than 1 µs. Triplets on chains without end trap groups transfer to chains with end traps on a slower time scale. Rate constants for these bimolecular triplet transfer reactions were found to increase with the length of the accepting chain, as did rate constants for triplet transfer to the chains from small molecules like biphenyl. As a result, a second set of polyfluorenes with 2-butyloctyl side chains was found to have a much lower completeness of end capping.

  19. Photosensitized cis-trans isomerization in aqueous solution. pH effect on the efficiency of triplet-triplet energy transfer to maleic acid

    SciTech Connect

    Gupta, A.; Mukhtar, R.; Seltzer, S.

    1980-09-18

    Aromatic ketones, made water soluble by the introduction of ionic substituents, photosensitize cis reversible transfer isomerization in the maleic-fumaric acid system. The photostationary-state cis/trans ratio depends on the triplet energy of the sensitizer and the pH of the medium. All sensitizers studied show a pH effect on the cis/trans ratio which varies from 2.8 to 1.2 and is independent of whether the sensitizer is negatively or positively charged. Parallel quenching studies show the major part of this stems from a pH effect on the relative rates of energy transfer from the sensitizer to cis and trans acids. A smaller pH effect, in the opposite direction, is found with the relative rates of decay of the triplet to ground-state cis and trans isomers. Direct photoisomerization was also found to show this same pH effect in the decay of the lowest excited singlet to ground-state molecules. A rationalization is presented. 22 references, 4 figures, 3 tables.

  20. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra.

    PubMed

    Basavaraja, Jana; Suresh Kumar, H M; Inamdar, S R; Wari, M N

    2016-02-01

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of ???(?) transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (?e). It is observed that dipole moment value of excited state (?e) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state. PMID:26529635

  1. Singlet and triplet energy transfer in the peridinin-chlorophyll a-protein from Amphidinium carterae

    SciTech Connect

    Bautista, J.A.; Frank, H.A.; Hiller, R.G.; Sharples, F.P.; Gosztola, D.; Wasielewski, M.

    1999-04-08

    The spectroscopic properties of peridinin in solution, and the efficiency and dynamics of energy transfer from peridinin to chlorophyll a in the peridinin-chlorophyll-protein (PCP) from Amphidinium carterae, were studied by steady-state absorption, fluorescence, fluorescence excitation, and fast transient optical spectroscopy. Steady-state measurements of singlet energy transfer from peridinin to chlorophyll revealed an 88 {+-} 2% efficiency. Fast-transient absorption experiments showed that the excited S{sub 1} state of peridinin decayed in 13.4 {+-} 0.6 ps in methanol and 3.1 {+-} 0.4 ps in the PCP complex after direct excitation of the carotenoid. The onset of the bleaching of the chlorophyll absorption band at 672 nm, signifying the arrival of the excitation from the carotenoid, occurred in 3.2 {+-} 0.3 ps. These data show that the primary route of energy transfer from peridinin to chlorophyll in the PCP complex is through the S{sub 1} state of peridinin. Nanosecond time-resolved transient optical spectroscopy revealed that chlorophyll triplet states are efficiently quenched by peridinin whose triplet state subsequently decays with a lifetime of 10 {+-} 1 {micro}s in the PCP complex. Close association between the peridinins and chlorophyll, which is clearly evident in the 3-D structure of the PCP complex, along with proper alignment of pigments and energy state matching are responsible for the high efficiencies of the photochemical processes.

  2. Identification of redundant and synergetic circuits in triplets of electrophysiological data

    NASA Astrophysics Data System (ADS)

    Erramuzpe, Asier; Ortega, Guillermo J.; Pastor, Jesus; de Sola, Rafael G.; Marinazzo, Daniele; Stramaglia, Sebastiano; Cortes, Jesus M.

    2015-12-01

    Objective. Neural systems are comprised of interacting units, and relevant information regarding their function or malfunction can be inferred by analyzing the statistical dependencies between the activity of each unit. While correlations and mutual information are commonly used to characterize these dependencies, our objective here is to extend interactions to triplets of variables to better detect and characterize dynamic information transfer. Approach. Our approach relies on the measure of interaction information (II). The sign of II provides information as to the extent to which the interaction of variables in triplets is redundant (R) or synergetic (S). Three variables are said to be redundant when a third variable, say Z, added to a pair of variables (X, Y), diminishes the information shared between X and Y. Similarly, the interaction in the triplet is said to be synergetic when conditioning on Z enhances the information shared between X and Y with respect to the unconditioned state. Here, based on this approach, we calculated the R and S status for triplets of electrophysiological data recorded from drug-resistant patients with mesial temporal lobe epilepsy in order to study the spatial organization and dynamics of R and S close to the epileptogenic zone (the area responsible for seizure propagation). Main results. In terms of spatial organization, our results show that R matched the epileptogenic zone while S was distributed more in the surrounding area. In relation to dynamics, R made the largest contribution to high frequency bands (14-100 Hz), while S was expressed more strongly at lower frequencies (1-7 Hz). Thus, applying II to such clinical data reveals new aspects of epileptogenic structure in terms of the nature (redundancy versus synergy) and dynamics (fast versus slow rhythms) of the interactions. Significance. We expect this methodology, robust and simple, can reveal new aspects beyond pair-interactions in networks of interacting units in other setups with multi-recording data sets (and thus, not necessarily in epilepsy, the pathology we have approached here).

  3. Star Identification Using a Triplet Algorithm

    NASA Technical Reports Server (NTRS)

    Hashmall, Joseph A.

    2003-01-01

    The stars observed by onboard star trackers must be identified in order for the star tracker information to be used for attitude determination. Star identification associates the observed stars in the body frame with catalog stars, the positions of which in an inertial frame are well known. If the attitude is approximately known (from less accurate sensors) identification is relatively simple, but if there is no prior attitude knowledge (the Lost in Space problem) star identification is quite difficult. A new, reliable, and accurate star identification algorithm has been developed for use in a batch, ground-based attitude determination system. The identification algorithm uses input from one or more star trackers, each of which can observe three or more stars simultaneously. If observations are available at different times, rate data is used to relate them. The algorithm includes the following steps that are automatically performed: 1) Observations are examined to determine the optimal set of simultaneous star observations in a single tracker. 2) The selected optimal observations are identified using a triplet match. 3) The identified stars in the selected tracker at the selected time are used to compute an attitude at that time. 4) The rate data is refined by determination of biases that minimize the dispersion of repeated observations of the same stars. 5) The refined rate data is used to propagate the attitude to the times of each star observation. 6) The attitude at each time is used to associate all stars observed at that time, in each tracker, with catalog stars. The overall algorithm is very dependable at producing accurate star identification with no initial attitude input.

  4. Hybrid spin and valley quantum computing with singlet-triplet qubits.

    PubMed

    Rohling, Niklas; Russ, Maximilian; Burkard, Guido

    2014-10-24

    The valley degree of freedom in the electronic band structure of silicon, graphene, and other materials is often considered to be an obstacle for quantum computing (QC) based on electron spins in quantum dots. Here we show that control over the valley state opens new possibilities for quantum information processing. Combining qubits encoded in the singlet-triplet subspace of spin and valley states allows for universal QC using a universal two-qubit gate directly provided by the exchange interaction. We show how spin and valley qubits can be separated in order to allow for single-qubit rotations. PMID:25379928

  5. Hybrid Spin and Valley Quantum Computing with Singlet-Triplet Qubits

    NASA Astrophysics Data System (ADS)

    Rohling, Niklas; Russ, Maximilian; Burkard, Guido

    2015-03-01

    The valley degree of freedom in the electronic band structure of silicon, graphene, and other materials is often considered to be an obstacle for quantum computing (QC) based on electron spins in quantum dots. Here we show that control over the valley state opens new possibilities for quantum information processing. Combining qubits encoded in the singlet-triplet subspace of spin and valley states allows for universal QC using a universal two-qubit gate directly provided by the exchange interaction. We show how spin and valley qubits can be separated in order to allow for single-qubit rotations.

  6. Low-temperature (77 K) phosphorescence of triplet chlorophyll in isolated reaction centers of photosystem II.

    PubMed

    Neverov, Konstantin V; Krasnovsky, Alexander A; Zabelin, Alexey A; Shuvalov, Vladimir A; Shkuropatov, Anatoly Ya

    2015-08-01

    Phosphorescence characterized by the main emission band at 952 ± 1 nm (1.30 eV), the lifetime of 1.5 ± 0.1 ms and the quantum yield nearly equal to that for monomeric chlorophyll a in aqueous detergent dispersions, has been detected in isolated reaction centers (RCs) of spinach photosystem II at 77 K. The excitation spectrum shows maxima corresponding to absorption bands of chlorophyll a, pheophytin a, and ?-carotene. The phosphorescence intensity strongly depends upon the redox state of RCs. The data suggest that the phosphorescence signal originates from the chlorophyll triplet state populated via charge recombination in the radical pair [Formula: see text]. PMID:25712165

  7. Short-Range Characterization of the MeAr (Me=Zn, Cd) Ground-State Potentials from Fluorescence Spectra

    NASA Astrophysics Data System (ADS)

    Koperski, J.; Czajkowski, M.

    2002-04-01

    First-time observed D1(1?)v?=10?X0+(1?) fluorescence in ZnAr, and A0+(3?)v?=4?X0+ and D1(1?)v?=7,8?X0+ fluorescence in CdAr van der Waals (vdW) molecules were produced in a continuous supersonic molecular beam crossed with a pulsed dye-laser beam, following excitation of single vibronic levels. The dispersed fluorescence spectra displayed characteristic Condon internal diffraction (CID) patterns consisting of bound-free, reflection type, continuous spectra, and, in certain cases, bound-bound discrete features. An analysis of the A0+?X0+ and D1?X0+ bound-bound spectra indicates that Morse functions are adequate representations of the X0+ potential energy (PE) curves below their dissociation limits. In simulation of the A0+?X0+ and D1?X0+ bound-free spectra, the Morse, Lennard-Jones L-J(n-6), and Maitland-Smith M-S(n0,n1) functions were tested, and the respective M-S(11.3, 9.0) and M-S(10.6, 7.0) potentials were found to be good representations for the repulsive walls of the X0+ PE curves of ZnAr and CdAr, respectively, over the short range, R=2.45-4.38 Å (ZnAr) and R=2.85-4.31 Å (CdAr), of internuclear separations.

  8. Effects induced by gamma-irradiation and thermal treatment on the infrared spectra of ferrocene in its disordered state

    NASA Astrophysics Data System (ADS)

    Gaffar, M. A.; Abd-Elrahman, M. I.

    2004-10-01

    Lattice, rotation and intramolecular vibrations of ferrocene, Fe(C5H5)(2), crystallites of the C-2h(5) factor group in the disordered phase are calculated using the correlation theorem based on group theory. The correlation between the species of the C-1 site symmetry occupied by cyclopentadienyl molecules and those of the factor group C-2h, of the crystal are calculated. The number of lattice vibrations of the cyclopentadienyl molecules is found to be 12. with active modes in Raman and infrared (IR) spectra. The same number of rotations for the cyclopentadienyl molecules is expected to be allowed in both spectra. The active number of intramolecular vibrations for the cyclopentadienyl molecules having D-5 molecular symmetry is expected to be 80 vibrations in both the Raman and the IR spectra. The effect of gamma-irradiation with different doses and heat treatment at different temperatures on the IR spectra of ferrocene in the energy range 4000-200 cm(-1) is discussed. A number of bands continuously shifted their position, and a decrease in intensity with increasing gamma-dose is observed. New bands appeared in this spectral region for different annealing temperatures and different gamma-doses. These changes are discussed in terms of intermolecular interactions between molecules within the unit cell.

  9. Thermodynamic analysis of spectra

    NASA Astrophysics Data System (ADS)

    Mitchell, G. E.; Shriner, J. F.

    2008-04-01

    Although random matrix theory had its initial application to neutron resonances, there is a relative scarcity of suitable nuclear data. The primary reason for this is the sensitivity of the standard measures used to evaluate spectra—the spectra must be essential pure (no state with a different symmetry) and complete (no states missing). Additional measures that are less sensitive to these experimental limitations are of significant value. The standard measure for long range order is the ?3 statistic. In the original paper that introduced this statistic, Dyson and Mehta also attempted to evaluate spectra with thermodynamic variables obtained from the circular orthogonal ensemble. We consider the thermodynamic "internal energy" and evaluate its sensitivity to experimental limitations such as missing and spurious levels. Monte Carlo simulations suggest that the internal energy is less sensitive to mistakes than is ?3, and thus the internal energy can serve as a addition to the tool kit for evaluating experimental spectra.

  10. The Character of the Long-Lived State Formed from S_1 of Phenylacetylene

    NASA Astrophysics Data System (ADS)

    Johnson, Philip M.; Sears, Trevor J.

    2013-06-01

    Compared to other small aromatic molecules, phenylacetylene (PA) and benzonitrile exhibit strikingly anomalous photophysics on excitation to the S_1 state. Firstly, products are formed on S_1 excitation of a beam-cooled sample that seem to live indefinitely (as defined by the flight time through the apparatus), while action spectra of their formation mirror the rotationally-resolved absorption spectrum of the monomer. Secondly, the long lived products appear immediately during the nsec. laser pulse rather than build up during the lifetime of the singlet level, as is seen in benzene, for example. The question has therefore arisen: is the long lived product of the S_1 excitation the triplet state, as is assumed in all previous work on other molecules, or is it an isomer of some sort? New pump-probe ionization mass spectroscopy experiments have been performed to study the distribution of fragments and metastable ions produced by PA cation derived from the neutral S_1 state, and from the long-lived species. These combined with other experimental results showing weak long-lived components in both the S_1 fluorescence and pump-probe photoelectron spectra that we interpret as recurrence behavior, definitively show the long-lived state is a triplet state of PA, not an isomer. PA with a singlet-triplet gap of 10000 cm^{-1} is acting like intermediate case molecules with much smaller singlet-triplet gaps such as pyrazine and pyrimidine. Calculations point to the existence of four triplet states of PA at or below the energy of S_1 providing a very large density of vibronic states in which to distribute the energy from singlet-triplet crossing. PA T_1 is calculated to be non-planar, in contrast to what is found in benzene, possibly helping to explain the different photophysics. Acknowledgments: We gratefully acknowledge G. V. Lopez for his contributions to some of the experimental masurements. Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. J. Hofstein, H. Xu, T. J. Sears and P. M. Johnson, J. Phys. Chem. A 112, 1195-1201 (1999)

  11. Negative Ion Photoelectron Spectroscopy Confirms the Prediction that (CO)5 and (CO)6 Each Has a Singlet Ground State

    SciTech Connect

    Bao, Xiaoguang; Hrovat, David; Borden, Weston; Wang, Xue B.

    2013-03-20

    Cyclobutane-1,2,3,4-tetraone has been both predicted and found to have a triplet ground state, in which a b2g MO and an a2u MO is each singly occupied. In contrast, (CO)5 and (CO)6 have each been predicted to have a singlet ground state. This prediction has been tested by generating the (CO)5 - and (CO)6 - anions in the gas-phase by electrospray vaporization of solutions of, respectively, the croconate (CO)52- and rhodizonate (CO)62- dianions. The negative ion photoelectron (NIPE) spectra of the (CO)5•- radical anion give electron affinity (EA) = 3.830 eV and a singlet ground state for (CO)5, with the triplet higher in energy by 0.850 eV (19.6 kcal/mol). The NIPE spectra of the (CO)6•- radical anion give EA = 3.785 eV and a singlet ground state for (CO)6, with the triplet higher in energy by 0.915 eV (21.1 kcal/mol). (RO)CCSD(T)/aug-cc-pVTZ//(U)B3LYP/6-311+G(2df) calculations give EA values that are only ca. 1 kcal/mol lower than those measured and EST values that are only 2 - 3 kcal/mol higher than those obtained from the NIPE spectra. Thus, the calculations support the interpretations of the NIPE spectra and the finding, based on the spectra, that (CO)5 and (CO)6 both have a singlet ground state.

  12. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra

    SciTech Connect

    Fujihashi, Yuta; Ishizaki, Akihito; Fleming, Graham R.

    2015-06-07

    Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications.

  13. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra.

    PubMed

    Fujihashi, Yuta; Fleming, Graham R; Ishizaki, Akihito

    2015-06-01

    Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications. PMID:26049423

  14. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra

    NASA Astrophysics Data System (ADS)

    Fujihashi, Yuta; Fleming, Graham R.; Ishizaki, Akihito

    2015-06-01

    Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications.

  15. Transport of triplet excitons along continuous 100 nm polyfluorene chains

    DOE PAGESBeta

    Xi, Liang; Bird, Matthew; Mauro, Gina; Asaoka, Sadayuki; Cook, Andrew R.; Chen, Hung -Cheng; Miller, John R.

    2014-12-03

    Triplet excitons created in poly-2,7-(9,9-dihexyl)fluorene (pF) chains with end trap groups in solution are efficiently transported to and captured by the end groups. The triplets explore the entire lengths of the chains, even for ~100 nm long chains enabling determination of the completeness of end capping. The results show that the chains continuous: they may contain transient barriers or traps, such as those from fluctuations of dihedral angles, but are free of major defects that stop motion of the triplets. Quantitative determinations are aided by the addition of a strong electron donor, TMPD, which removes absorption bands of the end-trappedmore »triplets. For chains having at least one end trap, triplet capture is quantitative on the 1 µs timescale imposed by the use of the donor. Fractions of chains having no end traps were 0.15 for pF samples with anthraquinone (AQ) end traps and 0.063 with naphthylimide (NI) end traps. These determinations agreed with measurements by NMR for short (« less

  16. Triplet pregnancy: is the mode of conception related to perinatal outcomes?

    PubMed

    Fennessy, Kristy M; Doyle, Lex W; Naud, Kentia; Reidy, Karen; Umstad, Mark P

    2015-06-01

    Many triplets are conceived as a consequence of assisted reproductive technology (ART). Concerns have been raised that triplet pregnancies conceived by ART are more complicated than those conceived spontaneously. The purpose of this study was to evaluate all triplet pregnancies managed over a 12-year period to determine if there were any differences in outcome based on the mode of conception. All triplet pregnancies between 1999 and 2011 that reached at least 20 weeks' gestation and that were managed at the Royal Women's Hospital (RWH), Melbourne, Victoria were identified. Maternal and neonatal outcomes were compared between ART conceived and spontaneously conceived triplets. In the study period, 53 sets of triplets managed in our institution met the eligibility criteria. Twenty-five triplet sets were conceived by ART and 28 were conceived spontaneously. More ART conceptions resulted in trichorionic triamniotic (TCTA) triplets than did spontaneous conceptions (p = .015). There were no differences between ART and spontaneously conceived triplets for any of the maternal or neonatal complications studied. Trichorionic (TC) triplets delivered at a later gestation than other triplets: 32.1 (SD 2.9) versus 30.4 (SD 3.9) weeks (p = .08). TC triplets were significantly less likely to die than monochorionic (MC) or dichorionic (DC) triplets: 3/93 (3%) versus 13/66 (20%) (p = .025). In conclusion, triplets conceived by ART are more likely to have TCTA placentation and TCTA triplet sets had lower mortality rates than other triplet combinations. Outcomes for triplets conceived by ART were similar to those of triplets conceived spontaneously. PMID:25926295

  17. The wings of the calcium infrared triplet lines in solar-type stars

    NASA Astrophysics Data System (ADS)

    Smith, G.; Drake, J. J.

    1987-07-01

    Profiles of the IR triplet lines of ionized Ca (8494, 8542, and 8662 A) have been calculated in the LTE approximation using model atmospheres representative of solar-type stars. The depth of absorption in the line wings is found to be particularly insensitive to surface gravity. Provided that the relative abundance (RA) of Ca is consistent with the metallicity of the model atmosphere, the depth of absorption becomes more sensitive to metallicity with increasing effective temperature. These conclusions have been tested against accurate measurements of IR triplet line profiles in Tau Ceti (G8 V) and Eta Cas A (G0 V). Using spectra recorded at a dispersion of 1 A/mm and with S/N of about 100, the T(eff), log g, Fe/H, and Ca/H were derived. Line profiles in Tau Ceti were found to be extremely narrow, indicating low rotational and turbulent broadening. The difference in RA between Ca and Fe in this star is consistent with other recent analyses of metal-deficient dwarfs in the Galactic disk. If the RAs of the alpha-particle elements are assumed to follow the Ca abundance rather than the Fe abundance, there is good agreement between observed and calculated profiles. In the case of Eta Cas A, where there appears to be no difference in RA between Ca and Fe, a small discrepancy between observed and calculated line wings is found.

  18. DNA CTG triplet repeats involved in dynamic mutations of neurologically related gene sequences form stable duplexes

    NASA Technical Reports Server (NTRS)

    Smith, G. K.; Jie, J.; Fox, G. E.; Gao, X.

    1995-01-01

    DNA triplet repeats, 5'-d(CTG)n and 5'-d(CAG)n, are present in genes which have been implicated in several neurodegenerative disorders. To investigate possible stable structures formed by these repeating sequences, we have examined d(CTG)n, d(CAG)n and d(CTG).d(CAG)n (n = 2 and 3) using NMR and UV optical spectroscopy. These studies reveal that single stranded (CTG)n (n > 2) forms stable, antiparallel helical duplexes, while the single stranded (CAG)n requires at least three repeating units to form a duplex. NMR and UV melting experiments show that the Tm increases in the order of [(CAG)3]2 < [(CTG)3]2 << (CAG)3.(CTG)3. The (CTG)3 duplex is stable and exhibits similar NMR spectra in solutions containing 0.1-4 M NaCl and at a pH range from 4.6 to 8.8. The (CTG)3 duplex, which contains multiple-T.T mismatches, displays many NMR spectral characteristics similar to those of B-form DNA. However, unique NOE and 1H-31P coupling patterns associated with the repetitive T.T mismatches in the CTG repeats are discerned. These results, in conjunction with recent in vitro studies suggest that longer CTG repeats may form hairpin structures, which can potentially cause interruption in replication, leading to dynamic expansion or deletion of triplet repeats.

  19. Ab initio configuration interaction study of excited states of LiNa3 and Li2Na2 clusters: Interpretation of absorption spectra

    NASA Astrophysics Data System (ADS)

    Bona?i?-Koutecký, V.; Gaus, J.; Guest, M. F.; Koutecký, J.

    1992-04-01

    The ab initio configuration-interaction (CI) study of excited states of mixed alkali metal tetramers LiNa3 and Li2Na2 accounts for spectroscopic patterns obtained from the depletion spectra of neutral species, reproduces observed excitation energies and intensities for allowed transitions, and permits an assignment of cluster structures. For both mixed tetramers, the rhombic forms with a Li atom or atoms on the short diagonal are the most stable structures and give rise to predicted spectra in full agreement with the measured ones. The exact location of Li atoms seems to be more important in Li2Na2 than in LiNa3 since in the former case, only one isomer reproduces all features of the recorded spectrum.

  20. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states

    NASA Astrophysics Data System (ADS)

    Godtliebsen, Ian H.; Christiansen, Ove

    2015-10-01

    It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde.

  1. Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra

    E-print Network

    Fujihashi, Yuta; Ishizaki, Akihito

    2015-01-01

    Recently, nuclear vibrational contribution signatures in 2D electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the e...

  2. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states.

    PubMed

    Godtliebsen, Ian H; Christiansen, Ove

    2015-10-01

    It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde. PMID:26450293

  3. Low-spin states of /sup 250/Cf populated in the electron capture decay of 2. 22-h /sup 250/Es. [ULTIPOLE TRANSITIONS; PARITY; ROTATIONAL STATES; SPIN; VIBRATIONAL STATES; GAMMA SPECTRA

    SciTech Connect

    Ahmad, I.; Sjoblom, R.K.

    1980-09-01

    Low-spin states of /sup 250/Cf have been investigated by measuring ..gamma.. rays and conversion electrons associated with the electron capture decay of 2.22-h /sup 250/Es. Mass-separated /sup 250/Es samples produced by the /sup 249/Cf(d,n) reaction were used for these measurements. The ..gamma..-ray spectra were measured with a 25-cm/sup 3/ coaxial Ge(Li) spectrometer and the electron spectra were measured with a cooled Si(Li) detector. Multipolarities of intense transitions in /sup 250/Cf were deduced and logft values of electron capture transitions were derived from measured electron capture intensities. On the basis of the results of the present investigation the following bandheads were identified in /sup 250/Cf: E (keV),K,I..pi..=871.6, 2,2-; 1031.9, 2,2+; 1154.2, 0,0+; 1175.5, 1,1-; 1210.0, 2,2-; 1244.4, 2,2+; 1266.5, 0,0+; and 1658.1, 2,2+. The 2.22-h state in /sup 250/Es has been given a spin-parity assignment of 1- with configuration )n(734)9/2-; p(633)7/2+)/sub 1//sub -/.

  4. Time-dependent density functional study of the electronic spectra of oligoacenes in the charge states -1, 0, +1, and +2

    NASA Astrophysics Data System (ADS)

    Malloci, G.; Mulas, G.; Cappellini, G.; Joblin, C.

