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Sample records for ir multiple-photon excitation

  1. Multiple photon excited SF6 interaction with silicon surfaces

    NASA Astrophysics Data System (ADS)

    Chuang, T. J.

    1981-01-01

    Infrared laser induced SF6-silicon interactions have been studied and the surface reaction yields have been determined as a function of the laser frequency, the laser intensity, and the gas pressure in both perpendicular and parallel beam incidences on the solid surfaces. The results clearly show that vibrationally excited SF6 molecules promoted by CO2 laser pulses are very reactive to silicon, particularly when the solid is simultaneously exposed to the intense ir radiation. The laser excitation of the Si substrate alone cannot cause the heterogeneous reaction to occur. The present gas-solid system thus provides an example which clearly establishes the direct correlation between surface reactivity and vibrational activation. Additional experimental measurements also demonstrate that the thermal fluorine atoms generated by SF6 multiple photon dissociation at high laser intensities can react with silicon to form volatile product. The study thus provides further insight into the silicon-fluorine reaction dynamics.

  2. Double resonance spectroscopy of multiple-photon excited molecules

    NASA Technical Reports Server (NTRS)

    Steinfeld, J. I.; Melzer, J. E.

    1977-01-01

    Multiple infrared photon absorption is a quite general process which molecules can undergo when placed in a high flux of infrared energy, such as the focussed beam of a CO2 laser. In order to understand how this process works, one must be able to follow the evolution of the molecules through their internal states, populated by photon absorption. Double-resonance spectroscopy is the method of a choice for getting at this information. A system pumped by CO2 laser radiation can be examined with a tunable laser probe beam, such as that from a lead-salt diode laser. From such an experiment, one can directly observe Rabi modulation of the absorption lines, determine elementary state-to-state relaxation pathways, and locate higher excited vibrational states. Systems currently under investigation include SF6 and vinyl chloride. In suitable cases, the probe beam can be a tunable visible or UV source, such as a dye laser. Fluorescence spectroscopy can then be used to monitor the transient absorptions produced by multiple-photon excitation. Among the systems which can be examined are biacetyl and glyoxal.

  3. Multiple-photon excitation and dissociation of polyatomic molecules

    SciTech Connect

    Cantrell, C.D.

    1986-01-01

    This book is Volume 35 in Springer's Topics in Current Physics series designed to provide the interested reader perspective on a rapidly developing research field by gathering together review articles by major players. The editor has accurately highlighted the major results of the multiple-photon excitation (MPE) shock wave of research activity that propagated through the gas-phase chemical physics community during the 1970's. Throughout this period three questions intrigued the photochemists: (1) how is it possible that virtually any polyatomic molecule can efficiently absorb scores of infrared photons from a pulsed CO/sub 2/ TEA laser to achieve bond fission. (2) can insight into the dissociation dynamic be gained from this process, and in particular can bonds be made to break selectively. (3) could MPE be used to separate heavy isotopes. The answers to the first two questions are thoroughly examined and answered in the excellent review by Y.T. Lee et al., which itself is worth the price of the book. The question of isotope separation is discussed in two articles, one by Ambartzumian and the other by Cantrell. However, the recent glut of cheap uranium on world energy markets and the decision of DOE to develop atomic multiphoton ionization as the process of choice have resulted in a rapid deflation of interest in MPE separation schemes.

  4. Processes of multiple photon and thermal excitation of carriers of charge in low dimensional nanostructures

    NASA Astrophysics Data System (ADS)

    Aksenov, V. P.; Mikhailova, G. N.

    2006-06-01

    The question of multiple photon and thermal excitation in low-dimensional nanostructures with deep holes, induced by x-radiation was considered. There are strong grounds for believing that observed thermally stimulated effective luminescence from x-irradiated porous Si (D.W. Cooke et al [1]) connected with generation by x-radiation of Dirac points in nanostructures.

  5. Intensity-resolved IR multiple photon ionization and fragmentation of C60.

    PubMed

    Bakker, Joost M; Lapoutre, Vivike J F; Redlich, Britta; Oomens, Jos; Sartakov, Boris G; Fielicke, André; von Helden, Gert; Meijer, Gerard; van der Meer, Alexander F G

    2010-02-21

    The sequential absorption of multiple infrared (IR) photons by isolated gas-phase species can lead to their dissociation and/or ionization. Using the newly constructed "Free-Electron Laser for IntraCavity Experiments" (FELICE) beam line at the FELIX facility, neutral C(60) molecules have been exposed to an extremely high number (approximately 10(23)) of photons/cm(2) for a total time duration of up to 5 micros. At wavelengths around 20 microm, resonant with allowed IR transitions of C(60), ionization and extensive fragmentation of the fullerenes are observed. The resulting photofragment distributions are attributed to absorption in fragmentation products formed once C(60) is excited to internal energies at which fragmentation or ionization takes place within the duration of the laser pulse. The high IR intensities available combined with the large interaction volume permit spatially resolved detection of the ions inside the laser beam, thereby disentangling the contributions from different IR intensities. The use of spatial imaging reveals intensity dependent mass distributions that are substantially narrower than what has been observed previously, indicating rather narrow energy distributions. A simple rate-equation modeling of the excitation process supports the experimental observations.

  6. Multiple-photon excitation imaging with an all-solid-state laser

    NASA Astrophysics Data System (ADS)

    Wokosin, David L.; Centonze, Victoria F.; White, John G.; Hird, Steven N.; Sepsenwol, S.; Malcolm, Graeme P. A.; Maker, Gareth T.; Ferguson, Allister I.

    1996-05-01

    Two-photon excitation imaging is a recently described optical sectioning technique where fluorophore excitation is confined to--and therefore defines--the optical section being observed. This characteristic offers a significant advantage over laser-scanning confocal microscopy; the volume of fluorophore excited in the minimum necessary for imaging, thereby minimizing the destructive effects of fluorophore excitation in living tissues. In addition, a confocal pinhole is not required for optical scattering--thus further reducing the excitation needed for efficient photon collection. We have set up a two-photon excitation imaging system which uses an all-solid-state, short-pulse, long-wavelength laser as an excitation source. The source is a diode-pumped, mode-locked Nd:YLF laser operating in the infrared (1047 nm). This laser is small, has modest power requirements, and has proven reliable and stable in operation. The short laser pulses from the laser are affected by the system optical path; this has been investigated with second harmonic generation derived from a nonlinear crystal. The system has been specifically designed for the study of live biological specimens. Two cell types especially sensitive to high-energy illumination, the developing Caenorhabditis elegans embryo and the crawling sperm of the nematode, Ascaris, were used to demonstrate the dramatic increase in viability when fluorescence is generated by two-photon excitation. The system has the capability of switching between two-photon and confocal imaging modes to facilitate direct comparison of theory of these two optical sectioning techniques on the same specimen. A heavily stained zebra fish embryo was used to demonstrate the increase in sectioning depth when fluorescence is generated by infrared two- photon excitation. Two-photon excitation with the 1047 nm laser produces bright images with a variety of red emitting fluorophores, and some green emitting fluorophores, commonly used in biological

  7. Generation of Multiple Excitons in Ag2S Quantum Dots: Single High-Energy versus Multiple-Photon Excitation.

    PubMed

    Sun, Jingya; Yu, Weili; Usman, Anwar; Isimjan, Tayirjan T; DGobbo, Silvano; Alarousu, Erkki; Takanabe, Kazuhiro; Mohammed, Omar F

    2014-02-20

    We explored biexciton generation via carrier multiplication (or multiple-exciton generation) by high-energy photons and by multiple-photon absorption in Ag2S quantum dots (QDs) using femtosecond broad-band transient absorption spectroscopy. Irrespective of the size of the QDs and how the multiple excitons are generated in the Ag2S QDs, two distinct characteristic time constants of 9.6-10.2 and 135-175 ps are obtained for the nonradiative Auger recombination of the multiple excitons, indicating the existence of two binding excitons, namely, tightly bound and weakly bound excitons. More importantly, the lifetimes of multiple excitons in Ag2S QDs were about 1 and 2 orders of magnitude longer than those of comparable size PbS QDs and single-walled carbon nanotubes, respectively. This result is significant because it suggests that by utilizing an appropriate electron acceptor, there is a higher possibility to extract multiple electron-hole pairs in Ag2S QDs, which should improve the performance of QD-based solar cell devices.

  8. Laser isotope separation by multiple photon absorption

    DOEpatents

    Robinson, C.P.; Rockwood, S.D.; Jensen, R.J.; Lyman, J.L.; Aldridge, J.P. III.

    1987-04-07

    Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, is the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO[sub 2] laser light may be used to highly enrich [sup 34]S in natural SF[sub 6] and [sup 11]B in natural BCl[sub 3]. 8 figs.

  9. Laser isotope separation by multiple photon absorption

    DOEpatents

    Robinson, C. Paul; Rockwood, Stephen D.; Jensen, Reed J.; Lyman, John L.; Aldridge, III, Jack P.

    1987-01-01

    Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, is the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO.sub.2 laser light may be used to highly enrich .sup.34 S in natural SF.sub.6 and .sup.11 B in natural BCl.sub.3.

  10. Laser isotope separation by multiple photon absorption

    DOEpatents

    Robinson, C. Paul; Rockwood, Stephen D.; Jensen, Reed J.; Lyman, John L.; Aldridge, III, Jack P.

    1977-01-01

    Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, in the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO.sub.2 laser light may be used to highly enrich .sup.34 S in natural SF.sub.6 and .sup.11 B in natural BCl.sub.3.

  11. Electronic excitations in γ -Li2IrO3

    NASA Astrophysics Data System (ADS)

    Li, Ying; Winter, Stephen M.; Jeschke, Harald O.; Valentí, Roser

    2017-01-01

    We investigate the electronic properties of the three-dimensional stripyhoneycomb γ -Li2IrO3 via relativistic density functional theory calculations as well as exact diagonalization of finite clusters and explore the details of the optical conductivity. Our analysis of this quantity reveals the microscopic origin of the experimentally observed (i) optical transitions and (ii) anisotropic behavior along the various polarization directions. In particular, we find that the optical excitations are overall dominated by transitions between jeff=1 /2 and 3/2 states and the weight of transitions between jeff=1 /2 states at low frequencies can be correlated to deviations from a pure Kitaev description. We furthermore reanalyze within this approach the electronic excitations in the known two-dimensional honeycomb systems α -Li2IrO3 and Na2IrO3 and discuss the results in comparison to γ -Li2IrO3 .

  12. CO excitation in four IR luminous galaxies

    NASA Astrophysics Data System (ADS)

    Radford, Simon J. E.; Solomon, P. M.; Downes, Dennis

    1990-07-01

    The correlation between the CO and far infrared luminosities of spiral galaxies is well established. The luminosity ration, LFIR/L sub CO in IR luminous active galaxies is, however, systematically five to ten times higher than in ordinary spirals and molecular clouds in our Galaxy. Furthermore, the masses of molecular hydrogen in luminous galaxies are large, M (H2) approx. equals 1010 solar magnitude, which indicates the observed luminosity ratios are due to an excess of infrared output, rather than a deficiency of molecular gas. These large amounts of molecular gas may fuel luminous galaxies through either star formation or nuclear activity. This interpretation rests on applying the M (H2)/LCO ratio calibrated in our Galaxy to galaxies with strikingly different luminosity ratios. But are the physical conditions of the molecular gas different in galaxies with different luminosity ratios. And, if so, does the proportionality between CO and H2 also vary among galaxies. To investigate these questions researchers observed CO (2 to 1) and (1 to 0) emission from four luminous galaxies with the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope. Researchers conclude that most of the CO emission from these Arp 193, Arp 220, and Mrk 231 arises in regions with moderate ambient densities similar to the clouds in the Milky Way molecular ring. The emission is neither from dense hot cloud cores nor from the cold low density gas characteristic of the envelopes of dark clouds.

  13. CO excitation in four IR luminous galaxies

    NASA Technical Reports Server (NTRS)

    Radford, Simon J. E.; Solomon, P. M.; Downes, Dennis

    1990-01-01

    The correlation between the CO and far infrared luminosities of spiral galaxies is well established. The luminosity ration, L sub FIR/L sub CO in IR luminous active galaxies is, however, systematically five to ten times higher than in ordinary spirals and molecular clouds in our Galaxy. Furthermore, the masses of molecular hydrogen in luminous galaxies are large, M (H2) approx. equals 10(exp 10) solar magnitude, which indicates the observed luminosity ratios are due to an excess of infrared output, rather than a deficiency of molecular gas. These large amounts of molecular gas may fuel luminous galaxies through either star formation or nuclear activity. This interpretation rests on applying the M (H2)/L sub CO ratio calibrated in our Galaxy to galaxies with strikingly different luminosity ratios. But are the physical conditions of the molecular gas different in galaxies with different luminosity ratios. And, if so, does the proportionality between CO and H2 also vary among galaxies. To investigate these questions researchers observed CO (2 to 1) and (1 to 0) emission from four luminous galaxies with the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope. Researchers conclude that most of the CO emission from these Arp 193, Arp 220, and Mrk 231 arises in regions with moderate ambient densities similar to the clouds in the Milky Way molecular ring. The emission is neither from dense hot cloud cores nor from the cold low density gas characteristic of the envelopes of dark clouds.

  14. A combined IR/IR and IR/UV spectroscopy study on the proton transfer coordinate of isolated 3-hydroxychromone in the electronic ground and excited state.

    PubMed

    Stamm, A; Weiler, M; Brächer, A; Schwing, K; Gerhards, M

    2014-10-21

    In this paper the excited state proton transfer (ESPT) of isolated 3-hydroxychromone (3-HC), the prototype of the flavonols, is investigated for the first time by combined IR/UV spectroscopy in molecular beam experiments. The IR/UV investigations are performed both for the electronically excited and electronic ground state indicating a spectral overlap of transitions of the 3-HC monomer and clusters with water in the electronic ground state, whereas in the excited state only the IR frequencies of the proton-transferred monomer structure are observed. Due to the loss of isomer and species selectivity with respect to the UV excitations IR/IR techniques are applied in order to figure out the assignment of the vibrational transitions in the S0 state. In this context the quadruple resonance IR/UV/IR/UV technique (originally developed to distinguish different isomers in the electronically excited state) could be applied to identify the OH stretching vibration of the monomer in the electronic ground state. In agreement with calculations the OH stretching frequency differs significantly from the corresponding values of substituted hydroxychromones.

  15. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    DOE PAGES

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; ...

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the searchmore » for high temperature superconductivity in this system.« less

  16. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    SciTech Connect

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; Upton, M. H.; Qi, T.; Gog, T.; Cao, Y.; Lin, J. Q.; Meyers, D.; Ding, H.; Cao, G.; Hill, J. P.

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the search for high temperature superconductivity in this system.

  17. Magnetic and Orbital Excitations in Sr3CuIrO6

    NASA Astrophysics Data System (ADS)

    Hill, J. P.; Liu, X.; Dean, M.; Yin, W.; Tsvelik, A.; Kim, J.; Casa, D.; Upton, M. H.; Gretarsson, H.; Kim, Y.-J.; Qi, T.; Cao, G.; Hozoi, L.; Katukuri, V.; Brink, J. V. D.

    2012-02-01

    We report resonant inelastic x-ray scattering studies of the one-dimensional Sr3CuIrO6 at the Ir L3 edge, with δE=40 meV. At high energies, we find peaks at 0.6 eV, 0.9 eV, 3 eV, 4 eV and 6 eV. These peaks are non-dispersive, well-defined excitations. On the basis of quantum chemistry calculations, we are able to identify the first two as excitations within the t2g manifold and the next two as between the t2g and eg manifolds, together with charge transfer excitations from the O 2p to the Ir 5d. The 6 eV feature is another t2g - eg excitation. From these we are able to determine both the spin-orbit and non-cubic crystal field splittings. We find that they are of comparable strength. In addition, magnetic excitations are observed, corresponding to excitations of the j1/2 isospin. We find these are highly dispersive along the chain direction with a bandwidth of 20 meV and a gap of 30 meV. These results allow a complete modeling of the spin and orbital degrees of freedom in this model compound and we conclude an atomic, spin-orbit coupled description works well.

  18. Conformality or confinement: (IR)relevance of topological excitations

    SciTech Connect

    Poppitz, Erich; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept.

    2010-08-26

    What distinguishes two asymptotically-free non-abelian gauge theories on R{sup 4}, one of which is just below the conformal window boundary and confines, while the other is slightly above the boundary and flows to an infrared conformal field theory? In this work, we aim to answer this question for non-supersymmetric Yang-Mills theories with fermions in arbitrary chiral or vectorlike representations. We use the presence or absence of mass gap for gauge fluctuations as an identifier of the infrared behavior. With the present-day understanding of such gauge theories, the mass gap for gauge fluctuations cannot be computed on R{sup 4}. However, recent progress allows its non-perturbative computation on R{sup 3} x S{sup 1} by using either the twisted partition function or deformation theory, for a range of sizes of S{sup 1} depending on the theory. For small number of fermions, N{sub f}, we show that the mass gap increases with increasing radius, due to the non-dilution of monopoles and bions - the topological excitations relevant for confinement on R{sup 3} x S{sup 1}. For sufficiently large N{sub f}, we show that the mass gap decreases with increasing radius. In a class of theories, we claim that the decompactification limit can be taken while remaining within the region of validity of semiclassical techniques, giving the first examples of semiclassically solvable Yang-Mills theories at any size S{sup 1}. For general non-supersymmetric vectorlike or chiral theories, we conjecture that the change in the behavior of the mass gap on R{sup 3} x S{sup 1} as a function of the radius occurs near the lower boundary of the conformal window and give non-perturbative estimates of its value. For vectorlike theories, we compare our estimates of the conformal window with existing lattice results, truncations of the Schwinger-Dyson equations, NSVZ beta function-inspired estimates, and degree of freedom counting criteria. For multi-generation chiral gauge theories, to the best of our

  19. Photofunctional triplet excited states of cyclometalated Ir(III) complexes: beyond electroluminescence.

    PubMed

    You, Youngmin; Nam, Wonwoo

    2012-11-07

    The development of cyclometalated Ir(III) complexes has enabled important breakthroughs in electroluminescence because such complexes permit the efficient population of triplet excited states that give rise to luminescent transitions. The triplet states of Ir(III) complexes are advantageous over those of other transition metal complexes in that their electronic transitions and charge-transfer characteristics are tunable over wide ranges. These favorable properties suggest that Ir(III) complexes have significant potential in a variety of photofunctions other than electroluminescence. In this critical review, we describe recent photonic applications of novel Ir(III) complexes. Ir(III) complexes have been shown to affect the exciton statistics in the active layers of organic photovoltaic cells, thereby improving the photon-to-current conversion efficiencies. Nonlinear optical applications that take advantage of the strong charge-transfer properties of triplet transitions are also discussed. The tunability of the electrochemical potentials facilitates the development of efficient photocatalysis in the context of water photolysis or organic syntheses. The photoredox reactivities of Ir(III) complexes have been employed in studies of charge migration along DNA chains. The photoinduced cytotoxicity of Ir(III) complexes on live cells suggests that the complexes may be useful in photodynamic therapy. Potential biological applications of the complexes include phosphorescence labeling and sensing. Intriguing platforms based on cyclometalated Ir(III) complexes potentially provide novel protein tagging and ratiometric detection. We envision that future research into the photofunctionality of Ir(III) complexes will provide important breakthroughs in a variety of photonic applications.

  20. Synthetic control of excited-state properties in cyclometalated Ir(III) complexes using ancillary ligands.

    PubMed

    Li, Jian; Djurovich, Peter I; Alleyne, Bert D; Yousufuddin, Muhammed; Ho, Nam N; Thomas, J Christopher; Peters, Jonas C; Bau, Robert; Thompson, Mark E

    2005-03-21

    The synthesis and photophysical characterization of a series of (N,C(2')-(2-para-tolylpyridyl))2 Ir(LL') [(tpy)2 Ir(LL')] (LL' = 2,4-pentanedionato (acac), bis(pyrazolyl)borate ligands and their analogues, diphosphine chelates and tert-butylisocyanide (CN-t-Bu)) are reported. A smaller series of [(dfppy)2 Ir(LL')] (dfppy = N,C(2')-2-(4',6'-difluorophenyl)pyridyl) complexes were also examined along with two previously reported compounds, (ppy)2 Ir(CN)2- and (ppy)2 Ir(NCS)2- (ppy = N,C(2')-2-phenylpyridyl). The (tpy)2 Ir(PPh2CH2)2 BPh2 and [(tpy)2 Ir(CN-t-Bu)2](CF3SO3) complexes have been structurally characterized by X-ray crystallography. The Ir-C(aryl) bond lengths in (tpy)2 Ir(CN-t-Bu)2+ (2.047(5) and 2.072(5) A) and (tpy)2 Ir(PPh2CH2)2 BPh2 (2.047(9) and 2.057(9) A) are longer than their counterparts in (tpy)2 Ir(acac) (1.982(6) and 1.985(7) A). Density functional theory calculations carried out on (ppy)2 Ir(CN-Me)2+ show that the highest occupied molecular orbital (HOMO) consists of a mixture of phenyl-pi and Ir-d orbitals, while the lowest unoccupied molecular orbital is localized primarily on the pyridyl-pi orbitals. Electrochemical analysis of the (tpy)2 Ir(LL') complexes shows that the reduction potentials are largely unaffected by variation in the ancillary ligand, whereas the oxidation potentials vary over a much wider range (as much as 400 mV between two different LL' ligands). Spectroscopic analysis of the cyclometalated Ir complexes reveals that the lowest energy excited state (T1) is a triplet ligand-centered state (3LC) on the cyclometalating ligand admixed with 1MLCT (MLCT = metal-to-ligand charge-transfer) character. The different ancillary ligands alter the 1MLCT state energy mainly by changing the HOMO energy. Destabilization of the 1MLCT state results in less 1MLCT character mixed into the T1 state, which in turn leads to an increase in the emission energy. The increase in emission energy leads to a linear decrease in ln(k(nr)) (k

  1. Vortexlike excitations in the heavy-fermion superconductor CeIrIn5

    DOE PAGES

    Luo, Yongkang; Rosa, P. F. S.; Bauer, E. D.; ...

    2016-05-05

    Here, we report a systematic study of temperature- and field-dependent charge (ρ) and entropy (S) transport in the heavy-fermion superconductor CeIrIn5. Its large positive thermopower Sxx is typical of Ce-based Kondo lattice systems, and strong electronic correlations play an important role in enhancing the Nernst signal Sxy. By separating the off-diagonal Peltier coefficient αxy from Sxy, we find that αxy becomes positive and greatly enhanced at temperatures well above the bulk Tc. Compared with the nonmagnetic analog LaIrIn5, these results suggest vortexlike excitations in a precursor state to unconventional superconductivity in CeIrIn5. This study sheds light on the similarity ofmore » heavy-fermion and cuprate superconductors and on the possibility of states not characterized by the amplitude of an order parameter.« less

  2. Vortexlike excitations in the heavy-fermion superconductor CeIrIn5

    NASA Astrophysics Data System (ADS)

    Luo, Yongkang; Rosa, P. F. S.; Bauer, E. D.; Thompson, J. D.

    2016-05-01

    We report a systematic study of temperature- and field-dependent charge (ρ ) and entropy (S ) transport in the heavy-fermion superconductor CeIrIn5. Its large positive thermopower Sx x is typical of Ce-based Kondo lattice systems, and strong electronic correlations play an important role in enhancing the Nernst signal Sx y. By separating the off-diagonal Peltier coefficient αx y from Sx y, we find that αx y becomes positive and greatly enhanced at temperatures well above the bulk Tc. Compared with the nonmagnetic analog LaIrIn5, these results suggest vortexlike excitations in a precursor state to unconventional superconductivity in CeIrIn5. This study sheds light on the similarity of heavy-fermion and cuprate superconductors and on the possibility of states not characterized by the amplitude of an order parameter.

  3. Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction

    DOE PAGES

    Manbeck, Gerald F.; Garg, Komal; Shimoda, Tomoe; ...

    2016-12-01

    Here, we prepared electron-rich derivatives of [Ir(tpy)(ppy)Cl]+ with modification of the bidentate (ppy) or tridentate (tpy) ligands in attempt to increase the reactivity for CO2 reduction and the ability to transfer hydrides (hydricity). Density functional theory (DFT) calculations reveal that complexes with dimethyl-substituted ppy have similar hydricities to the non-substituted parent complex, and photocatalytic CO2 reduction studies show selective CO formation. Substitution of tpy for bis(benzimidazole)-phenyl or -pyridine (L3 and L4, respectively) induces changes in the physical properties much more pronounced than addition of methyl groups to ppy. Theoretical data predict [Ir(L3)(ppy)(H)] is the strongest hydride donor among complexes studiedmore » in this work, but [Ir(L3)(ppy)(NCCH3)]+ cannot be reduced photochemically because the excited state reduction potential is only 0.52 V due to the negative ground state potential of –1.91 V. The excited state [Ir(L4)(ppy)(NCCH3)]2+ is the strongest oxidant among complexes studied in this work and the singly reduced species is formed readily upon photolysis in the presence of tertiary amines. Both [Ir(L3)(ppy)(NCCH3)]+ and [Ir(L4)(ppy)(NCCH3)]2+ exhibit electrocatalytic current for CO2 reduction. While a significantly greater overpotential is needed for the L3 complex, a small amount of formate (5-10 %) generation in addition to CO was observed as predicted by the DFT calculations.« less

  4. Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction.

    PubMed

    Manbeck, Gerald F; Garg, Komal; Shimoda, Tomoe; Szalda, David J; Ertem, Mehmed Z; Muckerman, James T; Fujita, Etsuko

    2017-03-10

    We prepared electron-rich derivatives of [Ir(tpy)(ppy)Cl](+) with modification of the bidentate (ppy) or tridentate (tpy) ligands in an attempt to increase the reactivity for CO2 reduction and the ability to transfer hydrides (hydricity). Density functional theory (DFT) calculations reveal that complexes with dimethyl-substituted ppy have similar hydricities to the non-substituted parent complex, and photocatalytic CO2 reduction studies show selective CO formation. Substitution of tpy by bis(benzimidazole)-phenyl or -pyridine (L3 and L4, respectively) induces changes in the physical properties that are much more pronounced than from the addition of methyl groups to ppy. Theoretical data predict [Ir(L3)(ppy)(H)] as the strongest hydride donor among complexes studied in this work, but [Ir(L3)(ppy)(NCCH3)](+) cannot be reduced photochemically because the excited state reduction potential is only 0.52 V due to the negative ground state potential of -1.91 V. The excited state of [Ir(L4)(ppy)(NCCH3)](2+) is the strongest oxidant among complexes studied in this work and the singly-reduced species is formed readily upon photolysis in the presence of tertiary amines. Both [Ir(L3)(ppy)(NCCH3)](+) and [Ir(L4)(ppy)(NCCH3)](2+) exhibit electrocatalytic current for CO2 reduction. While a significantly greater overpotential is needed for the L3 complex, a small amount of formate (5-10%) generation in addition to CO was observed as predicted by the DFT calculations.

  5. Sonic IR crack detection of aircraft turbine engine blades with multi-frequency ultrasound excitations

    SciTech Connect

    Zhang, Ding; Han, Xiaoyan; Newaz, Golam

    2014-02-18

    Effectively and accurately detecting cracks or defects in critical engine components, such as turbine engine blades, is very important for aircraft safety. Sonic Infrared (IR) Imaging is such a technology with great potential for these applications. This technology combines ultrasound excitation and IR imaging to identify cracks and flaws in targets. In general, failure of engine components, such as blades, begins with tiny cracks. Since the attenuation of the ultrasound wave propagation in turbine engine blades is small, the efficiency of crack detection in turbine engine blades can be quite high. The authors at Wayne State University have been developing the technology as a reliable tool for the future field use in aircraft engines and engine parts. One part of the development is to use finite element modeling to assist our understanding of effects of different parameters on crack heating while experimentally hard to achieve. The development has been focused with single frequency ultrasound excitation and some results have been presented in a previous conference. We are currently working on multi-frequency excitation models. The study will provide results and insights of the efficiency of different frequency excitation sources to foster the development of the technology for crack detection in aircraft engine components.

  6. Infrared Multiple Photon Dissociation Spectroscopy Of Metal Cluster-Adducts

    NASA Astrophysics Data System (ADS)

    Cox, D. M.; Kaldor, A.; Zakin, M. R.

    1987-01-01

    Recent development of the laser vaporization technique combined with mass-selective detection has made possible new studies of the fundamental chemical and physical properties of unsupported transition metal clusters as a function of the number of constituent atoms. A variety of experimental techniques have been developed in our laboratory to measure ionization threshold energies, magnetic moments, and gas phase reactivity of clusters. However, studies have so far been unable to determine the cluster structure or the chemical state of chemisorbed species on gas phase clusters. The application of infrared multiple photon dissociation IRMPD to obtain the IR absorption properties of metal cluster-adsorbate species in a molecular beam is described here. Specifically using a high power, pulsed CO2 laser as the infrared source, the IRMPD spectrum for methanol chemisorbed on small iron clusters is measured as a function of the number of both iron atoms and methanols in the complex for different methanol isotopes. Both the feasibility and potential utility of IRMPD for characterizing metal cluster-adsorbate interactions are demonstrated. The method is generally applicable to any cluster or cluster-adsorbate system dependent only upon the availability of appropriate high power infrared sources.

  7. IR excitation of contaminant water by oxygen for the space shuttle at low Earth orbit altitude

    NASA Technical Reports Server (NTRS)

    Zhou, D. K.; Pendleton, W. R., Jr.; Bingham, G. E.; Thompson, D. C.; Raitt, W. J.; Nadile, R. M.

    1994-01-01

    As the water outgas of a space shuttle passes through the rarefied atmosphere at orbital altitude, collisions occur between the gases with sufficient energy to excite infrared-active water molecules to various vibrational and rotational states. An infrared contaminant model (IR model) has been developed to study the shuttle-induced excitation and emission of water molecules outgassed from the space shuttle. The focus of the first application of the model is translation-to-vibration (T-V) energy transfer since estimates suggest that this process should dominate the production of vibrationally excited H2O under typical low Earth orbit conditions. Using the velocity and position distribution functions of interacting neutral gases obtained from a neutral gases interaction model, the spatial distributions of excitation and IR radiation from contaminant water are computed, and typical results are presented. Infrared spectral data (450 - 2500/cm), measured by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) sensor on STS-39 (April 28 to May 6, 1991) at an altitude near 265 km, are used to test model predictions. The dependence of the radiant emission structure and brightness on outgassing rates and altitudes is discussed. The time history of the contaminant water outgassing rate is inferred for STS-39, and it is compared with the mass-spectrometer-based results for STS-4 (June 26 to July 4, 1982). Also, estimates of H2O column density at mission elapsed time (MET) 50 hours are compared for missions STS-2, STS-3, STS-4, and STS-39.

  8. IR excitation of contaminant water by oxygen for the space shuttle at low Earth orbit altitude

    NASA Technical Reports Server (NTRS)

    Zhou, D. K.; Pendleton, W. R., Jr.; Bingham, G. E.; Thompson, D. C.; Raitt, W. J.; Nadile, R. M.

    1994-01-01

    As the water outgas of a space shuttle passes through the rarefied atmosphere at orbital altitude, collisions occur between the gases with sufficient energy to excite infrared-active water molecules to various vibrational and rotational states. An infrared contaminant model (IR model) has been developed to study the shuttle-induced excitation and emission of water molecules outgassed from the space shuttle. The focus of the first application of the model is translation-to-vibration (T-V) energy transfer since estimates suggest that this process should dominate the production of vibrationally excited H2O under typical low Earth orbit conditions. Using the velocity and position distribution functions of interacting neutral gases obtained from a neutral gases interaction model, the spatial distributions of excitation and IR radiation from contaminant water are computed, and typical results are presented. Infrared spectral data (450 - 2500/cm), measured by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) sensor on STS-39 (April 28 to May 6, 1991) at an altitude near 265 km, are used to test model predictions. The dependence of the radiant emission structure and brightness on outgassing rates and altitudes is discussed. The time history of the contaminant water outgassing rate is inferred for STS-39, and it is compared with the mass-spectrometer-based results for STS-4 (June 26 to July 4, 1982). Also, estimates of H2O column density at mission elapsed time (MET) 50 hours are compared for missions STS-2, STS-3, STS-4, and STS-39.

  9. Infrared FEL photochemistry: Multiple-photon dissociation of Freon gas

    SciTech Connect

    Newnam, B.E.; Early, J.W.; Lyman, J.L.

    1993-10-01

    Wavelength tunability, synchrotron sidebands, and picosecond pulse structure are inherent FEL characteristics that should be advantageous for photochemistry involving infrared multiple-photon photodissociation. Tuned to an absorption resonance, the FEL sideband structure will overlap the broad, excited-state spectral absorption and should lead to enhanced dissociation. The Los Alamos APEX FEL was operated with and without sidebands to test this hypothesis on CFCl{sub 3} (Freon 11), an inert chlorofluorocarbon widely used in refrigeration systems and one of the gases implicated as depleting the ozone in the Earth`s stratospheric layer. The FEL wavelength was set at the C-Cl stretch absorption resonance at 11.8-{mu}m, the oscillator cavity length was detuned first to minimize and then to maximize the spectral bandwidth, and the beam was focused through a pair of test cells (1.0 Torr Freon+1.7 Torr air). Comparison of final and initial absorbance spectra indicated the CFCl{sub 3} photodissociation yield was 1.2% for the cell exposed with sideband spectra (3% FWHM) and 9-ns micropulse separation. Negligible effect was seen without sidebands, albeit at lower total beam fluence. Although the result of this single experiment is not large enough to be conclusive, it does provide a basis for optimizing the FEL temporal and spectral parameters to attain higher photodissociation yield in future tests.

  10. Infrared FEL photochemistry: Multiple-photon dissociation of freon gas

    NASA Astrophysics Data System (ADS)

    Newnam, B. E.; Early, J. W.; Lyman, J. L.

    Wavelength tunability, synchrotron sidebands, and picosecond pulse structure are inherent FEL characteristics that should be advantageous for photochemistry involving infrared multiple-photon photodissociation. Tuned to an absorption resonance, the FEL sideband structure will overlap the broad, excited-state spectral absorption and should lead to enhanced dissociation. The Los Alamos APEX FEL was operated with and without sidebands to test this hypothesis on CFCl3 (Freon 11), an inert chlorofluorocarbon widely used in refrigeration systems and one of the gases implicated as depleting the ozone in the Earth's stratospheric layer. The FEL wavelength was set at the C-Cl stretch absorption resonance at 11.8-microns, the oscillator cavity length was detuned first to minimize and then to maximize the spectral bandwidth, and the beam was focused through a pair of test cells (1.0 Torr Freon + 1.7 Torr air). Comparison of final and initial absorbance spectra indicated the CFCl3 photodissociation yield was 1.2% for the cell exposed with sideband spectra (3% FWHM) and 9-ns micropulse separation. Negligible effect was seen without sidebands, albeit at lower total beam fluence. Although the result of this single experiment is not large enough to be conclusive, it does provide a basis for optimizing the FEL temporal and spectral parameters to attain higher photodissociation yield in future tests.

  11. Infrared FEL photochemistry: multiple-photon dissociation of Freon gas

    NASA Astrophysics Data System (ADS)

    Newnam, Brian E.; Early, James W.; Lyman, John L.

    1994-03-01

    Wavelength tunability, synchrotron sidebands, and picosecond pulse structure are inherent characteristics of free-electron lasers (FELs) that should be advantageous for photochemistry involving infrared multiple-photon photodissociation. Tuned to an absorption resonance, the FEL sideband structure will overlap the broad, red-shifted, quasi-continuous excited-state absorption spectra and should lead to enhanced dissociation. The Los Alamos APEX FEL was operated with and without sidebands to test this hypothesis on CFCl 3 (Freon 11), one of the gases implicated as depleting the ozone in the Earth's stratospheric layer. The FEL wavelength was set at the CCl stretch absorption resonance at 11.8 μm, the oscillator cavity length was detuned first to minimize and then to maximize the spectral bandwidth, and the beam was focused through a pair of test cells. Comparison of final and initial absorbance spectra indicated the CFCl 3 photodissociation yield was 1.2% for the cell exposed with sideband spectra (3% FWHM) and 9-ns micropulse separation. Negligible effect was seen without sidebands, albeit at lower total beam fluence.

  12. Gas-phase infrared multiple photon dissociation spectroscopy of isolated SF6- and SF5- anions.

    PubMed

    Steill, Jeffrey D; Oomens, Jos; Eyler, John R; Compton, Robert N

    2008-12-28

    Resonantly enhanced multiple photon dissociation of gas-phase SF(6) (-) and SF(5) (-) is studied using tunable infrared light from the FELIX free electron laser. The photodissociation spectrum of the sulfur hexafluoride anion, producing SF(5) (-), is recorded over the spectral range of 250-1650 cm(-1). The infrared multiple photon dissociation cross section exhibits a strong, broad resonance enhancement at 675 cm(-1) in agreement with the calculated value of nu(3), one of the two IR-active fundamental vibrational modes predicted for the O(h)-symmetry ion. Much weaker absorption features are observed in the spectral region of 300-450 cm(-1) as well as at 580 cm(-1) that are not easily assigned to the other IR-active fundamental of SF(6) (-) since these resonances are observed at a much higher energy than the calculated values for the IR-active nu(4) mode. The potential role of binary combination bands is considered. Photodissociation from the sulfur pentafluoride anion produced only F(-), but photodetachment was also observed through SF(6) associative electron capture. The IR multiple photon dissociation spectrum of SF(5) (-) shows multiple resonances within the region of 400-900 cm(-1) and agreement with calculations is clear, including the observation of three fundamental frequencies: nu(1) at 780 cm(-1), nu(7) at 595 cm(-1), and nu(8) at 450 cm(-1). Comparisons of the measured frequencies with ab initio and density functional theory calculations confirm an SF(5) (-) anion of C(4v) symmetry. Similar comparisons for SF(6) (-) are not inconsistent with an anion of O(h) symmetry.

  13. Fuel Cell Manufacturing Diagnostic Techniques: IR Thermography with Reactive Flow through Excitation

    SciTech Connect

    Manak, A. J.; Ulsh, M.; Bender, G.

    2012-01-01

    While design and material considerations for PEMFCs have a large impact on cost, it is also necessary to consider a transition to high volume production of fuel cell systems, including MEA components, to enable economies of scale and reduce per unit cost. One of the critical manufacturing tasks is developing and deploying techniques to provide in‐process measurement of fuel cell components for quality control. This effort requires a subsidiary task: The study of the effect of manufacturing defects on performance and durability with the objective to establish validated manufacturing tolerances for fuel cell components. This work focuses on the development of a potential quality control method for gas diffusion electrodes (GDEs). The method consists of infrared (IR) thermography combined with reactive flow through (RFT) excitation. Detection of catalyst loading reduction defects in GDE catalyst layers will be presented.

  14. Photo-redox activated drug delivery systems operating under two photon excitation in the near-IR.

    PubMed

    Guardado-Alvarez, Tania M; Devi, Lekshmi Sudha; Vabre, Jean-Marie; Pecorelli, Travis A; Schwartz, Benjamin J; Durand, Jean-Olivier; Mongin, Olivier; Blanchard-Desce, Mireille; Zink, Jeffrey I

    2014-05-07

    We report the design and synthesis of a nano-container consisting of mesoporous silica nanoparticles with the pore openings covered by "snap-top" caps that are opened by near-IR light. A photo transducer molecule that is a reducing agent in an excited electronic state is covalently attached to the system. Near IR two-photon excitation causes inter-molecular electron transfer that reduces a disulfide bond holding the cap in place, thus allowing the cargo molecules to escape. We describe the operation of the "snap-top" release mechanism by both one- and two-photon activation. This system presents a proof of concept of a near-IR photoredox-induced nanoparticle delivery system that may lead to a new type of photodynamic drug release therapy.

  15. Resonant Infrared Multiple Photon Dissociation Spectroscopy of Anionic Nucleotide Monophosphate Clusters.

    PubMed

    Ligare, Marshall R; Rijs, Anouk M; Berden, Giel; Kabeláč, Martin; Nachtigallova, Dana; Oomens, Jos; de Vries, Mattanjah S

    2015-06-25

    We report mid-infrared spectra and potential energy surfaces of four anionic, 2'-deoxynucleotide-5'-monophosphates (dNMPs) and the ionic DNA pairs [dGMP-dCMP-H](1-), [dAMP-dTMP-H](1-) with a total charge of the complex equal to -1. We recorded IR action spectra by resonant IR multiple-photon dissociation (IRMPD) using the FELIX free electron laser. The potential energy surface study employed an on-the-fly molecular dynamics quenching method (MD/Q), using a semiempirical AM1 method, followed by an optimization of the most stable structures using density functional theory. By employing infrared multiple-photon dissociation (IRMPD) spectroscopy in combination with high-level computational methods, we aim at a better understanding of the hydrogen bonding competition between the phosphate moieties and the nucleobases. We find that, unlike in multimer double stranded DNA structures, the hydrogen bonds in these isolated nucleotide pairs are predominantly formed between the phosphate groups. This intermolecular interaction appears to exceed the stabilization energy resulting from base pairing and directs the overall cluster structure and alignment.

  16. Mapping and controlling ultrafast dynamics of highly excited H2 molecules by VUV-IR pump-probe schemes

    DOE PAGES

    Sturm, F. P.; Tong, X. M.; Palacios, A.; ...

    2017-01-09

    Here, we used ultrashort femtosecond vacuum ultraviolet (VUV) and infrared (IR) pulses in a pump-probe scheme to map the dynamics and nonequilibrium dissociation channels of excited neutral H2 molecules. A nuclear wave packet is created in the B1Σmore » $$+\\atop{u}$$ state of the neutral H2 molecule by absorption of the ninth harmonic of the driving infrared laser field. Due to the large stretching amplitude of the molecule excited in the B1Σ$$+\\atop{u}$$ electronic state, the effective H2+ ionization potential changes significantly as the nuclear wave packet vibrates in the bound, highly electronically and vibrationally excited B potential-energy curve. We probed such dynamics by ionizing the excited neutral molecule using time-delayed VUV-or-IR radiation. We identified the nonequilibrium dissociation channels by utilizing three-dimensional momentum imaging of the ion fragments. We also found that different dissociation channels can be controlled, to some extent, by changing the IR laser intensity and by choosing the wavelength of the probe laser light. Furthermore, we concluded that even in a benchmark molecular system such as H2*, the interpretation of the nonequilibrium multiphoton and multicolor ionization processes is still a challenging task, requiring intricate theoretical analysis.« less

  17. Mapping and controlling ultrafast dynamics of highly excited H2 molecules by VUV-IR pump-probe schemes

    NASA Astrophysics Data System (ADS)

    Sturm, F. P.; Tong, X. M.; Palacios, A.; Wright, T. W.; Zalyubovskaya, I.; Ray, D.; Shivaram, N.; Martín, F.; Belkacem, A.; Ranitovic, P.; Weber, Th.

    2017-01-01

    We used ultrashort femtosecond vacuum ultraviolet (VUV) and infrared (IR) pulses in a pump-probe scheme to map the dynamics and nonequilibrium dissociation channels of excited neutral H2 molecules. A nuclear wave packet is created in the B Σ+1u state of the neutral H2 molecule by absorption of the ninth harmonic of the driving infrared laser field. Due to the large stretching amplitude of the molecule excited in the B Σ+1u electronic state, the effective H2+ ionization potential changes significantly as the nuclear wave packet vibrates in the bound, highly electronically and vibrationally excited B potential-energy curve. We probed such dynamics by ionizing the excited neutral molecule using time-delayed VUV-or-IR radiation. We identified the nonequilibrium dissociation channels by utilizing three-dimensional momentum imaging of the ion fragments. We found that different dissociation channels can be controlled, to some extent, by changing the IR laser intensity and by choosing the wavelength of the probe laser light. Furthermore, we concluded that even in a benchmark molecular system such as H2*, the interpretation of the nonequilibrium multiphoton and multicolor ionization processes is still a challenging task, requiring intricate theoretical analysis.

  18. Conformational Changes in Thiazole-2-carboxylic Acid Selectively Induced by Excitation with Narrowband Near-IR and UV Light.

    PubMed

    Halasa, Anna; Reva, Igor; Lapinski, Leszek; Nowak, Maciej J; Fausto, Rui

    2016-04-07

    Conformers and photoinduced conformational transformations were studied for monomers of thiazole-2-carboxylic acid (TCA). The matrix-isolation technique and excitations with narrowband near-IR and UV light, tuned in an optical parametric oscillator, were used for this purpose. Form I, with the carboxylic moiety in the trans orientation and with the hydrogen atom of the OH group directed toward the nitrogen atom of the ring, was the most abundant in low-temperature argon or nitrogen matrixes. Conformer II, differing from I by 180° rotation of the OH group around the C-O bond, was also trapped in the matrixes, but in much smaller amount. The abundance of form II was experimentally determined as ∼6% of the total amount of TCA molecules. Selective excitation of I with narrowband near-IR laser light resulted in I → II transformation. This near-IR-induced conformational change was photoreversible: form II converted back to I upon selective excitation of II with near-IR light of different wavelength. Conformational conversions of I into II, or vice versa, were also induced in TCA monomers by narrowband UV excitations at 300 nm (for I → II transformation) and at 305 nm (for II → I transformation). A spontaneous conversion of photogenerated II into the most stable form I was observed for the compound trapped in the matrix at 15 K and kept in the dark. This process was very slow; the estimated half-life time of conformer II was longer than 50 h. Finally, TCA was shown to thermally decompose at room temperature, yielding CO2 and thiazole.

  19. Prediction and identification of multiple-photon resonant ionization processes

    SciTech Connect

    Smith, D.H.; McKown, H.S.; Young, J.P.; Shaw, R.W.; Donohue, D.L.

    1988-08-01

    Many single-color, multiple-photon transitions leading to ionization are observed for lanthanide and actinide elements in experiments using resonance ionization mass spectrometry (RIMS). It is desirable both to identify the energy levels involved in observed transitions and to be able to predict in advance their location. A computer code, ETRANS, has been written to perform these functions. Examples of both types of operation are given.