    2007-11-01

    We present a systematic theoretical study of the five smallest oligoacenes (naphthalene, anthracene, tetracene, pentacene, and hexacene) in their anionic, neutral, cationic, and dicationic charge states. We used density functional theory (DFT) to obtain the ground-state optimised geometries, and time-dependent DFT (TD-DFT) to evaluate the electronic absorption spectra. Total-energy differences enabled us to evaluate the electron affinities and first and second ionisation energies, the quasiparticle correction to the HOMO-LUMO energy gap and an estimate of the excitonic effects in the neutral molecules. Electronic absorption spectra have been computed by combining two different implementations of TD-DFT: the frequency-space method to study general trends as a function of charge-state and molecular size for the lowest-lying in-plane long-polarised and short-polarised ? ? ? ? electronic transitions, and the real-time propagation scheme to obtain the whole photo-absorption cross-section up to the far-UV. Doubly ionised PAHs are found to display strong electronic transitions of ? ? ? ? character in the near-IR, visible, and near-UV spectral ranges, like their singly charged counterparts. While, as expected, the broad plasmon-like structure with its maximum at about 17-18 eV is relatively insensitive to the charge-state of the molecule, a systematic decrease with increasing positive charge of the absorption cross-section between ˜6 and ˜12 eV is observed for each member of the class.

  5. Fast and long-range triplet exciton diffusion in metal-organic frameworks for photon upconversion at ultralow excitation power.

    PubMed

    Mahato, Prasenjit; Monguzzi, Angelo; Yanai, Nobuhiro; Yamada, Teppei; Kimizuka, Nobuo

    2015-09-01

    The conversion of low-energy light into photons of higher energy based on sensitized triplet-triplet annihilation upconversion (TTA-UC) has emerged as a promising wavelength-shifting methodology because it permits UC at excitation powers as low as the solar irradiance. However, its application has been significantly hampered by the slow diffusion of excited molecules in solid matrices. Here, we introduce metal-organic frameworks (MOFs) that promote TTA-UC by taking advantage of triplet exciton migration among fluorophores that are regularly aligned with spatially controlled chromophore orientations. We synthesized anthracene-containing MOFs with different molecular orientations, and the analysis of TTA-UC emission kinetics unveiled a high triplet diffusion rate with a micrometre-scale diffusion length. Surface modification of MOF nanocrystals with donor molecules and their encapsulation in glassy poly(methyl methacrylate) (PMMA) allowed the construction of molecular-diffusion-free solid-state upconverters, which lead to an unprecedented maximization of overall UC quantum yield at excitation powers comparable to or well below the solar irradiance. PMID:26237125

  6. The memory conjunction error paradigm: normative data for conjunction triplets.

    PubMed

    Leding, Juliana K; Lampinen, James Michael; Edwards, Norman W; Odegard, Timormy N

    2007-11-01

    In the typical memory conjunction experiment, participants are presented with two "parent" stimulus items (e.g., blackmail and jailbird) that are later recombined to form a "conjunction lure" (e.g., blackbird). This paradigm is an efficient way to test false memories because participants frequently show false recognition for the recombined features of the previously studied stimuli. Two experiments are reported in which normative data for 96 memory conjunction triplets are presented. The first experiment provides descriptive statistics for how often the conjunction triplets show true and false recognition. Due to the variance in the rates of false recognition for the conjunction lure, the second experiment was conducted to help build an understanding of the factors that affect the rate of false recognition of the conjunction lures. Conceptual overlap of the first parent word and the conjunction item predicted false recognition. Digital files containing norms for 96 memory conjunction triplets may be downloaded from www.psychonomic.org/archive. PMID:18183909

  7. Theoretical calculations and vibrational spectra of 1,4-benzodioxan in its S 1(?, ? *) electronic excited state

    NASA Astrophysics Data System (ADS)

    Yang, Juan; Choo, Jaebum; Kwon, Ohyun; Laane, Jaan

    2007-12-01

    The structure and vibrational frequencies of 1,4-benzodioxan in its S 1(?, ? *) electronic state have been calculated using the GAUSSIAN 03 and TURBOMOLE programs. The results have been compared to experimental data and also to the ground state. Structural data for the T 1(?, ? *) state have also been calculated. The theoretical frequencies agree very well with the experimental values for the S 0 electronic ground state but are less accurate for the S 1 excited state. Nonetheless, they provide valuable guidance for excited state calculations.

  8. Analysis of leptogenesis in a supersymmetric triplet seesaw model

    SciTech Connect

    Chun, Eung Jin; Scopel, Stefano

    2007-01-15

    We analyze leptogenesis in a supersymmetric triplet seesaw scenario that explains the observed neutrino masses, adopting a phenomenological approach where the decay branching ratios of the triplets and the amount of CP violation in its different decay channels are assumed as free parameters. We find that the solutions of the relevant Boltzmann equations lead to a rich phenomenology, in particular, much more complex compared to the nonsupersymmetric case, mainly due to the presence of an additional Higgs doublet. Several unexpected and counter-intuitive behaviors emerge from our analysis: the amount of CP violation in one of the decay channels can prove to be irrelevant to the final lepton asymmetry, leading to successful leptogenesis even in scenarios with a vanishing CP violation in the leptonic sector; gauge annihilations can be the dominant effect in the determination of the evolution of the triplet density up to very high values of its mass, leading anyway to a sizeable final lepton asymmetry, which is also a growing function of the washout parameter K{identical_to}{gamma}{sub d}/H, defined as usual as the ratio between the triplet decay amplitude {gamma}{sub d} and the Hubble constant H; on the other hand, cancellations in the Boltzmann equations may lead to a vanishing lepton asymmetry if in one of the decay channels both the branching ratio and the amount of CP violation are suppressed, but not vanishing. The present analysis suggests that in the supersymmetric triplet seesaw model successful leptogenesis can be attained in a wide range of scenarios, provided that an asymmetry in the decaying triplets can act as a lepton-number reservoir.

  9. Analysis of Leptogenesis in Supersymmetric Triplet Seesaw Model

    E-print Network

    E. J. Chun; S. Scopel

    2006-09-26

    We analyze leptogenesis in a supersymmetric triplet seesaw scenario that explains the observed neutrino masses, adopting a phenomenological approach where the decay branching ratios of the triplets and the amount of CP--violation in its different decay channels are assumed as free parameters. We find that the solutions of the relevant Boltzmann equations lead to a rich phenomenology, in particular much more complex compared to the non--supersymmetric case, mainly due to the presence of an additional Higgs doublet. Several unexpected and counter--intuitive behaviors emerge from our analysis: the amount of CP violation in one of the decay channels can prove to be be irrelevant to the final lepton asymmetry, leading to successful leptogenesis even in scenarios with a vanishing CP violation in the leptonic sector; gauge annihilations can be the dominant effect in the determination of the evolution of the triplet density up to very high values of its mass, leading anyway to a sizeable final lepton asymmetry, which is also a growing function of the wash--out parameter K=Gamma_d/H, defined as usual as the ratio between the triplet decay amplitude Gamma_d and the Hubble constant H; on the other hand, cancellations in the Boltzmann equations may lead to a vanishing lepton asymmetry if in one of the decay channels both the branching ratio and the amount of CP violation are suppressed, but not vanishing. The present analysis suggests that in the supersymmetric triplet see-saw model successful leptogenesis can be attained in a wide range of scenarios, provided that an asymmetry in the decaying triplets can act as a lepton--number reservoir.

  10. Binding energies of triplet excimers in poly(N-vinylcarbazole) solid films from laser-based kinetic spectroscopy between 15 and 55 K

    SciTech Connect

    Burkhart, R.D.; Chakraborty, D.K. )

    1990-05-17

    Time-resolved delayed luminescence spectra from solid films of poly(N-vinylcarbazole) have been recorded in the temperature interval between 15 and 55 K. Below 40 K the phosphorescence spectra are primarily nonexcimeric in character but become totally excimeric at 55 K. Rate constants for the phosphorescence decay in this same temperature interval yield linear Arrhenius plots but with a discontinuous change in slope at 40 K. The activation energy above 40 K is 2.0 kJ/mol and is associated with the trapping of nonexcimeric triplets. When combined with previous determinations of the activation energies for detrapping of triplet excimers, binding energies of 2.5 and 12.1 kJ/mol are found for the shallow and deep excimers relative to the energy of the limited free rotor, the energy of which corresponds to the top of the activation barrier.

  11. Chromospheric Polarization in the Photospheric Solar Oxygen Infrared Triplet

    E-print Network

    Alemán, T del Pino

    2015-01-01

    We present multilevel radiative transfer modeling of the scattering polarization observed in the solar O I infrared triplet around 777 nm. We demonstrate that the scattering polarization pattern observed on the solar disk forms in the chromosphere, far above the photospheric region where the bulk of the emergent intensity profiles originates. We study the sensitivity of the polarization pattern to the thermal structure of the solar atmosphere and to the presence of weak magnetic fields (0.01 - 100 G) through the Hanle effect, showing that the scattering polarization signals of the oxygen infrared triplet encode information on the magnetism of the solar chromosphere.

  12. Proximity-induced triplet superconductivity in Rashba materials

    NASA Astrophysics Data System (ADS)

    Reeg, Christopher R.; Maslov, Dmitrii L.

    2015-10-01

    We study a proximity junction between a conventional s -wave superconductor and a conductor with Rashba spin-orbit coupling, with a specific focus on the spin structure of the induced pairing amplitude. We find that spin-triplet pairing correlations are induced by spin-orbit coupling in both one- and two-dimensional systems due to the lifted spin degeneracy. Additionally, this induced triplet pairing has a component with an odd frequency dependence that is robust to disorder. Our predictions are based on the solutions of the exact Gor'kov equations and are beyond the quasiclassical approximation.

  13. The SLUGGS survey: calcium triplet-based spectroscopic metallicities for over 900 globular clusters

    NASA Astrophysics Data System (ADS)

    Usher, Christopher; Forbes, Duncan A.; Brodie, Jean P.; Foster, Caroline; Spitler, Lee R.; Arnold, Jacob A.; Romanowsky, Aaron J.; Strader, Jay; Pota, Vincenzo

    2012-10-01

    Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index-metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In six of the eight galaxies with sufficient numbers of high-quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that most massive early-type galaxies have bimodal metallicity as well as colour distributions. This bimodality suggests that most massive early-type galaxies experienced two periods of star formation.

  14. Triplet excimer-monomer equilibria as structural probes in pure and molecularly doped polymers

    SciTech Connect

    Burkhart, R.D.; Jhon, Nam-In

    1993-12-31

    Solid films of vinyl aromatic polymers usually emit an excimeric type of phosophorescence at temperatures of 77 K or greater. At temperatures near 10 K these emission spectra are definitely nonexcimeric and at intermediate temperatures the two types of emission coexist. Using the assumption that triplet excimers are formed by trapping at an excimer-forming site, activation energies have been determined for both trapping and detrapping by measuring rates of decay of the excimeric and nonexcimeric emission. The activation energies for trapping of a given chromophore are independent of whether that chromophore is bonded to a chain backbone or present as a small molecule dopant in a polystyrene matrix. The activation energies for detrapping are potentially valuable as an indicator of microstructure for polymers containing a chromphoric group that is phosphorescent. 14 refs., 2 figs., 1 tab.

  15. Measurements of Ca II Infrared Triplet Lines of Young Stellar Objects

    E-print Network

    Moto'oka, Keiko

    2015-01-01

    Equivalent widths and line widths of Ca II infrared triplet emission lines were measured in high-resolution optical spectra of 39 young stellar objects.We found that the equivalent widths of the emission lines decrease with stellar evolution. It has been often claimed that strong chromospheric activity is generated by a dynamo process caused by fast rotation of the photosphere. However, we found no clear correlation between the strength of the Ca II lines and the stellar rotation velocity. Instead, we found that the objects with high mass accretion rates had stronger Ca II emission lines. This correlation supports the turbulent chromosphere model or the magnetic accretion theory for classical T Tauri stars. We also noticed that the equivalent widths of Ca II lines of transitional disk objects are one-tenth of those of classical T Tauri stars, even if the masses of the circumstellar disks are comparable.

  16. Singlet-Triplet Excitations in the Unconventional Spin-Peierls System TiOBr

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gaulin, B. D.; Adams, C. P.; Granroth, G. E.; Kolesnikov, A. I.; Sherline, T. E.; Chou, F. C.

    2011-03-01

    TiOBr belongs to a select group of quasi-one-dimensional materials which undergo a spin-Peierls (SP) phase transition and develop a dimerized singlet ground state at low temperatures. However, unlike conventional SP systems, TiOBr exhibits not one, but two successive phase transitions upon cooling: a continuous transition into an incommensurate SP state at TC 2 ~ 48 K, followed by a discontinuous transition into a commensurate SP state at TC 1 ~ 27 K. We have performed time-of-flight neutron scattering measurements on powder samples of TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the Spallation Neutron Source. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate SP phases, which we associate with n = 1 and n = 2 triplet excitations out of the singlet ground state. This study represents the first direct measure of the singlet-triplet energy gap in TiOBr, which we have determined to be Eg = 21.2 +/- 1.0 meV.

  17. Higgs triplets at like-sign linear colliders and neutrino mixing

    SciTech Connect

    Rodejohann, Werner; Zhang He

    2011-04-01

    We study the phenomenology of the type-II seesaw model at a linear e{sup -}e{sup -} collider. We show that the process e{sup -}e{sup -}{yields}{alpha}{sup -}{beta}{sup -} ({alpha}, {beta}=e, {mu}, {tau} being charged leptons) mediated by a doubly charged scalar is very sensitive to the neutrino parameters, in particular, the absolute neutrino mass scale and the Majorana CP-violating phases. We identify the regions in parameter space in which appreciable collider signatures in the channel with two like-sign muons in the final state are possible. This includes Higgs triplet masses beyond the reach of the LHC.

  18. Spectral triplets, statistical mechanics and emergent geometry in non-commutative quantum mechanics

    E-print Network

    F. G. Scholtz; B. Chakraborty

    2012-10-12

    We show that when non-commutative quantum mechanics is formulated on the Hilbert space of Hilbert-Schmidt operators (referred to as quantum Hilbert space) acting on a classical configuration space, spectral triplets as introduced by Connes in the context of non-commutative geometry arise naturally. A distance function as defined by Connes can therefore also be introduced. We proceed to give a simple and general algorithm to compute this function. Using this we compute the distance between pure and mixed states on quantum Hilbert space and demonstrate a tantalizing link between statistics and geometry.

  19. Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Gopinath, T.; Veglia, Gianluigi

    2013-05-01

    We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

  20. Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

    PubMed Central

    Gopinath, T.; Veglia, Gianluigi

    2013-01-01

    We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils. PMID:23676036

  1. The covariance of the differences between experimental and theoretical chemical shifts as an aid for assigning two-dimensional heteronuclear correlation solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Czernek, Ji?í; Brus, Ji?í

    2014-07-01

    A robust method for the assignment of two-dimensional heteronuclear correlations in the solid-state NMR spectra is described. It statistically evaluates the differences between measured and theoretical (obtained from first-principles calculations of the NMR chemical shielding property of periodic materials) chemical shifts. The values of the covariance of these differences, and of the standard deviations of the respective linear correlations, are elucidative for the spectral assignment process. The efficacy of the method is demonstrated for three crystalline systems: L-tyrosine hydrochloride, L-tyrosine ansolvate, and the polymorphic form I of o-acetylsalicylic acid.

  2. 78 FR 35658 - Spectra Energy Corp., Application for a New or Amended Presidential Permit

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-13

    ...DEPARTMENT OF STATE [Public Notice 8353] Spectra Energy Corp., Application for a New...State. ACTION: Notice of Receipt of Spectra Energy Corp., Application for a New...Department of State (DOS) has received from Spectra Energy Corp (``Spectra...

  3. Rich Information on Quantum States and Ways to Calculate It in The Absorption Spectra of Au144 Gold Cluster Compound

    NASA Astrophysics Data System (ADS)

    Lopez-Lozano, Xochitl; Whetten, Robert L.; Weissker, Hans-Christian

    2015-03-01

    In recent decades, the prevalent view has been that noble-metal clusters of intermediate size necessarily have smooth optical absorption spectra of low information content in the near-IR, VIS and near-UV regions. At most, one expects a broad, smooth localized surface plasmon resonance feature. Recently, we demonstrate that, in contradistinction to the commonly held view, the optical absorption of the most widely applied gold cluster, the thiolate-protected Au144 cluster, exhibits a rich spectrum of bands that are individually visible over the entire near-IR, VIS and near-UV regions (1.0-4.0 eV), demonstrating high information content related to the quantum size effects which distinguish the nanoparticles from the bulk materials. In the calculation, the result is sensitive to the details of the structure. In the present work, we systematically compare the different structures actually used to date. We studied aspects like symmetry, geometry and type of ligands. In particular, we discuss the effect of their differences on the optical absorption spectra as well as how the theoretical methodology influences the final results.

  4. High-efficiency fluorescent organic light-emitting diodes enabled by triplet-triplet annihilation and horizontal emitter orientation

    SciTech Connect

    Mayr, Christian Schmidt, Tobias D.; Brütting, Wolfgang

    2014-11-03

    A green organic light-emitting diode with the fluorescent emitter Coumarin 545T shows an external quantum efficiency (?{sub EQE}) of 6.9%, clearly exceeding the classical limit of 5% for fluorescent emitters. The analysis of the angular dependent photoluminescence spectrum of the emission layer reveals that 86% of the transition dipole moments are horizontally oriented. Furthermore, transient electroluminescence measurements demonstrate the presence of a delayed emission originating from triplet-triplet annihilation. A simulation based efficiency analysis reveals quantitatively the origin for the high ?{sub EQE}: a radiative exciton fraction higher than 25% and a light-outcoupling efficiency of nearly 30%.

  5. Non-Standard Neutrino Interactions from a Triplet Seesaw Model

    E-print Network

    Michal Malinsky; Tommy Ohlsson; He Zhang

    2008-12-03

    We investigate non-standard neutrino interactions (NSIs) in the triplet seesaw model featuring non-trivial correlations between NSI parameters and neutrino masses and mixing parameters. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus, these NSIs could lead to quite significant signals of lepton flavor violating decays such as \\mu^- \\to e^- \

  6. Augmenting Ridge Curves with Minutiae Triplets for Fingerprint Indexing

    E-print Network

    Ross, Arun Abraham

    Augmenting Ridge Curves with Minutiae Triplets for Fingerprint Indexing Arun Ross and Rajiv, Morgantown, WV 26506 ABSTRACT Given a query fingerprint, the goal of indexing is to identify and retrieve a set of candidate fingerprints from a large database in order to determine a possible match

  7. Spin polarization enhanced by spin-triplet pairing in Sr2RuO4 probed by NMR

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Manago, M.; Yamanaka, T.; Fukazawa, H.; Mao, Z. Q.; Maeno, Y.; Miyake, K.

    2015-09-01

    We report a phenomenon intimately related to the spin-triplet superconductivity. It is well known that the spin susceptibility decreases below the superconducting transition temperature in almost all superconductors because of spin-singlet pair formation, while it may remain unchanged in a handful of spin-triplet exceptions. Here we report the observation in Sr2RuO4 with nuclear magnetic resonance that the spin susceptibility originating from the Ru-4 d electron slightly i n c r e a s e s by ˜2 % of the total and becomes inhomogeneous in the superconducting state. These are reasonably explained if the electron pairs form the equal-spin pairing in the mixed state. A similar phenomenon was predicted for superfluid 3He40 years ago, but had never been demonstrated in any superconductor.

  8. Simulating one-photon absorption and resonance Raman scattering spectra using analytical excited state energy gradients within time-dependent density functional theory

    SciTech Connect

    Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus JJ; Jensen, Lasse

    2013-12-10

    A parallel implementation of analytical time-dependent density functional theory gra- dients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G and a molecular host-guest complex (TTF?CBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host-guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experiment for most exchange-correlation functionals. However, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.

  9. Einstein Observatory SSS and MPC observations of the complex X-ray spectra of Seyfert galaxies. [Solid State Spectrometer and Monitor Proportional Counter

    NASA Technical Reports Server (NTRS)

    Turner, T. J.; Weaver, K. A.; Mushotzky, R. F.; Holt, S. S.; Madejski, G. M.

    1991-01-01

    The X-ray spectra of 25 Seyfert galaxies measured with the Solid State Spectrometer on the Einstein Observatory have been investigated. This new investigation utilizes simultaneous data from the Monitor Proportional Counter, and automatic correction for systematic effects in the Solid State Spectrometer which were previously handled subjectively. It is found that the best-fit single-power-law indices generally agree with those previously reported, but that soft excesses of some form are inferred for about 48 percent of the sources. One possible explanation of the soft excess emission is a blend of soft X-ray lines, centered around 0.8 keV. The implications of these results for accretion disk models are discussed.

  10. Delayed fluorescence of a poly (p-phenylenevinylene) derivative: Triplet-triplet annihilation versus geminate pair recombination

    NASA Astrophysics Data System (ADS)

    Gerhard, A.; Bässler, H.

    2002-10-01

    The question of the origin of delayed fluorescence from a phenyl-substituted poly(p-phenylenevinylene)-type copolymer (Ph-PPV) is addressed. Two origins have to be considered, i.e., triplet-triplet annihilation and recombination of geminate electron-hole pairs. Ph-PPV is investigated in the form of two different samples, namely diluted in 2-methyltetrahydrofuran (MTHF) glass at 80 K and as a thin film of optical density of 0.6. It will be shown that in the diluted solution, delayed fluorescence is due to triplet-triplet annihilation and in the thin film, it is due to geminate pair recombination. The assignment of delayed fluorescence to geminate pair recombination in the thin film could be made due to delayed fluorescence experiments under applying an electric field of 2×106 V/cm. The delayed fluorescence is strongly influenced by the electric field which is a sign that charged species, i.e., geminate electron-hole pairs, are involved in the process of delayed fluorescence.

  11. Sulphur abundances in halo giants from the [S I] line at 1082 nm and the S I triplet around 1045 nm

    E-print Network

    Jönsson, H; Nissen, P E; Collet, R; Eriksson, K; Asplund, M; Gustafsson, B

    2011-01-01

    It is still debated whether or not the Galactic chemical evolution of sulphur in the halo followed the constant or flat trend with [Fe/H], ascribed to the result of explosive nucleosynthesis in type II SNe. The aim of this study is to try to clarify this situation by measuring the sulphur abundance in a sample of halo giants using two diagnostics; the S I triplet around 1045 nm and the [S I] line at 1082 nm. The latter of the two is not believed to be sensitive to non-LTE effects. We can thereby minimize the uncertainties in the diagnostic used and estimate the usefulness of the triplet in sulphur determination in halo K giants. We will also be able to compare our sulphur abundance differences from the two diagnostics with the expected non-LTE effects in the 1045 nm triplet previously calculated by others. High-resolution near-infrared spectra of ten K giants were recorded using the spectrometer CRIRES mounted on VLT. Two standard settings were used; one covering the S I triplet and one covering the [S I] lin...

  12. Characterization of the excited states of indigo derivatives in their reduced forms.

    PubMed

    Rondão, Raquel; Seixas de Melo, J Sérgio; Voss, Gundula

    2010-06-21

    A comprehensive characterization of the electronic spectral and photophysical properties of the leuco (reduced) form of several indigo derivatives, including indigo and Tyrian Purple, with di-, tetra-, and hexa-substitution, was obtained in solution. The characterization involves absorption, fluorescence, and triplet-triplet absorption spectra, together with quantitative measurements of quantum yields of fluorescence, phi(F) (0.46-0.04), intersystem crossing, phi(Tau) (0.013-0.034), internal conversion, phi(IC), and the corresponding lifetimes. The position and degree of substitution promote differences in the spectral and photophysical properties displayed by the investigated leuco derivatives. The phi(F) values are about two orders of magnitude higher than those previously obtained for the corresponding keto forms. Also in contrast with the behavior found for the keto forms, the S(1) approximately approximately -->T(1) intersystem crossing is an efficient route for the excited-state deactivation channel. These findings strengthen the fact that, in contrast to keto indigo where the internal conversion dominates the deactivation of the excited-state, with leuco indigo (and derivatives), the excited state deactivation involves competition between internal conversion, triplet state formation, and fluorescence. A time-resolved investigation of one of the compounds in glycerol showed the presence of a photoisomerization process. PMID:20401897

  13. Reliable Prediction with Tuned Range-Separated Functionals of the Singlet-Triplet Gap in Organic Emitters for Thermally Activated Delayed Fluorescence.

    PubMed

    Sun, Haitao; Zhong, Cheng; Brédas, Jean-Luc

    2015-08-11

    The thermally activated delayed fluorescence (TADF) mechanism has recently attracted significant interest in the field of organic light-emitting diodes (OLEDs). TADF relies on the presence of a very small energy gap between the lowest singlet and triplet excited states. Here, we demonstrate that time-dependent density functional theory in the Tamm-Dancoff approximation can be very successful in calculations of the lowest singlet and triplet excitation energies and the corresponding singlet-triplet gap when using nonempirically tuned range-separated functionals. Such functionals provide very good estimates in a series of 17 molecules used in TADF-based OLED devices with mean absolute deviations of 0.15 eV for the vertical singlet excitation energies and 0.09 eV [0.07 eV] for the adiabatic [vertical] singlet-triplet energy gaps as well as low relative errors and high correlation coefficients compared to the corresponding experimental values. They significantly outperform conventional functionals, a feature which is rationalized on the basis of the amount of exact-exchange included and the delocalization error. The present work provides a reliable theoretical tool for the prediction and development of novel TADF-based materials with low singlet-triplet energetic splittings. PMID:26574466

  14. Neutral Higgs Bosons in the Higgs Triplet Model with nontrivial mixing

    E-print Network

    Fatemeh Arbabifar; Sahar Bahrami; Mariana Frank

    2012-11-29

    We revisit the neutral Higgs sector of the Higgs Triplet Model, with non-negligible mixing in the CP-even Higgs sector. We examine the possibility that one of the Higgs boson state is the particle observed at the LHC at 125 GeV, and the other is either the small LEP excess at 98 GeV; or the CMS excess at 136 GeV; or that the neutral Higgs bosons are (almost) degenerate and have both mass 125 GeV. We show that, under general considerations, an (unmixed) neutral Higgs boson cannot have an enhanced decay branching ratio into gamma gamma with respect to the Standard Model one. An enhancement is however possible for the mixed case, but only for the heavier of the two neutral Higgs bosons, and not for mass-degenerate Higgs bosons. At the same time the branching ratios into WW^*,ZZ^*, bb and tau tau are similar to the Standard Model, or reduced. We correlate the branching ratios of both Higgs states into Z gamma to those into gamma gamma for the three scenarios. The mixed neutral sector of the Higgs triplet model exhibits some features which could distinguish it from other scenarios at the LHC.

  15. Nonequilibrium dynamics of a singlet-triplet Anderson impurity near the quantum phase transition.

    PubMed

    Roura Bas, P; Aligia, A A

    2010-01-20

    We study the singlet-triplet Anderson model (STAM) in which a configuration with a doublet is hybridized with another containing a singlet and a triplet, as a minimal model to describe two-level quantum dots coupled to two metallic leads in effectively a one-channel fashion. The model has a quantum phase transition which separates regions of a doublet and a singlet ground state. The limits of integer valence of the STAM (which include a model similar to the underscreened spin-1 Kondo model) are derived and used to predict the behavior of the conductance through the system on both sides of the transition, where it jumps abruptly. At a special quantum critical line, the STAM can be mapped to an infinite- U ordinary Anderson model (OAM) plus a free spin 1/2. We use this mapping to obtain the spectral densities of the STAM as a function of those of the OAM at the transition. Using the non-crossing approximation (NCA), we calculate the spectral densities and conductance through the system as a function of temperature and bias voltage, and determine the changes that take place at the quantum phase transition. The separation of the spectral density into a singlet and a triplet part allows us to shed light on the underlying physics and to explain a shoulder observed recently in the zero bias conductance as a function of temperature in transport measurements through a single fullerene molecule (Roch et al 2008 Nature 453 633). The structure with three peaks observed in nonequilibrium transport in these experiments is also explained. PMID:21386260

  16. Reactivity of bovine whey proteins, peptides, and amino acids toward triplet riboflavin as studied by laser flash photolysis.

    PubMed

    Cardoso, Daniel R; Franco, Douglas W; Olsen, Karsten; Andersen, Mogens L; Skibsted, Leif H

    2004-10-20

    The reaction between the triplet excited state of riboflavin and amino acids, peptides, and bovine whey proteins was investigated in aqueous solution in the pH range from 4 to 9 at 24 degrees C using nanosecond laser flash photolysis. Only tyrosine and tryptophan (and their peptides) were found to compete with oxygen in quenching the triplet state of riboflavin in aqueous solution, with second-order rate constants close to the diffusion limit, 1.75 x 10(9) and 1.40 x 10(9) L mol(-1) s(-1) for tyrosine and tryptophan, respectively, with beta-lactoglobulin and bovine serum albumin having comparable rate constants of 3.62 x 10(8) and 2.25 x 10(8) L mol(-1) s(-1), respectively. Tyrosine, tryptophan, and their peptides react with the photoexcited triplet state of riboflavin by electron transfer from the tyrosine and tryptophan moieties followed by a fast protonation of the resulting riboflavin anion rather than by direct H-atom abstraction, which could be monitored by time-resolved transient absorption spectroscopy as a decay of triplet riboflavin followed by a rise in riboflavin anion radical absorption. For cysteine- and thiol-containing peptides, second-order rate constants depend strongly on pH, for cysteine corresponding to pKaRSH = 8.35. H-atom abstraction seems to operate at low pH, which with rising pH gradually is replaced by electron transfer from the thiol anion. From the pH dependence of the second-order rate constant, the respective values for the H-atom abstraction (k = 1.64 x 10(6) L mol(-1) s(-1)) and for the electron transfer (k = 1.20 x 10(9) L mol(-1) s(-1)) were determined. PMID:15479029

  17. UV-vis spectra of singlet state cationic polycyclic aromatic hydrocarbons: Time-dependent density functional theory study

    SciTech Connect

    Dominikowska, Justyna Domagala, Malgorzata; Palusiak, Marcin

    2014-01-28

    A theoretical study of singlet state cations of polycyclic aromatic hydrocarbons is performed. Appropriate symmetry suitable for further calculations is chosen for each of the systems studied. The excitation states of such species are obtained by the time dependent density functional theory (TD-DFT) method. The computations are performed using both Pople and electronic response properties basis sets. The results obtained with the use of different basis sets are compared. The electronic transitions are described and the relationships for the lowest-lying transitions states of different species are found. The properties of in-plane and out-of-plane transitions are also delineated. The TD-DFT results are compared with the experimental data available.

  18. Homofusion and heterofusion of triplet excitons in a ``real'' organic mixed crystal: Biphenyl host-naphthalene and pyrene guests system

    NASA Astrophysics Data System (ADS)

    Talapatra, Gautam Buddha; Misra, T. N.

    1982-09-01

    The prompt and delayed emission spectra of a biphenyl host with naphthalene and pyrene both as guests mixed crystal have been studied. The fluorescence of naphthalene and pyrene and the excimer fluorescence of pyrene have been observed. The delayed emissions are observed from pyrene and naphthalene as delayed fluorescence of pyrene, phosphorescence of naphthalene, and pyrene. The investigations of excitation spectra of these emissions have shown to be very useful to understand the mechanism of delayed fluorescence generation. The heterogeneous defect-naphthalene and homogeneous naphthalene-naphthalene triplet-triplet annihilation are responsible for the production of delayed fluorescence of pyrene. The kinetic analyses from the decays and buildups have been made. The delayed luminescence decays at various temperatures have found to be nonexponential. However, in the long time region they are nearly exponential. Even in the long time region, the pyrene delayed fluorescence decays and buildups are nonexponential in the temperature range above 130 K. It has been established from the various Arrhenius plots that in this mixed crystal the temperature dependence of the phosphorescence lifetime is controlled by the thermal processes The kinetic scheme described satisfactorily explains the experimental results.

  19. Infrared and Microwave Spectra and Force Field of DBO: The Coriolis Interaction between the nu1 and nu2 + nu3 States.

    PubMed

    Kawashima; Colarusso; Zhang; Bernath; Hirota

    1998-11-01

    The nu1 and nu3 bands of D11BO and the nu1 band of D10BO were observed by using an infrared diode laser spectrometer. The DBO molecule was generated by an ac discharge in a mixture of BCl3, D2, O2, and He. As inferred previously, a strong Coriolis interaction was in fact found to take place between the nu1 and nu2 + nu3 states, and an analysis of the observed nu1 spectra, which explicitly took into account this Coriolis interaction, predicted the pure rotational transition frequencies of DBO in the nu1 state. Pure rotational lines were then detected by microwave spectroscopy, confirming the validity of the infrared assignment. In the microwave experiment DBO molecules were generated by a discharge in a mixture of B2D6 and O2. The three fundamental bands and a hot band of D11BO, as well as the nu1 and nu3 bands of D10BO, were subsequently recorded in emission with a Fourier transform infrared spectrometer. DBO molecules were generated by the reaction of D2 with HBO at temperatures above 800 degreesC in a ceramic tube furnace. All of the observed spectra were simultaneously subjected to a least-squares analysis to obtain molecular parameters in the ground, nu1, nu2, nu3, and nu2 + nu3 states. The results thus obtained improved the force field and molecular structure of the HBO/DBO molecules reported in a previous study (Y. Kawashima, Y. Endo, and E. Hirota, 1989, J. Mol. Spectrosc. 133, 116-127). Copyright 1998 Academic Press. PMID:9770398

  20. Influences of quantum mechanically mixed electronic and vibrational pigment states in 2D electronic spectra of photosynthetic systems: Strong electronic coupling cases

    E-print Network

    Yuta Fujihashi; Graham R. Fleming; Akihito Ishizaki

    2015-06-03

    In 2D electronic spectroscopy studies, long-lived quantum beats have recently been observed in photosynthetic systems, and it has been suggested that the beats are produced by quantum mechanically mixed electronic and vibrational states. Concerning the electronic-vibrational quantum mixtures, the impact of protein-induced fluctuations was examined by calculating the 2D electronic spectra of a weakly coupled dimer with vibrational modes in the resonant condition [J. Chem. Phys. 142, 212403 (2015)]. This analysis demonstrated that quantum mixtures of the vibronic resonance are rather robust under the influence of the fluctuations at cryogenic temperatures, whereas the mixtures are eradicated by the fluctuations at physiological temperatures. However, this conclusion cannot be generalized because the magnitude of the coupling inducing the quantum mixtures is proportional to the inter-pigment coupling. In this study, we explore the impact of the fluctuations on electronic-vibrational quantum mixtures in a strongly coupled dimer. with an off-resonant vibrational mode. Toward this end, we calculate electronic energy transfer (EET) dynamics and 2D electronic spectra of a dimer that corresponds to the most strongly coupled bacteriochlorophyll molecules in the Fenna-Matthews-Olson complex in a numerically accurate manner. The quantum mixtures are found to be robust under the exposure of protein-induced fluctuations at cryogenic temperatures, irrespective of the resonance. At 300 K, however, the quantum mixing is disturbed more strongly by the fluctuations, and therefore, the beats in the 2D spectra become obscure even in a strongly coupled dimer with a resonant vibrational mode. Further, the overall behaviors of the EET dynamics are demonstrated to be dominated by the environment and coupling between the 0-0 vibronic transitions as long as the Huang-Rhys factor of the vibrational mode is small.

  1. Transient photocurrent in molecular junctions: singlet switching on and triplet blocking.

    PubMed

    Petrov, E G; Leonov, V O; Snitsarev, V

    2013-05-14

    The kinetic approach adapted to describe charge transmission in molecular junctions, is used for the analysis of the photocurrent under conditions of moderate light intensity of the photochromic molecule. In the framework of the HOMO-LUMO model for the single electron molecular states, the analytic expressions describing the temporary behavior of the transient and steady state sequential (hopping) as well as direct (tunnel) current components have been derived. The conditions at which the current components achieve their maximal values are indicated. It is shown that if the rates of charge transmission in the unbiased molecular diode are much lower than the intramolecular singlet-singlet excitation/de-excitation rate, and the threefold degenerated triplet excited state of the molecule behaves like a trap blocking the charge transmission, a possibility of a large peak-like transient switch-on photocurrent arises. PMID:23676066

  2. Resonant energy transfer of triplet excitons from pentacene to PbSe nanocrystals.

    PubMed

    Tabachnyk, Maxim; Ehrler, Bruno; Gélinas, Simon; Böhm, Marcus L; Walker, Brian J; Musselman, Kevin P; Greenham, Neil C; Friend, Richard H; Rao, Akshay

    2014-11-01

    The efficient transfer of energy between organic and inorganic semiconductors is a widely sought after property, but has so far been limited to the transfer of spin-singlet excitons. Here we report efficient resonant-energy transfer of molecular spin-triplet excitons from organic semiconductors to inorganic semiconductors. We use ultrafast optical absorption spectroscopy to track the dynamics of triplets, generated in pentacene through singlet exciton fission, at the interface with lead selenide (PbSe) nanocrystals. We show that triplets transfer to PbSe rapidly (<1 ps) and efficiently, with 1.9 triplets transferred for every photon absorbed in pentacene, but only when the bandgap of the nanocrystals is close to resonance (±0.2 eV) with the triplet energy. Following triplet transfer, the excitation can undergo either charge separation, allowing photovoltaic operation, or radiative recombination in the nanocrystal, enabling luminescent harvesting of triplet exciton energy in light-emitting structures. PMID:25282509

  3. Simulation of a tetramer form of 5-chlorouracil: the vibrational spectra and molecular structure in the isolated and in the solid state by using DFT calculations.

    PubMed

    Ortiz, S; Alcolea Palafox, M; Rastogi, V K; Akitsu, T; Hubert Joe, I; Kumar, Satendra

    2013-06-01

    A Raman and FT-IR study of the biomolecule 5-chlorouracil in the solid state was carried out. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. They were performed to clarify the assignments of the experimentally observed bands in the spectra. Calculations in the monomer form and comparisons with the experimental data in Ar matrix were also carried out. The error in the calculated frequencies was analyzed and reduced by using scaling equations and scaling factors deduced from the uracil molecule. The calculations with the B3LYP method and with the 6-31G(d,p) and 6-311+G(2d,p) basis set, appear in general to be useful, when combining with a scaling equation procedure or with the specific scale factors, for interpretation of the general features of the IR and Raman spectra. The scaled values were used in the reassignment of the IR and Raman experimental bands. Comparison of the results with those determined in uracil and 5-halogenated derivatives were performed. The substitution at 5-position of the uracil ring by a chlorine atom has a little effect on the geometric parameters. PMID:23583877

  4. Unification scale versus electroweak-triplet mass in the SU(5)+24F model at three loops

    NASA Astrophysics Data System (ADS)

    Di Luzio, Luca; Mihaila, Luminita

    2013-06-01

    It was shown recently that the original SU(5) theory of Georgi and Glashow, augmented with an adjoint fermionic multiplet 24F, can be made compatible both with neutrino masses and gauge coupling unification. In particular, the model predicts that either electroweak-triplet states are light, within the reach of the Large Hadron Collider (LHC), or proton decay will become accessible at the next generation of megaton-scale facilities. In this paper, we present the computation of the correlation function between the electroweak-triplet masses and the unification scale at the next-to-next-to-leading order. Such an accuracy on the theory side is necessary in order to settle the convergence of the perturbative expansion and to match the experimental precision on the determination of the electroweak gauge couplings at the Z-boson mass scale.

  5. A Climatology of Tropospheric CO over the Central and Southeastern United States and the Southwestern Pacific Ocean Derived from Space, Air, and Ground-based Infrared Interferometer Spectra

    NASA Technical Reports Server (NTRS)

    McMillian, W. Wallace; Strow, L. Larrabee; Revercomb, H.; Knuteson, R.; Thompson, A.

    2003-01-01

    This final report summarizes all research activities and publications undertaken as part of NASA Atmospheric Chemistry and Modeling Analysis Program (ACMAP) Grant NAG-1-2022, 'A Climatology of Tropospheric CO over the Central and Southeastern United States and the Southwestern Pacific Ocean Derived from Space, Air, and Ground-based Infrared Interferometer Spectra'. Major project accomplishments include: (1) analysis of more than 300,000 AERI spectra from the ARM SGP site yielding a 5-year (1998-2002) timeseries of CO retrievals from the Lamont, OK AERI; (2) development of a prototype CO profile retrieval algorithm for AERI spectra; (3) validation and publication of the first CO retrievals from the Scanning High-resolution Interferometer Sounder (SHIS); and (4) development of a prototype AERI tropospheric O3 retrieval algorithm. Compilation and publication of the 5-year Lamont, OK timeseries is underway including a new collaboration with scientists at the Lawrence Berkeley National Laboratory. Public access to this data will be provided upon article submission. A comprehensive CO analysis of the archive of HIS spectra of remains as the only originally proposed activity with little progress. The greatest challenge faced in this project was motivating the University of Wisconsin Co-Investigators to deliver their archived HIS and AERIOO data along with the requisite temperature and water vapor profiles in a timely manner. Part of the supplied HIS dataset from ASHOE may be analyzed as part of a Master s Thesis under a separate project. Our success with the SAFARI 2000 SHIS CO analysis demonstrates the utility of such aircraft remote sensing data given the proper support from the instrument investigators. In addition to the PI and Co-I s, personnel involved in this CO climatology project include one Post Doctoral Fellow, one Research Scientist, two graduate students, and two undergraduate students. A total of fifteen presentations regarding research related to this project were delivered at eleven different scientific meetings. Thus far, three publications have resulted from this project with another five in preparation. No subject inventions resulted from this research project.

  6. Vibrational spectra and structures of urazole and 4-methylurazole: DFT calculations of the normal modes in aqueous solution and in the solid state, and the influence of hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Ryall, John P.; Dines, Trevor J.; Chowdhry, Babur Z.; Leharne, Stephen A.; Withnall, Robert

    2010-08-01

    Solid-state IR and Raman as well as aqueous solution state Raman spectra are reported for urazole, 4-methylurazole and their deuterated derivatives. DFT calculations, at the B3-LYP/cc-pVTZ level, established that the structures and vibrational spectra of the molecules can be interpreted using models with hydrogen-bonded water molecules, in conjunction with the polarizable continuum solvation method. The vibrational spectra were computed at the optimised molecular geometry in each case, enabling normal coordinate analysis, which yielded satisfactory agreement with the experimental IR and Raman data. Computed potential energy distributions of the normal modes provided detailed vibrational assignments. Solid-state pseudopotential-plane-wave DFT calculations, using the PW91 functional were also carried out, reflecting the importance of intermolecular hydrogen bonding in the solid state.

  7. HEAT EXCHANGER DESIGN STUDIES FOR AN LHC INNER TRIPLET UPGRADE

    SciTech Connect

    Rabehl, R. J.; Huang, Y.

    2008-03-16

    A luminosity upgrade of the CERN Large Hadron Collider (LHC) is planned to coincide with the expected end of life of the existing inner triplet quadrupole magnets. The upgraded inner triplet will have much larger heat loads to be removed from the magnets by the cryogenics system. A number of cryogenics design studies have been completed under the LHC Accelerator Research Program (LARP), including investigations of required heat exchanger characteristics to transfer this heat from the pressurized He II bath to the saturated He II system. This paper discusses heat exchangers both external to the magnet cold mass and internal to the magnet cold mass. A possible design for a heat exchanger external to the magnet cold mass is also presented.

  8. Composite Heavy Vector Triplet in the ATLAS Diboson Excess

    NASA Astrophysics Data System (ADS)

    Thamm, Andrea; Torre, Riccardo; Wulzer, Andrea

    2015-11-01

    Vector triplets of the standard model SU (2 )L group are a universal prediction of "natural" new physics models involving a new composite sector and are therefore among the most plausible new particles that the LHC could discover. We consider the possibility that one such triplet could account for the ATLAS excess in the boson-tagged jets analysis and we assess the compatibility of this hypothesis with all other relevant searches. We find that the hypothesis is not excluded and that the predicted signal is close to the expected sensitivity of several channels, some of which show an upper fluctuation of the observed limit while others do not. An accurate study of the signal compatibility with these fluctuations could only be performed by the experimental collaborations.

  9. Influences of quantum mechanically mixed electronic and vibrational pigment states in 2D electronic spectra of photosynthetic systems: Strong electronic coupling cases

    E-print Network

    Fujihashi, Yuta; Ishizaki, Akihito

    2015-01-01

    In 2D electronic spectroscopy studies, long-lived quantum beats have recently been observed in photosynthetic systems, and it has been suggested that the beats are produced by quantum mechanically mixed electronic and vibrational states. Concerning the electronic-vibrational quantum mixtures, the impact of protein-induced fluctuations was examined by calculating the 2D electronic spectra of a weakly coupled dimer with vibrational modes in the resonant condition [J. Chem. Phys. 142, 212403 (2015)]. This analysis demonstrated that quantum mixtures of the vibronic resonance are rather robust under the influence of the fluctuations at cryogenic temperatures, whereas the mixtures are eradicated by the fluctuations at physiological temperatures. However, this conclusion cannot be generalized because the magnitude of the coupling inducing the quantum mixtures is proportional to the inter-pigment coupling. In this study, we explore the impact of the fluctuations on electronic-vibrational quantum mixtures in a strongl...

  10. Abundance gradients in cooling flow clusters: Ginga Large Area Counters and Einstein Solid State Spectrometer spectra of A496, A1795, A2142, and A2199

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III; Day, C. S. R.; Hatsukade, Isamu; Hughes, John P.

    1994-01-01

    We analyze the Ginga Large Area Counters (LAC) and Einstein Solid State Spectrometer (SSS) spectra of four cooling flow clusters, A496, A1795, A2142, and A2199, each of which shows firm evidence of a relatively cool component. The inclusion of such cool spectral components in joint fits of SSS and LAC data leads to somewhat higher global temperatures than are derived from the high-energy LAC data alone. We find little evidence of cool emission outside the SSS field of view. Metal abundances appear to be centrally enhanced in all four clusters, with varying degrees of model dependence and statistical significance: the evidence is statistically strongest for A496 and A2142, somewhat weaker for A2199 and weakest for A1795. We also explore the model dependence in the amount of cold, X-ray-absorbing matter discovered in these clusters by White et al.

  11. Calculation of quasi-static helium triplet diffuse line profiles

    NASA Technical Reports Server (NTRS)

    Scott, C. D.

    1972-01-01

    Calculated spectral line profiles (intensity distributions) of the helium triplet diffuse series were obtained using the quasi-static approximation for ions and electrons. In these calculations, Doppler broadening, although negligible in most of the cases, was included as a device to avoid singularities. Plots and tabulations of the calculated profiles are presented, in addition to a discussion of the computational procedure and the validity of the calculations.

  12. The Triplet Genetic Code had a Doublet Predecessor

    E-print Network

    Apoorva Patel

    2004-10-28

    Information theoretic analysis of genetic languages indicates that the naturally occurring 20 amino acids and the triplet genetic code arose by duplication of 10 amino acids of class-II and a doublet genetic code having codons NNY and anticodons $\\overleftarrow{\\rm GNN}$. Evidence for this scenario is presented based on the properties of aminoacyl-tRNA synthetases, amino acids and nucleotide bases.

  13. Anomalous Josephson Hall effect in magnet/triplet superconductor junctions

    NASA Astrophysics Data System (ADS)

    Yokoyama, Takehito

    2015-11-01

    We investigate anomalous Hall effect in a magnet coupled to a triplet superconductor under phase gradient. It is found that the anomalous Hall supercurrent arises from the nontrivial structure of the magnetization. The magnetic structure manifested in the Hall supercurrent is characterized by even order terms of the exchange coupling, essentially different from that discussed in the context of anomalous Hall effect, reflecting the dissipationless nature of the supercurrent. We also discuss a possible candidate for magnetic structure to verify our prediction.

  14. Deconfined SU(2) phase with a massive vector boson triplet

    E-print Network

    Bernd A. Berg

    2010-11-29

    We introduce a model of SU(2) and U(1) vector fields with a local U(2) symmetry. Its action can be obtained in the London limit of a gauge invariant regularization involving two scalar fields. Evidence from lattice simulations of the model supports a (zero temperature) SU(2) deconfining phase transition through breaking of the SU(2) center symmetry, and a massive vector boson triplet is found in the deconfined phase.

  15. Coronavirus phylogeny based on triplets of nucleic acids bases

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Liu, Yanshu; Li, Renfa; Zhu, Wen

    2006-04-01

    We considered the fully overlapping triplets of nucleotide bases and proposed a 2D graphical representation of protein sequences consisting of 20 amino acids and a stop code. Based on this 2D graphical representation, we outlined a new approach to analyze the phylogenetic relationships of coronaviruses by constructing a covariance matrix. The evolutionary distances are obtained through measuring the differences among the two-dimensional curves.

  16. Singlet-triplet gaps in large multireference systems: Spin-flip-driven alternatives for bioinorganic modeling

    NASA Astrophysics Data System (ADS)

    de la Lande, Aurélien; Moliner, Vicent; Parisel, Olivier

    2007-01-01

    The proper description of low-spin states of open-shell systems, which are commonly encountered in the field of bioinorganic chemistry, rigorously requires using multireference ab initio methodologies. Such approaches are unfortunately very CPU-time consuming as dynamic correlation effects also have to be taken into account. The broken-symmetry unrestricted (spin-polarized) density functional theory (DFT) technique has been widely employed up to now to bypass that drawback, but despite a number of relative successes in the determination of singlet-triplet gaps, this framework cannot be considered as entirely satisfactory. In this contribution, we investigate some alternative ways relying on the spin-flip time-dependent DFT approach [Y. Shao et al. J. Chem. Phys. 118, 4807 (2003)]. Taking a few well-documented copper-dioxygen adducts as examples, we show that spin-flip (SF)-DFT computed singlet-triplet gaps compare very favorably to either experimental results or large-scale CASMP2 computations. Moreover, it is shown that this approach can be used to optimize geometries at a DFT level including some multireference effects. Finally, a clear-cut added value of the SF-DFT computations is drawn: if pure ab initio data are required, then the electronic excitations revealed by SF-DFT can be considered in designing dramatically reduced zeroth-order variational spaces to be used in subsequent multireference configuration interaction or multireference perturbation treatments.