  20. Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction

    SciTech Connect

    Manbeck, Gerald F.; Garg, Komal; Shimoda, Tomoe; Szalda, David J.; Ertem, Mehmed Z.; Muckerman, James T.; Fujita, Etsuko

    2016-12-01

    Here, we prepared electron-rich derivatives of [Ir(tpy)(ppy)Cl]+ with modification of the bidentate (ppy) or tridentate (tpy) ligands in attempt to increase the reactivity for CO2 reduction and the ability to transfer hydrides (hydricity). Density functional theory (DFT) calculations reveal that complexes with dimethyl-substituted ppy have similar hydricities to the non-substituted parent complex, and photocatalytic CO2 reduction studies show selective CO formation. Substitution of tpy for bis(benzimidazole)-phenyl or -pyridine (L3 and L4, respectively) induces changes in the physical properties much more pronounced than addition of methyl groups to ppy. Theoretical data predict [Ir(L3)(ppy)(H)] is the strongest hydride donor among complexes studied in this work, but [Ir(L3)(ppy)(NCCH3)]+ cannot be reduced photochemically because the excited state reduction potential is only 0.52 V due to the negative ground state potential of –1.91 V. The excited state [Ir(L4)(ppy)(NCCH3)]2+ is the strongest oxidant among complexes studied in this work and the singly reduced species is formed readily upon photolysis in the presence of tertiary amines. Both [Ir(L3)(ppy)(NCCH3)]+ and [Ir(L4)(ppy)(NCCH3)]2+ exhibit electrocatalytic current for CO2 reduction. While a significantly greater overpotential is needed for the L3 complex, a small amount of formate (5-10 %) generation in addition to CO was observed as predicted by the DFT calculations.

  1. Probing single magnon excitations in Sr₂IrO₄ using O K-edge resonant inelastic x-ray scattering

    DOE PAGES

    Liu, X.; Dean, M. P. M.; Liu, J.; ...

    2015-04-28

    Resonant inelastic X-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin-orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr₂IrO₄, where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edgemore » RIXS energy resolutions in the hard X-ray region is usually poor.« less

  2. Probing single magnon excitations in Sr₂IrO₄ using O K-edge resonant inelastic x-ray scattering

    SciTech Connect

    Liu, X.; Dean, M. P. M.; Liu, J.; Chiuzbaian, S. G.; Jaouen, N.; Nicolaou, A.; Yin, W. G.; Rayan Serrao, C.; Ramesh, R.; Ding, H.; Hill, J. P.

    2015-04-28

    Resonant inelastic X-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin-orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr₂IrO₄, where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edge RIXS energy resolutions in the hard X-ray region is usually poor.

  3. On the biphoton excitation of the fluorescence of the bacteriochlorophyll molecules of purple photosynthetic bacteria by powerful near IR femto-picosecond pulses

    NASA Astrophysics Data System (ADS)

    Borisov, A. Yu.

    2011-11-01

    The authors of a number of experimental works detected nonresonance biphoton excitation of bacteriochlorophyll molecules, which represent the main pigment in the light-absorbing natural "antenna" complexes of photosynthesizing purple bacteria, by femtosecond IR pulses (1250-1500 nm). They believe that IR quanta excite hypothetic forbidden levels of the pigments of these bacteria in the double frequency range 625-750 nm. We propose and ground an alternative triplet mechanism to describe this phenomenon. According to our hypothesis, the mechanism of biphoton excitation of molecules by IR quanta can manifest itself specifically, through high triplet levels of molecules in the high fields induced by femtosecond-picosecond laser pulses.

  4. On the biphoton excitation of the fluorescence of the bacteriochlorophyll molecules of purple photosynthetic bacteria by powerful near IR femto-picosecond pulses

    SciTech Connect

    Borisov, A. Yu.

    2011-11-15

    The authors of a number of experimental works detected nonresonance biphoton excitation of bacteriochlorophyll molecules, which represent the main pigment in the light-absorbing natural 'antenna' complexes of photosynthesizing purple bacteria, by femtosecond IR pulses (1250-1500 nm). They believe that IR quanta excite hypothetic forbidden levels of the pigments of these bacteria in the double frequency range 625-750 nm. We propose and ground an alternative triplet mechanism to describe this phenomenon. According to our hypothesis, the mechanism of biphoton excitation of molecules by IR quanta can manifest itself specifically, through high triplet levels of molecules in the high fields induced by femtosecond-picosecond laser pulses.

  5. Driving Force Dependence of Electron Transfer from Electronically Excited [Ir(COD)(μ-Me2pz)]2 to Photo-Acid Generators.

    PubMed

    Sattler, Wesley; Rachford, Aaron A; LaBeaume, Paul J; Coley, Suzanne M; Thackeray, James W; Cameron, James F; Müller, Astrid M; Winkler, Jay R; Gray, Harry B

    2017-09-28

    We report the rates of electron transfer (ET) reactions of electronically excited [Ir(COD)(μ-Me2pz)]2 with onium salt photoacid generators (PAGs). The reduction potentials of the PAGs span a large electrochemical window that allows determination of the driving force dependence of the ET reactions. Rate constants of ET from electronically excited [Ir(COD)(μ-Me2pz)]2 to onium PAGs are determined by the reaction driving force until the diffusion limit in acetonitrile is reached.

  6. Structure Determination and Excited State Proton Transfer Reaction of 1-NAPHTHOL-AMMONIA Clusters in the S_{1} State Studied by Uv-Ir Mid-Ir Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Shunpei; Miyazaki, Mitsuhiko; Martin, Weiler; Ishikawa, Haruki; Fujii, Masaaki

    2013-06-01

    1-naphthol ammonia clusters have been studied long time as a benchmark system of the excited state proton transfer (ESPT) reactions. Understanding the ESPT reaction in this system has still not been fully established. To detect the cluster size dependence of the S_{1} state properties, many researcher extensively investigated such as emission spectra, lifetime, solvents (ammonia) evaporation pattern. Curiously, cluster structure that is fundamental to discuss the reaction has not been determined for the system. Thus we applied an IR spectroscopy to the S_{1} states of the system to determine the cluster structure and to discuss the minimum size inducing the ionic dissociation of the O-H bond in the S_{1} state. IR spectra were recorded not only the O-H and N-H stretching region (3 {μ}m) but also the skeletal vibrational region (5.5-10 {μ}m). Though O-H and N-H stretching vibrations do not provide useful structural information due to the broadness, the skeletal vibrations hold the sharpness even in the S_{1} states. Changes in the skeletal vibrations due to the ammonia solvation, e.g. C-O stretching and C-O-H bending, will be discussed based on a comparison with theoretical calculations. O. Cheshnovsky and S. Leutwylar, J. Chem. Phys. 1, 4127 (1988). S. K. Kim et al., Chem. Phys. lett. 228, 369 (1994). C. Dedonder-Lardeux et al., Phys. Chem, Chem, Phys. 3, 4316 (2001).

  7. Photonics of a conjugated organometallic Pt-Ir polymer and its model compounds exhibiting hybrid CT excited states.

    PubMed

    Soliman, Ahmed M; Fortin, Daniel; Zysman-Colman, Eli; Harvey, Pierre D

    2012-04-13

    Trans- dichlorobis(tri-n-butylphosphine)platinum(II) reacts with bis(2- phenylpyridinato)-(5,5'-diethynyl-2,2'-bipyridine)iridium(III) hexafluorophosphate to form the luminescent conjugated polymer poly[trans-[(5,5'-ethynyl-2,2'-bipyridine)bis(2- phenylpyridinato)-iridium(III)]bis(tri-n-butylphosphine)platinum(II)] hexafluorophosphate ([Pt]-[Ir])n. Gel permeation chromatography indicates a degree of polymerization of 9 inferring the presence of an oligomer. Comparison of the absorption and emission band positions and their temperature dependence, emission quantum yields, and lifetimes with those for models containing only the [Pt] or the [Ir] units indicates hybrid excited states including features from both chromophores.

  8. Raman scattering study of vibrational and magnetic excitations in Sr2 -xLaxIrO4

    NASA Astrophysics Data System (ADS)

    Gretarsson, H.; Sauceda, J.; Sung, N. H.; Höppner, M.; Minola, M.; Kim, B. J.; Keimer, B.; Le Tacon, M.

    2017-09-01

    We have measured the doping and temperature dependence of lattice vibrations and magnetic excitations in the prototypical doped spin-orbit Mott insulator Sr2 -xLaxIrO4 (x =0 , 0.015, and 0.10). Our findings show that the pseudospin-lattice coupling—responsible for the renormalization of several low energy phonon modes—is preserved even when long-range magnetic order is suppressed by doping. In our most highly doped sample, the single magnon (Γ point) excitation disappears while the two-magnon mode softens and becomes heavily damped. Doping-induced electron-phonon coupling is also observed in a higher energy phonon mode. We observe two different electron-phonon interaction channels, which provide evidence of the coexistence of fluctuating magnetic moments and mobile carriers in doped iridates.

  9. Rotationally resolved IR-diode laser studies of ground-state CO2 excited by collisions with vibrationally excited pyridine.

    PubMed

    Johnson, Jeremy A; Kim, Kilyoung; Mayhew, Maurine; Mitchell, Deborah G; Sevy, Eric T

    2008-03-27

    Relaxation of highly vibrationally excited pyridine (C5NH5) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot pyridine (E' = 40,660 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Pyridine then collides with CO2, populating the high rotational CO2 states with large amounts of translational energy. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these CO2 rotational states. Doppler spectroscopy was used to measure the CO2 recoil velocity distribution for J = 58-80 of the 00(0)0 state. The energy-transfer distribution function, P(E,E'), from E' - E approximately 1300-7000 cm(-1) was obtained by re-sorting the state-indexed energy-transfer probabilities as a function of DeltaE. P(E,E') is fit to an exponential or biexponential function to determine the average energy transferred in a single collision between pyridine and CO2. Also obtained are fit parameters that can be compared to previously studied systems (pyrazine, C6F6, methylpyrazine, and pyrimidine/CO2). Although the rotational and translational temperatures that describe pyridine/CO2 energy transfer are similar to previous systems, the energy-transfer probabilities are much smaller. P(E,E') fit parameters for pyridine/CO2 and the four previously studied systems are compared to various donor molecular properties. Finally, P(E,E') is analyzed in the context of two models, one indicating that P(E,E') shape is primarily determined by the low-frequency out-of-plane donor vibrational modes, and the other that indicates that P(E,E') shape can be determined from how the donor molecule final density of states changes with DeltaE.

  10. Excitation transfer mechanism along the visible to the Near-IR in rhodamine J-heteroaggregates.

    PubMed

    Sánchez-Valencia, Juan R; Toudert, Johann; González-García, Lola; González-Elipe, Agustín R; Barranco, Angel

    2010-06-28

    An enhanced fluorescent emission of the dye Rhodamine 800 in the Near-IR is observed in the presence of other xanthene dye molecules (RhX) when they are hosted in different matrices due to the formation of a new type of fluorescent J-heteroaggregates. This enhanced emission of the acceptor occurs despite the low spectral overlapping and the low quantum yield of Rh800.

  11. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    SciTech Connect

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; Upton, M. H.; Qi, T.; Gog, T.; Cao, Y.; Lin, J. Q.; Meyers, D.; Ding, H.; Cao, G.; Hill, J. P.

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the search for high temperature superconductivity in this system.

  12. 2D-IR spectroscopy of hydrogen-bond-mediated vibrational excitation transfer.

    PubMed

    Chuntonov, Lev

    2016-05-18

    Vibrational excitation transfer along the hydrogen-bond-mediated pathways in the complex of methyl acetate (MA) and 4-cyanophenol (4CP) was studied by dual-frequency femtosecond two-dimensional infrared spectroscopy. We excited the energy-donating ester carbonyl stretching vibrational mode and followed the transfer to the energy-accepting benzene ring and cyano stretching vibrations. The complexes with no, one, and two hydrogen-bonded 4CP molecules were studied. Vibrational relaxation of the carbonyl mode is more efficient in both hydrogen-bonded complexes as compared with free MA molecules. The inter-molecular transport in a hydrogen-bonded complex involving a single 4CP molecule is slower than that in a complex with two 4CP molecules. In the former, vibrational relaxation leads to local heating, as shown by the spectroscopy of the carbonyl mode, whereas the local heating is suppressed in the latter because the excitation redistribution is more efficient. At early times, the transfer to the benzene ring is governed by its direct coupling with the energy-donating carbonyl mode, whereas at later times intermediate states are involved. The transfer to a more distant site of the cyano group in 4CP involves intermediate states at all times, since no direct coupling between the energy-donating and accepting modes was observed. We anticipate that our findings will be of importance for spectroscopic studies of bio-molecular structures and dynamics, and inter- and intra-molecular signaling pathways, and for developing molecular networking applications.

  13. Panchromatic Light Capture and Efficient Excitation Transfer Leading to Near-IR Emission of BODIPY Oligomers.

    PubMed

    Sharma, Ritambhara; Gobeze, Habtom B; D'Souza, Francis; Ravikanth, Mangalampalli

    2016-08-18

    All-BODIPY-based (BODIPY=boron-dipyrromethene) donor-acceptor systems capable of wide-band absorbance leading to efficient energy transfer in the near-IR region are reported. A covalently linked 3-pyrrolyl BODIPY-BODIPY dimer building block bearing an ethynyl group at the meso-aryl position is synthesized and coupled with three different monomeric BODIPY/pyrrolyl BODIPY building blocks with a bromo/iodo group under Pd(0) coupling conditions to obtain three covalently linked 3-pyrrolyl-BODIPY-based donor-acceptor oligomers in 19-29 % yield. The oligomers are characterized in detail by 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, and optical spectroscopy. Due to the presence of different functionalized BODIPY derivatives in the oligomers, panchromatic light capture (300-725 nm) is witnessed. Fluorescence studies reveal singlet-singlet energy transfer from BODIPY monomer to BODIPY dimer leading to emission in the 700-800 nm range. Theoretical modeling according to the Förster mechanism predicts ultrafast energy transfer due to good spectral overlap of the donor and acceptor entities. Femtosecond transient absorption studies confirm this to be the case and thus show the relevance of the currently developed all-BODIPY-based energy-funneling supramolecular sytems with near-IR emission to solar-energy harvesting applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Visible to near IR luminescence spectrum of Radachlorin under excitation at 405 nm

    NASA Astrophysics Data System (ADS)

    Belik, V. P.; Gadzhiev, I. M.; Petrenko, M. V.; Petrov, M. A.; Semenova, I. V.; Vasyutinskii, O. S.

    2016-11-01

    The luminescence spectrum of Radachlorin dissolved in water in the 600-1350 nm spectral range excited by 405 nm light has been recorded at the first time. The spectrum contains a wide band with peaks centered at 662, 715, 940, and 1274 nm. Relative contributions to the spectrum from different sources have been evaluated. Ratio of the singlet oxygen signal to the total signal intensity averaged over the 1240-1300 nm spectral range was determined to be 40%. Isolation of the singlet oxygen signal from the total signal at 1274 nm has been achieved by means of a spectral-resolved TCSPC detection technique.

  15. Middle UV to near-IR spectrum of electron-excited SO2

    USGS Publications Warehouse

    Ajello, J.M.; Aguilar, A.; Mangina, R.S.; James, G.K.; Geissler, P.; Trafton, L.

    2008-01-01

    We investigated the electron impact–induced fluorescence spectrum of SO2 to provide excitation cross sections for modeling Io's emission spectrum and analyzing Cassini Imaging Science Subsystem observations. The electron-excited middle-ultraviolet visible optical near-infrared (VOIR) emission spectrum of SO2 gas was generated in the laboratory and studied from 2000 to 11,000 Å at a resolution of Δλ ∼ 2.5 Å full width at half maximum (FWHM). The VOIR laboratory spectrum longward of 6000 Å consists entirely of S I, II and O I, II multiplets for electron impact energies above ∼15 eV. Between 2000 and 6000 Å, we find previously identified molecular bands from both SO and SO2. This work represents a significant improvement in spectral resolution over our earlier work done at 18 Å FWHM. From a measurement of the medium-resolution spectrum, we provide detailed 25- and 100-eV emission cross sections for spectral features from 2000 to 11,000 Å. On the basis of these data, we suggest future ground-based and satellite telescopic observations in the VOIR that are of promise for understanding Io's atmosphere.

  16. Velocity dependent O atom IR excitation cross sections: Connections with flight data

    NASA Astrophysics Data System (ADS)

    Oakes, D. B.; Sonnenfroh, D. M.; Caledonia, G. E.; Blumberg, W. A. M.

    1994-12-01

    A fast oxygen atom source has been used to study the velocity dependence of O atom infrared excitation reactions with various molecular species in a crossed beam experiment. These short wave infrared (SWIR) measurements are performed under single collision conditions, simulating the low Earth orbit environment. Such data are fundamental to the analysis and interpretation of atmospheric oxygen atom interaction with plume exhaust species and with the local environment about structures in low Earth orbit. Measurements have been performed over the oxygen atom velocity range of 6 to 12 km/s. These are the first such experimental measurements, and they may be used to validate theoretical estimates presently used in predictive models. We specifically discuss the velocity dependent cross sections for the reaction O + N2 yields NO(v) + N. This reaction is endothermic for O atom velocities less than or equal tto 8 km/s. Preliminary data are also shown for the reaction O + CO2 yields CO2 nu(sub3) + O yields CO(v) + O2. Both band integral and spectrally resolved results will be presented. The spectrally resolved data provide information on the rotation/vibrational distribution of the excited states. Limited observations of infrared emissions resulting from atmospheric interactions have become available in recent years from both shuttle- and rocket-borne experiments. Comparisons between our experiemental database and selected data from several different flight experiments are provided. These comparisons clearly identify the kinetic mechanisms responsible for the flight observations.

  17. Single photon infrared emission spectroscopy: a study of IR emission from UV laser excited PAHs between 3 and 15 micrometers

    NASA Technical Reports Server (NTRS)

    Cook, D. J.; Schlemmer, S.; Balucani, N.; Wagner, D. R.; Harrison, J. A.; Steiner, B.; Saykally, R. J.

    1998-01-01

    Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-micrometers (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs. Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.

  18. Single photon infrared emission spectroscopy: a study of IR emission from UV laser excited PAHs between 3 and 15 micrometers

    NASA Technical Reports Server (NTRS)

    Cook, D. J.; Schlemmer, S.; Balucani, N.; Wagner, D. R.; Harrison, J. A.; Steiner, B.; Saykally, R. J.

    1998-01-01

    Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-micrometers (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs. Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.

  19. Optical Emission Studies of Copper Plasma Induced Using Infrared Transversely Excited Atmospheric (IR TEA) Carbon Dioxide Laser Pulses.

    PubMed

    Momcilovic, Milos; Kuzmanovic, Miroslav; Rankovic, Dragan; Ciganovic, Jovan; Stoiljkovic, Milovan; Savovic, Jelena; Trtica, Milan

    2015-04-01

    Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm. The effect of surrounding air pressure, in the pressure range 0.1 to 1013 mbar, on plasma formation and its characteristics was investigated. A linear dependence of intensity threshold for plasma formation on logarithm of air pressure was found. Lowering of the air pressure reduces the extent of gas breakdown, enabling better laser-target coupling and thus increases ablation. Optimum air pressure for target plasma formation was 0.1 mbar. Under that pressure, the induced plasma consisted of two clearly distinguished and spatially separated regions. The maximum intensity of emission, with sharp and well-resolved spectral lines and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The estimated excitation temperature in this zone was around 7000 K. The favorable signal to background ratio obtained in this plasma region indicates possible analytical application of TEA CO2 laser produced copper plasma. Detection limits of trace elements present in the Cu sample were on the order of 10 ppm (parts per million). Time-resolved measurements of spatially selected plasma zones were used to find a correlation between the observed spatial position and time delay.

  20. Observation of the long-lived triplet excited state of perylenebisimide (PBI) in C^N cyclometalated Ir(III) complexes and application in photocatalytic oxidation.

    PubMed

    Sun, Jifu; Zhong, Fangfang; Zhao, Jianzhang

    2013-07-14

    Perylenebisimide (PBI) was used to prepare C^N cyclometalated Ir(III) complexes that show strong absorption of visible light and it is the first time the long-lived triplet excited state of PBI chromophore was observed in a transition metal complex (τT = 22.3 μs). Previously, the lifetime of the triplet state of PBI in transition metal complexes was usually shorter than 1.0 μs. Long-lived triplet excited states are useful for applications in photocatalysis or other photophysical processes concerning triplet-triplet-energy-transfer. PBI and amino-PBI were used for preparation of cyclometalated Ir(III) complexes (Ir-2 and Ir-3), in which the PBI chromophore was connected to the coordination center via C≡C π-conjugation bond. The new complexes show strong absorption in visible region (ε = 34,200 M(-1) cm(-1) at 541 nm for Ir-2, and ε = 19,000 at 669 nm for Ir-3), compared to the model complex Ir(ppy)(bpy)[PF6] Ir-1 (ε < 5000 M(-1) cm(-1) in the region beyond 400 nm). The nanosecond time-resolved transient absorption and DFT calculations indicated that PBI-localized long-lived (3)IL states were populated for Ir-2 and Ir-3 upon photoexcitation. The complexes were used as triplet photosensitizers for (1)O2-mediated photooxidation of 1,5-dihydronaphthalene to produce juglone, an important intermediate for preparation of anti-cancer compounds. (1)O2 quantum yields (Φ(Δ)) up to 91% were observed for the new Ir(III) complexes and the overall photosensitizing ability is much higher than the conventional Ir(III) complex Ir-1, which shows the typical weak visible light absorption in visible region. Our results are useful for preparation of transition metal complexes that show strong absorption of visible light and long-lived triplet excited state and for the application of these complexes in photocatalysis.

  1. Infrared Multiple Photon Dissociation Spectroscopy of Sodium and Potassium Chlorate Anions

    SciTech Connect

    Ryan P. Dain; Christopher M. Leavitt; Jos Oomens; Jeffrey D. Steill; Gary S. Groenewold; Michael J. van Stipdonk

    2010-01-01

    The structures of gas-phase, metal chlorate anions with the formula [M(ClO3)2]-, M=Na and K, were determined using tandem mass spectrometry and infrared multiple photon dissociation (IRMPD) spectroscopy. Structural assignments for both anions are based on comparisons of the experimental vibrational spectra for the two species to those predicted by density functional theory and involve conformations that feature either bidentate or tridentate coordination of the cation by chlorate. Our results strongly suggest that a structure in which both chlorate anions are bidentate ligands is preferred for [Na(ClO3)2]-. However, for [K(ClO3)2]- the best agreement between experimental and theoretical spectra is obtained from a composite of predicted spectra for which the chlorate anions are either both bidentate or both tridentate ligands. In general, we find that the overall accuracy of DFT calculations for prediction of IR spectra is dependent on both functional and basis set, with best agreement achieved using frequencies generated at the B3LYP/6-311+g(3df) level of theory.

  2. Infrared multiple photon dissociation spectroscopy of ciprofloxacin: Investigation of the protonation site

    NASA Astrophysics Data System (ADS)

    Bodo, E.; Ciavardini, A.; Giardini, A.; Paladini, A.; Piccirillo, S.; Rondino, F.; Scuderi, D.