  17. Semantic similarity: normative ratings for 185 Spanish noun triplets.

    PubMed

    Moldovan, Cornelia D; Ferré, Pilar; Demestre, Josep; Sánchez-Casas, Rosa

    2015-09-01

    The present study introduces the first Spanish database with normative ratings of semantic similarity for 185 word triplets. Each word triplet is constituted by a target word (e.g., guisante [pea]) and two semantically related and nonassociatively related words: a word highly related in meaning to the target (e.g., judía [bean]), and a word less related in meaning to the target (e.g., patata [potato]). The degree of meaning similarity was assessed by 332 participants by using a semantic similarity rating task on a 9-point scale. Pairs having a value of semantic similarity ranging from 5 to 9 were classified as being more semantically related, whereas those with values ranging from 2 to 4.99 were considered as being less semantically related. The relative distance between the two pairs for the same target ranged from 0.48 to 5.07 points. Mean comparisons revealed that participants rated the more similar words as being significantly more similar in meaning to the target word than were the less similar words. In addition to the semantic similarity norms, values of concreteness and familiarity of each word in a triplet are provided. The present database can be a very useful tool for scientists interested in designing experiments to examine the role of semantics in language processing. Since the variable of semantic similarity includes a wide range of values, it can be used as either a continuous or a dichotomous variable. The full database is available in the supplementary materials. PMID:24984982

  18. Heavy triplet neutrinos as a new dark-matter option

    NASA Astrophysics Data System (ADS)

    Chardonnet, Pascal; Fayet, Pierre; Salati, Pierre

    1993-04-01

    We propose a new scheme where dark matter is made of heavy stable neutral particles N, possibly even lighter than 1/2mZ, but uncoupled to the Z0. Such particles should be given an efficient way to annihilate, otherwise their fossil density would overclose the universe. In this scheme, the annihilation results from a delicate interplay between N and its heavier charged electroweak partner E+/-. A closure density may be naturally reached if the mass splitting is ~10 GeV, which suggests that the E+/- may be discovered at LEP 200. The species N results from the mixing between a singlet and the neutral member of a triplet, here induced by the vacuum expectation value of a Higgs triplet. The latter is kept naturally small with respect to the electroweak scale, as a result of a new approximate discrete symmetry, the triplet-parity Tp. We discuss various implications of this model for astrophysics and particle physics. Unité propre de Recherche du CNRS, associée à l'Ecole Normale Supérieure et à l'Université de Paris-Sud.

  19. Millimeter wave and terahertz spectra and global fit of torsion-rotation transitions in the ground, first and second excited torsional states of 13CH3OH methanol

    NASA Astrophysics Data System (ADS)

    Xu, Li-Hong; Lees, R. M.; Hao, Yun; Müller, H. S. P.; Endres, C. P.; Lewen, F.; Schlemmer, S.; Menten, K. M.

    2014-09-01

    Methanol is observed in a wide range of astrophysical sources throughout the universe, and comprehensive databases of the millimeter and THz spectra of CH3OH and its principal isotopologues represent important tools for the astronomical community. A previous combined analysis of microwave and millimeter wave spectra of 13CH3OH together with Fourier transform far-infrared spectra was limited to the first two torsional states, ?t = 0 and 1, for J values up to 20. The limits on frequency and quantum number coverage have recently been extended by new millimeter and THz measurements on several different spectrometers in the Cologne laboratory in the frequency windows 34-70 GHz, 75-120 GHz, 240-340 GHz, 360-450 GHz and 1.12-1.50 THz. With the new data, the global treatment has now been expanded to include the first three torsional states for J values up to 30. The current 13CH3OH data set contains about 2300 microwave, millimeter-wave, sub-millimeter and THz lines and about 17,100 Fourier-transform far-infrared lines, representing the most recent available information in the quantum number ranges J ? 30, K ? 13 and ?t ? 2. The transitions have been successfully fitted to within the assigned measurement uncertainties of ±50 kHz for most of the frequency-measured (i.e. MW, MMW, Sub-MMW, THz) lines and ±6 MHz for the FIR lines. A convergent global fit was achieved using 103 adjustable parameters to reach an overall weighted standard deviation of 1.37. Our new C-13 methanol database is improved substantially compared to the existing one (Li-Hong et al., 1997), and will be available in the Cologne Database for Molecular Spectroscopy, CDMS (http://www.astro.uni-koeln.de/cdms/), in support of astronomical studies associated with results from HIFI (Heterodyne Instrument for the Far-Infrared) on the Herschel Space Observatory and new observations from SOFIA (Stratospheric Observatory For Infrared Astronomy) and ALMA (Atacama Large Millimeter/Submillimeter Array).

  20. Spin supercurrent and phase-tunable triplet Cooper pairs via magnetic insulators

    NASA Astrophysics Data System (ADS)

    Gomperud, Ingvild; Linder, Jacob

    2015-07-01

    We demonstrate theoretically that a dissipationless spin current can flow a long distance through a diffusive normal metal by using superconductors interfaced with magnetic insulators. The magnitude of this spin supercurrent is controlled via the magnetization orientation of the magnetic insulators. The spin supercurrent obtained in this way is conserved in the normal metal just like the charge current and interestingly has a term that is independent of the superconducting phase difference. The quantum state of the system can be switched between 0 and ? by reversing the insulators from a parallel to antiparallel configuration with an external field. We show that the spin current is carried through the normal metal by superconducting triplet (odd-frequency) correlations and that the superconducting phase difference can be used to enhance these, leaving clear spectroscopic fingerprints in the density of states.

  1. Observation of a phononic Mollow triplet in a multimode hybrid spin-nanomechanical system

    NASA Astrophysics Data System (ADS)

    Pigeau, B.; Rohr, S.; Mercier de Lépinay, L.; Gloppe, A.; Jacques, V.; Arcizet, O.

    2015-10-01

    Reminiscent of the bound character of a qubit's dynamics confined on the Bloch sphere, the observation of a Mollow triplet in the resonantly driven qubit fluorescence spectrum represents one of the founding signatures of quantum electrodynamics. Here we report on its observation in a hybrid spin-nanomechanical system, where a nitrogen-vacancy spin qubit is magnetically coupled to the vibrations of a silicon carbide nanowire. A resonant microwave field turns the originally parametric hybrid interaction into a resonant process, where acoustic phonons are now able to induce transitions between the dressed qubit states, leading to synchronized spin-oscillator dynamics. We further explore the vectorial character of the hybrid coupling to the bidimensional deformations of the nanowire. The demonstrated microwave assisted synchronization of the spin-oscillator dynamics opens novel perspectives for the exploration of spin-dependent forces, the key ingredient for quantum state transfer.

  2. Spontaneous Fluctuations of Transition Dipole Moment Orientation in OLED Triplet Emitters.

    PubMed

    Steiner, Florian; Bange, Sebastian; Vogelsang, Jan; Lupton, John M

    2015-03-19

    The efficiency of an organic light-emitting diode (OLED) depends on the microscopic orientation of transition dipole moments of the molecular emitters. The most effective materials used for light generation have 3-fold symmetry, which prohibits a priori determination of dipole orientation due to the degeneracy of the fundamental transition. Single-molecule spectroscopy reveals that the model triplet emitter tris(1-phenylisoquinoline)iridium(III) (Ir(piq)3) does not behave as a linear dipole, radiating with lower polarization anisotropy than expected. Spontaneous symmetry breaking occurs in the excited state, leading to a random selection of one of the three ligands to form a charge-transfer state with the metal. This nondeterministic localization is revealed in switching of the degree of linear polarization of phosphorescence. Polarization scrambling likely raises out-coupling efficiency and should be taken into account when deriving molecular orientation of the guest emitter within the OLED host from ensemble angular emission profiles. PMID:26262859

  3. Observation of a phononic Mollow triplet in a multimode hybrid spin-nanomechanical system

    PubMed Central

    Pigeau, B.; Rohr, S.; Mercier de Lépinay, L.; Gloppe, A.; Jacques, V.; Arcizet, O.

    2015-01-01

    Reminiscent of the bound character of a qubit's dynamics confined on the Bloch sphere, the observation of a Mollow triplet in the resonantly driven qubit fluorescence spectrum represents one of the founding signatures of quantum electrodynamics. Here we report on its observation in a hybrid spin-nanomechanical system, where a nitrogen-vacancy spin qubit is magnetically coupled to the vibrations of a silicon carbide nanowire. A resonant microwave field turns the originally parametric hybrid interaction into a resonant process, where acoustic phonons are now able to induce transitions between the dressed qubit states, leading to synchronized spin-oscillator dynamics. We further explore the vectorial character of the hybrid coupling to the bidimensional deformations of the nanowire. The demonstrated microwave assisted synchronization of the spin-oscillator dynamics opens novel perspectives for the exploration of spin-dependent forces, the key ingredient for quantum state transfer. PMID:26477639

  4. Spontaneous fluctuations of transition dipole moment orientation in OLED triplet emitters

    E-print Network

    Steiner, Florian; Vogelsang, Jan; Lupton, John M

    2015-01-01

    The efficiency of an organic light-emitting diode (OLED) depends on the microscopic orientation of transition dipole moments of the molecular emitters. The most effective materials used for light generation have threefold symmetry, which prohibit a priori determination of dipole orientation due to the degeneracy of the fundamental transition. Single-molecule spectroscopy reveals that the model triplet emitter tris(2-phenylisoquinoline)iridium(III) (Ir(piq)3) does not behave as a linear dipole, radiating with lower polarization anisotropy than expected. Spontaneous symmetry breaking occurs in the excited state, leading to a random selection of one of the three ligands to form a charge transfer state with the metal. This non-deterministic localization is revealed in switching of the degree of linear polarization of phosphorescence. Polarization scrambling likely raises out-coupling efficiency and should be taken into account when deriving molecular orientation of the guest emitter within the OLED host from ense...

  5. Observation of a phononic Mollow triplet in a multimode hybrid spin-nanomechanical system.

    PubMed

    Pigeau, B; Rohr, S; Mercier de Lépinay, L; Gloppe, A; Jacques, V; Arcizet, O

    2015-01-01

    Reminiscent of the bound character of a qubit's dynamics confined on the Bloch sphere, the observation of a Mollow triplet in the resonantly driven qubit fluorescence spectrum represents one of the founding signatures of quantum electrodynamics. Here we report on its observation in a hybrid spin-nanomechanical system, where a nitrogen-vacancy spin qubit is magnetically coupled to the vibrations of a silicon carbide nanowire. A resonant microwave field turns the originally parametric hybrid interaction into a resonant process, where acoustic phonons are now able to induce transitions between the dressed qubit states, leading to synchronized spin-oscillator dynamics. We further explore the vectorial character of the hybrid coupling to the bidimensional deformations of the nanowire. The demonstrated microwave assisted synchronization of the spin-oscillator dynamics opens novel perspectives for the exploration of spin-dependent forces, the key ingredient for quantum state transfer. PMID:26477639

  6. The Triplet Measured by Aerial Camera Using Line Segments Line Matching-Based Relative Orientation Using Triplet Camera

    NASA Astrophysics Data System (ADS)

    Tanaka, S.; Nakagawa, M.

    2015-05-01

    In urgent observations after disasters, we can mention that the image matching processing is an essential technique to establish more stable and rapid 3D data generation. Particularly, multi-images taken from various viewpoints are useful in the disaster monitoring. Thus, feature and corresponded point detection would be designed for a multi-image matching. Recently, Structure from Motion (SfM) is often applied to generate 3D data. The SfM is useful approach to generate 3D data from images of random viewpoints. However, Scale-Invariant Feature Transform (SIFT) requires a plenty of time to detect feature points and corresponded points from multi-images. Therefore, we proposed a methodology to improve triplet matching and SfM with line segments extracted from images. Moreover, we evaluated our methodology using multi-images taken from aerial triplet camera.

  7. Triplet-Polaron Interaction Induced Upconversion from Triplet to Singlet: a New Way to Obtain Highly Efficient OLEDs

    E-print Network

    Obolda, Ablikim; He, Chuanyou; Zhang, Tian; Ren, Jiajun; Ma, Hongwei; Shuai, Zhigang; Li, Feng

    2015-01-01

    The triplet harvesting is a main challenge in organic light-emitting devices (OLEDs), due to the radiative decay of triplet is spin-forbidden. Here, we designed and synthesized two D-A type molecules, TPA-TAZ and TCP. The OLEDs based on them exhibit deep-blue emission and the singlet formation ratios are higher than the simple spin-statistics of 25 %. Specially, a TPA-TAZ-based OLED achieves a maximum EQE of 6.8 %, which is the largest value of the undoped OLEDs with CIE(y)chemistry computation. Our results may offer a new route to break through the 25 % upper limit of IQE of fluorescent OLEDs, especially, the deep-blue fluore...

  8. Spectroscopic evidence for the coexistence of tetragonal and trigonal minima within the exited state adiabatic potential energy surfaces of hexachlorotellurate and -selenate complexes

    NASA Astrophysics Data System (ADS)

    Cremers, C.; Degen, J.

    1998-11-01

    Coexistence of Jahn-Teller minima resulting from the coupling to different accepting modes within the adiabatic potential energy surface (APES) is not possible within the framework of linear vibronic coupling theory. For the lowest exited triplet state 3T1u of inorganic complexes with s2 electronic ground-state configuration, such a coexistence, due to quadratic coupling effects, is discussed. As a direct experimental evidence two vibronic progressions with different accepting modes in the emission spectra resulting from a single electronic state are observed in the emission spectra of the title compounds. The observation of vibronic finestructure in the emission spectra of [TeCl6]2- is reported for the first time.

  9. High-Resolution Spectroscopy of Trilobite-Like States of 85Rb2

    NASA Astrophysics Data System (ADS)

    Carollo, Ryan; Eyler, Edward; Gould, Phillip; Stwalley, William

    2014-05-01

    We present high-resolution spectra of low- n trilobite-like states in 85Rb2. Trilobite states are novel long-range molecular states consisting of a ground-state atom embedded in the Rydberg wavefunction of a second atom. We utilize a bound-bound excitation to populate these states from photoassociated ultracold molecules in high- v levels of the lowest triplet state. The excitation is stimulated by a frequency-doubled pulse-amplified CW laser for narrow linewidth. Upon excitation, the trilobite-like states rapidly autoionize and are mass-selectively detected by an ion detector. Previous detection of these states was done by a broader linewidth conventional pulsed laser as reported in Ref.. This work is supported by the NSF and AFOSR.

  10. Light Colour-Triplet Higgs is Compatible with Proton Stability: An alternative approach to the doublet-triplet splitting problem

    E-print Network

    Gia Dvali

    1995-11-04

    It is usually assumed that the proton stability requires the coloured triplet partner of the electroweak Higgs doublet to be superheavy (with a mass $\\sim M_{GUT}$). We show that this is a very model-dependent statement and the colour triplet can be as light as the weak doublet without leading to the proton decay problem: instead of using the mass difference the splitting can occur between the doublet and triplet Yukawa coupling constants. In this scenario the GUT symmetry breaking automatically induces an extremely strong suppression $\\sim M_W/M_{GUT}$ of the coloured Higgs effective Yukawa coupling; this happens without any fine--tuning, just because of the Clebsch factors. Conceptual differences of the above picture are: (1) an essentially stable proton: both $d = 5$ and $d = 6$ proton decay mediating operators are suppressed by the same factors $\\sim (M_w/M_{GUT})^2$; (2) the possibility of solving the $\\mu$ problem by the light gauge singlet field (this fact would lead to the destabilization of the hierarchy in the standard case); (3) the existence of the long--lived, light, coloured and charged supermultiplet in the 100 GeV mass region. We construct two explicit SO(10) examples with the above properties, with superpotentials most general under the symmetries.

  11. A POSSIBLE ROLE FOR TRIPLET H{sub 2}CN{sup +} ISOMERS IN THE FORMATION OF HCN AND HNC IN INTERSTELLAR CLOUDS

    SciTech Connect

    Allen, Thomas L.; Goddard, John D.; Schaefer, III, Henry F.

    1980-02-01

    The structures and energies of the lowest triplet states of four isomers of H{sub 2}CN{sup +} have been determined by self-consistent field and configuration interaction calculations. When both hydrogen atoms are attached to the nitrogen atom, H{sub 2}NC{sup +}, the molecule has its lowest triplet state energy, which is 97.2 kcal mol{sup -1} above the energy of the linear singlet ground state. The structure has C{sub 2{nu}} symmetry, with an HCH bond angle of 116.8{degrees}, and bond lengths of 1.009 {Angstrom} (H--N) and 1.268 {Angstrom} (N-C). Other isomers investigated include the H{sub 2}CN{sup +} isomer at 104.7, the cis-HCNH{sup +} isomer at 105.3, and the trans-HCNH{sup +} isomer at 113.6 kcal mol{sup -1}. The H{sub 2}CN{sup +} isomer has an unusual "carbonium nitrene" structure, with a C--N bond length of 1.398 {Angstrom}. It is suggested that the triplet H{sub 2}NC{sup +} isomer may play a role in determining the relative yields of HCN and HNC from the reaction of C{sup +} and NH{sub 3}. Specifically, a triplet path is postulated in which C{sup +} and NH{sub 3} yield the triplet H{sub 2}NC{sup +} isomer, which then yields the singlet H{sub 2}NC{sup +} isomer by phosphorescent emission. Because this emission removes a large amount of energy, the singlet H{sub 2}NC{sup +} isomer may have insufficient energy to isomerize to the linear singlet ground state. Subsequent dissociative recombination would yield the HNC isomer exclusively.

  12. Applications of an Energy Transfer Model to Three Problems in Planetary Regoliths: The Solid-State Greenhouse, Thermal Beaming, and Emittance Spectra

    NASA Technical Reports Server (NTRS)

    Hapke, Bruce

    1996-01-01

    Several problems of interest in planetary infrared remote sensing are investigated using a new radiative-conductive model of energy transfer in regoliths: the solid-state greenhouse effect, thermal beaming, and reststrahlen spectra. The results of the analysis are as follows: (1) The solid-state greenhouse effect is self-limiting to a rise of a few tens of degrees in bodies of the outer solar system. (2) Non-Lambertian directional emissivity can account for only about 20% of the observed thermal beaming factor. The remainder must have another cause, presumably surface roughness effects. (3) The maximum in a reststrahlen emissivity spectrum does not occur exactly at the Christiansen wavelength where, by definition, the real part of the refractive index equals one, but rather at the first transition minimum in reflectance associated with the transition from particle scattering being dominated by volume scattering to that dominated by strong surface scattering. The transparency feature is at the second transition minimum and does not require the presence of a second band at longer wavelength for its occurance. Subsurface temperature gradients have only a small effect on emissivity bands.

  13. Development of the triplet singularity for the analysis of wings and bodies in supersonic flow

    NASA Technical Reports Server (NTRS)

    Woodward, F. A.

    1981-01-01

    A supersonic triplet singularity was developed which eliminates internal waves generated by panels having supersonic edges. The triplet is a linear combination of source and vortex distributions which gives directional properties to the perturbation flow field surrounding the panel. The theoretical development of the triplet singularity is described together with its application to the calculation of surface pressures on wings and bodies. Examples are presented comparing the results of the new method with other supersonic methods and with experimental data.

  14. Galaxy triplets in Sloan Digital Sky Survey Data Release 7 - III. Analysis of configuration and dynamics

    NASA Astrophysics Data System (ADS)

    Duplancic, Fernanda; Alonso, Sol; Lambas, Diego G.; O'Mill, Ana Laura

    2015-02-01

    We analyse the spatial configuration and the dynamical properties of a sample of 92 galaxy triplets obtained from the Data Release 7 of Sloan Digital Sky Survey (SDSS-DR7; SDSS-triplets) restricted to have members with spectroscopic redshifts in the range 0.01 ? z ? 0.14 and absolute r-band luminosities brighter than Mr = -20.5. The configuration analysis was performed through Agekyan & Anosova map (AA-map). We estimated dynamical parameters, namely the radius of the system, the velocity dispersion, a dimensionless crossing-time and the virial mass. We compared our results with those obtained for a sample of triplets from the catalogue `Isolated Triplets of Galaxies' (K-triplets) and a sample of Compact Groups. We have also studied a mock catalogue in order to compare real and projected configurations, and to estimate the three-dimensional dynamical parameters of the triple systems. We found that the SDSS-triplets prefer alignment configurations while K-triplets present a uniform distribution in the AA-map. From the dynamical analysis we conclude that the SDSS-triplets, K-triplets and Compact Groups present a similar behaviour comprising compact systems with low crossing-time values, with velocity dispersions and virial masses similar to those of low-mass loose groups. Moreover, we found that observed and simulated triplets present similar dynamical parameters. We also performed an analysis of the dark matter content of galaxy triplets finding that member galaxies of mock triplets belong to the same dark matter halo, showing a dynamical co-evolution of the system. These results suggest that the configuration and dynamics of triple systems favour galaxy interactions and mergers.

  15. The supersonic triplet - A new aerodynamic panel singularity with directional properties. [internal wave elimination

    NASA Technical Reports Server (NTRS)

    Woodward, F. A.; Landrum, E. J.

    1979-01-01

    A new supersonic triplet singularity has been developed which eliminates internal waves generated by panels having supersonic edges. The triplet is a linear combination of source and vortex distributions which provides the desired directional properties in the flow field surrounding the panel. The theoretical development of the triplet is described, together with its application to the calculation of surface pressure on arbitrary body shapes. Examples are presented comparing the results of the new method with other supersonic panel methods and with experimental data.

  16. Millimeter and Submillimeter Wave Spectra of the HCOO^{13}CH_{3} Isotopolog of Methylformate in the Ground State and in the First Excited Torsional State.

    NASA Astrophysics Data System (ADS)

    Haykal, I.; Margules, L.; Huet, T. R.; Motiyenko, R. A.; Carvajal, M.; Kleiner, I.; Guillemin, J. C.; Tercero, B.; Cernicharo, J.

    2013-06-01

    The detection of nineteen new rotational transitions of the parent molecule of methylformate (HCOOCH_{3}) in the second lowest excited torsional mode (?_{t} =2) was recently reported in Orion-KL, as well as the detection of eighty new lines corresponding to the two ^{18}O isotopologs of methylformate in their ground states. The laboratory work on HCOO^{13}CH_{3} was continued. A wide spectral range from 50 to 940 GHz was recorded in Lille with the submillimeter-wave spectrometer based on harmonic generation of a microwave synthesizer source, using a multiplication chain of solid state sources (50-100 and 150-940 GHz) and a backward wave oscillator (100-150 GHz), and coupled to a 2.2 m cell. The absolute accuracy of the line positions is better than 30 kHz up to 630 GHz and 50 kHz above. The two states (?_{t} = 0 and 1) were fitted together using the RAM Hamiltonian of the BELGI program and a new set of 45 parameters was accurately determined. The fit contains 7050 lines corresponding to the ground state up to J = 78 and K_{a} = 34 and 1907 lines related to ?_{t} =1 up to J = 59 and K_{a} = 24. The detection of new ?_{t} =1 lines in Orion KL will be reported and discussed. This work is supported by the French Programme National de Physico-Chimie du Milieu Interstellaire (CNRS), by CNES, and by the Spanish Government through the grants FIS2011-28738-C02-02 and CONSOLIDER 2009-00038. S. Takano, Y. Sakai, S. Kakimoto, M. Sasaki, and K. Kobayashi PASJ. {64}, 89, 2012. B. Tercero, et al. A& A. {538}, A199, 2012. M. Carvajal, et al. A& A. {500}, 1109, 2009.

  17. Dynamics of the excited states of [Ir(ppy)2bpy]+ with triple phosphorescence.

    PubMed

    Wu, Shih-Hsiang; Ling, Jung-Wei; Lai, Szu-Hsueh; Huang, Min-Jie; Cheng, Chien Hong; Chen, I-Chia

    2010-09-30

    We investigated the relaxation dynamics of bis(2-phenylpyridinato-)(2,2'-bipyridine)iridium(III), [Ir(ppy)(2)bpy](+) using the technique of time-resolved spectroscopy. In the visible emission spectra this molecule exhibits triple phosphorescence: displaying blue, green, and orange bands. From the dependence of spectral shifts with polarity of solvent, decay lifetimes, and the results of calculations using time-dependent density functional theory, we assigned these three emitting states to be triplet interligand charge-transfer ((3)LLCT), metal-to-ligand ppy charge transfer ((3)MLCT(ppy)), and metal-to-ligand bpy charge transfer ((3)MLCT(bpy)) states. The blue states were formed promptly after excitation at wavelength 355 nm; the one lying at higher energy decaying with a time coefficient 0.79-2.56 ns is assigned to be a triplet MLCT, and the other at lower energy decaying in 1.5-2.8 ?s is assigned to (3)LLCT(A), A symmetry. This decay time coefficient of (3)LLCT(A) decreases with increasing dielectric constant of the solvent indicating this state mixing of some MLCT character. The green state (3)MLCT(ppy) decays in 0.13-4.8 ns to a nearby intermediate state either (3)MLCT(ppy) or (3)MLCT(bpy). The orange state (3)MLCT(bpy) is coupled to the intermediate state to have a rise time about 0.36-0.84 ns and decays in 425-617 ns. Although many triplet states exist in a small energy range, they couple weakly to display triple emission. All (3)LLCT and (3)MCLT states are coupled to the singlet (1)LLCT manifold directly and/or indirectly and contribute to the emission in the visible range. PMID:20809643

  18. Contradictions about Fine Structures in Meson Spectra and Proposed High-Resolution Hadron Spectrometer Using ``Interactive'' Solid-State Hydrogen Target

    NASA Astrophysics Data System (ADS)

    Maglich, Bogdan C.