    2012-04-01

    The vibrational spectrum of isolated protonated ciprofloxacin was recorded in the range 1100-2000 cm-1 by means of infrared multiple photon dissociation (IRMPD) spectroscopy. The spectrum was obtained by electrospraying a methanol solution of ciprofloxacin in a Paul ion trap, coupled to the tunable IR radiation of a free electron laser. This spectroscopic study has been complemented by quantum chemical calculations at the DFT and MP2 levels of theory to identify the possible structures present under our experimental conditions. Several low-energy isomers with protonation occurring at the piperazinyl amino group and at the carbonyl group are predicted in the energy range 0-84 kJ mol-1. A good agreement between the measured IRMPD spectrum and the calculated absorption spectrum is observed for the isomer protonated at the piperazinyl amino group. This isomer is calculated at MP2 level of theory to lie about 76 kJ/mol above the most stable isomer which is protonated at the quinone carbonyl group. This discrepancy can be rationalized by assuming that the protonation at the piperazinyl amino group, typical of the zwitterionic form that is found in protic solvents, is retained in the ESI process. The vibrational bands observed in the IRMPD spectrum are assigned to normal modes of the isomer protonated at the piperazinyl amino group, with deviations of less than 20 cm-1 between measured and calculated frequencies.

  3. Intramolecular Vibrational Energy Redistribution in 2-Thiocytosine: SH Rotamerization Induced by Near-IR Selective Excitation of NH2 Stretching Overtone.

    PubMed

    Halasa, Anna; Lapinski, Leszek; Rostkowska, Hanna; Nowak, Maciej J

    2015-09-03

    Near-IR-induced transformations, converting one amino-thiol conformer of 2-thiocytosine into another, were observed for monomers of the compound isolated in Ne, Ar, and N2 low-temperature matrixes. The two conformers involved in this phototransformation differ from each other by 180° rotation of the SH group. To induce the conversion, conformers of 2-thiocytosine were selectively excited to the overtone (or combination) NH2 stretching vibrational states, using very narrowband (fwhm <1 MHz) near-IR light generated in a tunable diode laser. The conformational changes were monitored by IR spectroscopy. The conformational transformation observed in the current work provides a clear evidence of the vibrational energy redistribution from the initially excited NH2 moiety to the remote SH group that changes its orientation.

  4. Raman spectroscopic signature of fractionalized excitations in the harmonic-honeycomb iridates β- and γ-Li2IrO3

    PubMed Central

    Glamazda, A.; Lemmens, P.; Do, S. -H.; Choi, Y. S.; Choi, K. -Y.

    2016-01-01

    The fractionalization of elementary excitations in quantum spin systems is a central theme in current condensed matter physics. The Kitaev honeycomb spin model provides a prominent example of exotic fractionalized quasiparticles, composed of itinerant Majorana fermions and gapped gauge fluxes. However, identification of the Majorana fermions in a three-dimensional honeycomb lattice remains elusive. Here we report spectroscopic signatures of fractional excitations in the harmonic-honeycomb iridates β- and γ-Li2IrO3. Using polarization-resolved Raman spectroscopy, we find that the dynamical Raman response of β- and γ-Li2IrO3 features a broad scattering continuum with distinct polarization and composition dependence. The temperature dependence of the Raman spectral weight is dominated by the thermal damping of fermionic excitations. These results suggest the emergence of Majorana fermions from spin fractionalization in a three-dimensional Kitaev–Heisenberg system. PMID:27457278

  5. Probing single magnon excitations in Sr2IrO4 using O K-edge resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Liu, X.; Dean, M. P. M.; Liu, J.; Chiuzbăian, S. G.; Jaouen, N.; Nicolaou, A.; Yin, W. G.; Rayan Serrao, C.; Ramesh, R.; Ding, H.; Hill, J. P.

    2015-05-01

    Resonant inelastic x-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin-orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr2IrO4, where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edge RIXS energy resolution in the hard x-ray region is usually poor.

  6. A cyclometallated fluorenyl Ir(iii) complex as a potential sensitiser for two-photon excited photodynamic therapy (2PE-PDT).

    PubMed

    Boreham, Elizabeth M; Jones, Lucy; Swinburne, Adam N; Blanchard-Desce, Mireille; Hugues, Vincent; Terryn, Christine; Miomandre, Fabien; Lemercier, Gilles; Natrajan, Louise S

    2015-09-28

    A new Ir(iii) cyclometallated complex bearing a fluorenyl 5-substituted-1,10-phenanthroline ligand ([Ir(ppy)2()][PF6], ppy = 2-phenylpyridine) is presented which exhibits enhanced triplet oxygen sensing properties. The efficacy of this complex to act as a photosensitiser for altering the morphology of C6 Glioma cells that represent malignant nervous tumours has been evaluated. The increased heavy metal effect and related spin-orbit coupling parameters on the photophysical properties of this complex are evidenced by comparison with Ru(ii) analogues. The complex [Ir(ppy)2()][PF6] is shown to exhibit relatively high two-photon absorption efficiencies for the lowest energy MLCT electronic transitions with two-photon absorption cross sections that range from 50 to 80 Goeppert-Mayer units between 750 to 800 nm. Quantum yields for the complex were measured up to 23% and the Stern-Volmer quenching constant, KSV was determined to be 40 bar(-1) in acetonitrile solution, confirming the high efficiency of the complex as a triplet oxygen sensitiser. Preliminary in vitro experiments with C6 Glioma cells treated with [Ir(ppy)2()][PF6], show that the complex is an efficient sensitizer for triplet oxygen, producing cytotoxic singlet oxygen ((1)O2) by two-photon excitation at 740 nm resulting in photodynamic effects that lead to localised cell damage and death.

  7. Long-lived room-temperature deep-red-emissive intraligand triplet excited state of naphthalimide in cyclometalated Ir(III) complexes and its application in triplet-triplet annihilation-based upconversion.

    PubMed

    Sun, Jifu; Wu, Wanhua; Zhao, Jianzhang

    2012-06-25

    Cyclometalated Ir(III) complexes with acetylide ppy and bpy ligands were prepared (ppy = 2-phenylpyridine, bpy = 2,2'-bipyridine) in which naphthal (Ir-2) and naphthalimide (NI) were attached onto the ppy (Ir-3) and bpy ligands (Ir-4) through acetylide bonds. [Ir(ppy)(3)] (Ir-1) was also prepared as a model complex. Room-temperature phosphorescence was observed for the complexes; both neutral and cationic complexes Ir-3 and Ir-4 showed strong absorption in the visible range (ε=39,600  M(-1)  cm(-1) at 402 nm and ε=25,100  M(-1)  cm(-1) at 404 nm, respectively), long-lived triplet excited states (τ(T)=9.30 μs and 16.45 μs) and room-temperature red emission (λ(em)=640 nm, Φ(p)=1.4 % and λ(em)=627 nm, Φ(p)=0.3 %; cf. Ir-1: ε=16,600  M(-1)  cm(-1) at 382 nm, τ(em)=1.16 μs, Φ(p)=72.6 %). Ir-3 was strongly phosphorescent in non-polar solvent (i.e., toluene), but the emission was completely quenched in polar solvents (MeCN). Ir-4 gave an opposite response to the solvent polarity, that is, stronger phosphorescence in polar solvents than in non-polar solvents. Emission of Ir-1 and Ir-2 was not solvent-polarity-dependent. The T(1) excited states of Ir-2, Ir-3, and Ir-4 were identified as mainly intraligand triplet excited states ((3)IL) by their small thermally induced Stokes shifts (ΔE(s)), nanosecond time-resolved transient difference absorption spectroscopy, and spin-density analysis. The complexes were used as triplet photosensitizers for triplet-triplet annihilation (TTA) upconversion and quantum yields of 7.1 % and 14.4 % were observed for Ir-2 and Ir-3, respectively, whereas the upconversion was negligible for Ir-1 and Ir-4. These results will be useful for designing visible-light-harvesting transition-metal complexes and for their applications as triplet photosensitizers for photocatalysis, photovoltaics, TTA upconversion, etc. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Excitation and dissociation of molecules by femtosecond IR laser radiation in the gas phase and on dielectric surfaces

    SciTech Connect

    Kompanets, V O; Laptev, Vladimir B; Makarov, Aleksandr A; Pigulskii, S V; Ryabov, Evgenii A; Chekalin, Sergei V

    2013-04-30

    This paper presents an overview of early studies and new experimental data on the effect of near-IR (0.8-1.8 {mu}m) and mid-IR (3.3-5.8 {mu}m) intense femtosecond (130-350 fs) laser pulses on polyatomic molecules in the gas phase and on the surface of substrates. We examine the vibrational dynamics of nine molecules containing a C=O chromophore group, which are initiated by resonance femtosecond IR laser radiation at a wavelength of {approx}5 {mu}m, and report measured characteristic times of intramolecular vibrational redistribution. The characteristic time of molecules containing a single C=O group lies in the range 2.4-20 ps and that of the Fe(CO){sub 5} and Cr(CO){sub 6} molecules lies in the nanosecond range ({approx}1.0 and {approx}1.5 ns, respectively). Carbon structures have been observed for the first time to result from the decomposition of (CF{sub 3}){sub 2}CCO molecules on the surface of metal fluorides under the effect of femtosecond IR laser radiation in the wavelength range 3.3-5.4 {mu}m with no gas-phase decomposition of the molecules. (extreme light fields and their applications)

  9. Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Studies of Triethyl Phosphate Complexes: Effects of Protonation and Sodium Cationization on Structure

    NASA Astrophysics Data System (ADS)

    Fales, B. S.; Fujamade, N. O.; Oomens, J.; Rodgers, M. T.

    2011-10-01

    The gas-phase structures of protonated and sodium cationized complexes of triethyl phosphate, [TEP + H]+ and [TEP + Na]+, are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer with an electrospray ionization source, and theoretical electronic structure calculations. Measured IRMPD action spectra are compared to linear IR spectra calculated at the B3LYP/6-31 G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral TEP are also performed. Sodium cationization and protonation produce changes in the central phosphate geometry, including an increase in the alkoxy ∠OPO bond angle and shortening of the alkoxy P-O bond. Changes associated with protonation are more pronounced than those produced by sodium cationization.

  10. Continuous-variable quantum teleportation with non-Gaussian entangled states generated via multiple-photon subtraction and addition

    NASA Astrophysics Data System (ADS)

    Wang, Shuai; Hou, Li-Li; Chen, Xian-Feng; Xu, Xue-Fen

    2015-06-01

    We theoretically analyze the Einstein-Podolsky-Rosen (EPR) correlation, the quadrature squeezing, and the continuous-variable quantum teleportation when considering non-Gaussian entangled states generated by applying multiple-photon subtraction and multiple-photon addition to a two-mode squeezed vacuum state (TMSVs). Our results indicate that in the case of the multiple-photon-subtracted TMSVs with symmetric operations, the corresponding EPR correlation, the two-mode squeezing degree, the sum squeezing, and the fidelity of teleporting a coherent state or a squeezed vacuum state can be enhanced for any squeezing parameter r and these enhancements increase with the number of subtracted photons in the low-squeezing regime, while asymmetric multiple-photon subtractions will generally reduce these quantities. For the multiple-photon-added TMSVs, although it holds stronger entanglement, its EPR correlation, two-mode squeezing, sum squeezing, and the fidelity of a coherent state are always smaller than that of the TMSVs. Only when considering the case of teleporting a squeezed vacuum state does the symmetric photon addition make somewhat of an improvement in the fidelity for large-squeezing parameters. In addition, we analytically prove that a one-mode multiple-photon-subtracted TMSVs is equivalent to that of the one-mode multiple-photon-added one. And one-mode multiple-photon operations will diminish the above four quantities for any squeezing parameter r .

  11. Near-IR emission of Er3+ ions in CsCl-Ga-Ge-S glasses excited by visible light

    NASA Astrophysics Data System (ADS)

    Bunton, J.; Calvez, L.; Kadan, V.; Blonskyi, I.; Shpotyuk, O.; Golovchak, R.

    2017-10-01

    Fluorescence of 65GeS2-25Ga2S3-10CsCl glasses doped with Er has been investigated at room and liquid nitrogen temperatures. Strong emission lines at ∼1 and ∼1.5 μm are observed at room temperature in Er-doped samples when excited with ∼530 nm wavelength. At cryogenic temperature, this fluorescence is observed even at lower excitation wavelengths (∼400-450 nm). The other observed emission and absorption lines agree well with known energy level transitions of Er3+ ions incorporated in the glass matrix and temperature behavior of absorption spectra. The difference between room and liquid nitrogen temperature up-conversion emission is observed under femtosecond pulsed 800 nm laser excitation.

  12. The near-IR spectrum of NO(X̃(2)Π)-Ne detected through excitation into the Ã-state continuum: A joint experimental and theoretical study.

    PubMed

    Kłos, J; Zhang, S G; Meyer, H

    2016-03-21

    We present new measurements of the near IR spectrum of NO-Ne in the region of the first NO overtone transition. The IR absorption is detected by exciting the vibrationally excited complex to the Ã-state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. Spectra of the two lowest bands, A and B, are recorded. The spectra are compared with calculated spectra based on bound states derived from a new set of high level ab initio potential energy surfaces (PESs). For the calculation, the PESs are used with either fixed NO intermolecular distance or averaged for the vibrational states of NO (X̃, v = 0 or 2). Spectra based on the new PESs reproduce the experimental spectra better than theoretical spectra based on the older PESs of M. H. Alexander et al. [J. Chem. Phys. 114, 5588 (2001)]. Especially, spectra based on the two different vibrationally averaged PESs show a marked improvement in comparison to the one based on the fixed internuclear NO-distance. A fitted set of spectroscopic constants allows to reproduce most of the finer details of the measured spectra. Monitoring simultaneously the NO fragment ion and the parent ion channels while scanning the UV wavelength through the NO A-X hot-band region enabled us to confirm the NO-Ne Ã-state dissociation limit of 44233 ± 5 cm(-1). These measurements also confirm the absence of a structured NO-Ne spectrum involving the Ã-state.

  13. The near-IR spectrum of NO(X˜ 2Π )-Ne detected through excitation into the Östate continuum: A joint experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Kłos, J.; Zhang, S. G.; Meyer, H.

    2016-03-01

    We present new measurements of the near IR spectrum of NO-Ne in the region of the first NO overtone transition. The IR absorption is detected by exciting the vibrationally excited complex to the A ˜ -state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. Spectra of the two lowest bands, A and B, are recorded. The spectra are compared with calculated spectra based on bound states derived from a new set of high level ab initio potential energy surfaces (PESs). For the calculation, the PESs are used with either fixed NO intermolecular distance or averaged for the vibrational states of NO (X ˜ , v = 0 or 2). Spectra based on the new PESs reproduce the experimental spectra better than theoretical spectra based on the older PESs of M. H. Alexander et al. [J. Chem. Phys. 114, 5588 (2001)]. Especially, spectra based on the two different vibrationally averaged PESs show a marked improvement in comparison to the one based on the fixed internuclear NO-distance. A fitted set of spectroscopic constants allows to reproduce most of the finer details of the measured spectra. Monitoring simultaneously the NO fragment ion and the parent ion channels while scanning the UV wavelength through the NO A-X hot-band region enabled us to confirm the NO-Ne A ˜ -state dissociation limit of 44233 ± 5 cm-1. These measurements also confirm the absence of a structured NO-Ne spectrum involving the A ˜ -state.

  14. Excited-state distortions of cyclometalated Ir(III) complexes determined from the vibronic structure in luminescence spectra.

    PubMed

    Wang, Xianghuai; Li, Jian; Thompson, Mark E; Zink, Jeffrey I

    2007-05-03

    The luminescence spectra of [(tpy)(2)Ir(CN-t-Bu)2](CF(3)SO(3)) in methylcyclohexane glass and frozen n-nonane at 15 K reveal well-resolved vibronic fine structure. The vibronic peaks are assigned by comparison with the vibrational frequencies obtained from Raman and IR spectra and those obtained using DFT electronic structure calculations. The magnitudes of the distortions along the normal coordinates are calculated by fitting the emission spectra using the time-dependent theory of spectroscopy. Broadening effects and the MIME frequency observed at room temperature are interpreted. The most highly distorted normal modes involve atomic motions on the tpy ligand, consistent with the metal to ligand/ligand centered assignment of the electronic transition.

  15. Vortexlike excitations in the heavy-fermion superconductor CeIrIn5

    SciTech Connect

    Luo, Yongkang; Rosa, P. F. S.; Bauer, E. D.; Thompson, J. D.

    2016-05-05

    Here, we report a systematic study of temperature- and field-dependent charge (ρ) and entropy (S) transport in the heavy-fermion superconductor CeIrIn5. Its large positive thermopower Sxx is typical of Ce-based Kondo lattice systems, and strong electronic correlations play an important role in enhancing the Nernst signal Sxy. By separating the off-diagonal Peltier coefficient αxy from Sxy, we find that αxy becomes positive and greatly enhanced at temperatures well above the bulk Tc. Compared with the nonmagnetic analog LaIrIn5, these results suggest vortexlike excitations in a precursor state to unconventional superconductivity in CeIrIn5. This study sheds light on the similarity of heavy-fermion and cuprate superconductors and on the possibility of states not characterized by the amplitude of an order parameter.

  16. Vortexlike excitations in the heavy-fermion superconductor CeIrIn5

    SciTech Connect

    Luo, Yongkang; Rosa, P. F. S.; Bauer, E. D.; Thompson, J. D.

    2016-05-05

    Here, we report a systematic study of temperature- and field-dependent charge (ρ) and entropy (S) transport in the heavy-fermion superconductor CeIrIn5. Its large positive thermopower Sxx is typical of Ce-based Kondo lattice systems, and strong electronic correlations play an important role in enhancing the Nernst signal Sxy. By separating the off-diagonal Peltier coefficient αxy from Sxy, we find that αxy becomes positive and greatly enhanced at temperatures well above the bulk Tc. Compared with the nonmagnetic analog LaIrIn5, these results suggest vortexlike excitations in a precursor state to unconventional superconductivity in CeIrIn5. This study sheds light on the similarity of heavy-fermion and cuprate superconductors and on the possibility of states not characterized by the amplitude of an order parameter.

  17. IR/UV spectroscopy on jet cooled 3-hydroxyflavone (H2O)n (n=1,2) clusters along proton transfer coordinates in the electronic ground and excited states

    NASA Astrophysics Data System (ADS)

    Bartl, K.; Funk, A.; Gerhards, M.

    2008-12-01

    The structure and reactivity of isolated 3-hydroxyflavone (3-HF) aggregates with one and two water molecules has been investigated by applying combined infrared/ultraviolet (IR/UV) spectroscopy in a supersonic jet both for the electronic ground and excited states. In combination with density functional theory (DFT) calculations, the IR spectra of the S0 states recorded from the upper fingerprint region to the OH stretching vibrations are assigned to the most stable isomers of the clusters. For the first electronically excited (ππ∗) state of the 3-HF(H2O)2 cluster structural information are obtained from the IR spectra in combination with time-dependent-DFT (TD-DFT) calculations. No proton transfer structure is observed in the case of a low excess energy within the electronically excited state. By raising the excitation energy, additional bands appear that can be assigned to a tautomeric form indicating the induction of a proton transfer reaction.

  18. High resolution IR diode laser study of collisional energy transfer between highly vibrationally excited monofluorobenzene and CO2: the effect of donor fluorination on strong collision energy transfer.

    PubMed

    Kim, Kilyoung; Johnson, Alan M; Powell, Amber L; Mitchell, Deborah G; Sevy, Eric T

    2014-12-21

    Collisional energy transfer between vibrational ground state CO2 and highly vibrationally excited monofluorobenzene (MFB) was studied using narrow bandwidth (0.0003 cm(-1)) IR diode laser absorption spectroscopy. Highly vibrationally excited MFB with E' = ∼41,000 cm(-1) was prepared by 248 nm UV excitation followed by rapid radiationless internal conversion to the electronic ground state (S1→S0*). The amount of vibrational energy transferred from hot MFB into rotations and translations of CO2 via collisions was measured by probing the scattered CO2 using the IR diode laser. The absolute state specific energy transfer rate constants and scattering probabilities for single collisions between hot MFB and CO2 were measured and used to determine the energy transfer probability distribution function, P(E,E'), in the large ΔE region. P(E,E') was then fit to a bi-exponential function and extrapolated to the low ΔE region. P(E,E') and the biexponential fit data were used to determine the partitioning between weak and strong collisions as well as investigate molecular properties responsible for large collisional energy transfer events. Fermi's Golden rule was used to model the shape of P(E,E') and identify which donor vibrational motions are primarily responsible for energy transfer. In general, the results suggest that low-frequency MFB vibrational modes are primarily responsible for strong collisions, and govern the shape and magnitude of P(E,E'). Where deviations from this general trend occur, vibrational modes with large negative anharmonicity constants are more efficient energy gateways than modes with similar frequency, while vibrational modes with large positive anharmonicity constants are less efficient at energy transfer than modes of similar frequency.

  19. IR Transition Moments and Collisional Dynamics of Vibrationally Excited OH Radicals via Time-Resolved Laser Absorption Spectroscopy

    DTIC Science & Technology

    1990-03-30

    reactions such as OH + RH - H 20 + R which is an important step in both combustive as well as atmospheric oxidation of hydrocarbons. The flash kinetic IR...communication). 19. R. D. Kenner, F. Rohrer, Th. Papenbrock, and F. Stuhl, J. Phys. Chem. 90, 1294 (1986). 20. G. S. Jolly, D. L. Singleton , D. J. McKerney...and G. Paraskevopoulos, J. Chem. Phys. 84, 6662 (1986); A. R. Ravishankara, F. L. Elsele, and P. H. Wine , J. Phys. Chem. 86, 1854 (1982); H. S

  20. Electronic excitations and structure of Li{sub 2}IrO{sub 3} thin films grown on ZrO{sub 2}:Y (001) substrates

    SciTech Connect

    Jenderka, Marcus Schmidt-Grund, Rüdiger; Grundmann, Marius; Lorenz, Michael

    2015-01-14

    Thin films are a prerequisite for application of the emergent exotic ground states in iridates that result from the interplay of strong spin-orbit coupling and electronic correlations. We report on pulsed laser deposition of Li{sub 2}IrO{sub 3} films on ZrO{sub 2}:Y (001) single crystalline substrates. X-ray diffraction confirms preferential (001) and (10-1) out-of-plane crystalline orientations with well defined in-plane orientation. Resistivity between 35 and 300 K is dominated by a three-dimensional variable range hopping mechanism. The dielectric function is determined by means of spectroscopic ellipsometry and, complemented by Fourier transform infrared transmission spectroscopy, reveals a small optical gap of ≈300 meV, a splitting of the 5d-t{sub 2g} manifold, and several in-gap excitations attributed to phonons and possibly magnons.

  1. Ultrafast Dynamics of Hydrogen Bond Breaking and Making in the Excited State of Fluoren-9-one: Time-Resolved Visible Pump-IR Probe Spectroscopic Study.