    2004-08-01

    High resolution has been discouraged in meson spectrometry for 4 decades by the Doctrine of Experiments Incompatible with Theory (DEIT). DEIT a priori rejects narrow hadron resonances on the paradigm that only broad hadron peaks, ?? 100 MeV, can exist — in spite of the accumulated evidence to the contrary. The facts are: Mesons 2 orders of magnitude narrower than `allowed' for hadrons, have been confirmed; a new one was announced at this conference. Narrow meson structures have been repeatedly reported at high momentum transfer, |t| >0.2, while they are absent at the low transfer, |t| ˜0.01, where 99% of the experiments are performed. Modification of meson mass and width as a function of the density of nuclear matter in which they are produced, have been recently reported. We postulate for meson spectra: (1) Intrinsic (`true') width, ?, is different from the observable (`apparent') width, ?': ?< ?' (2) ? of all meson states are narrow and can be observed only at or near the maximum |t| reachable in the reaction, and (3) ? of all meson resonances are subject to broadening as |t| decreases. Since both ?' and the production ? are inversely proportional to |t|, most of the observed spectra are produced at the lowest |t| <0.01 and thus the peaks appear broad. We have conceptually designed a novel type hadron spectrometer with an order of magnitude better resolution (0.1 MeV). It would operate at 2 orders of magnitude higher |t| (0.3< |t| <1 (GeV/c)2, than most experiments to date (|t| <0.01). Mesons in the mass region 0.5 state hydrogen target' consisting of an array of plastic scintillator fibers, CH; collisions with C are electronically rejected. Missing mass of P is measured in the region of the maximum recoil angle. Story of the suppression by DEIT for 17 years of the observation of a theoretically unexplained narrow peak, which turned out to be ??2?, and the related correspondence between Werner Heisenberg and this author, is narrated.

  19. Triplets contribute to both an increase and loss in fluorescent yield in organic light emitting diodes.

    PubMed

    Zhang, Yifan; Forrest, Stephen R

    2012-06-29

    Nonradiative triplets in fluorescent organic light emitting diodes (OLEDs) can lead to increased efficiency through triplet-triplet annihilation, or to decreased efficiency due to singlet-triplet annihilation. We study the tradeoff between the two processes from the electroluminescence transients of an OLED comprising a tetraphenyldibenzoperiflanthene (DBP) doped rubrene emissive layer, whose emission spectrum peaks at a wavelength of 610 nm. The electroluminescent transients in the current density range, 4 mA/cm(2)triplet density dynamics. Our analysis shows that triplets positively contribute to the OLED efficiency at J<2.2 A/cm(2), while decreasing the efficiency at higher J. The high OLED peak external quantum efficiency of 6.7% and rapid efficiency roll-off with J are quantitatively explained by the tradeoff between triplet-triplet and singlet-triplet annihilation. The model suggests optimal materials properties needed for achieving high efficiency at high brightness in fluorescent OLEDs. PMID:23005014

  20. Nonstandard neutrino interactions from a triplet seesaw model

    NASA Astrophysics Data System (ADS)

    Malinský, Michal; Ohlsson, Tommy; Zhang, He

    2009-01-01

    We investigate nonstandard neutrino interactions (NSIs) in the triplet seesaw model featuring nontrivial correlations between NSI parameters and neutrino masses and mixing parameters. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus, these NSIs could lead to quite significant signals of lepton flavor violating decays such as ?-?e-?e?¯? and ?+?e+?¯e?? at a future neutrino factory, effects adding to the uncertainty in determination of the Earth matter density profile, as well as characteristic patterns of the doubly charged Higgs decays observable at the Large Hadron Collider.

  1. Beyond the modulational approximation in the wave triplet interaction

    NASA Astrophysics Data System (ADS)

    Iorra, P.; Marini, S.; Peter, E.; Pakter, R.; Rizzato, F. B.

    2015-10-01

    The present work investigates the breakdown of the traditional modulational approximation in the three wave nonlinear interaction, the wave triplet interaction. A common way to describe the interaction of three high-frequency carriers is to assume that amplitudes and phases are slowly modulated. This is the basis of the modulational approach, which is accurate when the three wave coupling is weak. We examine the types of dynamics arising when the coupling rises from very small to large values. At large values we detect an abrupt transition where the limited amplitude excursions of the modulational regime reach much larger regions of the appropriate configuration space. Extensions to similar cases are also investigated.

  2. Tsallis’ q-triplet and the ozone layer

    NASA Astrophysics Data System (ADS)

    Ferri, G. L.; Reynoso Savio, M. F.; Plastino, A.

    2010-05-01

    Tsallis’ q-triplet [C. Tsallis, Dynamical scenario for nonextensive statistical mechanics, Physica A 340 (2004) 1-10] is the best empirical quantifier of nonextensivity. Here we study it with reference to an experimental time-series related to the daily depth-values of the stratospheric ozone layer. Pertinent data are expressed in Dobson units and range from 1978 to 2005. After the evaluation of the three associated Tsallis’ indices one concludes that nonextensivity is clearly a characteristic of the system under scrutiny.

  3. High Fidelity Singlet-Triplet S-T_ Qubits in Inhomogeneous Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Wong, Clement; Eriksson, Mark; Coppersmith, Sue; Friesen, Mark

    2015-03-01

    We propose an optimal set of quantum gates for a singlet-triplet qubit in a double quantum dot with two electrons utilizing the S-T- subspace. Qubit rotations are driven by the applied magnetic field and an orthogonal field gradient provided by a micromagnet. We optimize the fidelity of this qubit as a function of magnetic fields, taking advantage of ``sweet spots'' where the rotation frequencies are independent of the energy level detuning, providing protection against charge noise. We simulate gate operations and qubit rotations in the presence of quasistatic noise from charge and nuclear spins as well as leakage to nonqubit states, and predict that in silicon quantum dots gate fidelities greater than 99 % can be achieved for two nearly-orthogonal rotation axes. This work was supported in part by NSF, ARO, UW-Madison Bridge Funding, and the Intelligence Community Postdoctoral Research Fellowship Program.

  4. High-fidelity singlet-triplet S -T- qubits in inhomogeneous magnetic fields

    NASA Astrophysics Data System (ADS)

    Wong, Clement H.; Eriksson, M. A.; Coppersmith, S. N.; Friesen, Mark

    2015-07-01

    We propose an optimized set of quantum gates for a singlet-triplet qubit in a double quantum dot with two electrons utilizing the S -T- subspace. Qubit rotations are driven by the applied magnetic field and a field gradient provided by a micromagnet. We optimize the fidelity of this qubit as a function of the magnetic fields, taking advantage of "sweet spots" where the rotation frequencies are independent of the energy level detuning, providing protection against charge noise. We simulate gate operations and qubit rotations in the presence of quasistatic noise from charge and nuclear spins as well as leakage to nonqubit states. Our results show that, for silicon quantum dots, gate fidelities greater than 99 % should be realizable, for rotations about two nearly orthogonal axes.

  5. Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

    NASA Astrophysics Data System (ADS)

    Alidoust, Mohammad; Halterman, Klaus; Valls, Oriol T.

    2015-07-01

    Using a self-consistent Bogoliubov-de Gennes approach, we theoretically study the proximity-induced density of states (DOS) in clean SFF spin valves with noncollinear exchange fields. Our results clearly demonstrate a direct correlation between the presence of a zero-energy peak (ZEP) in the DOS spectrum and the persistence of spin-1 triplet pair correlations. By systematically varying the geometrical and material parameters governing the spin valve, we point out experimentally optimal system configurations where the ZEPs are most pronounced, and which can be effectively probed via scanning tunneling microscopy. We complement these findings in the ballistic regime by employing the Usadel formalism in the full proximity limit to investigate their diffusive SFF counterparts. We determine the optimal normalized ferromagnetic layer thicknesses which result in the largest ZEPs. Our results can serve as guidelines in designing samples for future experiments.

  6. A novel SAR fusion image segmentation method based on triplet Markov field

    NASA Astrophysics Data System (ADS)

    Wang, Jiajing; Jiao, Shuhong; Sun, Zhenyu

    2015-03-01

    Markov random field (MRF) has been widely used in SAR image segmentation because of the advantage of directly modeling the posterior distribution and suppresses the speckle on the influence of the segmentation result. However, when the real SAR images are nonstationary images, the unsupervised segmentation results by MRF can be poor. The recent proposed triplet Markov field (TMF) model is well appropriate for nonstationary SAR image processing due to the introduction of an auxiliary field which reflects the nonstationarity. In addition, on account of the texture features of SAR image, a fusion image segmentation method is proposed by fusing the gray level image and texture feature image. The effectiveness of the proposed method in this paper is demonstrated by a synthesis SAR image and the real SAR images segmentation experiments, and it is better than the state-of-art methods.

  7. Zero Energy Peak and Triplet Correlations in Nanoscale SFF Spin-Valves

    E-print Network

    Mohammad Alidoust; Klaus Halterman; Oriol T. Valls

    2015-06-17

    Using a self-consistent Bogoliubov-de Gennes approach, we theoretically study the proximity-induced density of states (DOS) in clean SFF spin-valves with noncollinear exchange fields. Our results clearly demonstrate a direct correlation between the presence of a zero energy peak (ZEP) in the DOS spectrum and the persistence of spin-1 triplet pair correlations. By systematically varying the geometrical and material parameters governing the spin-valve, we point out to experimentally optimal system configurations where the ZEPs are most pronounced, and which can be effectively probed via scanning tunneling microscopy. We complement these findings in the ballistic regime by employing the Usadel formalism in the full proximity limit to investigate their diffusive SFF counterparts. We determine the optimal normalized ferromagnetic layer thicknesses which result in the largest ZEPs. Our results can serve as guidelines in designing samples for future experiments.

  8. End injection of triplet electronic excitation energy into a polymer molecule using chromophores bound at chain ends

    SciTech Connect

    Burrows, J.A.J.; Haggquist, G.W.; Burkhart, R.D. )

    1990-01-01

    Polystyrene molecules labeled at opposite ends with naphthalene and aromatic carbonyl (AC) groups were prepared and their triplet photophysical properties investigated. By use of excitation at 337 nm the aromatic carbonyl was photoexcited selectively and time-resolved phosphorescence spectra were recorded at delay times from 100{mu}s to 100 ms. The AC phosphorescence was inhomogeneously broadened at the shortest delay times but becomes narrow and more structured with increasing delay time at 77K. At ambient temperature the spectrum remains broad and structureless even at long delay times. Using dye laser excitation at 360 nm a narrow structured band is observed even at 150{mu}s after the excitation pulse. Energy transfer to the naphthalene group occurs efficiently and may take place either by direct transfer from excited AC groups or by an indirect process involving backbone phenyl groups. Electronically excited phenyl groups are thought to be produced by energy transfer from that set of triplet AC chromophores lying at the high-energy edge of the inhomogeneously broadened manifold. The resulting emission spectrum suggests the possibility of exciplex formation.

  9. The photospheric solar oxygen project: IV. 3D-NLTE investigation of the 777 nm triplet lines

    E-print Network

    Steffen, M; Caffau, E; Ludwig, H -G; Bonifacio, P; Cayrel, R; Ku?inskas, A; Livingston, W C

    2015-01-01

    The solar photospheric oxygen abundance is still widely debated. Adopting the solar chemical composition based on the "low" oxygen abundance, as determined with the use of three-dimensional (3D) hydrodynamical model atmospheres, results in a well-known mismatch between theoretical solar models and helioseismic measurements that is so far unresolved. We carry out an independent redetermination of the solar oxygen abundance by investigating the center-to-limb variation of the OI IR triplet lines at 777 nm in different sets of spectra with the help of detailed synthetic line profiles based on 3D hydrodynamical CO5BOLD model atmospheres and 3D non-LTE line formation calculations with NLTETD. The idea is to simultaneously derive the oxygen abundance,A(O), and the scaling factor SH that describes the cross-sections for inelastic collisions with neutral hydrogen relative the classical Drawin formula. The best fit of the center-to-limb variation of the triplet lines achieved with the CO5BOLD 3D solar model is clearly...

  10. Storm Spectra

    NASA Technical Reports Server (NTRS)

    2007-01-01

    These images, taken with the LEISA infrared camera on the New Horizons Ralph instrument, show fine details in Jupiter's turbulent atmosphere using light that can only be seen using infrared sensors. These are 'false color' pictures made by assigning infrared wavelengths to the colors red, green and blue. LEISA (Linear Etalon Imaging Spectral Array) takes images across 250 IR wavelengths in the range from 1.25 to 2.5 microns, allowing scientists to obtain an infrared spectrum at every location on Jupiter. A micron is one millionth of a meter.

    These pictures were taken at 05:58 UT on February 27, 2007, from a distance of 2.9 million kilometers (1.6 million miles). They are centered at 8 degrees south, 32 degrees east in Jupiter 'System III' coordinates. The large oval-shaped feature is the well-known Great Red Spot. The resolution of each pixel in these images is about 175 kilometers (110 miles); Jupiter's diameter is approximately 145,000 kilometers (97,000 miles).

    The image on the left is an altitude map made by assigning the color red to 1.60 microns, green to 1.89 microns and blue to 2.04 microns. Because Jupiter's atmosphere absorbs light strongly at 2.04 microns, only clouds at very high altitude will reflect light at this wavelength. Light at 1.89 microns can go deeper in the atmosphere and light at 1.6 microns can go deeper still. In this map, bluish colors indicate high clouds and reddish colors indicate lower clouds. This picture shows, for example, that the Great Red Spot extends far up into the atmosphere.

    In the image at right, red equals 1.28 microns, green equals 1.30 microns and blue equals 1.36 microns, a range of wavelengths that similarly probes different altitudes in the atmosphere. This choice of wavelengths highlights Jupiter's high-altitude south polar hood of haze. The edge of Jupiter's disk at the bottom of the panel appears slightly non-circular because the left-hand portion is the true edge of the disk, while the right portion is defined by the day/night boundary (known as the terminator).

    These two images illustrate only a small fraction of the information contained in a single LEISA scan, highlighting just one aspect of the power of infrared spectra for atmospheric studies.

  11. Understanding the Control of Singlet-Triplet Splitting for Organic Exciton Manipulating: A Combined Theoretical and Experimental Approach

    PubMed Central

    Chen, Ting; Zheng, Lei; Yuan, Jie; An, Zhongfu; Chen, Runfeng; Tao, Ye; Li, Huanhuan; Xie, Xiaoji; Huang, Wei

    2015-01-01

    Developing organic optoelectronic materials with desired photophysical properties has always been at the forefront of organic electronics. The variation of singlet-triplet splitting (?EST) can provide useful means in modulating organic excitons for diversified photophysical phenomena, but controlling ?EST in a desired manner within a large tuning scope remains a daunting challenge. Here, we demonstrate a convenient and quantitative approach to relate ?EST to the frontier orbital overlap and separation distance via a set of newly developed parameters using natural transition orbital analysis to consider whole pictures of electron transitions for both the lowest singlet (S1) and triplet (T1) excited states. These critical parameters revealed that both separated S1 and T1 states leads to ultralow ?EST; separated S1 and overlapped T1 states results in small ?EST; and both overlapped S1 and T1 states induces large ?EST. Importantly, we realized a widely-tuned ?EST in a range from ultralow (0.0003?eV) to extra-large (1.47?eV) via a subtle symmetric control of triazine molecules, based on time-dependent density functional theory calculations combined with experimental explorations. These findings provide keen insights into ?EST control for feasible excited state tuning, offering valuable guidelines for the construction of molecules with desired optoelectronic properties. PMID:26161684

  12. Understanding the Control of Singlet-Triplet Splitting for Organic Exciton Manipulating: A Combined Theoretical and Experimental Approach

    NASA Astrophysics Data System (ADS)

    Chen, Ting; Zheng, Lei; Yuan, Jie; An, Zhongfu; Chen, Runfeng; Tao, Ye; Li, Huanhuan; Xie, Xiaoji; Huang, Wei

    2015-07-01

    Developing organic optoelectronic materials with desired photophysical properties has always been at the forefront of organic electronics. The variation of singlet-triplet splitting (?EST) can provide useful means in modulating organic excitons for diversified photophysical phenomena, but controlling ?EST in a desired manner within a large tuning scope remains a daunting challenge. Here, we demonstrate a convenient and quantitative approach to relate ?EST to the frontier orbital overlap and separation distance via a set of newly developed parameters using natural transition orbital analysis to consider whole pictures of electron transitions for both the lowest singlet (S1) and triplet (T1) excited states. These critical parameters revealed that both separated S1 and T1 states leads to ultralow ?EST separated S1 and overlapped T1 states results in small ?EST and both overlapped S1 and T1 states induces large ?EST. Importantly, we realized a widely-tuned ?EST in a range from ultralow (0.0003?eV) to extra-large (1.47?eV) via a subtle symmetric control of triazine molecules, based on time-dependent density functional theory calculations combined with experimental explorations. These findings provide keen insights into ?EST control for feasible excited state tuning, offering valuable guidelines for the construction of molecules with desired optoelectronic properties.

  13. C NMR Spectra C NMR Spectra

    E-print Network

    Collum, David B.

    S16 1 H and 13 C NMR Spectra (see p S3) Me N-i-Pr #12;S17 1 H and 13 C NMR Spectra (see p S3) Me NBn #12;S18 1 H and 13 C NMR Spectra (see p S4) NBn #12;S19 1 H and 13 C NMR Spectra (see p S4) NBn Me Me Me #12;S20 1 H and 13 C NMR Spectra (see p S4) N-n-Bu Me Me Me #12;S21 1 H and 13 C NMR Spectra

  14. Solvent effects on the optical spectra and excited-state decay of triphenylamine-thiadiazole with hybridized local excitation and intramolecular charge transfer.

    PubMed

    Fan, Di; Yi, Yuanping; Li, Zhendong; Liu, Wenjian; Peng, Qian; Shuai, Zhigang

    2015-05-28

    The triphenylamine-thiadiazole molecule (TPA-NZP) is a newly popular, highly efficient OLED fluorescent emitter with exciton utilization efficiency exceeding the upper limit of spin statistics (25%). In this work, the optical spectra and the radiative and nonradiative decay rate constants have been investigated theoretically for TPA-NZP in hexane, ethyl ether, tetrahydrofuran, and dimethylformamide solvents, in comparison with the gas phase. We observed the evolutions of the excited states from the hybridized local and charge-transfer (HLCT) character to complete intramolecular charge transfer (CT) character with the increase of the solvent polarities. It is found that upon increasing the solvent polarity, the amount of red shift in the absorption peak is much less than that of emission, resulting in breakdown of the mirror symmetry. This is because that 0-0 transition energy is red-shifted but the vibrational relaxation increases with the solvent polarity, leading to subtraction in absorption while addition in emission. The radiative decay rate constant is calculated to be almost independent of polarity. The nonradiative decay rate increases by almost one order of magnitude from that in nonpolar hexane to the strongly polarized dimethylformamide, which is attributed to the dual effects of the red shift in the gap and enhancement of the vibrational relaxation by solvent polarity. PMID:25402947

  15. `Exotic vector-like pair' of color-triplet scalars

    NASA Astrophysics Data System (ADS)

    Addazi, Andrea

    2015-04-01

    We propose a minimal extension of Standard Model, generating a Majorana mass for neutron, connected with a mechanism of Post-Sphaleron Baryogenesis. We consider an `exotic vector-like pair' of color-triplet scalars, an extra Majorana fermion ?, and a scalar field ?, giving mass to ?. The vector-like pair is defined `exotic' because of a peculiar mass term of the color-triplet scalars, violating Baryon number as ? B = 1. Such a mass term could be generated by exotic instantons in a class of string-inspired completions of the Standard Model: open (un-)oriented strings attached between D-brane stacks and Euclidean D-branes. A Post-Sphaleron Baryogenesis is realized through ?-decays into six quarks (antiquarks), or through ?-decays into three quarks (antiquarks). This model suggests some intriguing B-violating signatures, testable in the next future, in Neutron-Antineutron physics and LHC. We also discuss limits from FCNC. Sterile fermion can also be light as 1 - 100GeV. In this case, the sterile fermion could be (meta)-stable and n - oscillation can be indirectly generated by two n - ?, ? - oscillations, without needing of an effective Majorana mass for neutron. Majorana fermion ? can be a good candidate for WIMP-like dark matter.

  16. Magnetism-induced massive Dirac spectra and topological defects in the surface state of Cr-doped Bi2Se3-bilayer topological insulators

    NASA Astrophysics Data System (ADS)

    Chen, C.-C.; Teague, M. L.; He, L.; Kou, X.; Lang, M.; Fan, W.; Woodward, N.; Wang, K.-L.; Yeh, N.-C.

    2015-11-01

    Proximity-induced magnetic effects on the surface Dirac spectra of topological insulators are investigated by scanning tunneling spectroscopic studies of bilayer structures consisting of undoped Bi2Se3 thin films on top of Cr-doped Bi2Se3 layers. For thickness of the top Bi2Se3 layer equal to or smaller than 3 quintuple layers, a spatially inhomogeneous surface spectral gap ? opens up below a characteristic temperature {{T}{{c}}}2{{D}}, which is much higher than the bulk Curie temperature {{T}{{c}}}3{{D}} determined from the anomalous Hall resistance. The mean value and spatial homogeneity of the gap ? generally increase with increasing c-axis magnetic field (H) and increasing Cr doping level (x), suggesting that the physical origin of this surface gap is associated with proximity-induced c-axis ferromagnetism. On the other hand, the temperature (T) dependence of ? is non-monotonic, showing initial increase below {{T}{{c}}}2{{D}}, which is followed by a ‘dip’ and then rises again, reaching maximum at T ? {{T}{{c}}}3{{D}}. These phenomena may be attributed to proximity magnetism induced by two types of contributions with different temperature dependences: a three-dimensional contribution from the bulk magnetism that dominates at low T, and a two-dimensional contribution associated with the RKKY interactions mediated by surface Dirac fermions, which dominates at {{T}{{c}}}3{{D}} ? T < {{T}{{c}}}2{{D}}. In addition to the observed proximity magnetism, spatially localized sharp resonant spectra are found along the boundaries of gapped and gapless regions. These spectral resonances are long-lived at H = 0, with their occurrences being most prominent near {{T}{{c}}}2{{D}} and becoming suppressed under strong c-axis magnetic fields. We attribute these phenomena to magnetic impurity-induced topological defects in the spin texture of surface Dirac fermions, with the magnetic impurities being isolated Cr impurities distributed near the interface of the bilayer system. The long-term stability of these topologically protected two-level states may find potential applications to quantum information technology.

  17. Highly efficient greenish-blue platinum-based phosphorescent organic light-emitting diodes on a high triplet energy platform

    SciTech Connect

    Chang, Y. L. Gong, S. White, R.; Lu, Z. H.; Wang, X.; Wang, S.; Yang, C.

    2014-04-28

    We have demonstrated high-efficiency greenish-blue phosphorescent organic light-emitting diodes (PHOLEDs) based on a dimesitylboryl-functionalized C^N chelate Pt(II) phosphor, Pt(m-Bptrz)(t-Bu-pytrz-Me). Using a high triplet energy platform and optimized double emissive zone device architecture results in greenish-blue PHOLEDs that exhibit an external quantum efficiency of 24.0% and a power efficiency of 55.8?lm/W. This record high performance is comparable with that of the state-of-the-art Ir-based sky-blue organic light-emitting diodes.

  18. The photospheric solar oxygen project. IV. 3D-NLTE investigation of the 777 nm triplet lines

    NASA Astrophysics Data System (ADS)

    Steffen, M.; Prakapavi?ius, D.; Caffau, E.; Ludwig, H.-G.; Bonifacio, P.; Cayrel, R.; Ku?inskas, A.; Livingston, W. C.

    2015-11-01

    Context. The solar photospheric oxygen abundance is still widely debated. Adopting the solar chemical composition based on the "low" oxygen abundance, as determined with the use of three-dimensional (3D) hydrodynamical model atmospheres, results in a well-known mismatch between theoretical solar models and helioseismic measurements that is so far unresolved. Aims: We carry out an independent redetermination of the solar oxygen abundance by investigating the center-to-limb variation of the O i IR triplet lines at 777 nm in different sets of spectra. Methods: The high-resolution and high signal-to-noise solar center-to-limb spectra are analyzed with the help of detailed synthetic line profiles based on 3D hydrodynamical CO5BOLD model atmospheres and 3D non-LTE line formation calculations with NLTE3D. The idea is to exploit the information contained in the observations at different limb angles to simultaneously derive the oxygen abundance, A(O), and the scaling factor SH that describes the cross-sections for inelastic collisions with neutral hydrogen relative to the classical Drawin formula. Using the same codes and methods, we compare our 3D results with those obtained from the semi-empirical Holweger-Müller model atmosphere as well as from different one-dimensional (1D) reference models. Results: With the CO5BOLD 3D solar model, the best fit of the center-to-limb variation of the triplet lines is obtained when the collisions by neutral hydrogen atoms are assumed to be efficient, i.e., when the scaling factor SH is between 1.2 and 1.8, depending on the choice of the observed spectrum and the triplet component used in the analysis. The line profile fits achieved with standard 1D model atmospheres (with fixed microturbulence, independent of disk position ?) are clearly of inferior quality compared to the 3D case, and give the best match to the observations when ignoring collisions with neutral hydrogen (SH = 0). The results derived with the Holweger-Müller model are intermediate between 3D and standard 1D. Conclusions: The analysis of various observations of the triplet lines with different methods yields oxygen abundance values (on a logarithmic scale where A(H) = 12) that fall in the range 8.74 triplet. Appendices E and F are available in electronic form at http://www.aanda.org

  19. A top condensate model with a Higgs doublet and a Higgs triplet

    E-print Network

    Renata Jora; Salah Nasri; Joseph Schechter

    2013-04-26

    We reconsider top condensate models from the perspective that not only two quark composite fields can form but also four quark ones. We obtain a model which contains a Higgs doublet and a Higgs triplet, where one of the neutral components of the Higgs triplet identifies with the Higgs boson found at the LHC. We discuss some of the phenomenological consequences.

  20. Parent-Infant Synchrony and the Social-Emotional Development of Triplets

    ERIC Educational Resources Information Center

    Feldman, Ruth; Eidelman, Arthur I.

    2004-01-01

    To study the social-emotional development of triplets, 23 sets of triplets, 23 sets of twins, and 23 singleton infants (N=138) were followed from birth to 2 years. Maternal depression and social support were assessed in the postpartum period, mother-infant and father-infant interaction and the home environment were observed at 3 months, a…

  1. Photon-Upconverting Ionic Liquids: Effective Triplet Energy Migration in Contiguous Ionic Chromophore Arrays.

    PubMed

    Hisamitsu, Shota; Yanai, Nobuhiro; Kimizuka, Nobuo

    2015-09-21

    Inspired by the bicontinuous ionic-network structure of ionic liquids (ILs), we developed a new family of photofunctional ILs which show efficient triplet energy migration among contiguously arrayed ionic chromophores. A novel fluorescent IL, comprising an aromatic 9,10-diphenylanthracene 2-sulfonate anion and an alkylated phosphonium cation, showed pronounced interactions between chromophores, as revealed by its spectral properties. Upon dissolving a triplet sensitizer, the IL demonstrated photon upconversion based on triplet-triplet annihilation (TTA-UC). Interestingly, the TTA-UC process in the chromophoric IL was optimized at a much lower excitation intensity compared to the previous nonionic liquid TTA-UC system. The superior TTA-UC in this IL system is characterized by a relatively high triplet diffusion constant (1.63×10(-6)?cm(2)?s(-1)) which is ascribed to the presence of ionic chromophore networks in the IL. PMID:26288261

  2. Cooperative singlet and triplet exciton transport in tetracene crystals visualized by ultrafast microscopy

    NASA Astrophysics Data System (ADS)

    Wan, Yan; Guo, Zhi; Zhu, Tong; Yan, Suxia; Johnson, Justin; Huang, Libai

    2015-10-01

    Singlet fission presents an attractive solution to overcome the Shockley-Queisser limit by generating two triplet excitons from one singlet exciton. However, although triplet excitons are long-lived, their transport occurs through a Dexter transfer, making them slower than singlet excitons, which travel by means of a Förster mechanism. A thorough understanding of the interplay between singlet fission and exciton transport is therefore necessary to assess the potential and challenges of singlet-fission utilization. Here, we report a direct visualization of exciton transport in single tetracene crystals using transient absorption microscopy with 200?fs time resolution and 50?nm spatial precision. These measurements reveal a new singlet-mediated transport mechanism for triplets, which leads to an enhancement in effective triplet exciton diffusion of more than one order of magnitude on picosecond to nanosecond timescales. These results establish that there are optimal energetics of singlet and triplet excitons that benefit both singlet fission and exciton diffusion.

  3. An optical--near-IR study of a triplet of super star clusters in the starburst core of M82

    E-print Network

    Westmoquette, M S; Smith, L J; Seth, A C; Gallagher, J S; O'Connell, R W; Ryon, J E; Silich, S; Mayya, Y D; Munoz-Tunon, C; Gonzalez, D Rosa

    2014-01-01

    We present HST/STIS optical and Gemini/NIFS near-IR IFU spectroscopy, and archival HST imaging of the triplet of super star clusters (A1, A2 and A3) in the core of the M82 starburst. Using model fits to the STIS spectra, and the weakness of red supergiant CO absorption features (appearing at ~6 Myr) in the NIFS H-band spectra, the ages of A2 and A3 are $4.5\\pm1.0$~Myr. A1 has strong CO bands, consistent with our previously determined age of $6.4\\pm0.5$~Myr. The photometric masses of the three clusters are 4--$7\\times10^5$~\\Msol, and their sizes are $R_{\\rm eff}=159$, 104, 59~mas ($\\sim$2.8, 1.8, 1.0~pc) for A1,2 and 3. The STIS spectra yielded radial velocities of $320\\pm2$, $330\\pm6$, and $336\\pm5$~\\kms\\ for A1,2, and 3, placing them at the eastern end of the $x_2$ orbits of M82's bar. Clusters A2 and A3 are in high density (800--1000~\\cmt) environments, and like A1, are surrounded by compact H\\two\\ regions. We suggest the winds from A2 and A3 have stalled, as in A1, due to the high ISM ambient pressure. We ...

  4. Quantum Monte Carlo calculation of the singlet--triplet splitting in methylene

    SciTech Connect

    Reynolds, P.J.; Dupuis, M.; Lester W.A. Jr.

    1985-02-15

    The fixed-node quantum Monte Carlo (QMC) method is used to calculate the total energy of CH/sub 2/ in the /sup 3/B/sub 1/ and /sup 1/A/sub 1/ states. For both states, the best QMC variationally bounded energies lie more than 15 kcal/mol (0.024 h) below the best previous variational calculations. Subtracting these energies to obtain the singlet--triplet splitting yields T/sub e/ = 9.4 +- 2.2 kcal/mol. Adjusting for zero-point energies and relativistic effects, we obtain T/sub 0/ = 8.9 +- 2.2 kcal/mol. This result is in excellent agreement with the recent direct measurements of McKellar et al. of T/sub 0/ = 9.05 +- 0.06 kcal/mol, and of Leopold et al. of approx.9 kcal/mol, as well as with recent threoretical investigations which indicate an energy gap of 9--11 kcal/mol. We summarize the QMC method, discuss a possible scheme for iteratively correcting the procedure, and note that the present results were obtained using only single determinant functions for both states, in contrast to conventional ab initio approaches which must use at least two configurations to properly describe the singlet state.

  5. Triplet photophysics of polystyrene with and without selected terminating substituents

    SciTech Connect

    Burkhart, R.D.; Burrows, J.A.J.; Haggquist, G.W.

    1989-01-01

    Polystyrene molecules selectively terminated with an acetophenone-like (AC) group at one end and a naphthyl group at the opposite end have been prepared and their triplet photophysics investigated. Photoexcitation of solid films of these polymers using a nitrogen laser (337 nm) yields phosphorescence bands attributable to the AC group and the naphthalene group. Using 337 nm excitation and viewing the emission at 0.1 msec after the excitation pulse, a broad phosphorescence band overlaps the AC signal. At longer delay times the typical structured AC emissions emerges if the sample temperature is at 77 K but at ambient temperature the broad band persists. Apparently the AC emission is inhomogeneously broadened with an inhomogeneous band width large enough so that spectral diffusion can occur at 77 K. Luminescence decay kinetics provide information about possible modes of energy transfer from initially excited AC species to the naphthyl group. 6 refs., 3 figs.

  6. Discovery of a tidal dwarf galaxy in the Leo Triplet

    SciTech Connect

    Nikiel-Wroczy?ski, B.; Soida, M.; Urbanik, M.; Bomans, D. J. E-mail: soida@oa.uj.edu.pl E-mail: bomans@astro.rub.de

    2014-05-10

    We report the discovery of a dwarf galaxy in the Leo Triplet. Analysis of the neutral hydrogen distribution shows that it rotates independently of the tidal tail of NGC 3628, with a radial velocity gradient of 35-40 km s{sup –1} over approximately 13 kpc. The galaxy has an extremely high neutral gas content, accounting for a large amount of its total dynamic mass and suggesting a low amount of dark matter. It is located at the tip of the gaseous tail, which strongly suggests a tidal origin. If this is the case, it would be one of the most confident and nearest (to the Milky Way) detections of a tidal dwarf galaxy and, at the same time, the object most detached from its parent galaxy (?140 kpc) of this type.

  7. Nonstandard neutrino interactions from a triplet seesaw model

    SciTech Connect

    Malinsky, Michal; Ohlsson, Tommy; Zhang He

    2009-01-01

    We investigate nonstandard neutrino interactions (NSIs) in the triplet seesaw model featuring nontrivial correlations between NSI parameters and neutrino masses and mixing parameters. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus, these NSIs could lead to quite significant signals of lepton flavor violating decays such as {mu}{sup -}{yields}e{sup -}{nu}{sub e}{nu}{sub {mu}} and {mu}{sup +}{yields}e{sup +}{nu}{sub e}{nu}{sub {mu}} at a future neutrino factory, effects adding to the uncertainty in determination of the Earth matter density profile, as well as characteristic patterns of the doubly charged Higgs decays observable at the Large Hadron Collider.

  8. The scalar singlet-triplet dark matter model

    SciTech Connect

    Fischer, O.; Van der Bij, J.J. E-mail: vdbij@physik.uni-freiburg.de

    2014-01-01

    We consider a model for cold dark matter, which combines a real scalar singlet and a real scalar SU(2){sub L} triplet field, both of which are residing in the odd representation of a global Z{sub 2} symmetry. The parameter space of the model is constrained by the inferred dark matter abundance from the WMAP and Planck data, the most recent results from the direct dark matter search experiment LUX, the Z boson decay width from LEP-I and perturbativity of the coupling parameters. The phenomenology of the remaining parameter space is studied. We find that the model allows for DM masses near the electroweak scale and a variety of decay scenarios.

  9. Manufacturing experience for the LHC inner triplet quadrupole cables

    SciTech Connect

    Scanlan, R.M.; Higley, H.C.; Bossert, R.; Kerby, J.; Gosh, A.K.; Boivin, M.; Roy, T.

    2001-06-12

    The design for the U.S. LHC Inner Triplet Quadrupole magnet requires a 37 strand (inner layer) and a 46 strand (outer layer) cable. This represents the largest number of strands attempted to date for a production quantity of Rutherford-type cable. The cable parameters were optimized during the production of a series of short prototype magnets produced at FNAL. These optimization studies focused on critical current degradation, dimensional control, coil winding, and interstrand resistance. After the R&D phase was complete, the technology was transferred to NEEW and a new cabling machine was installed to produce these cables. At present, about 60 unit lengths, out of 90 required for the entire production series of magnets, have been completed for each type of cable. The manufacturing experience with these challenging cables will be reported. Finally, the implications for even larger cables, with more strands, will be discussed.

  10. cctbx news: Fast triplet generator for direct methods, Gallery of direct-space asymmetric units, et. al.

    E-print Network

    Grosse-Kunstleve, Ralf

    10 cctbx news: Fast triplet generator for direct methods, Gallery of direct-space asymmetric units crystallographic algorithms. In this article we give an overview of recent developments. Fast triplet generator for direct methods For almost a year the cctbx has included an experimental triplet generator in the cctbx

  11. Excited-state annihilation reduces power dependence of single-molecule FRET experiments.

    PubMed

    Nettels, Daniel; Haenni, Dominik; Maillot, Sacha; Gueye, Moussa; Barth, Anders; Hirschfeld, Verena; Hübner, Christian G; Léonard, Jérémie; Schuler, Benjamin

    2015-12-01

    Single-molecule Förster resonance energy transfer (FRET) experiments are an important method for probing biomolecular structure and dynamics. The results from such experiments appear to be surprisingly independent of the excitation power used, in contradiction to the simple photophysical mechanism usually invoked for FRET. Here we show that excited-state annihilation processes are an essential cause of this behavior. Singlet-singlet annihilation (SSA) is a mechanism of fluorescence quenching induced by Förster-type energy transfer between two fluorophores while they are both in their first excited singlet states (S1S1), which is usually neglected in the interpretation of FRET experiments. However, this approximation is only justified in the limit of low excitation rates. We demonstrate that SSA is evident in fluorescence correlation measurements for the commonly used FRET pair Alexa 488/Alexa 594, with a rate comparable to the rate of energy transfer between the donor excited state and the acceptor ground state (S1S0) that is exploited in FRET experiments. Transient absorption spectroscopy shows that SSA occurs exclusively via energy transfer from Alexa 488 to Alexa 594. Excitation-power dependent microsecond correlation experiments support the conclusion based on previously reported absorption spectra of triplet states that singlet-triplet annihilation (STA) analogously mediates energy transfer if the acceptor is in the triplet state. The results indicate that both SSA and STA have a pronounced effect on the overall FRET process and reduce the power dependence of the observed FRET efficiencies. The existence of annihilation processes thus seems to be essential for using FRET as a reliable spectroscopic ruler at the high excitation rates commonly employed in single-molecule spectroscopy. PMID:26584062

  12. Galaxy triplets in Sloan Digital Sky Survey Data Release 7 - I. Catalogue

    NASA Astrophysics Data System (ADS)

    O'Mill, Ana Laura; Duplancic, Fernanda; García Lambas, Diego; Valotto, Carlos; Sodré, Laerte

    2012-04-01

    We present a new catalogue of galaxy triplets derived from the Sloan Digital Sky Survey (SDSS) Data Release 7. The identification of systems was performed considering galaxies brighter than Mr=-20.5 and imposing constraints over the projected distances, radial velocity differences of neighbouring galaxies and isolation. To improve the identification of triplets, we employed a data pixelization scheme, which allows us to handle large amounts of data as in the SDSS photometric survey. Using spectroscopic and photometric data in the redshift range 0.01 ?z? 0.40, we obtain 5901 triplet candidates. We have used a mock catalogue to analyse the completeness and contamination of our methods. The results show a high level of completeness (˜80 per cent) and low contamination (˜5 per cent). By using photometric and spectroscopic data, we have also addressed the effects of fibre collisions in the spectroscopic sample. We have defined an isolation criterion considering the distance of the triplet brightest galaxy to the closest neighbour cluster, to describe a global environment, as well as the galaxies within a fixed aperture, around the triplet brightest galaxy, to measure the local environment. The final catalogue comprises 1092 isolated triplets of galaxies in the redshift range 0.01 ?z? 0.40. Our results show that photometric redshifts provide very useful information, allowing us to complete the sample of nearby systems whose detection is affected by fibre collisions, as well as extending the detection of triplets to large distances, where spectroscopic redshifts are not available.

  13. Symmetry breaking in cationic polymethine dyes, part 1: Ground state potential energy surfaces and solvent effects on electronic spectra of streptocyanines

    NASA Astrophysics Data System (ADS)

    Iordanov, Tzvetelin D.; Davis, Jesse L.; Masunov, Artëm E.; Levenson, Andrew; Przhonska, Olga V.; Kachkovski, Alexei D.

    Charge localization and dynamics in conjugated organic molecules, as well as their spectral signatures are of great importance for photonic and photovoltaic applications. Intramolecular charge delocalization in polymethine dyes occurs through ?-conjugated bridges and contributes to the appearance of low-energy excited states that strongly influence their linear and nonlinear optical (NLO) properties. When the chain length in symmetrical cations exceeds the characteristic size of the soliton, the positive charge may localize at one of the terminal groups of the molecule and induce symmetry breaking of both the electron density distribution and molecular geometry. This charge localization is coupled with molecular vibrations and solvent effects. We investigated the mechanism of symmetry breaking in a series of cationic streptocyanines with different conjugated chain length and qualitatively predicted their electronic absorption spectra. This class of organic molecules is chosen as a model system to develop methodology which can subsequently be used to evaluate more complicated compounds for NLO applications. Our calculations show that the minimum number of vinylene groups in the conjugated chain necessary to break the symmetry of streptocyanines is eight in the gas phase and six in cyclohexane. We constructed the ground state potential energy surface (PES) in two dimensions using symmetry breaking and symmetry adapted coordinates. These were defined as the difference and the sum of the two central carbon-carbon bonds, respectively. This PES was found to have two equivalent minima for systems with symmetry breaking. The energy barrier between these two minima was estimated in the gas phase and in solution, which was taken into account by the polarizable continuum model. Charge localization in each minimum was found to be asymmetric. It is additionally stabilized by the solvent reaction field, which increases the energy barrier. The electronic absorption spectrum in solution is red shifted as compared to the gas phase. As the symmetry breaks, additional excited states with large oscillator strengths appear in the electronic spectrum. Geometry optimization and spectral predictions were also performed in a uniform external electric field in order to simulate nonequilibrium solvation effects due to the finite relaxation time of solvent molecules. Two asymmetric minima with different depths appear on the resulting PES. The lower minimum has charge localized at one of the two molecular terminal groups which is additionally stabilized by the solvent field, while the higher one has charge localized on another terminal group. This finding demonstrates the possibility that two forms with different charge distributions coexist in polar solvents. Our results suggest that nonequilibrium solvation may be a cause of absorption band broadening and splitting. This work is a first step in a larger study aimed at the analysis of the linear and nonlinear properties of long ?-conjugated systems of interest for NLO applications and plastic photovoltaics.

  14. Spin-triplet current in half metal/conical helimagnet/superconductor heterojunctions

    NASA Astrophysics Data System (ADS)

    Jin, Li-Jing; Wang, Yue; Wen, Lin; Zha, Guo-Qiao; Zhou, Shi-Ping

    2012-07-01

    The BTK theory is extended to investigate spin-triplet current and differential conductance spectrum in the half metal/conical helimagnet (Holmium)/s-wave superconductor heterojunctions. We show that the effective spin-split and spin-flip scatterings of the Holmium layer control the conversion efficiency between the spin-singlet and equal-spin triplet pair correlations, leading to a tunneling current oscillation with the thickness of the Holmium layer. This can provide qualitative explanations on the current oscillation in Ho/Co/Ho-based Josephson junction experiment. The differential conductance spectrum confirms spin-flip Andreev reflection induced long-ranged equal-spin triplet pair correlations.

  15. Direct imaging of anisotropic exciton diffusion and triplet diffusion length in rubrene single crystals.

    PubMed

    Irkhin, Pavel; Biaggio, Ivan

    2011-07-01

    We visualize exciton diffusion in rubrene single crystals using localized photoexcitation and spatially resolved detection of excitonic luminescence. We show that the exciton mobility in this material is strongly anisotropic with long-range diffusion by several micrometers associated only with the direction of molecular stacking in the crystal, along the b axis. We determine a triplet exciton diffusion length of 4.0 ± 0.4 ?m from the spatial exponential decay of the photoluminescence that originates from singlet excitons formed by triplet-triplet fusion. PMID:21797572

  16. Orbifold Grand Unification: A Solution to the Doublet-Triplet Problem

    E-print Network

    Bei Jia; Jiang-Hao Yu

    2014-12-17

    To solve the doublet-triplet splitting problem in SU(5) grand unified theories, we propose a four dimensional orbifold grand unified theory by acting Z2 on the SU(5) gauge group. Without an adjoint Higgs, the orbifold procedure breaks the SU(5) gauge symmetry down to the standard model gauge group, and removes the triplet component of the fundamental SU(5) Higgs. In the supersymmetric framework, we show that the orbifold procedure removes two triplet superfields of the Higgs multiplets and leaves us with the minimal supersymmetric standard model, which also solves the hierarchy problem and realizes gauge coupling unification. We also discuss possible UV completions of the orbifold theories.

  17. DNA energy landscapes via calorimetric detection of microstate ensembles of metastable macrostates and triplet repeat diseases

    PubMed Central

    Völker, Jens; Klump, Horst H.; Breslauer, Kenneth J.

    2008-01-01

    Biopolymers exhibit rough energy landscapes, thereby allowing biological processes to access a broad range of kinetic and thermodynamic states. In contrast to proteins, the energy landscapes of nucleic acids have been the subject of relatively few experimental investigations. In this study, we use calorimetric and spectroscopic observables to detect, resolve, and selectively enrich energetically discrete ensembles of microstates within metastable DNA structures. Our results are consistent with metastable, “native” DNA states being composed of an ensemble of discrete and kinetically stable microstates of differential stabilities, rather than exclusively being a single, discrete thermodynamic species. This conceptual construct is important for understanding the linkage between biopolymer conformational/configurational space and biological function, such as in protein folding, allosteric control of enzyme activity, RNA and DNA folding and function, DNA structure and biological regulation, etc. For the specific DNA sequences and structures studied here, the demonstration of discrete, kinetically stable microstates potentially has biological consequences for understanding the development and onset of DNA expansion and triplet repeat diseases. PMID:19015511

  18. Singlet and triplet excitons and charge polarons in cycloparaphenylenes. A density functional theory study

    DOE PAGESBeta

    Liu, Jin; Adamska, Lyudmyla; Doorn, Stephen K.; Tretiak, Sergei

    2015-05-14

    Conformational structure and the electronic properties of various electronic excitations in cycloparaphenylenes (CPPs) are calculated using hybrid Density Functional Theory (DFT). The results demonstrate that wavefunctions of singlet and triplet excitons as well as the positive and negative polarons remain fully delocalized in CPPs. In contrast, these excitations in larger CPP molecules become localized on several phenyl rings, which are locally planarized, while the undeformed ground state geometry is preserved on the rest of the hoop. As evidenced by the measurements of bond-length alternation and dihedral angles, localized regions show stronger hybridization between neighboring bonds and thus enhanced electronic communication.more »This effect is even more significant in the smaller hoops, where phenyl rings have strong quinoid character in the ground state. Thus, upon excitation, electron–phonon coupling leads to the self-trapping of the electronic wavefunction and release of energy from fractions of an eV up to two eVs, depending on the type of excitation and the size of the hoop. The impact of such localization on electronic and optical properties of CPPs is systematically investigated and compared with the available experimental measurements.« less

  19. Singlet and triplet excitons and charge polarons in cycloparaphenylenes. A density functional theory study

    SciTech Connect

    Liu, Jin; Adamska, Lyudmyla; Doorn, Stephen K.; Tretiak, Sergei

    2015-05-14

    Conformational structure and the electronic properties of various electronic excitations in cycloparaphenylenes (CPPs) are calculated using hybrid Density Functional Theory (DFT). The results demonstrate that wavefunctions of singlet and triplet excitons as well as the positive and negative polarons remain fully delocalized in CPPs. In contrast, these excitations in larger CPP molecules become localized on several phenyl rings, which are locally planarized, while the undeformed ground state geometry is preserved on the rest of the hoop. As evidenced by the measurements of bond-length alternation and dihedral angles, localized regions show stronger hybridization between neighboring bonds and thus enhanced electronic communication. This effect is even more significant in the smaller hoops, where phenyl rings have strong quinoid character in the ground state. Thus, upon excitation, electron–phonon coupling leads to the self-trapping of the electronic wavefunction and release of energy from fractions of an eV up to two eVs, depending on the type of excitation and the size of the hoop. The impact of such localization on electronic and optical properties of CPPs is systematically investigated and compared with the available experimental measurements.

  20. Forest Biomass Mapping from Prism Triplet, Palsar and Landsat Data

    NASA Astrophysics Data System (ADS)

    Ranson, J.; Sun, G.; Ni, W.

    2014-12-01

    The loss of sensitivity at higher biomass levels is a common problem in biomass mapping using optical multi-spectral data or radar backscattering data due to the lack of information on canopy vertical structure. Studies have shown that adding implicit information of forest vertical structure improves the performance of forest biomass mapping from optical reflectance and radar backscattering data. LiDAR, InSAR and stereo imager are the data sources for obtaining forest structural information. The potential of providing information on forest vertical structure by stereoscopic imagery data has drawn attention recently due to the availability of high-resolution digital stereo imaging from space and the advances of digital stereo image processing software. The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observation Satellite (ALOS) has acquired multiple global coverage from June 2006 to April 2011 providing a good data source for regional/global forest studies. In this study, five PRISM triplets acquired on June 14, 2008, August 19 and September 5, 2009; PALSAR dual-pol images acquired on July 12, 2008 and August 30, 2009; and LANDSAT 5 TM images acquired on September 5, 2009 and the field plot data collected in 2009 and 2010 were used to map forest biomass at 50m pixel in an area of about 4000 km2in Maine, USA ( 45.2 deg N 68.6 deg W). PRISM triplets were used to generate point cloud data at 2m pixel first and then the average height of points above NED (National Elevation Dataset) within a 50m by 50m pixel was calculated. Five images were mosaicked and used as canopy height information in the biomass estimation along with the PALSAR HH, HV radar backscattering and optical reflectance vegetation indices from L-5 TM data. A small portion of this region was covered by the Land Vegetation and Ice Sensor (LVIS) in 2009. The biomass maps from the LVIS data was used to evaluate the results from combined use of PRISM, PALSAR and LANDSAT data. The results show that the canopy height index from PRISM stereo images significantly improves the biomass mapping accuracy and extends the saturation level of biomass, and results in a biomass map comparable with those generated from LVIS data.