    PubMed

    Ghosh, Rajib; Mora, Aruna K; Nath, Sukhendu; Palit, Dipak K

    2017-02-09

    The fluoren-9-one (FL) molecule, with a single hydrogen bond-accepting site (C═O group), has been used as a probe for investigation of the dynamics of a hydrogen bond in its lowest excited singlet (S1) state using the subpicosecond time-resolved visible pump-IR probe spectroscopic technique. In 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), a strong hydrogen bond-donating solvent, the formation of an FL-alcohol hydrogen-bonded complex in the ground electronic (S0) state is nearly complete, with a negligible concentration of the FL molecule remaining free in solution. In addition to the presence of a band due to the hydrogen-bonded complex in the transient IR spectrum recorded immediately after photoexcitation of FL in HFIP solution, appearance of the absorption band due to a free C═O stretch provides confirmatory evidence of ultrafast photodissociation of hydrogen bonds in some of the complexes formed in the S0 state. The peak-shift dynamics of the C═O stretch bands reveal two major relaxation pathways, namely, vibrational relaxation in the S1 state of the free FL molecules and the solvent reorganization process in the hydrogen-bonded complex. The latter process follows bimodal exponential dynamics involving hydrogen bond-making and hydrogen bond-reorganization processes. The similar lifetimes of the S1 states of the FL molecules, both free and hydrogen-bonded, suggest establishment of a dynamic equilibrium between these two species in the excited state. However, investigations in two other weaker hydrogen bond-donating solvents, namely, trifluoroethanol (TFE) and perdeuterated methanol (CD3OD), reveal different features of peak-shift dynamics because of the prominence of the vibrational relaxation process over the hydrogen bond-reorganization process during the early time.

  2. The near-IR spectrum of NO(X̃(2)Π)-He detected through excitation into the Ã-state continuum: A joint experimental and theoretical study.

    PubMed

    Beutner, V; Zhang, S G; Meyer, H; Kłos, J

    2016-09-28

    We present the first measurement of a bound-state spectrum of the NO-He complex. The recorded spectrum is associated with the first overtone transition of the NO moiety. The IR absorption is detected by exciting the vibrationally excited complex to the Ã-state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. We recorded two bands centered around the NO monomer rotational lines, Q11(0.5) and R11(0.5), consistent with an almost free rotation of the NO fragment within the complex. The origin of the spectrum is found at 3724.06 cm(-1) blue shifted by 0.21 cm(-1) from the corresponding NO monomer origin. The rotational structures of the spectrum are found to be in very good agreement with calculated spectra based on bound states derived from a set of high level ab initio potential energy surfaces [Kłos et al. J. Chem. Phys. 112, 2195 (2000)].

  3. The near-IR spectrum of NO(X˜ 2Π )-He detected through excitation into the A ˜ -state continuum: A joint experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Beutner, V.; Zhang, S. G.; Meyer, H.; Kłos, J.

    2016-09-01

    We present the first measurement of a bound-state spectrum of the NO-He complex. The recorded spectrum is associated with the first overtone transition of the NO moiety. The IR absorption is detected by exciting the vibrationally excited complex to the A ˜ -state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. We recorded two bands centered around the NO monomer rotational lines, Q11(0.5) and R11(0.5), consistent with an almost free rotation of the NO fragment within the complex. The origin of the spectrum is found at 3724.06 cm-1 blue shifted by 0.21 cm-1 from the corresponding NO monomer origin. The rotational structures of the spectrum are found to be in very good agreement with calculated spectra based on bound states derived from a set of high level ab initio potential energy surfaces [Kłos et al. J. Chem. Phys. 112, 2195 (2000)].

  4. Tritium removal from contaminated water via infrared laser multiple-photon dissociation

    SciTech Connect

    Maienschein, J.L.; Magnotta, F.; Herman, I.P.; Aldridge, F.T.; Hsiao, P.

    1983-01-01

    Isotope separation by means of infrared-laser multiple-photon dissociation offers an efficient way to recover tritium from contaminated light or heavy water found in fission and fusion reactors. For tritium recovery from heavy water, chemical exchange of tritium into deuterated chloroform is followed by selective laser dissociation of tritiated chloroform and removal of the tritiated photoproduct, TCl. The single-step separation factor is at least 2700 and is probably greater than 5000. Here we present a description of the tritium recovery process, along with recent accomplishments in photochemical studies and engineering analysis of a recovery system.

  5. Non-linear effects of QED multiple-photon processes on cyclotron spectra

    NASA Technical Reports Server (NTRS)

    Meszaros, P.

    1992-01-01

    The relativistic magnetic resonant multiple-photon processes are discussed up to order alpha(f)exp 2, in particular two-photon scattering and two-photon emission. The latter also contributes to the opacity and photon production, although more weakly than the scattering. These processes are nonlinear in the radiation field, and therefore the transfer depends sensitively on the cross sections. We show model spectra including three cyclotron harmonics for the accreting pulsar Her X-1 and the gamma-ray burster GB880205. The lines are highly polarized, and their depth is sensitive to the polarization treatment.

  6. Molecular structures and excited states of CpM(CO)(2) (Cp = eta(5)-C(5)H(5); M = Rh, Ir) and [Cl(2)Rh(CO)(2)](-). Theoretical evidence for a competitive charge transfer mechanism.

    PubMed

    Hu, Zhenming; Boyd, Russell J; Nakatsuji, Hiroshi

    2002-03-20

    Molecular structures and excited states of CpM(CO)(2) (Cp = eta(5)-C(5)H(5); M = Rh, Ir) and [Cl(2)Rh(CO)(2)](-) complexes have been investigated using the B3LYP and the symmetry-adapted cluster (SAC)/SAC-configuration interaction (SAC-CI) theoretical methods. All the dicarbonyl complexes have singlet ground electronic states with large singlet-triplet separations. Thermal dissociations of CO from the parent dicarbonyls are energetically unfavorable. CO thermal dissociation is an activation process for [Cl(2)Rh(CO)(2)](-) while it is a repulsive potential for CpM(CO)(2). The natures of the main excited states of CpM(CO)(2) and [Cl(2)Rh(CO)(2)](-) are found to be quite different. For [Cl(2)Rh(CO)(2)](-), all the strong transitions are identified to be metal to ligand CO charge transfer (MLCT) excitations. A significant feature of the excited states of CpM(CO)(2) is that both MLCT excitation and a ligand Cp to metal and CO charge transfer excitation are strongly mixed in the higher energy states with the latter having the largest oscillator strength. A competitive charge transfer excited state has therefore been identified theoretically for CpRh(CO)(2) and CpIr(CO)(2). The wavelength dependence of the quantum efficiencies for the photoreactions of CpM(CO)(2) reported by Lees et al. can be explained by the existence of two different types of excited states. The origin of the low quantum efficiencies for the C-H/S-H bond activations of CpM(CO)(2) can be attributed to the smaller proportion of the MLCT excitation in the higher energy states.

  7. INFRARED MULTIPLE-PHOTON PHOTODISSOCIATION OF GAS-PHASE GROUP II METAL-NITRATE ANIONS

    SciTech Connect

    Jos Oomens; Linda Myers; Ryan Dain; Chris Leavitt; Vy Pham; Garold Gresham; Gary Groenewold; Mike Van Stipdonk

    2008-06-01

    Infrared spectra of gas-phase metal-nitrate anions M(NO3)3-, where M=Mg2+, Ca2+, Sr2+ and Ba2+, were recorded by infrared multiple photon dissociation (IRMPD) spectroscopy. Photodissociation of each of the precursors produces NO3- through the elimination of a neutral M(NO3)2 unit. An absorption pattern characteristic of metal nitrates is observed in the IRMPD spectra, including the symmetric and antisymmetric NO3 stretches. The latter is split into high and low frequency components as a result of perturbation of the nitrate symmetry by complexation to the metal ion, and the magnitude of the splitting decreases following the trend Mg2+ > Ca2+ > Sr2+ ? Ba2+. The experimental spectra are in good general agreement with those obtained from density functional theory calculations.

  8. Infrared spectroscopy of hydrated alkali metal cations: Evidence of multiple photon absorption

    NASA Astrophysics Data System (ADS)

    Beck, Jordan P.; Lisy, James M.

    2011-07-01

    Infrared predissociation spectra of M+(H2O)4-7, where M = alkali metal, are presented. Hydrogen bonding O-H stretching features are strongly dependent on which fragmentation channel is monitored. Spectra recorded by monitoring the loss of multiple waters show a preference for one absorption feature in the hydrogen-bonded region centered at ˜3430-3500 cm-1, which is assigned to linear-type hydrogen bonded OH stretches. Cyclic- and bent-type hydrogen bonded OH stretches have diminished photodissociation cross sections in the multiple ligand loss channels. Evidence from Rice-Ramsperger-Kassel-Marcus-evaporative ensemble calculations and laser fluence dependence experiments indicates that the multiple water loss channels are primarily the result of multiple photon absorption which we propose could be due to multiple, independent oscillators within a cluster ion each absorbing a photon during a single, 10 ns laser pulse.

  9. Quasiperiodic one-dimensional photonic crystals with adjustable multiple photonic bandgaps.

    PubMed

    Vyunishev, Andrey M; Pankin, Pavel S; Svyakhovskiy, Sergey E; Timofeev, Ivan V; Vetrov, Stepan Ya

    2017-09-15

    We propose an elegant approach to produce photonic bandgap (PBG) structures with multiple photonic bandgaps by constructing quasiperiodic photonic crystals (QPPCs) composed of a superposition of photonic lattices with different periods. Generally, QPPC structures exhibit both aperiodicity and multiple PBGs due to their long-range order. They are described by a simple analytical expression, instead of quasiperiodic tiling approaches based on substitution rules. Here we describe the optical properties of QPPCs exhibiting two PBGs that can be tuned independently. PBG interband spacing and its depth can be varied by choosing appropriate reciprocal lattice vectors and their amplitudes. These effects are confirmed by the proof-of-concept measurements made for the porous silicon-based QPPC of the appropriate design.

  10. Herschel-PACS Observations of Far-IR CO Line Emission in NGC 1068: Highly Excited Molecular Gas in the Circumnuclear Disk

    NASA Astrophysics Data System (ADS)

    Hailey-Dunsheath, S.; Sturm, E.; Fischer, J.; Sternberg, A.; Graciá-Carpio, J.; Davies, R.; González-Alfonso, E.; Mark, D.; Poglitsch, A.; Contursi, A.; Genzel, R.; Lutz, D.; Tacconi, L.; Veilleux, S.; Verma, A.; de Jong, J. A.

    2012-08-01

    We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 11 transitions in the J upper = 14-30 (E upper/kB = 580-2565 K) range, all of which are consistent with arising from within the central 10'' (700 pc). The detected transitions are modeled as arising from two different components: a moderate-excitation (ME) component close to the galaxy systemic velocity and a high-excitation (HE) component that is blueshifted by ~80 km s-1. We employ a large velocity gradient model and derive n H2 ~ 105.6 cm-3, T kin ~ 170 K, and M H2 ~ 106.7 M ⊙ for the ME component and n H2 ~ 106.4 cm-3, T kin ~ 570 K, and M H2 ~ 105.6 M ⊙ for the HE component, although for both components the uncertainties in the density and mass are ±(0.6-0.9) dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution and find that the ME transitions are consistent with these lines arising in the ~200 pc diameter ring of material traced by H2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H2 ring, but a better kinematic match is found with a clump of infalling gas ~40 pc north of the active galactic nucleus (AGN). We consider potential heating mechanisms and conclude that X-ray- or shock heating of both components is viable, while far-UV heating is unlikely. We discuss the prospects of placing the HE component near the AGN and conclude that while the moderate thermal pressure precludes an association with the ~1 pc radius H2O maser disk, the HE component could potentially be located only a few parsecs more distant from the AGN and might then provide the N H ~ 1025 cm-2 column obscuring the

  11. Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Studies of Diethyl Phosphate Complexes: Effects of Protonation and Sodium Cationization on Structure

    NASA Astrophysics Data System (ADS)

    Fales, B. S.; Fujamade, N. O.; Nei, Y.-W.; Oomens, J.; Rodgers, M. T.

    2011-01-01

    The gas-phase structures of deprotonated, protonated, and sodium-cationized complexes of diethyl phosphate (DEP) including [DEP - H]-, [DEP + H]+, [DEP + Na]+, and [DEP - H + 2Na]+ are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) with an electrospray ionization (ESI) source, and theoretical electronic structure calculations. Measured IRMPD spectra are compared to linear IR spectra calculated at the B3LYP/6-31G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral complexes are also performed. These experiments and calculations suggest that specific geometric changes occur upon the binding of protons and/or sodium cations, including changes correlating to nucleic acid backbone geometry, specifically P-O bond lengths and ∠OPO bond angles. Information from these observations may be used to gain insight into the structures of more complex systems, such as nucleotides and solvated nucleic acids.

  12. Identification of the Excited-State C═C and C═O Modes of trans-β-Apo-8'-carotenal with Transient 2D-IR-EXSY and Femtosecond Stimulated Raman Spectroscopy.

    PubMed

    Di Donato, Mariangela; Ragnoni, Elena; Lapini, Andrea; Kardaś, Tomasz M; Ratajska-Gadomska, Boźena; Foggi, Paolo; Righini, Roberto

    2015-05-07

    Assigning the vibrational modes of molecules in the electronic excited state is often a difficult task. Here we show that combining two nonlinear spectroscopic techniques, transient 2D exchange infrared spectroscopy (T2D-IR-EXSY) and femtosecond stimulated Raman spectroscopy (FSRS), the contribution of the C═C and C═O modes in the excited-state vibrational spectra of trans-β-apo-8'-carotenal can be unambiguously identified. The experimental results reported in this work confirm a previously proposed assignment based on quantum-chemical calculations and further strengthen the role of an excited state with charge-transfer character in the relaxation pathway of carbonyl carotenoids. On a more general ground, our results highlight the potentiality of nonlinear spectroscopic methods based on the combined use of visible and infrared pulses to correlate structural and electronic changes in photoexcited molecules.

  13. Infrared Multiple-Photon Dissociation spectroscopy of group II metal complexes with salicylate

    SciTech Connect

    Ryan P. Dain; Gary Gresham; Gary S. Groenewold; Jeffrey D. Steill; Jos Oomens; Michael J. van Stipdonk

    2011-07-01

    Ion-trap tandem mass spectrometry with collision-induced dissociation, and the combination of infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations were used to characterize singly-charged, 1:1 complexes of Ca2+, Sr2+ and Ba2+ with salicylate. For each metal-salicylate complex, the CID pathways are: (a) elimination of CO2 and (b) formation of [MOH]+ where M=Ca2+, Sr2+ or Ba2+. DFT calculations predict three minima for the cation-salicylate complexes which differ in the mode of metal binding. In the first, the metal ion is coordinated by O atoms of the (neutral) phenol and carboxylate groups of salicylate. In the second, the cation is coordinated by phenoxide and (neutral) carboxylic acid groups. The third mode involves coordination by the carboxylate group alone. The infrared spectrum for the metal-salicylate complexes contains a number of absorptions between 1000 – 1650 cm-1, and the best correlation between theoretical and experimental spectra for the structure that features coordination of the metal ion by phenoxide and the carbonyl group of the carboxylic acid group, consistent with calculated energies for the respective species.

  14. Excited-state characters and dynamics of [W(CO)(5)(4-cyanopyridine)] and [W(CO)(5)(piperidine)] studied by picosecond time-resolved IR and resonance Raman spectroscopy and DFT calculations: roles of W --> L and W --> CO MLCT and LF excited states revised.

    PubMed

    Zális, Stanislav; Busby, Michael; Kotrba, Tomás; Matousek, Pavel; Towrie, Mike; Vlcek, Antonín

    2004-03-08

    The characters, dynamics, and relaxation pathways of low-lying excited states of the complexes [W(CO)(5)L] [L = 4-cyanopyridine (pyCN) and piperidine (pip)] were investigated using theoretical and spectroscopic methods. DFT calculations revealed the delocalized character of chemically and spectroscopicaly relevant molecular orbitals and the presence of a low-lying manifold of CO pi-based unoccupied molecular orbitals. Traditional ligand-field arguments are not applicable. The lowest excited states of [W(CO)(5)(pyCN)] are W --> pyCN MLCT in character. They are closely followed in energy by W --> CO MLCT states. Excitation at 400 or 500 nm populates the (3)MLCT(pyCN) excited state, which was characterized by picosecond time-resolved IR and resonance Raman spectroscopy. Excited-state vibrations were assigned using DFT calculations. The (3)MLCT(pyCN) excited state is initially formed highly excited in low-frequency vibrations which cool with time constants between 1 and 20 ps, depending on the excitation wavelength, solvent, and particular high-frequency nu(CO) or nu(CN) mode. The lowest excited states of [W(CO)(5)(pip)] are W --> CO MLCT, as revealed by TD-DFT interpretation of a nanosecond time-resolved IR spectrum that was measured earlier in a low-temperature glass (Johnson, F. P. A.; George, M. W.; Morrison, S. L.; Turner, J. J. J. Chem. Soc., Chem. Commun. 1995, 391-393). MLCT(CO) excitation involves transfer of electron density from the W atom and, to a lesser extent, the trans CO to the pi orbitals of the four cis CO ligands. Optical excitation into MLCT(CO) transition of either complex in fluid solution triggers femtosecond dissociation of a W-N bond, producing [W(CO)(5)(solvent)]. It is initially vibrationally excited both in nu(CO) and anharmonicaly coupled low-frequency modes. Vibrational cooling occurs with time constants of 16-22 ps while the intramolecular vibrational energy redistribution from the v = 1 nu(CO) modes is much slower, 160-220 ps. No LF

  15. Structure Determination of Ornithine-Linked Cisplatin by Infrared Multiple Photon Dissociation Action Spectroscopy

    NASA Astrophysics Data System (ADS)

    He, Chenchen; Kimutai, Bett; Hamlow, Lucas; Roy, Harrison; Nei, Y.-W.; Bao, Xun; Gao, Juehan; Martens, Jonathan K.; Berden, Giel; Oomens, Jos; Maitre, Philippe; Steinmetz, Vincent; McNary, Christopher P.; Armentrout, Peter B.; Chow, C. S.; Rodgers, M. T.

    2016-06-01

    Cisplatin [(NH_3)_2PtCl_2], the first FDA-approved platinum-based anticancer drug, has been widely used in cancer chemotherapy. Its pharmacological mechanism has been identified as its ability to coordinate to genomic DNA with guanine as its major target. Amino acid-linked cisplatin derivatives are being investigated as alternatives for cisplatin that may exhibit altered binding selectivity such as that found for ornithine-linked cisplatin (Ornplatin, [(Orn)PtCl_2]), which exhibits a preference for adenine over guanine in RNA. Infrared multiple photon dissociation (IRMPD) action spectroscopy experiments and complementary electronic structure calculations are performed on a series of Ornplatin complexes to elucidate the nature of binding of the Orn amino acid to the Pt center and how that binding is influenced by the local environment. The complexes examined in the work include: [(Orn-H)PtCl_2]-, [(Orn)PtCl]+, [(Orn)Pt(H_2O)Cl]+, and [(Orn)PtCl_2+Na]+. In contrast to that found previously for the glycine-linked cisplatin complex (Glyplatin), which binds via the backbone amino and carboxylate groups, binding of Orn in these complexes is found to involve both the backbone and sidechain amino groups. Extensive broadening of the IRMPD spectrum for the [(Orn)Pt(H_2O)Cl]+ complex suggests that either multiple structures are contributing to the measured spectrum or strong intra-molecular hydrogen-binding interactions are present. The results for Ornplatin lead to an interesting discussion about the differences in selectivity and reactivity versus cisplatin.

  16. Structure Determination of Cisplatin-Amino Acid Analogues by Infrared Multiple Photon Dissociation Action Spectroscopy

    NASA Astrophysics Data System (ADS)

    He, Chenchen; Bao, Xun; Zhu, Yanlong; Strobehn, Stephen; Kimutai, Bett; Nei, Y.-W.; Chow, C. S.; Rodgers, M. T.; Gao, Juehan; Oomens, J.

    2015-06-01

    To gain a better understanding of the binding mechanism and assist in the optimization of relevant drug and chemical probe design, both experimental and theoretical studies were performed on a series of amino acid-linked cisplatin derivatives, including glycine-, lysine-, and ornithine-linked cisplatin, Gplatin, Kplatin, and Oplatin, respectively. Cisplatin, the first FDA-approved platinum-based anticancer drug, has been widely used in cancer chemotherapy. Its pharmacological mechanism has been identified as its ability to coordinate to genomic DNA, and guanine is its major target. In previous reports, cisplatin was successfully utilized as a chemical probe to detect solvent accessible sites in ribosomal RNA (rRNA). Among the amino-acid-linked cisplatin derivatives, Oplatin exhibits preference for adenine over guanine. The mechanism behind its different selectivity compared to cisplatin may relate to its potential of forming a hydrogen bond between the carboxylate group in Pt (II) complex and the 6-amino moiety of adenosine stabilizes A-Oplatin products. Tandem mass spectrometry analysis also indicates that different coordination sites of Oplatin on adenosine affect glycosidic bond stability. Infrared multiple photon dissociation (IRMPD) action spectroscopy experiments were performed on all three amino acid-linked cisplatin to characterize their structures. An extensive theoretical study has been performed on Gplatin to guide the selection of the most effective theory and basis set based on its geometric information. The results for Gplatin provide the foundation for characterization of the more complex amino acid-linked cisplatin derivatives, Oplatin and Kplatin. Structural and energetic information elucidated for these compounds, particularly Oplatin reveal the reason for its alternative selectivity compared to cisplatin.

  17. Differentiation of closely related isomers: application of data mining techniques in conjunction with variable wavelength infrared multiple photon dissociation mass spectrometry for identification of glucose-containing disaccharide ions.

    PubMed

    Stefan, Sarah E; Ehsan, Mohammad; Pearson, Wright L; Aksenov, Alexander; Boginski, Vladimir; Bendiak, Brad; Eyler, John R

    2011-11-15

    Data mining algorithms have been used to analyze the infrared multiple photon dissociation (IRMPD) patterns of gas-phase lithiated disaccharide isomers irradiated with either a line-tunable CO(2) laser or a free electron laser (FEL). The IR fragmentation patterns over the wavelength range of 9.2-10.6 μm have been shown in earlier work to correlate uniquely with the asymmetry at the anomeric carbon in each disaccharide. Application of data mining approaches for data analysis allowed unambiguous determination of the anomeric carbon configurations for each disaccharide isomer pair using fragmentation data at a single wavelength. In addition, the linkage positions were easily assigned. This combination of wavelength-selective IRMPD and data mining offers a powerful and convenient tool for differentiation of structurally closely related isomers, including those of gas-phase carbohydrate complexes.

  18. High resolution IR diode laser study of collisional energy transfer between highly vibrationally excited monofluorobenzene and CO{sub 2}: The effect of donor fluorination on strong collision energy transfer

    SciTech Connect

    Kim, Kilyoung; Johnson, Alan M.; Powell, Amber L.; Mitchell, Deborah G.; Sevy, Eric T.

    2014-12-21

    Collisional energy transfer between vibrational ground state CO{sub 2} and highly vibrationally excited monofluorobenzene (MFB) was studied using narrow bandwidth (0.0003 cm{sup −1}) IR diode laser absorption spectroscopy. Highly vibrationally excited MFB with E′ = ∼41 000 cm{sup −1} was prepared by 248 nm UV excitation followed by rapid radiationless internal conversion to the electronic ground state (S{sub 1}→S{sub 0}*). The amount of vibrational energy transferred from hot MFB into rotations and translations of CO{sub 2} via collisions was measured by probing the scattered CO{sub 2} using the IR diode laser. The absolute state specific energy transfer rate constants and scattering probabilities for single collisions between hot MFB and CO{sub 2} were measured and used to determine the energy transfer probability distribution function, P(E,E′), in the large ΔE region. P(E,E′) was then fit to a bi-exponential function and extrapolated to the low ΔE region. P(E,E′) and the biexponential fit data were used to determine the partitioning between weak and strong collisions as well as investigate molecular properties responsible for large collisional energy transfer events. Fermi's Golden rule was used to model the shape of P(E,E′) and identify which donor vibrational motions are primarily responsible for energy transfer. In general, the results suggest that low-frequency MFB vibrational modes are primarily responsible for strong collisions, and govern the shape and magnitude of P(E,E′). Where deviations from this general trend occur, vibrational modes with large negative anharmonicity constants are more efficient energy gateways than modes with similar frequency, while vibrational modes with large positive anharmonicity constants are less efficient at energy transfer than modes of similar frequency.

  19. Simulation of multi-photon emission isotopes using time-resolved SimSET multiple photon history generator

    SciTech Connect

    Chiang, Chih-Chieh; Lin, Hsin-Hon; Lin, Chang-Shiun; Chuang, Keh-Shih; Jan, Meei-Ling

    2015-07-01

    Abstract-Multiple-photon emitters, such as In-111 or Se-75, have enormous potential in the field of nuclear medicine imaging. For example, Se-75 can be used to investigate the bile acid malabsorption and measure the bile acid pool loss. The simulation system for emission tomography (SimSET) is a well-known Monte Carlo simulation (MCS) code in nuclear medicine for its high computational efficiency. However, current SimSET cannot simulate these isotopes due to the lack of modeling of complex decay scheme and the time-dependent decay process. To extend the versatility of SimSET for simulation of those multi-photon emission isotopes, a time-resolved multiple photon history generator based on SimSET codes is developed in present study. For developing the time-resolved SimSET (trSimSET) with radionuclide decay process, the new MCS model introduce new features, including decay time information and photon time-of-flight information, into this new code. The half-life of energy states were tabulated from the Evaluated Nuclear Structure Data File (ENSDF) database. The MCS results indicate that the overall percent difference is less than 8.5% for all simulation trials as compared to GATE. To sum up, we demonstrated that time-resolved SimSET multiple photon history generator can have comparable accuracy with GATE and keeping better computational efficiency. The new MCS code is very useful to study the multi-photon imaging of novel isotopes that needs the simulation of lifetime and the time-of-fight measurements. (authors)

  20. Efficient simulation of voxelized phantom in GATE with embedded SimSET multiple photon history generator

    NASA Astrophysics Data System (ADS)

    Lin, Hsin-Hon; Chuang, Keh-Shih; Lin, Yi-Hsing; Ni, Yu-Ching; Wu, Jay; Jan, Meei-Ling

    2014-10-01

    GEANT4 Application for Tomographic Emission (GATE) is a powerful Monte Carlo simulator that combines the advantages of the general-purpose GEANT4 simulation code and the specific software tool implementations dedicated to emission tomography. However, the detailed physical modelling of GEANT4 is highly computationally demanding, especially when tracking particles through voxelized phantoms. To circumvent the relatively slow simulation of voxelized phantoms in GATE, another efficient Monte Carlo code can be used to simulate photon interactions and transport inside a voxelized phantom. The simulation system for emission tomography (SimSET), a dedicated Monte Carlo code for PET/SPECT systems, is well-known for its efficiency in simulation of voxel-based objects. An efficient Monte Carlo workflow integrating GATE and SimSET for simulating pinhole SPECT has been proposed to improve voxelized phantom simulation. Although the workflow achieves a desirable increase in speed, it sacrifices the ability to simulate decaying radioactive sources such as non-pure positron emitters or multiple emission isotopes with complex decay schemes and lacks the modelling of time-dependent processes due to the inherent limitations of the SimSET photon history generator (PHG). Moreover, a large volume of disk storage is needed to store the huge temporal photon history file produced by SimSET that must be transported to GATE. In this work, we developed a multiple photon emission history generator (MPHG) based on SimSET/PHG to support a majority of the medically important positron emitters. We incorporated the new generator codes inside GATE to improve the simulation efficiency of voxelized phantoms in GATE, while eliminating the need for the temporal photon history file. The validation of this new code based on a MicroPET R4 system was conducted for 124I and 18F with mouse-like and rat-like phantoms. Comparison of GATE/MPHG with GATE/GEANT4 indicated there is a slight difference in energy

  1. Deuterium separation at high pressure by nanosecond CO2 laser multiple-photon dissociation

    NASA Astrophysics Data System (ADS)

    Marling, Jack B.; Herman, Irving P.; Thomas, Scott J.

    1980-05-01

    Photochemical deuterium separation is evaluated at pressures up to 1 atm using 2 ns duration CO2 laser pulses to achieve multiple-photon dissociation (MPD) as the isotopic separation step. Photochemical performance is compared for Freon 123 (2,2-dichloro-1,1,1-trifluoroethane), difluoromethane, and trifluoromethane based on deuterium optical selectivity in absorption, photoproduct yield, and single-step deuterium enrichment factor. The absorption coefficient versus energy fluence is measured from 0.01 to 3 J/cm2 fluence for CF3CDCl2, CDF3, and CHDF2; added buffer gas results in an order-of-magnitude increase in the CDF3 absorption coefficient. The deuterium optical selectivity in absorption at 0.5 J/cm2 fluence with added buffer is 80 for CF3CDCl2 at 10.65 μ, 800 for CHDF2 at 10.48 μ, and 2500 for CDF3 at 10.21 μ. The absorption coefficients and hence optical isotopic selectivities are dependent on fluence, and the optical selectivity attains a maximum value of 8000 for CDF3 below 0.01 J/cm2 fluence. The deuterium-bearing MPD photoproducts at high pressure are trifluoroethylene for Freon 123, hydrogen fluoride for trifluoromethane, and both hydrogen fluoride and monofluoroacetylene for difluoromethane. Yield data determined by gas chromatography are analyzed using a model describing MPD due to a focused Gaussian beam in an absorbing medium to remove compositional and geometrical effects; this analysis results in a saturation fluence (at which the dissociation probability approaches 100%) of 12±2 J/cm2 for CF3CDCl2, 20±2 J/cm2 for CDF3 buffered by 1 atm argon, 30±2 J/cm2 for CDF3 buffered by 60-400 Torr CHF3, and 22±3 J/cm2 for CHDF2 buffered by 100-400 Torr CH2F2. Near unity dissociation probabilities are obtained for samples unbuffered by argon with operating pressures up to 40 Torr for Freon 123, and up to 400 Torr for both difluoromethane and trifluoromethane; the methane derivatives are much more resistant to high pressure collisional quenching than

  2. Photon statistics of atomic fluorescence after {pi}-pulse excitation

    SciTech Connect

    Yoshimi, Kazuyoshi; Koshino, Kazuki

    2010-09-15

    The photon statistics of atomic fluorescence after {pi}-pulse excitation is investigated in a system in which the input and output ports are connected to an atom. Since spontaneous decay during input pulse excitation occurs, the output pulse generally contains a multiphoton component with a certain probability. We quantitatively evaluate the probability of the output pulse containing multiple photons and determine the conditions for ideal single-photon generation.

  3. Reliable source of conditional states from single-mode pulsed thermal fields by multiple-photon subtraction

    SciTech Connect

    Allevi, A.; Andreoni, A.; Bondani, M.; Genoni, M. G.; Olivares, S.

    2010-07-15

    We demonstrate the effect of multiple-photon subtraction on the generation of conditional states in the pulsed regime. Our experimental scheme relies on a beam splitter (BS) and a pair of linear photodetectors that are able to resolve up to tens of photons. We use a single-mode thermal field at the input port of the BS to test the reliability of our scheme, and we show good agreement with the theory by fully characterizing the conditional outgoing states in terms of photon-number statistics and non-Gaussianity.

  4. Vibrational Signatures of Isomeric Lithiated N-acetyl-D-hexosamines by Gas-Phase Infrared Multiple-Photon Dissociation (IRMPD) Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tan, Yanglan; Zhao, Ning; Liu, Jinfeng; Li, Pengfei; Stedwell, Corey N.; Yu, Long; Polfer, Nicolas C.

    2017-01-01

    Three lithiated N-acetyl-D-hexosamine (HexNAc) isomers, N-acetyl-D-glucosamine (GlcNAc), N-acetyl-D-galactosamine (GalNAc), and N-acetyl-D-mannosamine (ManNAc) are investigated as model monosaccharide derivatives by gas-phase infrared multiple-photon dissociation (IRMPD) spectroscopy. The hydrogen stretching region, which is attributed to OH and NH stretching modes, reveals some distinguishing spectral features of the lithium-adducted complexes that are useful in terms of differentiating these isomers. In order to understand the effect of lithium coordination on saccharide structure, and therefore anomericity, chair configuration, and hydrogen bonding networks, the conformational preferences of lithiated GlcNAc, GalNAc, and ManNAc are studied by comparing the experimental measurements with density functional theory (DFT) calculations. The experimental results of lithiated GlcNAc and GalNAc show a good match to the theoretical spectra of low-energy structures adopting a 4 C 1 chair conformation, consistent with this motif being the dominant conformation in condensed-phase monosaccharides. The epimerization effect upon going to lithiated ManNAc is significant, as in this case the 1 C 4 chair conformers give a more compelling match with the experimental results, consistent with their lower calculated energies. A contrasting computational study of these monosaccharides in their neutral form suggests that the lithium cation coordination with Lewis base oxygens can play a key role in favoring particular structural motifs (e.g., a 4 C 1 versus 1 C 4 ) and disrupting hydrogen bond networks, thus exhibiting specific IR spectral features between these closely related lithium-chelated complexes.

  5. Vibrational Signatures of Isomeric Lithiated N-acetyl-D-hexosamines by Gas-Phase Infrared Multiple-Photon Dissociation (IRMPD) Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tan, Yanglan; Zhao, Ning; Liu, Jinfeng; Li, Pengfei; Stedwell, Corey N.; Yu, Long; Polfer, Nicolas C.

    2017-03-01

    Three lithiated N-acetyl-D-hexosamine (HexNAc) isomers, N-acetyl-D-glucosamine (GlcNAc), N-acetyl-D-galactosamine (GalNAc), and N-acetyl-D-mannosamine (ManNAc) are investigated as model monosaccharide derivatives by gas-phase infrared multiple-photon dissociation (IRMPD) spectroscopy. The hydrogen stretching region, which is attributed to OH and NH stretching modes, reveals some distinguishing spectral features of the lithium-adducted complexes that are useful in terms of differentiating these isomers. In order to understand the effect of lithium coordination on saccharide structure, and therefore anomericity, chair configuration, and hydrogen bonding networks, the conformational preferences of lithiated GlcNAc, GalNAc, and ManNAc are studied by comparing the experimental measurements with density functional theory (DFT) calculations. The experimental results of lithiated GlcNAc and GalNAc show a good match to the theoretical spectra of low-energy structures adopting a 4 C 1 chair conformation, consistent with this motif being the dominant conformation in condensed-phase monosaccharides. The epimerization effect upon going to lithiated ManNAc is significant, as in this case the 1 C 4 chair conformers give a more compelling match with the experimental results, consistent with their lower calculated energies. A contrasting computational study of these monosaccharides in their neutral form suggests that the lithium cation coordination with Lewis base oxygens can play a key role in favoring particular structural motifs (e.g., a 4 C 1 versus 1 C 4 ) and disrupting hydrogen bond networks, thus exhibiting specific IR spectral features between these closely related lithium-chelated complexes.

  6. Zn(2+) and Cd(2+) cationized serine complexes: infrared multiple photon dissociation spectroscopy and density functional theory investigations.

    PubMed

    Coates, Rebecca A; Boles, Georgia C; McNary, Christopher P; Berden, Giel; Oomens, Jos; Armentrout, P B

    2016-08-10

    The gas-phase structures of zinc and cadmium dications bound to serine (Ser) are investigated by infrared multiple photon dissociation (IRMPD) action spectroscopy using the free electron laser FELIX, in combination with ab initio calculations. To identify the structures of the experimentally observed species, [Zn(Ser-H)CH3CN](+) and CdCl(+)(Ser), the measured action spectra are compared to linear absorption spectra calculated at the B3LYP/6-311+G(d,p) level for Zn(2+) containing complexes and B3LYP/def2-TZVP levels for Cd(2+) containing complexes. Good agreement between the observed IRMPD spectra and the predicted spectra allows identification of the isomers present. The intact amino acid interacting with cadmium chloride adopts a tridentate chelation involving the amino acid backbone amine and carbonyl groups as well as the hydroxyl group of the side-chain, [N,CO,OH]. The presence of two low-energy conformers is observed for the deprotonated serine-zinc complex, with the same tridentate coordination as for the cadmium complex but proton loss occurs at both the hydroxyl side-chain, [N,CO,O(-)], and the carboxylic acid of the amino acid backbone, [N,CO(-),OH]. These results are profitably compared with the analogous results previously obtained for comparable complexes with cysteine.

  7. Pulsed IR inductive lasers

    NASA Astrophysics Data System (ADS)

    Razhev, A. M.; Churkin, D. S.; Kargapol'tsev, E. S.

    2014-07-01

    Pulsed inductive discharge is a new alternative method of pumping active gas laser media. The work presents results of experimental investigations of near, mid, and far IR inductive gas lasers (H2, HF, and CO2) operating at different transitions of atoms and molecules with different mechanisms of formation of inversion population. The excitation systems of a pulsed inductive cylindrical discharge (pulsed inductively coupled plasma) and pulsed RF inductive discharge in the gases are developed. Various gas mixtures including H2, N2, He, Ne, F2, NF3, and SF6 are used. Characteristics of near IR H2 laser radiation are investigated. Maximal pulse peak power of 7 kW is achieved. The possibility of using a pulsed inductive discharge as a new method of pumping HF laser active medium is demonstrated. The pulsed RF inductive CO2 laser is created and a total efficiency of 17% is achieved.

  8. Infrared multiple photon dissociation spectroscopy of cationized asparagine: effects of metal cation size on gas-phase conformation.

    PubMed

    Heaton, A L; Bowman, V N; Oomens, J; Steill, J D; Armentrout, P B

    2009-05-14

    Gas-phase structures of cationized asparagine (Asn) including complexes with Li(+), Na(+), K(+), Rb(+), Cs(+), and Ba(2+), as well as protonated Asn, are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by a free electron laser. Experimental spectra for the alkali metal cation complexes exhibit systematic trends, whereas spectra for Ba(2+)(Asn) and H(+)(Asn) are more distinct. To identify the structures formed experimentally, measured IRMPD spectra are compared to spectra calculated at a B3LYP/6-311+G(d,p) level with several effective core potentials and basis sets evaluated for the heavy metal systems. The dominant conformation ascertained for complexes with the smaller metal cations, Li(+)(Asn) and Na(+)(Asn), is a charge-solvated, tridentate [N,CO,CO] structure that binds the metal cation with the amine group of the amino acid backbone and to the carbonyl oxygen atoms of the backbone and amino acid side chain. For the larger alkali metal cation complexes, K(+)(Asn), Rb(+)(Asn), and Cs(+)(Asn), an additional charge-solvated, tridentate [COOH,CO] structure that binds the metal cation with the two oxygen atoms of the backbone carboxylic acid group and the carbonyl oxygen atom of the Asn side chain may also be present. The Ba(2+)(Asn) spectrum is characteristic of a single charge-solvated [N,CO,CO] conformation, in contrast to Gly, Trp, Arg, Gln, Pro, Ser, Val, and Glu, which all take on a zwitterionic structure when complexed to Ba(2+). In no case do the cationized Asn complexes show definitive evidence of forming a zwitterionic structure in the complexes studied here. For H(+)(Asn), a mixture of two [N,CO] structures, which differ only in the orientation the side chain and are calculated to be nearly identical in energy, explains the experimental spectrum well.

  9. Infrared multiple photon dissociation spectroscopy of cationized methionine: effects of alkali-metal cation size on gas-phase conformation.

    PubMed

    Carl, Damon R; Cooper, Theresa E; Oomens, Jos; Steill, Jeff D; Armentrout, P B

    2010-04-14

    The gas-phase structures of alkali-metal cation complexes of the amino acid methionine (Met) as well as protonated methionine are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser. Spectra of Li(+)(Met) and Na(+)(Met) are similar and relatively simple, whereas the spectra of K(+)(Met), Rb(+)(Met), and Cs(+)(Met) include distinctive new bands. Measured IRMPD spectra are compared to spectra calculated at the B3LYP/6-311+G(d,p) level of theory to identify the conformations present in the experimental studies. For Li(+) and Na(+) complexes, the only conformation present is a charge-solvated, tridentate structure that binds the metal cation to the amine and carbonyl groups of the amino acid backbone and the sulfur atom of the side chain, [N,CO,S]. In addition to the [N,CO,S] conformer, bands corresponding to alkali-metal cation binding to a bidentate zwitterionic structure, [CO(2)(-)], are clearly present for the K(+), Rb(+), and Cs(+) complexes. Theoretical calculations of the lowest energy conformations of Rb(+) and Cs(+) complexes suggest that the experimental spectra could also include contributions from two additional charge-solvated structures, tridentate [COOH,S] and bidentate [COOH]. For H(+)(Met), the IRMPD action spectrum is reproduced by multiple low-energy [N,CO,S] conformers, in which the protonated amine group hydrogen bonds to the carbonyl oxygen atom and the sulfur atom of the amino acid side chain. These [N,CO,S] conformers only differ in their side-chain orientations.

  10. Infrared Multiple Photon Dissociation Spectroscopy of a Gas-Phase Oxo-Molybdenum Complex with 1,2-Dithiolene Ligands

    PubMed Central

    2015-01-01

    Electrospray ionization (ESI) in the negative ion mode was used to create anionic, gas-phase oxo-molybdenum complexes with dithiolene ligands. By varying ESI and ion transfer conditions, both doubly and singly charged forms of the complex, with identical formulas, could be observed. Collision-induced dissociation (CID) of the dianion generated exclusively the monoanion, while fragmentation of the monoanion involved decomposition of the dithiolene ligands. The intrinsic structure of the monoanion and the dianion were determined by using wavelength-selective infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The IRMPD spectrum for the dianion exhibits absorptions that can be assigned to (ligand) C=C, C–S, C—C≡N, and Mo=O stretches. Comparison of the IRMPD spectrum to spectra predicted for various possible conformations allows assignment of a pseudo square pyramidal structure with C2v symmetry, equatorial coordination of MoO2+ by the S atoms of the dithiolene ligands, and a singlet spin state. A single absorption was observed for the oxidized complex. When the same scaling factor employed for the dianion is used for the oxidized version, theoretical spectra suggest that the absorption is the Mo=O stretch for a distorted square pyramidal structure and doublet spin state. A predicted change in conformation upon oxidation of the dianion is consistent with a proposed bonding scheme for the bent-metallocene dithiolene compounds [Lauher, J. W.; Hoffmann, R. J. Am. Chem. Soc.1976, 98, 1729−1742], where a large folding of the dithiolene moiety along the S···S vector is dependent on the occupancy of the in-plane metal d-orbital. PMID:24988369

  11. Infrared multiple photon dissociation spectroscopy of group I and group II metal complexes with Boc-hydroxylamine.

    PubMed

    Dain, Ryan P; Gresham, Gary; Groenewold, Gary S; Steill, Jeffrey D; Oomens, Jos; Van Stipdonk, Michael J

    2013-08-30

    Hydroxamates are essential growth factors for some microbes, acting primarily as siderophores that solubilize iron for transport into a cell. Here we determined the intrinsic structure of 1:1 complexes between Boc-protected hydroxylamine and group I ([M(L)](+)) and group II ([M(L-H)](+)) cations, where M and L are the cation and ligand, respectively, which are convenient models for the functional unit of hydroxamate siderphores. The relevant complex ions were generated by electrospray ionization (ESI) and isolated and stored in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Infrared spectra of the isolated complexes were collected by monitoring (infrared) photodissociation yield as a function of photon energy. Experimental spectra were then compared to those predicted by density functional theory (DFT) calculations. The infrared multiple photon dissociation (IRMPD) spectra collected are in good agreement with those predicted to be lowest-energy by DFT. The spectra for the group I complexes contain six resolved absorptions that can be attributed to amide I and II type and hydroxylamine N-OH vibrations. Similar absorptions are observed for the group II cation complexes, with shifts of the amide I and amide II vibrations due to the change in structure with deprotonation of the hydroxylamine group. IRMPD spectroscopy unequivocally shows that the intrinsic binding mode for the group I cations involves the O atoms of the amide carbonyl and hydroxylamine groups of Boc-hydroxylamine. A similar binding mode is preferred for the group II cations, except that in this case the metal ion is coordinated by the O atom of the deprotonated hydroxylamine group. Copyright © 2013 John Wiley & Sons, Ltd.

  12. Infrared multiple photon dissociation spectroscopy of cationized histidine: effects of metal cation size on gas-phase conformation.

    PubMed

    Citir, Murat; Hinton, Christopher S; Oomens, Jos; Steill, Jeffrey D; Armentrout, P B

    2012-02-16

    The gas phase structures of cationized histidine (His), including complexes with Li(+), Na(+), K(+), Rb(+), and Cs(+), are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by a free electron laser, in conjunction with quantum chemical calculations. To identify the structures present in the experimental studies, measured IRMPD spectra are compared to spectra calculated at B3LYP/6-311+G(d,p) (Li(+), Na(+), and K(+) complexes) and B3LYP/HW*/6-311+G(d,p) (Rb(+) and Cs(+) complexes) levels of theory, where HW* indicates that the Hay-Wadt effective core potential with additional polarization functions was used on the metals. Single point energy calculations were carried out at the B3LYP, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set. On the basis of these experiments and calculations, the only conformation that reproduces the IRMPD action spectra for the complexes of the smaller alkali metal cations, Li(+)(His) and Na(+)(His), is a charge-solvated, tridentate structure where the metal cation binds to the backbone carbonyl oxygen, backbone amino nitrogen, and nitrogen atom of the imidazole side chain, [CO,N(α),N(1)], in agreement with the predicted ground states of these complexes. Spectra of the larger alkali metal cation complexes, K(+)(His), Rb(+)(His), and Cs(+)(His), have very similar spectral features that are considerably more complex than the IRMPD spectra of Li(+)(His) and Na(+)(His). For these complexes, the bidentate [CO,N(1)] conformer in which the metal cation binds to the backbone carbonyl oxygen and nitrogen atom of the imidazole side chain is a dominant contributor, although features associated with the tridentate [CO,N(α),N(1)] conformer remain, and those for the [COOH] conformer are also clearly present. Theoretical results for Rb(+)(His) and Cs(+)(His) indicate that both [CO,N(1)] and [COOH] conformers are low-energy structures, with different levels of theory predicting different

  13. B-side electron transfer promoted by absorbance of multiple photons in Rhodobacter sphaeroides R-26 reaction centers

    SciTech Connect

    Lin, S.; Jackson, J.A.; Taguchi, A.K.W.; Woodbury, N.W.