  1. X-ray spectra of supernova remnants

    NASA Technical Reports Server (NTRS)

    Szymkowiak, A. E.

    1985-01-01

    X-ray spectra were obtained from fields in three supernova remnants with the solid state spectrometer of the HEAO 2 satellite. These spectra, which contain lines from K-shell transitions of several abundant elements with atomic numbers between 10 and 22, were compared with various models, including some of spectra that would be produced by adiabatic phase remnants when the time-dependence of the ionization is considered.

  2. Triplet–triplet annihilation upconversion followed by FRET for the red light activation of a photodissociative ruthenium complex in liposomes† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5cp04352b

    PubMed Central

    Askes, Sven H. C.; Kloz, Miroslav; Bruylants, Gilles; Kennis, John T. M.

    2015-01-01

    Upconversion is a promising way to trigger high-energy photochemistry with low-energy photons. However, combining upconversion schemes with non-radiative energy transfer is challenging because bringing several photochemically active components in close proximity results in complex multi-component systems where quenching processes may deactivate the whole assembly. In this work, PEGylated liposomes were prepared that contained three photoactive components: a porphyrin dye absorbing red light, a perylene moiety emitting in the blue, and a light-activatable ruthenium prodrug sensitive to blue light. Time-dependent spectroscopic studies demonstrate that singlet perylene excited states are non-radiatively transferred to the nearby ruthenium complex by Förster resonance energy transfer (FRET). Under red-light irradiation of the three-component membranes, triplet–triplet annihilation upconversion (TTA-UC) occurs followed by FRET, which results in a more efficient activation of the ruthenium prodrug compared to a physical mixture of two-component upconverting liposomes and liposomes containing only the ruthenium complex. This work represents a rare example where TTA-UC and Förster resonance energy transfer are combined to achieve prodrug activation in the phototherapeutic window. PMID:26420663

  3. Compact magnetic quadrupole triplet for a low-energy high-current ion beam transport

    SciTech Connect

    Cho, Yong-Sub; Kim, Han-Sung; Kwon, Hyeok-Jung

    2008-02-15

    It is a difficult task to design a conventional quadrupole triplet as compact and simple as solenoids for high-current ion beam transport. In the design of a quadrupole triplet presented here, we installed three poles with the same orientation on a yoke and these were excited using two coils located between poles. This new design allows the easier fabrication of a compact quadrupole triplet compared to the conventional design. Simple equations for the preliminary design were obtained. A prototype with an aperture radius of 55 mm and a focusing power of 3.3 m{sup -1} for 50 keV proton beams was designed, fabricated, and tested. The measured field profile agreed well with the calculated profile. The length of the compact magnetic quadrupole triplet was comparable with a solenoid, and its electrical power consumption was about 40% that of a solenoid.

  4. Conjoined twins in a monochorionic triplet pregnancy after in vitro fertilization: a case report

    PubMed Central

    Talebian, Marzieh; Rahimi-Sharbaf, Fatemeh; Shirazi, Mahboobeh; Teimoori, Batool; Izadi-mood, Narges; Sarmadi, Soheila

    2015-01-01

    Background: Monozygotic monochorionic triplet pregnancy with conjoined twins is a very rare condition and is associated with many complications. Case: In this study, we describe a monochorionic–diamniotic triplet pregnancy after in vitro fertilization with an intracytoplasmic sperm injection. At a gestational age of 6 weeks and 4 days of pregnancy one gestational sac was observed, and at a gestational age of 12 weeks and 2 days, triplets with conjoined twins were diagnosed. After consulting with the parents, they chose fetal reduction of the conjoined twins. Selective feticide was successfully performed by radiofrequency ablation at 16 weeks of pregnancy. Unfortunately, the day after the procedure, the membrane ruptured, and 1 week later, all fetuses and placenta were spontaneously aborted. Conclusion: Monochorionic triplet pregnancy with conjoined twins is very rare. These pregnancies are associated with very serious complications. Intra cytoplasmic sperm injection increases the rate of monozygotic twinning and conjoined twins. Counseling with parents before IVF is very important.

  5. VizieR Online Data Catalog: Isolated galaxies, pairs and triplets (Argudo-Fernandez+, 2015)

    NASA Astrophysics Data System (ADS)

    Argudo-Fernandez, M.; Verley, S.; Bergond, G.; Duarte Puertas, S.; Ramos Carmona, E.; Sabater, J.; Fernandez, Lorenzo M.; Espada, D.; Sulentic, J.; Ruiz, J. E.; Leon, S.

    2015-04-01

    Catalogues of isolated galaxies, isolated pairs, and isolated triplets in the local Universe with positions, redshifts, and degrees of relation with their physical and large-scale environments. (5 data files).

  6. Actinide-silicon multiradical bonding: infrared spectra and electronic structures of the Si(?-X)AnF3 (An = Th, U; X = H, F) molecules.

    PubMed

    Hu, Han-Shi; Wei, Fan; Wang, Xuefeng; Andrews, Lester; Li, Jun

    2014-01-29

    We report a series of Si(?-X)AnF3 (An = Th, U; X = H, F) complexes with silicon-actinide(IV) single bonds and unexpected multiradical features that form rare triplet silylenes. These bridged molecules have been prepared in microscopic scale through reactions of laser-ablated uranium and thorium atoms with silicon fluorides and identified from infrared spectra in argon and neon matrixes and relativistic quantum chemical calculations. Similar neon matrix experiments for the reactions of uranium with CF4 and CHF3 were carried out for comparison. Our density functional theory calculations show that the Si-U single-bonded species Si(?-X)UF3 (X = H, F) with U(IV) oxidation state and the quasi-agostic bridge ligand of H or F are most stable among all the isomers, whereas the naively anticipated triple-bonded species XSi?UF3 with U(VI) oxidation state and the double-bonded species XSi(•)?(•)UF3 with U(V) oxidation state lie markedly higher in energy. Similar thorium products from reactions with XSiF3 are also found to prefer the Si(?-X)ThF3 structures with Si-Th single bonds and bridged H or F ligands. High level ab initio wave function theory calculations with the CCSD(T) and CASPT2 methods confirm that the ground states are quintet for Si(?-X)UF3 and triplet for Si(?-X)ThF3 with two unpaired electrons on the silylene group. These silicon-bearing molecules as the lowest-energy isomer of XSiAnF3 represent the first silicon-actinide systems with unusual "triplet" silylenes and Si-An single bonds with multiradical character. They are in dramatic contrast to the uranium-carbon analogs, XC?UF3, which form triple-bonded singlet ground states with C3v symmetry. The calculated vibrational frequencies of the Si(?-X)AnF3 complexes agree well with experimental observations. These results accentuate the critical difference of chemical bonding of 3p- and 2p-row main-group elements with actinides. The Lewis electron-pair model and the octet rule break down for these silicon compounds. PMID:24383992

  7. The J-triplet Cooper pairing with magnetic dipolar interactions

    PubMed Central

    Li, Yi; Wu, Congjun

    2012-01-01

    Recently, cold atomic Fermi gases with the large magnetic dipolar interaction have been laser cooled down to quantum degeneracy. Different from electric-dipoles which are classic vectors, atomic magnetic dipoles are quantum-mechanical matrix operators proportional to the hyperfine-spin of atoms, thus provide rich opportunities to investigate exotic many-body physics. Furthermore, unlike anisotropic electric dipolar gases, unpolarized magnetic dipolar systems are isotropic under simultaneous spin-orbit rotation. These features give rise to a robust mechanism for a novel pairing symmetry: orbital p-wave (L = 1) spin triplet (S = 1) pairing with total angular momentum of the Cooper pair J = 1. This pairing is markedly different from both the 3He-B phase in which J = 0 and the 3He-A phase in which J is not conserved. It is also different from the p-wave pairing in the single-component electric dipolar systems in which the spin degree of freedom is frozen. PMID:22550567

  8. Computer Simulation Studies of CTG Triplet Repeat Sequences

    NASA Astrophysics Data System (ADS)

    Rasaiah, Jayendran. C.; Lynch, Joshua

    1998-03-01

    Long segments of CTG trinucleotide repeats in human DNA are correlated with a class of neurological diseases (myotonic dystrophy, fragile-X syndrome, and Kenndy's disease). These diseases are characterized by genetic anticipation and are thought to arise from replication errors caused by unusual conformations of CTG repeat segments. We have studied the properties of a single short segment of double starnded DNA with CTG repeats in 0.5 M sodium chloride solution with molecular dynamics simulations. The simulations are carried out in the micro canonical ensemble using an all-atom force field with CHARMM parameters. The TIPS3 water model is used to simulate a molecular solvent. Electrostatic interactions are calculated by Ewald summation and the equations of motion integrated using a Verlet algorithm in conjunction with SHAKE constrained dynamics to maintain bond lengths. The simulation of CTG repeat sequence is compared with a control system containing CAG triplet repeats to determine possible differencesin the conformation and elasticity of the two sequences.

  9. The 3-3-1 model with inert scalar triplet

    E-print Network

    P. V. Dong; T. Phong Nguyen; D. V. Soa

    2013-11-06

    We show that the typical 3-3-1 models are only self-consistent if they contain interactions explicitly violating the lepton number. The 3-3-1 model with right-handed neutrinos can by itself work as an economical 3-3-1 model as a natural recognition of the above criteria while it also results an inert scalar triplet (\\eta) responsible for dark matter. This is ensured by a Z_2 symmetry (assigned so that only \\eta is odd while all other multiplets which perform the economical 3-3-1 model are even), which is not broken by the vacuum. The minimal 3-3-1 model can provide a dark matter by a similar realization. Taking the former into account, we show that the dark matter candidate (H_\\eta) contained in \\eta transforms as a singlet in effective limit under the standard model symmetry and being naturally heavy. The H_\\eta relic density and direct detection cross-section will get right values when the H_\\eta mass is in TeV range as expected. The model predicts the H_\\eta mass m_{H_\\eta}=\\lambda_5\\times 2 TeV and the H_\\eta-nucleon scattering cross-section \\sigma_{H_\\eta-N}=1.56\\times 10^{-44} cm^2, provided that the new neutral Higgs boson is heavy enough than the dark matter.

  10. Neutrino Masses and Heavy Triplet Leptons at the LHC: Testability of Type III Seesaw

    E-print Network

    Tong Li; Xiao-Gang He

    2009-11-03

    We study LHC signatures of Type III seesaw in which SU(2)_L triplet leptons are introduced to supply the heavy seesaw masses. To detect the signals of these heavy triplet leptons, one needs to understand their decays to standard model particles which depend on how light and heavy leptons mix with each other. We concentrate on the usual solutions with small light and heavy lepton mixing of order the square root of the ratio of light and heavy masses, (m_\

  11. The Behavior of the Paschen and Calcium Triplet Lines in Cepheid Variables I. ? Cephei

    NASA Astrophysics Data System (ADS)

    Wallerstein, George; Albright, Meagan B.; Ritchey, Adam M.

    2015-06-01

    We present new radial velocity curves for ? Cephei as a preliminary example for a series of papers on cepheids with periods from 10 to 20 days. The data are provided by the echelle spectrograph of the Apache Point Observatory 3.5-m telescope. Separate velocities are shown for lines formed at distinctly different optical depths. New data for the Paschen lines, the O i triplet at 7773 Å, and the Ca ii infrared triplet are included.

  12. Night Spectra Quest.

    ERIC Educational Resources Information Center

    Jacobs, Stephen

    1995-01-01

    Presents the Night Spectra Quest, a pocket-sized chart that identifies in color the spectra of all the common night lights and has an integrally mounted, holographic diffraction grating to look through. (JRH)

  13. Weak-triplet, color-octet scalars and the CDF dijet excess

    DOE PAGESBeta

    Dobrescu, Bogdan A.; Krnjaic, Gordan Z.

    2012-04-24

    We extend the standard model to include a weak-triplet and color-octet scalar. This 'octo-triplet' field consists of three particles, two charged and one neutral, whose masses and renormalizable interactions depend only on two new parameters. The charged octo-triplet decay into a W boson and a gluon is suppressed by a loop factor and an accidental cancellation. Thus, the main decays of the charged octo-triplet may occur through higher-dimensional operators, mediated by a heavy vectorlike fermion, into quark pairs. For an octo-triplet mass below the tb? threshold, the decay into Wb b? through an off-shell top quark has a width comparablemore »to that into cs? or cb?. Pair production with one octo-triplet decaying to two jets and the other decaying to a W and two soft b jets may explain the dijet-plus-W excess reported by the CDF Collaboration. The same higher-dimensional operators lead to CP violation in Bs-B?s mixing.« less

  14. Weak-triplet, color-octet scalars and the CDF dijet excess

    SciTech Connect

    Dobrescu, Bogdan A.; Krnjaic, Gordan Z.

    2012-04-24

    We extend the standard model to include a weak-triplet and color-octet scalar. This 'octo-triplet' field consists of three particles, two charged and one neutral, whose masses and renormalizable interactions depend only on two new parameters. The charged octo-triplet decay into a W boson and a gluon is suppressed by a loop factor and an accidental cancellation. Thus, the main decays of the charged octo-triplet may occur through higher-dimensional operators, mediated by a heavy vectorlike fermion, into quark pairs. For an octo-triplet mass below the tb? threshold, the decay into Wb b? through an off-shell top quark has a width comparable to that into cs? or cb?. Pair production with one octo-triplet decaying to two jets and the other decaying to a W and two soft b jets may explain the dijet-plus-W excess reported by the CDF Collaboration. The same higher-dimensional operators lead to CP violation in Bs-B?s mixing.

  15. Thermodynamics of the hydration equilibrium derived from the luminescence spectra of the solid state for the case of the Eu-EDTA system.

    PubMed

    Janicki, R; Mondry, A

    2015-11-28

    The luminescence properties of two compounds, [C(NH2)3][Eu(EDTA)(H2O)3] (I) and [C(NH2)3]2[Yb0.97Eu0.03(EDTA)(H2O)2]ClO4·6H2O (II), were determined. The weighted sum of luminescence spectra of I and II was used to reproduce the spectra of the Eu-EDTA system in aqueous solution in the temperature range 276-363 K. By implementing this method it was possible to determine the thermodynamic functions (?H = 18113 ± 506 J mole(-1) and ?S = 62.5 ± 4.9 J mole(-1) K(-1)) of the reaction [Eu(EDTA)(H2O)3](-)? [Eu(EDTA)(H2O)2](-) + H2O, which is difficult using other methods. PMID:26400410

  16. A precise determination of the triplet energy of C sub 60 by photoacoustic calorimetry

    SciTech Connect

    Hung, R.R.; Grabowski, J.J. )

    1991-08-08

    The relatively new technique of time-resolved, pulsed-laser photoacoustic calorimetry has been exploited to precisely determine the triplet-state energy of C{sub 60}, the newly discovered spheroidal allotrope of carbon. Excitation at 510 nm, in the long-wavelength absorption band of C{sub 60}, produces C{sub 60}(T{sub 1}) with unit efficiency; in the presence of dioxygen, triplet C{sub 60} is readily quenched by energy transfer. Photoacoustic waves were recorded for C{sub 60} in argon-saturated, air-saturated, and partially argon-saturated toluene solutions. Each experimental wave was then fit to a two-component model, the first component of which corresponds to production of C{sub 60}(T{sub 1}) and the second of which relates to its decay. The recovered heat-deposition parameters are {phi}{sub 1} = 0.359 {plus minus} 0.005 and {phi}{sub 2} = 0.237 {plus minus} 0.011; these correspond to the fraction of the absorbed photon energy that is released in forming C{sub 60}(T{sub 1}) and in the quenching of C{sub 60}(T{sub 1}) by dioxygen. Since the quantum yield for intersystem crossing of C{sub 60}, from S{sub 1} to T{sub 1}, is unity, {phi}{sub 1} corresponds to a C{sub 60}(T{sub 1}) energy of 36.0 {plus minus} 0.6 kcal mol{sup {minus}1}. Since the energy of C{sub 60}(T{sub 1}) is defined by {phi}{sub 1} and the energy of O{sub 2}({sup 1}{Delta}) is known {phi}{sub 2} is used to calculate a singlet oxygen sensitization quantum yield of 1.01 {plus minus} 0.03. The lifetime of C{sub 60}(T{sub 1}) in argon-saturated toluene is found to be > 10 {mu}s, and in air-saturated toluene, to be 290 {plus minus} 40 ns.

  17. Dark States in Ionic Oligothiophene BioprobesEvidence from Fluorescence Correlation Spectroscopy and Dynamic Light

    E-print Network

    , light- induced triplet state formation,3 photoinduced trans-cis isomerization,4 ionization, and radical, and if and to what extent the LCPs under study enter into dark states during the experiments. Such states can either

  18. Superfluid phases of triplet pairing and neutrino emission from neutron stars

    NASA Astrophysics Data System (ADS)

    Leinson, L. B.

    2010-12-01

    Neutrino energy losses through neutral weak currents in the triplet-spin superfluid neutron liquid are studied for the case of condensate involving several magnetic quantum numbers. Low-energy excitations of the multicomponent condensate in the timelike domain of the energy and momentum are analyzed. Along with the well-known excitations in the form of broken Cooper pairs, the theoretical analysis predicts the existence of collective waves of spin density in the one-component condensate at very low energy. Because of a rather small excitation energy of spin waves, their decay leads to a substantial neutrino emission at the lowest temperatures when all other mechanisms of neutrino energy loss are killed by a superfluidity. Neutrino energy losses caused by the pair recombination and spin-wave decays are examined in all of the multicomponent phases that might represent the ground state of the condensate, according to modern theories, and for the case when a phase transition occurs in the condensate at some temperature. Our estimate predicts a sharp increase in the neutrino energy losses followed by a decrease, along with a decrease in the temperature that takes place more rapidly than it would without the phase transition. We demonstrate the important role of the neutrino radiation caused by the decay of spin waves in the cooling of neutron stars.

  19. [Laser photolysis study on photo-oxidation reactions of aromatic amino acids with triplet 2-methylanthraquinone].

    PubMed

    Cao, Xi-Yan; Fu, Hai-Ying; Zhu, Li; Wu, Guo-Zhong

    2013-04-01

    The transient photo-sensitive oxidation between 2-methylanthraquinone (MAQ) and aromatic amino acids (namely tryptophan, tyrosine and phenylalanine) in acetonitrile/water (1 : 1, V/V) solution was investigated by laser photolysis techniques with the excitation wavelength of 355 nm. The triplet state absorption of 2-methylanthraquinone was attributed to 390, 450 and 590 nm and the anion radical absorption of MAQ was due to 390 and 490 nm identified by the electron transfer reactions from 4-diazabicyclo [2. 2. 2] octane (DABCO) or diphenylamine (DPA) to 3MAQ*. With the decay of 3 MAQ*, the MAQ*- at 490 nm appeared, which indicated that the electron transfer reactions between 3 MAQ* and amino acids occurred. Moreover, the rate constants were deduced to be 3.0 x 10(9), 1.1 x 10(9) and 1.8 x 10(8) L x mol(-1) x s(-1) for TrpH, TyrOH and PHE, respectively. On the other hand, the free energy changes (deltaG) of the reactions showed that the proposed electron transfer steps are thermodynamically feasible. PMID:23841398

  20. Improving desynchronization of parkinsonian neuronal network via triplet-structure coordinated reset stimulation.

    PubMed

    Fan, Denggui; Wang, Qingyun

    2015-04-01

    We investigate how the triplet-structure coordinated reset stimulations (CRS), which acts on the GPe, STN and GPi within the basal ganglia-thalamocortical motor circuit, can destabilize the strong synchronous state and improve the reliability of thalamic relay in the parkinsonian network. It is shown that compared with the permanent (1:0 ON-OFF) CRS or the classic deep brain stimulation paradigm, the periodic m:n ON-OFF CRS (i.e., m ON-cycles stimulation followed by n OFF-cycles stimulation) can significantly desynchronize the neuronal network of Parkinson's disease, and evidently improve the fidelity of thalamic relay. In addition, the CRS-induced desynchronization can be greatly enhanced when the STN subpopulation within the pathologic network is subjected to the synaptic plasticity. Furthermore, the desynchronization and reliability can also be further improved as the closed-loop CRS strategy is introduced. The obtained results can be helpful for us to understand the pathophysiology mechanism of Parkinson's disease, even though the feasibility of CRS still needs to be explored in clinic. PMID:25661071

  1. Monte Carlo study of efficiency roll-off of phosphorescent organic light-emitting diodes: Evidence for dominant role of triplet-polaron quenching

    SciTech Connect

    Eersel, H. van Coehoorn, R.; Bobbert, P. A.; Janssen, R. A. J.

    2014-10-06

    We present an advanced molecular-scale organic light-emitting diode (OLED) model, integrating both electronic and excitonic processes. Using this model, we can reproduce the measured efficiency roll-off for prototypical phosphorescent OLED stacks based on the green dye tris[2-phenylpyridine]iridium (Ir(ppy){sub 3}) and the red dye octaethylporphine platinum (PtOEP) and study the cause of the roll-off as function of the current density. Both the voltage versus current density characteristics and roll-off agree well with experimental data. Surprisingly, the results of the simulations lead us to conclude that, contrary to what is often assumed, not triplet-triplet annihilation but triplet-polaron quenching is the dominant mechanism causing the roll-off under realistic operating conditions. Simulations for devices with an optimized recombination profile, achieved by carefully tuning the dye trap depth, show that it will be possible to fabricate OLEDs with a drastically reduced roll-off. It is envisaged that J{sub 90}, the current density at which the efficiency is reduced to 90%, can be increased by almost one order of magnitude as compared to the experimental state-of-the-art.

  2. Sulphur abundances in halo giants from the [S I] line at 1082 nm and the [S I] triplet around 1045 nm

    NASA Astrophysics Data System (ADS)

    Jönsson, H.; Ryde, N.; Nissen, P. E.; Collet, R.; Eriksson, K.; Asplund, M.; Gustafsson, B.

    2011-06-01

    Context. It is still debated whether or not the Galactic chemical evolution of sulphur in the halo follows the flat trend with [Fe/H] that is ascribed to the result of explosive nucleosynthesis in type II SNe. It has been suggested that the disagreement between different investigations of sulphur abundances in halo stars might be owing to problems with the diagnostics used, that a new production source of sulphur might be needed in the early Universe, like hypernovae, or that the deposition of supernova ejecta into the interstellar medium is time-delayed. Aims: The aim of this study is to try to clarify this situation by measuring the sulphur abundance in a sample of halo giants using two diagnostics: the S i triplet around 1045 nm and the [S i] line at 1082 nm. The latter of the two is not believed to be sensitive to non-LTE effects. We can thereby minimize the uncertainties in the diagnostic used and estimate the usefulness of the triplet for the sulphur determination in halo K giants. We will also be able to compare our sulphur abundance differences from the two diagnostics with the expected non-LTE effects in the 1045 nm triplet previously calculated by others. Methods: High-resolution near-infrared spectra of ten K giants were recorded using the spectrometer CRIRES mounted at VLT. Two standard settings were used, one covering the S i triplet and one covering the [S i] line. The sulphur abundances were individually determined with equivalent widths and synthetic spectra for the two diagnostics using tailored 1D model atmospheres and relying on non-LTE corrections from the litterature. Effects of convective inhomogeneities in the stellar atmospheres are investigated. Results: The sulphur abundances derived from both the [S i] line and the non-LTE corrected 1045 nm triplet favor a flat trend for the evolution of sulphur. In contrast to some previous studies, we saw no "high" values of [S/Fe] in our sample. Conclusions: We corroborate the flat trend in the [S/Fe] vs. [Fe/H] plot for halo stars found in some previous studies but do not find a scatter or a rise in [S/Fe] as obtained in other works. We find the sulphur abundances deduced from the non-LTE corrected triplet to be somewhat lower than the abundances from the [S i] line, possibly indicating too large non-LTE corrections. Considering 3D modeling, however, they might instead be too small. Moreover, we show that the [S i] line can be used as a sulphur diagnostic down to [Fe/H] ~ -2.3 in giants. Based on observations collected at the European Southern Observatory, Chile (ESO program 080.D-0675(A)).

  3. Dem Generation with Short Base Length Pleiades Triplet

    NASA Astrophysics Data System (ADS)

    Jacobsen, K.; Topan, H.

    2015-03-01

    An image triplet of Pleiades images covering the area of Zonguldak, Turkey has been investigated. The height to base relation of the first to the last image is just 1:4.5 and for the first and the second image 1:9. This is quite below the usual height to base relation of 1:1.6 for a typical stereo pair of space images. The corresponding small angle of convergence influences the possible vertical accuracy, but images with such a small angle of convergence are more similar to each other as images with larger convergence angles. This enables a better image matching, improving the vertical accuracy and compensating partially the influence of poor intersection geometry. Even over forest areas no matching gaps occurred. Height models are generated with different base configurations and compared with a reference height model. Pleiades images are distributed with 50cm ground sampling distance instead of the physical size of 70cm, the image quality justifies this zooming and also the geometric results are in the range of other space images with originally 50cm GSD. The image orientation by bias corrected Rational Polynomial Coefficients (RPC) is leading with more as 160 ground control points (GCP) to root mean square (RMS) differences slightly below 1.0 GSD of the distributed images (0.5m GSD). Only negligible systematic errors have been identified. With the combination of the first and last image a standard deviation of the generated height model of 1.6m, respectively for flat terrain close to 1.0m has been reached in relation to a reference height model. The small angle of convergence is not as much influencing the height accuracy as according to simple geometric relation.