    1999-06-03

    Femtosecond transient absorbance spectra of quinone-depleted Rhodobacter sphaeroides R-26 reaction centers in the Q{sub X} transition region have been measured at 15 K under various excitation conditions. This study focuses on the excitation wavelength dependence and excitation intensity dependence of the formation of charge-separated states on the A- and B-side of the reaction center, judging from the bleaching of the 533 nm (B-side) and 544 nm (A-side) ground-state transitions of the reaction center bacteriopheophytins (H{sub A} and H{sub B}). Upon low-intensity selective excitation directly into the bacteriopheophytin Q{sub Y} transitions (near 760 nm), bleaching of both ground-state bacteriopheophytin Q{sub X} transitions appeared immediately, showing that initially either the A- or B-side bacteriopheophytin could be excited. However, both excited states ultimately resulted in P{sup +}H{sub A}{sup {minus}} formation under these conditions. Low-intensity excitation at any of the various wavelengths showed no difference in the kinetics of the A-side charge separation forming P{sup +}H{sub A}{sup {minus}} and no substantial formation of the B-side charge-separated state, P{sup +}H{sub B}{sup {minus}}. In contrast, high-intensity 595 nm excitation resulted in substantial long-lived bleaching of the B-side bacteriopheophytin ground-state transition at 533 nm. This 533 nm bleaching was formed with essentially the same time constant as the bleaching at 544 nm due to A-side charge separation. Both bleaching bands persisted at the longest times measured in quinone-removed reaction centers. The long-lived bleaching at 533 nm using high-intensity excitation most likely represents the formation of P{sup +}H{sub B}{sup {minus}} with a relative yield of nearly 40%. One possible mechanism for B-side electron transfer is that two-photon excitation of the reaction center resulting in the state P{sup *}B{sub B}{sup *} makes P{sup +}B{sub B}{sup {minus}} thermodynamically

  14. INFRARED SPECTRUM OF POTASSIUM-CATIONIZED TRIETHYLPHOSPHATE GENERATED USING TANDEM MASS SPECTROMETRY AND INFRARED MULTIPLE PHOTON DISSOCIATION

    SciTech Connect

    Gary S. Groenewold; Christopher M. Leavitt; Ryan P. Dain; Jos Oomens; Jeff Steill; van Stipdonk, Michael J.

    2009-09-01

    Tandem mass spectrometry and wavelength selective infrared photodissociation was used to generate an infrared spectrum of gas-phase triethylphosphate cationized by attachment of K+. Prominent absorptions were observed in the region of 900 to 1300 cm-1 that are characteristic of phosphate P=O and P-O-R stretches. The relative positions and intensities of the IR absorptions were reproduced well by density functional theory (DFT) calculations performed using the B3LYP functional and the 6-31+g(d), 6-311+g(d,p) and 6-311++G(3df,2pd) basis sets. Because of good correspondence between experiment and theory for the cation, DFT was then used to generate a theoretical spectrum for neutral triethylphosphate, which in turn accurately reproduces the IR spectrum of the neat liquid when solvent effects are included in the calculations.

  15. Infrared spectrum of potassium-cationized triethylphosphate generated using tandem mass spectrometry and infrared multiple photon dissociation.

    PubMed

    Groenewold, Gary S; Leavitt, Christopher M; Dain, Ryan P; Oomens, Jos; Steill, Jeffrey D; van Stipdonk, Michael J

    2009-09-01

    Tandem mass spectrometry and wavelength-selective infrared photodissociation were used to generate an infrared spectrum of gas-phase triethylphosphate cationized by attachment of K(+). Prominent absorptions were observed in the region of 900 to 1300 cm(-1) that are characteristic of phosphate P=O and P-O-R stretches. The relative positions and intensities of the IR absorptions were reproduced well by density functional theory (DFT) calculations performed using the B3LYP functional and the 6-31+G(d), 6-311+G(d,p) and 6-311++G(3df,2pd) basis sets. Because of good correspondence between experiment and theory for the cation, DFT was then used to generate a theoretical spectrum for neutral triethylphosphate, which in turn accurately reproduces the IR spectrum of the neat liquid when solvent effects are included in the calculations.

  16. Formation of molecular hydrogen from protonated 9,10-dihydroanthracene: Is the ejected H2 rotationally and vibrationally excited?

    NASA Astrophysics Data System (ADS)

    Vala, Margin; Szczepanski, Jan; Oomens, Jos

    2011-12-01

    The infrared multiple-photon dissociation (IRMPD) spectrum of protonated 9,10-dihydroanthracene ([DHA+H]+, m/z 181) has been recorded using an infrared free electron laser. Protonation was accomplished by electrospray ionization with subsequent mass-selection and trapping in a Fourier transform ion cyclotron mass spectrometer. IR-induced fragment ions were observed at m/z 179, 166, and 165. Density functional calculations (B3LYP/6-311++G(d,p)) of the infrared spectra of the two possible protonated isomers of DHA showed that the observed IRMPD spectrum is best fit to a mixture of the two isomers. Potential energy surfaces for the loss of atomic and molecular hydrogen from the aliphatic carbons of [DHA+H]+ have been calculated. The lowest energy barriers are for loss of H2. After H2 ejection, stabilization of the remaining fragment occurs by hydrogen migration from one of the aliphatic carbons to the bare ejection site. In all cases the stabilized fragment is computed to be 9-hydroanthracene. The IRMPD spectrum of the m/z 179 fragment has been recorded and is shown to correspond closely both to the calculated and previously recorded IRMPD spectrum of ionic 9-hydroanthracene. The highly asymmetric transition state conformation of the to-be-formed H2 and the remaining fragment is highly suggestive of rotational, vibrational, and, possibly, translational excitation of the ejected H2. Evidence for such excitation from astronomical observations that show the close proximity of PAHs and H2 in certain interstellar objects and that show H2 rotational excitation, which has been difficult to explain via either collisional activation or UV pumping, is reviewed.

  17. IR Windstreaks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Windstreaks are features caused by the interaction of wind and topographic landforms. The raised rims and bowls of impact craters causes a complex interaction such that the wind vortex in the lee of the crater can both scour away the surface dust and deposit it back in the center of the lee. If you look closely, you will see evidence of this in a darker 'rim' enclosing a brighter interior.

    This infrared image shows windstreaks in the region between Gordii Dorsum and Amazonis Mensa.

    Image information: IR instrument. Latitude -15.8, Longitude 215 East (145 West). 97 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. IR Windstreaks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Windstreaks are features caused by the interaction of wind and topographic landforms. The raised rims and bowls of impact craters causes a complex interaction such that the wind vortex in the lee of the crater can both scour away the surface dust and deposit it back in the center of the lee. If you look closely, you will see evidence of this in a darker 'rim' enclosing a brighter interior.

    This infrared image shows windstreaks in the region between Gordii Dorsum and Amazonis Mensa.

    Image information: IR instrument. Latitude -15.8, Longitude 215 East (145 West). 97 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. From Ultrafast Structure Determination to Steering Reactions: Mixed IR/Non-IR Multidimensional Vibrational Spectroscopies.

    PubMed

    van Wilderen, Luuk J G W; Bredenbeck, Jens

    2015-09-28

    Ultrafast multidimensional infrared spectroscopy is a powerful method for resolving features of molecular structure and dynamics that are difficult or impossible to address with linear spectroscopy. Augmenting the IR pulse sequences by resonant or nonresonant UV, Vis, or NIR pulses considerably extends the range of application and creates techniques with possibilities far beyond a pure multidimensional IR experiment. These include surface-specific 2D-IR spectroscopy with sub-monolayer sensitivity, ultrafast structure determination in non-equilibrium systems, triggered exchange spectroscopy to correlate reactant and product bands, exploring the interplay of electronic and nuclear degrees of freedom, investigation of interactions between Raman- and IR-active modes, imaging with chemical contrast, sub-ensemble-selective photochemistry, and even steering a reaction by selective IR excitation. We give an overview of useful mixed IR/non-IR pulse sequences, discuss their differences, and illustrate their application potential.

  20. Far-IR selected star formation regions

    NASA Technical Reports Server (NTRS)

    Jaffe, D. T.; Hildebrand, R. H.; Keene, J.; Harper, D. A.; Loewenstein, R. F.; Moran, J. M.

    1984-01-01

    Detailed far-IR observations and complemenary submillimeter, 5 GHz continuum and c(18)0 observations of a sample of far-IR selected luminous regions of star formation. The clouds and that the exciting stars lie deep within these condensations. The far-IR sources have diversely shaped 40 micron to 180 micron spectra even through their 60 micron to 100 micron color temperatures are similar. The radio and far-IR results together show that the exciting stars are in clusters containing either zero-age main sequence and pre-main sequence stars or consisting entirely of premain sequence objects. C(18)0 and submillimeter observations imply gas densities approximately .00005 - high enough to make t(sub dust) approximately t(sub gas).

  1. Indirect excitation of ultrafast demagnetization

    DOE PAGES

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; ...

    2016-01-06

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset andmore » at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.« less

  2. Indirect excitation of ultrafast demagnetization

    PubMed Central

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan

    2016-01-01

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. Our data thus confirm recent theoretical predictions. PMID:26733106

  3. Indirect excitation of ultrafast demagnetization

    SciTech Connect

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan

    2016-01-06

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.

  4. Cryogenic exciter

    DOEpatents

    Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

    2012-03-13

    The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

  5. Differentiation of Rubidiated Methyl-d-Glycoside Stereoisomers by Infrared Multiple-Photon Dissociation Spectroscopy in the O-H and C-H Stretching Regions.

    PubMed

    Pearson, Wright L; Contreras, Cesar; Powell, David; Berden, Giel; Oomens, Jos; Bendiak, Brad; Eyler, John R

    2015-10-15

    Four isomeric sugar methylglycosides (α- and β-d-gluco- and galactopyranosides) were evaluated as rubidium cation coordination adducts in the gas phase using variable-wavelength multiple-photon dissociation in the range from 2750 to 3750 cm(-1). The adducts dissociated following photon absorption to yield neutral sugars and the rubidium cation, resulting in infrared "action" spectra. Well-resolved hydroxyl stretching bands clearly differentiate stereoisomers that vary solely in their asymmetry at single carbons. Density functional theory calculations of the lowest-energy gas-phase complexes indicate that rubidium coordinates with lone pairs of oxygen atoms as either bi- or tridentate complexes and that more than one positional coordination isomer could adequately account for most of the O-H stretch frequencies observed for each methylglycoside.

  6. Suppression of multiple photon absorption in a SiC photonic crystal nanocavity operating at 1.55 μm.

    PubMed

    Yamada, Shota; Song, Bong-Shik; Upham, Jeremy; Asano, Takashi; Tanaka, Yoshinori; Noda, Susumu

    2012-07-02

    We show that a SiC photonic crystal cannot only inhibit two photon absorption completely, but also suppress higher-order multiple photon absorption significantly at telecommunication wavelengths, compared to conventional Si-based photonic crystal nanocavities. Resonant spectra of a SiC nanocavity maintain a Lorentzian profile even at input energies 100 times higher than what can be applied to a Si nanocavity without causing nonlinear effects. Theoretical fitting of the results indicates that the four photon absorption coefficient in the SiC nanocavity is less than 2.0 × 10(-5) cm(5)/GW(3). These results will contribute to the development of high-power applications of SiC nanocavities such as harmonic generation, parametric down conversion, and Raman amplification.

  7. IR Variability of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Smith, Nathan

    2008-02-01

    Every 5.5 years, η Carinae experiences a dramatic ``spectroscopic event'' when high-excitation lines in its UV, optical, and IR spectrum disappear, and its hard X-ray and radio continuum flux crash. This periodicity has been attributed to an eccentric binary system with a shell ejection occurring at periastron, and the next periastron event will occur at the very end of 2008. In addition, η Car shows long term changes as it is still recovering from its giant 19th century outburst. Both types of variability are directly linked to the current mass-loss rate and dust formation in its wind. Mid-IR images and spectra with T-ReCS provide a direct measure of changes in the current bolometric luminosity and a direct measure of the massw in dust formation episodes that may occur at periastron in the colliding wind shock. Near-IR emission lines trace related changes in the post-event wind and ionization changes in the circumstellar environment needed to test specific models for the cause of η Car's variability as it recovers from its recent ``event''. High resolution near-IR spectra with Phoenix will continue the important work of HST/STIS, investigating changes in the direct and reflected spectrum of the stellar wind, and ionization changes in the nebula.

  8. IR Variability of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Smith, Nathan

    2007-02-01

    Every 5.5 years, η Carinae experiences a dramatic ``spectroscopic event'' when high-excitation lines in its UV, optical, and IR spectrum disappear, and its hard X-ray and radio continuum flux crash. This periodicity has been attributed to an eccentric binary system with a shell ejection occurring at periastron. In addition, η Car shows long term changes as it is still recovering from its giant 19th century outburst. Both types of variability are directly linked to the current mass-loss rate and dust formation in its wind. Mid-IR images and spectra with T-ReCS provide a direct measure of changes in the current bolometric luminosity and trace dust formation episodes. This will provide a direct measurement of the mass ejected. Near-IR emission lines trace related changes in the post-event wind and ionization changes in the circumstellar environment needed to test specific models for the cause of η Car's variability as it recovers from its recent ``event''. High resolution near-IR spectra with GNIRS will continue the important work of HST/STIS, investigating changes in the direct and reflected spectrum of the stellar wind, and ionization changes in the nebula.

  9. Long-lived room temperature deep-red/near-IR emissive intraligand triplet excited state (3IL) of naphthalimide in cyclometalated platinum(II) complexes and its application in upconversion.

    PubMed

    Wu, Wenting; Guo, Huimin; Wu, Wanhua; Ji, Shaomin; Zhao, Jianzhang

    2011-11-21

    [C(^)NPt(acac)] (C(^)N = cyclometalating ligand; acac = acetylacetonato) complexes in which the naphthalimide (NI) moiety is directly cyclometalated (NI as the C donor of the C-Pt bond) were synthesized. With 4-pyrazolylnaphthalimide, isomers with five-membered (Pt-2) and six-membered (Pt-3) chelate rings were obtained. With 4-pyridinylnaphthalimide, only the complex with a five-membered chelate ring (Pt-4) was isolated. A model complex with 1-phenylpyrazole as the C(^)N ligand was prepared (Pt-1). Strong absorption of visible light (ε = 21,900 M(-1) cm(-1) at 443 nm for Pt-3) and room temperature (RT) phosphorescence at 630 nm (Pt-2 and Pt-3) or 674 nm (Pt-4) were observed. Long-lived phosphorescences were observed for Pt-2 (τ(P) = 12.8 μs) and Pt-3 (τ(P) = 61.9 μs). Pt-1 is nonphosphorescent at RT in solution because of the acac-localized T(1) excited state [based on density functional theory (DFT) calculations and spin density analysis], but a structured emission band centered at 415 nm was observed at 77 K. Time-resolved transient absorption spectra and spin density analysis indicated a NI-localized intraligand triplet excited state ((3)IL) for complexes Pt-2, Pt-3, and Pt-4. DFT calculations on the transient absorption spectra (T(1) → T(n) transitions, n > 1) also support the (3)IL assignment of the T(1) excited states of Pt-2, Pt-3, and Pt-4. The complexes were used as triplet sensitizers for triplet-triplet-annihilation (TTA) based upconversion, and the results show that Pt-3 is an efficient sensitizer with an upconversion quantum yield of up to 14.1%, despite its low phosphorescence quantum yield of 5.2%. Thus, we propose that the sensitizer molecules at the triplet excited state that are otherwise nonphosphorescent were involved in the TTA upconversion process, indicating that weakly phosphorescent or nonphosphorescent transition-metal complexes can be used as triplet sensitizers for TTA upconversion.

  10. High Excitation Gas and ISM

    NASA Technical Reports Server (NTRS)

    Peeters, E.; Martin-Hernandez, N. L.; Rodriguez-Fernandez, N. J.; Tielens, A. G. G. M.

    2004-01-01

    An overview is given of ISO results on regions of high excitation ISM and gas, i.e. HII regions, the Galactic Centre and Supernovae Remnants. IR emission due to fine-structure lines, molecular hydrogen, silicates, polycyclic aromatic hydrocarbons and dust are summarized, their diagnostic capabilities illustrated and their implications highlighted.

  11. Chirp excitation

    NASA Astrophysics Data System (ADS)

    Khaneja, Navin

    2017-09-01

    The paper describes the design of broadband chirp excitation pulses. We first develop a three stage model for understanding chirp excitation in NMR. We then show how a chirp π pulse can be used to refocus the phase of the chirp excitation pulse. The resulting magnetization still has some phase dispersion in it. We show how a combination of two chirp π pulses instead of one can be used to eliminate this dispersion, leaving behind a small residual phase dispersion. The excitation pulse sequence presented here allows exciting arbitrary large bandwidths without increasing the peak rf-amplitude. Experimental excitation profiles for the residual HDO signal in a sample of 99.5 % D2O are displayed as a function of resonance offset. Although methods presented in this paper have appeared elsewhere, we present complete analytical treatment that elucidates the working of these methods.

  12. Exciter switch

    NASA Technical Reports Server (NTRS)

    Mcpeak, W. L.

    1975-01-01

    A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

  13. Near-IR Photoluminescence of C60().

    PubMed

    Strelnikov, Dmitry V; Kern, Bastian; Kappes, Manfred M

    2017-10-05

    We have observed that C60(+) ions isolated in cryogenic matrices show distinct near-IR photoluminescence upon excitation in the near-IR range. By contrast, UV photoexcitation does not lead to measurable luminescence. Near-IR C60(+) photoluminescence is a one-photon process. The emission is mainly concentrated in one band and corresponds to (2)A1u ← (2)E1g relaxation. We present experimental data for the Stokes shift, power, and temperature dependencies as well as the quantum efficiency of the photoluminescence. Our findings may be relevant for astronomy, considering recent unequivocal assignment of five diffuse interstellar bands to near-IR absorption bands of C60(+).

  14. Hybrid quadrupole mass filter/quadrupole ion trap/time-of-flight-mass spectrometer for infrared multiple photon dissociation spectroscopy of mass-selected ions

    SciTech Connect

    Gulyuz, Kerim; Stedwell, Corey N.; Wang Da; Polfer, Nick C.

    2011-05-15

    We present a laboratory-constructed mass spectrometer optimized for recording infrared multiple photon dissociation (IRMPD) spectra of mass-selected ions using a benchtop tunable infrared optical parametric oscillator/amplifier (OPO/A). The instrument is equipped with two ionization sources, an electrospray ionization source, as well as an electron ionization source for troubleshooting. This hybrid mass spectrometer is composed of a quadrupole mass filter for mass selection, a reduced pressure ({approx}10{sup -5} Torr) quadrupole ion trap (QIT) for OPO irradiation, and a reflectron time-of-flight drift tube for detecting the remaining precursor and photofragment ions. A helium gas pulse is introduced into the QIT to temporarily increase the pressure and hence enhance the trapping efficiency of axially injected ions. After a brief pump-down delay, the compact ion cloud is subjected to the focused output from the continuous wave OPO. In a recent study, we implemented this setup in the study of protonated tryptophan, TrpH{sup +}, as well as collision-induced dissociation products of this protonated amino acid [W. K. Mino, Jr., K. Gulyuz, D. Wang, C. N. Stedwell, and N. C. Polfer, J. Phys. Chem. Lett. 2, 299 (2011)]. Here, we give a more detailed account on the figures of merit of such IRMPD experiments. The appreciable photodissociation yields in these measurements demonstrate that IRMPD spectroscopy of covalently bound ions can be routinely carried out using benchtop OPO setups.

  15. Exciting Pools

    ERIC Educational Resources Information Center

    Wright, Bradford L.

    1975-01-01

    Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

  16. Gas-phase structures of Pb(2+)-cationized phenylalanine and glutamic acid determined by infrared multiple photon dissociation spectroscopy and computational chemistry.

    PubMed

    Burt, Michael B; Fridgen, Travis D

    2013-02-14

    Infrared multiple photon dissociation (IRMPD) spectroscopy in the 3200-3800 cm(-1) region was used to determine the gas-phase structures of bare and monohydrated [Pb(Phe-H)](+) and [Pb(Glu-H)](+). These experiments were supported by infrared spectra calculated at the B3LYP/6-31+G(d,p) level of theory as well as 298 K enthalpies and Gibbs energies determined using the MP2(full)/6-311++G(2d,2p)//B3LYP/6-31+G(d,p) method. The gas-phase structure of [Pb(Phe-H)](+) has Pb(2+) bound in a tridentate fashion between Phe's amine nitrogen, one oxygen of the deprotonated carboxyl group, and the aromatic ring. The IRMPD spectrum of [Pb(Glu-H)](+) can be assigned to a structure where the side chain carboxyl group is deprotonated. The structure of [Pb(Phe-H)H(2)O](+) is simply the hydrated analogue of [Pb(Phe-H)](+) where water attaches to Pb(2+) in the same hemisphere as the ligated amino acid. The spectrum of [Pb(Glu-H)H(2)O](+) could not be assigned a unique structure. The IRMPD spectrum shows features attributed to symmetric and antisymmetric O-H stretching of water and a broad band characteristic of a hydrogen bonded O-H stretching vibration. These features can only be explained by the presence of at least two isomers and agree with the computational results that predict the four lowest energy structures to be within 6 kJ mol(-1) of one another.

  17. IOT Overview: IR Instruments

    NASA Astrophysics Data System (ADS)

    Mason, E.

    In this instrument review chapter the calibration plans of ESO IR instruments are presented and briefly reviewed focusing, in particular, on the case of ISAAC, which has been the first IR instrument at VLT and whose calibration plan served as prototype for the coming instruments.

  18. IR Hot Wave

    SciTech Connect

    Graham, T. B.

    2010-04-01

    The IR Hot Wave{trademark} furnace is a breakthrough heat treatment system for manufacturing metal components. Near-infrared (IR) radiant energy combines with IR convective heating for heat treating. Heat treatment is an essential process in the manufacture of most components. The controlled heating and cooling of a metal or metal alloy alters its physical, mechanical, and sometimes chemical properties without changing the object's shape. The IR Hot Wave{trademark} furnace offers the simplest, quickest, most efficient, and cost-effective heat treatment option for metals and metal alloys. Compared with other heat treatment alternatives, the IR Hot Wave{trademark} system: (1) is 3 to 15 times faster; (2) is 2 to 3 times more energy efficient; (3) is 20% to 50% more cost-effective; (4) has a {+-}1 C thermal profile compared to a {+-}10 C thermal profile for conventional gas furnaces; and (5) has a 25% to 50% smaller footprint.

  19. Photochemical Tuning of Tris-Bidentate Acridine- and Phenazine-Based Ir(III) Complexes.

    PubMed

    Deraedt, Quentin; Loiseau, Frédérique; Elias, Benjamin

    2016-11-01

    Five new Ir(III) complexes of the type [Ir(ppy)2L](+) (where ppy = 2-phenylpyridine, L = bidentate N^N ligand) bearing linear and elbow-shaped acridine- and phenazine-based extended planar aromatic ligands have been successfully synthesized and characterized. The electrochemical and photochemical studies revealed that all complexes allow emission in the range 589-601 nm from excited states corresponding to a charge transfer between an Ir-ppy fragment and the extended planar ligand. Luminescence quenching occurs in water for [Ir(ppy)2dpac](+) (Ir-DPAC), [Ir(ppy)2dpacF2](+) (Ir-DPACF 2 ), [Ir(ppy)2dpacF4](+) (Ir-DPACF 4 ) and [Ir(ppy)2bdppz](+) (Ir-BDPPZ), while solely partial quenching is observed for [Ir(ppy)2npp](+) (Ir-NPP). This "light-switch" effect has been ascribed to the possible formation of a non-emissive mono-hydrogen-bonded excited state for the four complexes. The "elbow shaped" of Ir-NPP is believed to prevent the non-chelating nitrogen atom of the npp ligand to form H-bond with solvent molecules. The results emphasized the potential of small chemical modifications of the extended planar ligand on the properties of the corresponding Ir(III) complexes. Their tunable properties make them ideal candidates for applications such as DNA photoprobes.