  4. An optical-near-IR study of a triplet of super star clusters in the starburst core of M82

    SciTech Connect

    Westmoquette, M. S.; Bastian, N.; Smith, L. J.; Seth, A. C.; Gallagher III, J. S.; Ryon, J. E.; O'Connell, R. W.; Silich, S.; Mayya, Y. D.; González, D. Rosa; Muñoz-Tuñón, C.

    2014-07-10

    We present HST/STIS optical and Gemini/NIFS near-IR IFU spectroscopy and archival Hubble Space Telescope (HST) imaging of the triplet of super star clusters (A1, A2, and A3) in the core of the M82 starburst. Using model fits to the Space Telescope Imaging Spectrograph (STIS) spectra and the weakness of red supergiant CO absorption features (appearing at ?6 Myr) in the NIFS H-band spectra, the ages of A2 and A3 are 4.5 ± 1.0 Myr. A1 has strong CO bands, consistent with our previously determined age of 6.4 ± 0.5 Myr. The photometric masses of the three clusters are 4-7 × 10{sup 5} M{sub ?}, and their sizes are R{sub eff} = 159, 104, 59 mas (?2.8, 1.8, 1.0 pc) for A1, A2, and A3. The STIS spectra yielded radial velocities of 320 ± 2, 330 ± 6, and 336 ± 5 km s{sup –1} for A1, A2, and A3, placing them at the eastern end of the x{sub 2} orbits of M82's bar. Clusters A2 and A3 are in high-density (800-1000 cm{sup –3}) environments, and like A1, are surrounded by compact H II regions. We suggest the winds from A2 and A3 have stalled, as in A1, due to the high ISM ambient pressure. We propose that the three clusters were formed in situ on the outer x{sub 2} orbits in regions of dense molecular gas subsequently ionized by the rapidly evolving starburst. The similar radial velocities of the three clusters and their small projected separation of ?25 pc suggest that they may merge in the near future unless this is prevented by velocity shearing.

  5. An Optical-Near-IR Study of a Triplet of Super Star Clusters in the Starburst Core of M82

    NASA Astrophysics Data System (ADS)

    Westmoquette, M. S.; Bastian, N.; Smith, L. J.; Seth, A. C.; Gallagher, J. S., III; O'Connell, R. W.; Ryon, J. E.; Silich, S.; Mayya, Y. D.; Muñoz-Tuñón, C.; Rosa González, D.

    2014-07-01

    We present HST/STIS optical and Gemini/NIFS near-IR IFU spectroscopy and archival Hubble Space Telescope (HST) imaging of the triplet of super star clusters (A1, A2, and A3) in the core of the M82 starburst. Using model fits to the Space Telescope Imaging Spectrograph (STIS) spectra and the weakness of red supergiant CO absorption features (appearing at ~6 Myr) in the NIFS H-band spectra, the ages of A2 and A3 are 4.5 ± 1.0 Myr. A1 has strong CO bands, consistent with our previously determined age of 6.4 ± 0.5 Myr. The photometric masses of the three clusters are 4-7 × 105 M ?, and their sizes are R eff = 159, 104, 59 mas (~2.8, 1.8, 1.0 pc) for A1, A2, and A3. The STIS spectra yielded radial velocities of 320 ± 2, 330 ± 6, and 336 ± 5 km s-1 for A1, A2, and A3, placing them at the eastern end of the x 2 orbits of M82's bar. Clusters A2 and A3 are in high-density (800-1000 cm-3) environments, and like A1, are surrounded by compact H II regions. We suggest the winds from A2 and A3 have stalled, as in A1, due to the high ISM ambient pressure. We propose that the three clusters were formed in situ on the outer x 2 orbits in regions of dense molecular gas subsequently ionized by the rapidly evolving starburst. The similar radial velocities of the three clusters and their small projected separation of ~25 pc suggest that they may merge in the near future unless this is prevented by velocity shearing. Based on observations with the NASA/ESA Hubble Space Telescope under program 11641 and the Gemini-North telescope under program GN-2010B-Q-4.

  6. Temperature dependence of differential conductance in normal-metal/chiral triplet superconductor junctions: The gap symmetry of SrRuO

    NASA Astrophysics Data System (ADS)

    Cheng, Q.; Jin, B.

    2010-01-01

    The tunneling differential conductance of a normal-metal/chiral spin-triplet superconductor junctions is calculated over whole ranges of temperature and barrier strength within the framework of generalized Blonder-Tinkham-Klapwijk (BTK) theory. We consider three kinds of superconducting gap functions with horizontal line nodes or vertical line nodes, which are currently investigated as the candidate states for SrRuO. In particular, we find that the conductance curves for the f-wave state depend seriously on the temperature even at T?Tc, giving rise to line shapes qualitatively compatible with the existing experimental results.

  7. Electronic spectra and photophysics of platinum(II) complexes with alpha-diimine ligands - Solid-state effects. I - Monomers and ligand pi dimers

    NASA Technical Reports Server (NTRS)

    Miskowski, Vincent M.; Houlding, Virginia H.

    1989-01-01

    Two types of emission behavior for Pt(II) complexes containing alpha-diimine ligands have been observed in dilute solution. If the complex also has weak field ligands such as chloride, ligand field (d-d) excited states become the lowest energy excited states. If only strong field ligands are present, a diimine 3(pi-pi/asterisk/) state becomes the lowest. In none of the cases studied did metal-to-ligand charge transfer excited state lie lowest.

  8. Decomposition of charge-state distributions for better understanding of electrospray mass spectra of bioorganic compounds. Part 2: application of the method.

    PubMed

    Raznikov, Valeriy V; Raznikova, Marina O

    2009-01-01

    The results of the analysis of electrospray mass spectra of b-endorphin and chicken egg lysozyme in different conditions of data acquisition using the method described in Part 1 of the work are reported. At least partial unfolding during the process of ion formation in the electrospray ion source of an initially native biomolecule of lyzozyme in solution should supposedly explain the received set of probabilities of proton retention by basic and acidic residues of this molecule for all considered conditions of data acquisition. PMID:19395773

  9. Plant cell wall profiling by fast maximum likelihood reconstruction (FMLR) and region-of-interest (ROI) segmentation of solution-state 2D 1H–13C NMR spectra

    PubMed Central

    2013-01-01

    Background Interest in the detailed lignin and polysaccharide composition of plant cell walls has surged within the past decade partly as a result of biotechnology research aimed at converting biomass to biofuels. High-resolution, solution-state 2D 1H–13C HSQC NMR spectroscopy has proven to be an effective tool for rapid and reproducible fingerprinting of the numerous polysaccharides and lignin components in unfractionated plant cell wall materials, and is therefore a powerful tool for cell wall profiling based on our ability to simultaneously identify and comparatively quantify numerous components within spectra generated in a relatively short time. However, assigning peaks in new spectra, integrating them to provide relative component distributions, and producing color-assigned spectra, are all current bottlenecks to the routine use of such NMR profiling methods. Results We have assembled a high-throughput software platform for plant cell wall profiling that uses spectral deconvolution by Fast Maximum Likelihood Reconstruction (FMLR) to construct a mathematical model of the signals present in a set of related NMR spectra. Combined with a simple region of interest (ROI) table that maps spectral regions to NMR chemical shift assignments of chemical entities, the reconstructions can provide rapid and reproducible fingerprinting of numerous polysaccharide and lignin components in unfractionated cell wall material, including derivation of lignin monomer unit (S:G:H) ratios or the so-called SGH profile. Evidence is presented that ROI-based amplitudes derived from FMLR provide a robust feature set for subsequent multivariate analysis. The utility of this approach is demonstrated on a large transgenic study of Arabidopsis requiring concerted analysis of 91 ROIs (including both assigned and unassigned regions) in the lignin and polysaccharide regions of almost 100 related 2D 1H–13C HSQC spectra. Conclusions We show that when a suitable number of replicates are obtained per sample group, the correlated patterns of enriched and depleted cell wall components can be reliably and objectively detected even prior to multivariate analysis. The analysis methodology has been implemented in a publicly-available, cross-platform (Windows/Mac/Linux), web-enabled software application that enables researchers to view and publish detailed annotated spectra in addition to summary reports in simple spreadsheet data formats. The analysis methodology is not limited to studies of plant cell walls but is amenable to any NMR study where ROI segmentation techniques generate meaningful results. Please see Research Article: http://www.biotechnologyforbiofuels.com/content/6/1/46/. PMID:23622232

  10. Analysis of carbon forms in chemically-modified peat humic acids by partial least squares regression analysis of solid-state nuclear magnetic resonance spectra

    NASA Astrophysics Data System (ADS)

    Almendros, G.; Hernández, Z.; González-Vila, F. J.; Sanz, J.; De la Rosa, J. M.; Knicker, H.

    2012-04-01

    Classical structural studies on soil organic matter often show that the natural variability in C- and N forms in soil humic acids (HAs) is in many cases not enough to distinguish significant differences amongst HAs from different origin. In the present research contrasting C-distribution patterns are obtained when the HAs are modified in the laboratory through chemical treatments (derivatization reactions or methods focused to incorporation or removal of specific structural constituents). For instance, oxygen functionality can be modified by introducing or blocking the major functional groups (methylation, acetylation, oximation, nitration, sulphonation, etc). Other treatments lead to selective hydrolysis or drastic peroxydation of the HA carbon backbone. Apart from this, N-groups can be introduced in the HA structure by e.g., nitration, oximation, amidation or ammonification. A series of chemically-modified HA preparations were obtained from a sapric peat (Vivero peat, Northern Spain) and their 13C nuclear magnetic resonance spectra (13C NMR) were obtained, showing the success of the above treatments which lead to contrasted NMR profiles. This set of 12 HA preparations was considered suitable material to assess the extent to which 13C NMR spectroscopy reflect the induced structural modifications, as well as to help the assignation of signals in conflicting chemical shift ranges. In order to improve the interpretation of the 13C NMR spectra, partial least squares regression (PLS) was used as a multivariate chemometric tool based on covariance. This is a convenient method in cases where the number of variables (spectral points in the 200-(-25) ppm spectral range with 1-ppm resolution) is high as regards the number of individuals (modified HAs), mainly when there is large redundancy in data sets of variables mutually correlated. The spectroscopic information in the spectral matrix is processed by successively examining independent variables from an external matrix of up to 150 HA descriptors (elementary composition, infrared-, visible- and fluorescence- spectroscopies, pyrolytic compounds, in vitro biodegradability, effects of HA on soil physical, chemical and agrobiological properties, etc). By means of PLS regression, a factor analysis is carried out to describe the data structure aiming to the automated interpretation the spectra. After selecting the models in which the independent variables are more significantly forecasted from the spectral data, the resulting values of variable importance for projection (VIP) for each independent variable were plotted in the whole chemical shift (after moving averages smoothing) to obtain a profile illustrating spectral signals explaining most of the variability of each of the independent factors. The results suggest the possibility of identifying characteristics of the HAs with a role on its environmental properties. The structural characteristics of the HAs studied here which were reflected in the whole 13C NMR spectra corresponded mainly to oxygen containing functional groups (r= 0.751), aromaticity as indicated by optical density at 465 nm (r= 0.651) and (inversely) by H/C atomic ratio (r= 0.638) or infrared spectroscopy (band at 1540 cm-1, r= 0.424). To a lower significance level, the raw NMR data showed promising predicting potential as regards HA molecular size, concentration of N-compounds and yield of typical pyrolytic fragments mainly alkylphenols. The VIPs also showed the interest of the some 13C NMR signals in forecasting important physical properties of soils treated (4 Mg ha-1) with these HAs (mainly water holding capacity and aggregate stability). Further studies based on the combined analysis of 13C and 15N spectra of HAs are in progress in order to examine distribution of N-forms in peat and its possible correlation with soil agroecological properties.

  11. Blind spots between quantum states

    E-print Network

    Eduardo Zambrano; Alfredo M Ozorio de Almeida

    2009-09-30

    The overlap of a large quantum state with its image, under tiny translations, oscillates swiftly. We here show that complete orthogonality occurs generically at isolated points. Decoherence, in the Markovian approximation, lifts the correlation minima from zero much more quickly than the Wigner function is smoothed into a positive phase space distribution. In the case of a superposition of coherent states, blind spots depend strongly on positions and amplitudes of the components, but they are only weakly affected by relative phases and the various degrees and directions of squeezing. The blind spots for coherent state triplets are special in that they lie close to an hexagonal lattice: Further superpositions of translated triplets, specified by nodes of one of the sublattices, are quasi-orthogonal to the original triplet and to any state, likewise constructed on the other sublattice.

  12. Triplet p + ip pairing correlations in the doped Kane-Mele-Hubbard model: A quantum Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Ma, Tianxing; Lin, Hai-Qing; Gubernatis, J. E.

    2015-08-01

    By using the constrained-phase quantum Monte Carlo method, we performed a systematic study of the pairing correlations in the ground state of the doped Kane-Mele-Hubbard model on a honeycomb lattice. We find that pairing correlations with d + id symmetry dominate close to half-filling, but pairing correlations with p + ip symmetry dominate as hole doping moves the system below three-quarters filling. We correlate these behaviors of the pairing correlations with the topology of the Fermi surfaces of the non-interacting problem. We also find that the effective pairing correlation is enhanced greatly as the interaction increases, and these superconducting correlations are robust against varying the spin-orbit coupling strength. Our numerical results suggest a possible way to realize spin triplet superconductivity in doped honeycomb-like materials or ultracold atoms in optical traps.

  13. Novel triplet repeat containing genes in human brain: Cloning, expression, and length polymorphisms

    SciTech Connect

    Li, Shi Hua; Margolis, R.L.; Ross, C.A.; McInnis, M.G.; Antonarakis, S.E. )

    1993-06-01

    Human genes containing triplet repeats may markedly expand in length and cause neuropsychiatric disease, explaining the phenomenon of anticipation (increasing severity or earlier age of onset in successive generations in a pedigree). To identify novel genes with triplet repeats, the authors screened a human brain cDNA library with oligonucleotide probes containing CTG or CCG triplet repeats. Fourteen of 40 clones encoded novel human genes, and 8 of these inserts have been sequenced on both strands. All contain repeats, and 5 of the 8 have 9 or more consecutive perfect repeats. All are expressed in brain. Chromosomal assignments reveal a distribution of these genes on multiple autosomes and the X-chromosome. Further, the repeat length in two of the genes is highly polymorphic, making them valuable index linkage markers. The authors predict that many triplet repeat-containing genes exist; screening with the CTG probe suggests approximately 50-100 genes containing this type of repeat are expressed in the human brain. Since additional disorders, such as Huntington's disease, bipolar affective disorder, and possibly others, show features of anticipation, they suggest that these novel human genes with triplet repeats are candidates for causing neuropsychiatric diseases.

  14. Native and induced triplet nitrogen-vacancy centers in nano- and micro-diamonds: Half-field electron paramagnetic resonance fingerprint

    SciTech Connect

    Shames, A. I.; Osipov, V. Yu.; Vul’, A. Ya.; Bardeleben, H.-J. von

    2014-02-10

    Multiple frequency electron paramagnetic resonance (EPR) study of small (4–25?nm) nanodiamonds obtained by various dynamic synthesis techniques reveals systematic presence in the half-field (HF) region a distinctive doublet fingerprint consisting of resolved g{sub HF1}?=?4.26 and g{sub HF2}?=?4.00 signals. This feature is attributed to “forbidden” ?M{sub S}?=?2 transitions in EPR spectra of two native paramagnetic centers of triplet (S?=?1) origin designated as TR1 and TR2, characterized by zero field splitting values D{sub 1}?=?0.0950?±?0.002?cm{sup ?1} and D{sub 2}?=?0.030?±?0.005?cm{sup ?1}. Nanodiamonds of ?50?nm particle size, obtained by crushing of Ib type nitrogen rich synthetic diamonds, show only HF TR2 signal whereas the same sample undergone high energy (20 MeV) electron irradiation and thermal annealing demonstrates rise of HF TR1 signal. The same HF TR1 signals appear in the process of fabrication of fluorescent nanodiamonds from micron-size synthetic diamond precursors. Results obtained allow unambiguous attribution of the half-field TR1 EPR signals with g{sub HF1}?=?4.26, observed in nano- and micron-diamond powders, to triplet negatively charged nitrogen-vacancy centers. These signals are proposed as reliable and convenient fingerprints in both qualitative and quantitative study of fluorescent nano- and micron-diamonds.

  15. Native and induced triplet nitrogen-vacancy centers in nano- and micro-diamonds: Half-field electron paramagnetic resonance fingerprint

    NASA Astrophysics Data System (ADS)

    Shames, A. I.; Osipov, V. Yu.; von Bardeleben, H.-J.; Boudou, J.-P.; Treussart, F.; Vul', A. Ya.

    2014-02-01

    Multiple frequency electron paramagnetic resonance (EPR) study of small (4-25 nm) nanodiamonds obtained by various dynamic synthesis techniques reveals systematic presence in the half-field (HF) region a distinctive doublet fingerprint consisting of resolved gHF1 = 4.26 and gHF2 = 4.00 signals. This feature is attributed to "forbidden" ?MS = 2 transitions in EPR spectra of two native paramagnetic centers of triplet (S = 1) origin designated as TR1 and TR2, characterized by zero field splitting values D1 = 0.0950 ± 0.002 cm-1 and D2 = 0.030 ± 0.005 cm-1. Nanodiamonds of ˜50 nm particle size, obtained by crushing of Ib type nitrogen rich synthetic diamonds, show only HF TR2 signal whereas the same sample undergone high energy (20 MeV) electron irradiation and thermal annealing demonstrates rise of HF TR1 signal. The same HF TR1 signals appear in the process of fabrication of fluorescent nanodiamonds from micron-size synthetic diamond precursors. Results obtained allow unambiguous attribution of the half-field TR1 EPR signals with gHF1 = 4.26, observed in nano- and micron-diamond powders, to triplet negatively charged nitrogen-vacancy centers. These signals are proposed as reliable and convenient fingerprints in both qualitative and quantitative study of fluorescent nano- and micron-diamonds.

  16. Triplets and Symmetries of Arithmetic mod p^k

    E-print Network

    N. F. Benschop

    2001-06-19

    The finite ring Z_k = Z(+,.) mod p^k of residue arithmetic with odd prime power modulus is analysed. The cyclic group of units G_k in Z_k(.) has order (p-1)p^{k-1}, implying product structure G_k = A_k B_k. Here core A_k of order p-1 is an extension for k >1 of Fermat's Small Theorem (FST*), where n^p == n (mod p^k) for each core residue, while extension subgroup B_k has order p^{k-1}. It is shown that each subgroup S >1 of core A_k has zero sum, and that p+1 generates subgroup B_k of all n == 1 (mod p) in G_k. The p-th power residues n^p mod p^k in G_k form an order |G_k|/p subgroup F_k, with |F_k|/|A_k| = p^{k-2}, so F_k properly contains core A_k for k >2. By quadratic analysis (mod p^3) rather than linear analysis (mod p^2, re Hensel's lemma [5]), the additive structure of subgroups G_k and F_k is derived. ... Successor function S(n)=n+1 combines with the two arithmetic symmetries -n (complement) and 1/n (inverse) to yield the "triplet structure" of G_k : three inverse pairs {n_i, 1/(n_i)} with (n_i)+1 = - 1/n_{i+1} (mod p^k), with indices mod 3, and product n_0.n_1.n_2 = 1 mod p^k. In case n_0 = n_1 = n_2 = n this reduces to the cubic root solution n+1 = -(1/n) = -(n^2) (mod p^k, p=1 mod 6). The property "EDS" of exponent p distributing over a sum of core residues: (x+y)^p == x+y == x^p + y^p (mod p^k), is employed to derive the known FLT inequality for integers. In other words, to any FLT(mod p^k) equivalence for k digits correspond p-th power integers of pk digits, and the (p-1)k "carries" make the difference, representing the sum of mixed-terms in the binomial expansion.

  17. Crack spectra analysis

    SciTech Connect

    Tiernan, M.

    1980-09-01

    Crack spectra derived from velocity data have been shown to exhibit systematics which reflect microstructural and textural differences between samples (Warren and Tiernan, 1980). Further research into both properties and information content of crack spectra have yielded the following: Spectral features are reproducible even at low pressures; certain observed spectral features may correspond to non-in-situ crack populations created during sample retrieval; the functional form of a crack spectra may be diagnostic of the sample's grain texture; hysteresis is observed in crack spectra between up and down pressure runs - it may be due to friction between the faces of closed crack populations.

  18. Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: Explicit treatment of the vibronic transitions

    SciTech Connect

    D’Abramo, Marco; Dipartimento di Chimica, Universitá Sapienza, P.le Aldo Moro, 5, 00185, Rome ; Aschi, Massimiliano; Amadei, Andrea

    2014-04-28

    Here, we extend a recently introduced theoretical-computational procedure [M. D’Alessandro, M. Aschi, C. Mazzuca, A. Palleschi, and A. Amadei, J. Chem. Phys. 139, 114102 (2013)] to include quantum vibrational transitions in modelling electronic spectra of atomic molecular systems in condensed phase. The method is based on the combination of Molecular Dynamics simulations and quantum chemical calculations within the Perturbed Matrix Method approach. The main aim of the presented approach is to reproduce as much as possible the spectral line shape which results from a subtle combination of environmental and intrinsic (chromophore) mechanical-dynamical features. As a case study, we were able to model the low energy UV-vis transitions of pyrene in liquid acetonitrile in good agreement with the experimental data.

  19. Carbon dioxide photolysis from 150 to 210 nm: Singlet and triplet channel dynamics, UV-spectrum, and isotope effects

    PubMed Central

    Schmidt, Johan A.; Johnson, Matthew S.; Schinke, Reinhard

    2013-01-01

    We present a first principles study of the carbon dioxide (CO2) photodissociation process in the 150- to 210-nm wavelength range, with emphasis on photolysis below the carbon monoxide + singlet channel threshold at ?167 nm. The calculations reproduce experimental absorption cross-sections at a resolution of ?0.5 nm without scaling the intensity. The observed structure in the 150- to 210-nm range is caused by excitation of bending motion supported by the deep wells at bent geometries in the and potential energy surfaces. Predissociation below the singlet channel threshold occurs via spin-orbit coupling to nearby repulsive triplet states. Carbon monoxide vibrational and rotational state distributions in the singlet channel as well as the triplet channel for excitation at 157 nm satisfactorily reproduce experimental data. The cross-sections of individual CO2 isotopologues (12C16O2, 12C17O16O, 12C18O16O, 13C16O2, and 13C18O16O) are calculated, demonstrating that strong isotopic fractionation will occur as a function of wavelength. The calculations provide accurate, detailed insight into CO2 photoabsorption and dissociation dynamics, and greatly extend knowledge of the temperature dependence of the cross-section to cover the range from 0 to 400 K that is useful for calculations of propagation of stellar light in planetary atmospheres. The model is also relevant for the interpretation of laboratory experiments on mass-independent isotopic fractionation. Finally, the model shows that the mass-independent fractionation observed in a series of Hg lamp experiments is not a result of hyperfine interactions making predissociation of 17O containing CO2 more efficient. PMID:23776249

  20. Carbon dioxide photolysis from 150 to 210 nm: singlet and triplet channel dynamics, UV-spectrum, and isotope effects.

    PubMed

    Schmidt, Johan A; Johnson, Matthew S; Schinke, Reinhard

    2013-10-29

    We present a first principles study of the carbon dioxide (CO2) photodissociation process in the 150- to 210-nm wavelength range, with emphasis on photolysis below the carbon monoxide + singlet channel threshold at ~167 nm. The calculations reproduce experimental absorption cross-sections at a resolution of ~0.5 nm without scaling the intensity. The observed structure in the 150- to 210-nm range is caused by excitation of bending motion supported by the deep wells at bent geometries in the and potential energy surfaces. Predissociation below the singlet channel threshold occurs via spin-orbit coupling to nearby repulsive triplet states. Carbon monoxide vibrational and rotational state distributions in the singlet channel as well as the triplet channel for excitation at 157 nm satisfactorily reproduce experimental data. The cross-sections of individual CO2 isotopologues ((12)C(16)O2, (12)C(17)O(16)O, (12)C(18)O(16)O, (13)C(16)O2, and (13)C(18)O(16)O) are calculated, demonstrating that strong isotopic fractionation will occur as a function of wavelength. The calculations provide accurate, detailed insight into CO2 photoabsorption and dissociation dynamics, and greatly extend knowledge of the temperature dependence of the cross-section to cover the range from 0 to 400 K that is useful for calculations of propagation of stellar light in planetary atmospheres. The model is also relevant for the interpretation of laboratory experiments on mass-independent isotopic fractionation. Finally, the model shows that the mass-independent fractionation observed in a series of Hg lamp experiments is not a result of hyperfine interactions making predissociation of (17)O containing CO2 more efficient. PMID:23776249