  20. IR in Norway

    NASA Astrophysics Data System (ADS)

    Haakenaasen, Randi; Lovold, Stian

    2003-01-01

    Infrared technology in Norway started at the Norwegian Defense Research Establishment (FFI) in the 1960s, and has since then spread to universities, other research institutes and industry. FFI has a large, integrated IR activity that includes research and development in IR detectors, optics design, optical coatings, advanced dewar design, modelling/simulation of IR scenes, and image analysis. Part of the integrated activity is a laboratory for more basic research in materials science and semiconductor physics, in which thin films of CdHgTe are grown by molecular beam epitaxy and processed into IR detectors by various techniques. FFI also has a lot of experience in research and development of tunable infrared lasers for various applications. Norwegian industrial activities include production of infrared homing anti-ship missiles, laser rangefinders, various infrared gas sensors, hyperspectral cameras, and fiberoptic sensor systems for structural health monitoring and offshore oil well diagnostics.

  1. IR Linearity Monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2012-10-01

    These observations will be used to monitor the signal non-linearity of the IR channel, as well as to update the IR channel non-linearity calibration reference file. The non-linearity behavior of each pixel in the detector will be investigated through the use of full frame and subarray flat fields, while the photometric behavior of point sources will be studied using observations of 47 Tuc. This is a continuation of the Cycle 19 non-linearity monitor, program 12696.

  2. IR linearity monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2013-10-01

    These observations will be used to monitor the signal non-linearity of the IR channel, as well as to update the IR channel non-linearity calibration reference file. The non-linearity behavior of each pixel in the detector will be investigated through the use of full frame and subarray flat fields, while the photometric behavior of point sources will be studied using observations of 47 Tuc. This is a continuation of the Cycle 20 non-linearity monitor, program 13079.

  3. Excited Delirium

    PubMed Central

    Takeuchi, Asia; Ahern, Terence L.; Henderson, Sean O.

    2011-01-01

    Excited (or agitated) delirium is characterized by agitation, aggression, acute distress and sudden death, often in the pre-hospital care setting. It is typically associated with the use of drugs that alter dopamine processing, hyperthermia, and, most notably, sometimes with death of the affected person in the custody of law enforcement. Subjects typically die from cardiopulmonary arrest, although the cause is debated. Unfortunately an adequate treatment plan has yet to be established, in part due to the fact that most patients die before hospital arrival. While there is still much to be discovered about the pathophysiology and treatment, it is hoped that this extensive review will provide both police and medical personnel with the information necessary to recognize and respond appropriately to excited delirium. PMID:21691475

  4. Voiced Excitations

    DTIC Science & Technology

    2004-12-01

    for purposes of vocoding in high noise environments: Task 1: Estimation of voiced excitation functions using skin surface vibration...High Noise Environments. The work on “ Voiced Excitations” shows that the surface vibrations of neck skin, during voicing , carry a great deal of...5 in this report). For field use, it may be better to obtain data from another location on the neck or face. A pressure function of voiced speech is

  5. Excited baryons

    SciTech Connect

    Mukhopadhyay, N.C.

    1986-01-01

    The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)

  6. Conformational dynamics in a dipeptide after single-mode vibrational excitation.

    PubMed

    Dian, Brian C; Longarte, Asier; Zwier, Timothy S

    2002-06-28

    The dynamics of conformational isomerization are explored in a methyl-capped dipeptide, N-acetyl-tryptophan methyl amide (NATMA), using infrared-ultraviolet (IR-UV) hole-filling and IR-induced population transfer spectroscopies. IR radiation selectively excites individual NH stretch vibrational fundamentals of single conformations of the molecule in the early portions of a gas-phase expansion, and then this excited population is collisionally recooled into its conformational minima for subsequent conformation-specific detection. Efficient isomerization is induced by the IR excitation that redistributes population between the same conformations that have population in the absence of IR excitation. The quantum yields for transfer of the population into the various conformational minima depend uniquely on which conformation is excited and on which NH stretch vibration is excited within a given conformation.

  7. Simulation of Wakefield Effect in ILC IR Chamber

    SciTech Connect

    Pei, S; Seryi, A.; Raubenheimer, T.O.; /SLAC

    2008-06-26

    To achieve super high luminosity, high current beams with very short bunch length are needed, which carry high intensity EM fields. For ILC, two bunch trains with bunch length of 300 {micro}m and bunch charge of 3.2nC are needed to collide at the IR to achieve the ILC luminosity goals. When the 300 {micro}m bunches pass through the IR chamber, wakefields will be excited, which will cause HOM power flowing through the IR chamber beam pipe to the final doublets due to the high frequency characteristic of the induced wakefields. Since superconducting technology is adopted for the final doublets of ILC BDS, whose operation stability might be affected by the HOM power produced at the IR chamber, quench might happen. In this paper, we did some analytical estimation and numerical simulation on the wakefield effects in ILC IR chamber.

  8. Sexual excitement.

    PubMed

    Stoller, R J

    1976-08-01

    Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.

  9. IR Gain Monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2012-10-01

    The gain of the IR channel of WFC3 will be measured using a series of internal flat fields. Using knowledge gained from ground testing and previous cycles, we propose to collect flat field ramps which will be used to create photon transfer curves and give a measure of the gain.

  10. IR gain monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2013-10-01

    The gain of the IR channel of WFC3 will be measured using a series of internal flat fields. Using knowledge gained from ground testing and previous cycles, we propose to collect flat field ramps which will be used to create photon transfer curves and give a measure of the gain. This continues the strategy of last cycle's gain monitor, in proposal 13080.

  11. Studying the nonlinearity in Sonic IR NDE

    NASA Astrophysics Data System (ADS)

    Yu, Qiuye; Obeidat, Omar; Han, Xiaoyan

    2017-02-01

    Sonic IR Imaging combines pulsed ultrasound excitation and infrared imaging to detect defects in materials. The sound pulse causes rubbing due to non--unison motion between faces of defects, and infrared sensors image the temperature map over the target to identify defects. It works in various materials, including metal/metal alloy, ceramics, and composite materials. Its biggest advantage is that it's a fast, wide area NDE technique. It takes only a fraction of a second or a few seconds, depending on the thermal properties of the target, for one test over a few square feet. However, due to the nonlinearity in the coupling between the ultrasound transducer and the target, the repeatability has been an issue, which affects its application. In this paper, we present our study on this issue in Sonic IR.

  12. Defect States in Copper Indium Gallium Selenide Solar Cells from Two-Wavelength Excitation Photoluminescence Spectroscopy

    SciTech Connect

    Jensen, Soren A.; Dippo, Patricia; Mansfield, Lorelle M.; Glynn, Stephen; Kuciauskas, Darius

    2016-11-21

    We use two-wavelength excitation photoluminescence spectroscopy to probe defect states in CIGS thin films. Above-Eg excitation is combined with a tunable IR bias light that modulates the population of the defect states. We find that IR illumination in the range of 1400-2000 nm (0.62-0.89 eV) causes a reduction of the PL intensity, the magnitude of which scales linearly with IR power. Further, KF post deposition treatment has only a modest influence on the effect of the IR excitation. Initial data suggest that we have developed an optical characterization tool for band-gap defect states.

  13. Luminescence properties of IR-emitting bismuth centres in SiO{sub 2}-based glasses in the UV to near-IR spectral region

    SciTech Connect

    Firstova, E G; Vel'miskin, V V; Firstov, S V; Dianov, E M; Bufetov, I A; Khopin, V F; Gur'yanov, A N; Bufetova, G A; Nishchev, K N

    2015-01-31

    We have studied UV excitation spectra of IR luminescence in bismuth-doped glasses of various compositions and obtained energy level diagrams of IR-emitting bismuth-related active centres (BACs) associated with silicon and germanium atoms up to ∼5.2 eV over the ground level. A possible energy level diagram of the BACs in phosphosilicate glass has been proposed. The UV excitation peaks for the IR luminescence of the BACs in the glasses have been shown to considerably overlap with absorption bands of the Bi{sup 3+} ion, suggesting that Bi{sup 3+} may participate in BAC formation. (optical fibres)

  14. Luminescence properties of IR-emitting bismuth centres in SiO2-based glasses in the UV to near-IR spectral region

    NASA Astrophysics Data System (ADS)

    Firstova, E. G.; Bufetov, I. A.; Khopin, V. F.; Vel'miskin, V. V.; Firstov, S. V.; Bufetova, G. A.; Nishchev, K. N.; Gur'yanov, A. N.; Dianov, E. M.

    2015-01-01

    We have studied UV excitation spectra of IR luminescence in bismuth-doped glasses of various compositions and obtained energy level diagrams of IR-emitting bismuth-related active centres (BACs) associated with silicon and germanium atoms up to ~5.2 eV over the ground level. A possible energy level diagram of the BACs in phosphosilicate glass has been proposed. The UV excitation peaks for the IR luminescence of the BACs in the glasses have been shown to considerably overlap with absorption bands of the Bi3+ ion, suggesting that Bi3+ may participate in BAC formation.

  15. Dunes in IR

    NASA Image and Video Library

    2017-03-09

    This image captured by NASA's 2001 Mars Odyssey spacecraft shows an infrared image of Kaiser Crater and the dune field on the crater floor. Brighter tones in the image are warmer surfaces. The basaltic dunes are dark in the visible, but bright in infrared. Orbit Number: 66814 Latitude: -47.0992 Longitude: 19.782 Instrument: IR Captured: 2017-01-05 08:54 http://photojournal.jpl.nasa.gov/catalog/PIA21504

  16. IR Detectors Technology

    DTIC Science & Technology

    2007-11-02

    per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and...2 1. Introduction The final report summarizes the results of continuing research and development of CZT substrates for fabrication of IR focal...agreed, that tasks 3 and 4 will be done in the first half of September based on time availability of the polishing lab and the summary will be sent

  17. The VISTA IR camera

    NASA Astrophysics Data System (ADS)

    Dalton, Gavin B.; Caldwell, Martin; Ward, Kim; Whalley, Martin S.; Burke, Kevin; Lucas, John M.; Richards, Tony; Ferlet, Marc; Edeson, Ruben L.; Tye, Daniel; Shaughnessy, Bryan M.; Strachan, Mel; Atad-Ettedgui, Eli; Leclerc, Melanie R.; Gallie, Angus; Bezawada, Nagaraja N.; Clark, Paul; Bissonauth, Nirmal; Luke, Peter; Dipper, Nigel A.; Berry, Paul; Sutherland, Will; Emerson, Jim

    2004-09-01

    The VISTA IR Camera has now completed its detailed design phase and is on schedule for delivery to ESO"s Cerro Paranal Observatory in 2006. The camera consists of 16 Raytheon VIRGO 2048x2048 HgCdTe arrays in a sparse focal plane sampling a 1.65 degree field of view. A 1.4m diameter filter wheel provides slots for 7 distinct science filters, each comprising 16 individual filter panes. The camera also provides autoguiding and curvature sensing information for the VISTA telescope, and relies on tight tolerancing to meet the demanding requirements of the f/1 telescope design. The VISTA IR camera is unusual in that it contains no cold pupil-stop, but rather relies on a series of nested cold baffles to constrain the light reaching the focal plane to the science beam. In this paper we present a complete overview of the status of the final IR Camera design, its interaction with the VISTA telescope, and a summary of the predicted performance of the system.

  18. Effect of intense laser IR fields on triatomic molecules

    NASA Astrophysics Data System (ADS)

    Ivanov, S. V.; Panchenko, V. Ia.; Chugunov, A. V.

    1986-04-01

    Theoretical and experimental results on the effect of intense laser IR fields on triatomic molecular gases are presented with particular emphasis on ozone. Experiments were conducted in single- and double-frequency IR fields at power densities ranging from 10 to the -6th to 10 GW/sq cm in the pulsed regime and 0.001 to 100 W/sq cm in the CW regime; studies were performed using a TEA CO2 laser system. Attention is given to: the nonlinear absorption spectrum; the dependence of absorption in ozone on the power density of incident radiation; results of numerical solutions; the analytical solution; two-photon resonances in the ozone absorption spectrum; the spectrum of double-frequency IR-IR absorption; cascade-excitation channels; and laser-stimulated explosion in ozone.

  19. IR and visible luminescence studies in the infrared multiphoton dissociation of 1,2-dibromo-1,1-difluoroethane

    NASA Astrophysics Data System (ADS)

    Pushpa, K. K.; Kumar, Awadhesh; Vatsa, R. K.; Naik, P. D.; Annaji Rao, K.; Mittal, J. P.; Parthasarathy, V.; Sarkar, S. K.

    1995-07-01

    The infrared multiphoton dissociation of 1,2-dibromo-1,1-difluoroethane gives rise to IR and visible luminescence. Vibrationally excited parent molecules dissociate via two primary channels yielding bromine and vibrationally excited HBr. The strong visible emission observed between 350 to 750 nm has been assigned to electronically excited carbene CF 2Br CH.

  20. IR Earth Flats Pathfinder

    NASA Astrophysics Data System (ADS)

    McCullough, Peter

    2009-07-01

    This program is an experimental path finder for Cycle 18 calibration. {The WFC3 UVIS version of this is program 11914 and contains additional detail in its description}. Infrared-wavelength flat fields will be obtained by observing the dark side of the Earth during periods of full moon illumination. The observations will consist of full-frame streaked WFC3 IR imagery: per single "dark-sky" orbit, we anticipate achieving Poisson S/N > 100 per pixel in each of three to five exposures, depending on sample sequence {SPARS25 or SPARS50}.Why not use the Sunlit Earth? It is too bright for WFC3 IR full-frame minimum exposure time of 3 sec. Similarly, for NICMOS the sunlit-Earth is too bright which saturates the detector too quickly and/or induces abnormal behaviors such as super-shading {Gilmore 1998, NIC 098-011}. In the narrowband IR filters the sunlit earth sometimes is faint enough to not saturate immediately, but based upon predictions {Cox et al. 1987 "Standard Astronomical Sources for HST: 6. Spatially Flat Fields."} and observations {Gilmore 1998}, we consider sunlit Earth unlikely to be successful unless it is twilight.Other possibilities? Cox et al.'s Section II.D addresses many other possible sources for flat fields, rejecting them for a variety of reasons. A remaining possibility would be the totally eclipsed moon. Such eclipses provide approximately 2 hours {1 HST orbit} of opportunity per year, so they are too rare to be generically useful. An advantage of the moon over the Earth is that the moon subtends less than 0.25 square degree, whereas the Earth subtends a steradian or more, so scattered light and light prior to the unshuttered exposure presents additional problems for the Earth. Also, we're unsure if HST can point 180 deg from the Sun.

  1. IR Spot Weld Inspect

    SciTech Connect

    Chen, Jian; Feng, Zhili

    2014-01-01

    In automotive industry, destructive inspection of spot welds is still the mandatory quality assurance method due to the lack of efficient non-destructive evaluation (NDE) tools. However, it is costly and time-consuming. Recently at ORNL, a new NDE prototype system for spot weld inspection using infrared (IR) thermography has been developed to address this problem. This software contains all the key functions that ensure the NDE system to work properly: system input/output control, image acquisition, data analysis, weld quality database generation and weld quality prediction, etc.

  2. The IRS-1 signaling system.

    PubMed

    White, M F

    1994-02-01

    IRS-1 is a principal substrate of the insulin receptor tyrosine kinase. It undergoes multi-site tyrosine phosphorylation and mediates the insulin signal by associating with various signaling molecules containing Src homology 2 domains. Interleukin-4 also stimulates IRS-1 phosphorylation, and it is suspected that a few more growth factors or cytokines will be added to form a select group of receptors that utilize the IRS-1 signaling pathway. More IRS-1-like adapter molecules, such as 4PS (IRS-2), may remain to be found.

  3. Tumor diagnostics using fiber optical IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Winter, Harald; Bindig, Uwe; Waesche, Wolfgang; Liebold, K.; Roggan, Andre; Frege, P.; Gross, U. M.; Mueller, G.

    1999-04-01

    Aim of the project is the development of an in vivo endoscopic method to differentiate between cancerous from healthy tissue. The method is based on IR spectra in which each diseased state of the tissue has its own characteristic pattern as already shown in previous experiments. Two regions (1245 - 1195) cm-1 and (1045 - 995) cm-1 within the fingerprint (less than 1500 cm-1) region were selected for analysis. This paper will present the technical design of the laboratory set up and outcome of the development as well as the experiments. Two lead-salt diode lasers were used as excitation sources. The IR-radiation was transmitted via silverhalide fibers to the tissue to be investigated. On the detection side another IR fiber was used to transmit the signal to an MCT-detector (Mercury-Cadmium-Telluride). Measurement modes are Attenuated Total Reflectance (ATR) and diffuse Reflection/Remission. Spatial resolution was 100 X 100 micrometer2. The tissue used for these experiments was human colon carcinoma under humidity conditions. Samples were mapped using a stepper motor powered x/y/z-translation stage with a resolution of 1 micrometer. Results were compared with measurements carried out using a FTIR-interferometer and an FTIR-microscope in the region from 4000 - 900 cm-1. Soft- and Hardware control of the experiment is done using Labwindows/CVI (National Instruments, USA).

  4. Spectroscopy and reactions of vibrationally excited transient molecules

    SciTech Connect

    Dai, H.L.

    1993-12-01

    Spectroscopy, energy transfer and reactions of vibrationally excited transient molecules are studied through a combination of laser-based excitation techniques and efficient detection of emission from the energized molecules with frequency and time resolution. Specifically, a Time-resolved Fourier Transform Emission Spectroscopy technique has been developed for detecting dispersed laser-induced fluorescence in the IR, visible and UV regions. The structure and spectroscopy of the excited vibrational levels in the electronic ground state, as well as energy relaxation and reactions induced by specific vibronic excitations of a transient molecule can be characterized from time-resolved dispersed fluorescence in the visible and UV region. IR emissions from highly vibrational excited levels, on the other hand, reveal the pathways and rates of collision induced vibrational energy transfer.

  5. Coherent IR radar technology

    NASA Astrophysics Data System (ADS)

    Gschwendtner, A. B.; Harney, R. C.; Hull, R. J.

    Recent progress in the development of coherent IR radar equipment is reviewed, focusing on the Firepond laser radar installation and the more compact systems derived for it. The design and capabilities of Firepond as a long-range satellite-tracking device are outlined. The technological improvements necessary to make laser radar mobile are discussed: a lightweight, stable 5-10-W transmitter laser for both CW and pulsed operation, a 12-element HgCdTe detector array, an eccentric-pupil Ritchey-Chretien telescope, and a combination of near-field phase modification and anamorphic expansion to produce a fan beam of relatively uniform intensity. Sample images obtained with a prototype system are shown, and the applicability of the mobile system to range-resolved coherent DIAL measurement is found to be similar to that of a baseline DIAL system.

  6. Integrated IR sensors

    NASA Astrophysics Data System (ADS)

    Tom, Michael; Trujillo, Edward

    1994-06-01

    Integrated infrared (IR) sensors which exploit modular avionics concepts can provide features such as operational flexibility, enhanced stealthiness, and ease of maintenance to meet the demands of tactical, airborne sensor systems. On-board, tactical airborne sensor systems perform target acquisition, tracking, identification, threat warning, missile launch detection, and ground mapping in support of situation awareness, self-defense, navigation, target attack, weapon support, and reconnaissance activities. The use of sensor suites for future tactical aircraft such as US Air Force's multirole fighter require a blend of sensor inputs and outputs that may vary over time. It is expected that special-role units of these tactical aircraft will be formed to conduct tasks and missions such as anti-shipping, reconnaissance, or suppression of enemy air defenses.

  7. The IRS-1 signaling system.

    PubMed

    Myers, M G; Sun, X J; White, M F

    1994-07-01

    Insulin-receptor substrate 1 (IRS-1) is a principal substrate of the receptor tyrosine kinase for insulin and insulin-like growth factor 1, and a substrate for a tyrosine kinase activated by interleukin 4. IRS-1 undergoes multisite tyrosine phosphorylation and mediates downstream signals by 'docking' various proteins that contain Src homology 2 domains. IRS-1 appears to be a unique molecule; however, 4PS, a protein found mainly in hemopoietic cells, may represent another member of this family.

  8. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  9. Photocycloaddition of anthracene to excited C-60

    SciTech Connect

    Gol`dshleger, N.F.; Denisov, N.N.; Lobach, A.S.

    1995-02-01

    The ability to participate in photochemical cycloaddition reactions is characteristic feature of chromophores with a carbon double bond. In this work, the authors demonstrate the formation of an adduct by cycloaddition of anthracene to the triplet-excited C-60 fullerene under anaerobic conditions, which provides a straight forward way to synthesize new derivatives of C-60 fullerenes. Reaction methods, conditions, and mechanisms are included along with the characterization of the fullerene derivative with IR, MS, and NMR methods.

  10. MMW/IR beam combiner with graphene IR window for MMW/IR compact range compound test

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Li, Yanhong; Pang, Xudong; Zhu, Weihua; Wang, Liquan; Liu, Zhigang; Wang, Tailei; Zhu, Shouzheng

    2017-06-01

    A millimeter wave (MMW)/infrared (IR) beam combiner with a graphene IR window for the MMW/IR compact range (CR) compound test is creatively proposed with comprehensive analysis and simulation. Graphene is used as the IR window material to transfer the IR feed signal behind a perforated MMW CR reflector for it has the unique property of high IR transmissivity and high MMW conductivity. This research shows that graphene IR windows have better IR transmissivity than conducting inductive mesh IR windows when the beam combiner meets the MMW CR test demanding. Graphene IR windows also show a better MMW test bandwidth than dielectric IR windows. Meanwhile, the graphene IR window MMW/IR beam combiner has a circular aperture test zone with which it is sufficient to test a cylindrical unit under test according to the requirement.

  11. Molecular hydrogen in the vicinity of NGC 7538 IRS 1 and IRS 2 - Temperature and ortho-to-para ratio

    NASA Technical Reports Server (NTRS)

    Hoban, Susan; Reuter, Dennis C.; Mumma, Michael J.; Storrs, Alex D.

    1991-01-01

    Near-infrared spectroscopic observations of the active star-forming region near NGC 7538 IRS 1 and IRS 2 were made. The relative intensities of the v = 1-0 Q(1), Q(3), and Q(5) lines of molecular hydrogen are used to calculate a rotational excitation temperature. Comparison of the measured intensity of the Q(2) transition relative to the intensity of Q(1) and Q(3) permitted the retrieval of the ratio of ortho-to-para hydrogen. It is found that an ortho-to-para ratio of between 1.6 and 2.35 is needed to explain the Q-branch line intensity ratios, depending on the excitation model used. This range in ortho-to-para ratios implies a range of molecular hydrogen formation temperature of approximately 105 K to 140 K.

  12. Cr:ZnSe planar waveguide mid-IR laser

    NASA Astrophysics Data System (ADS)

    Willimas, J. E.; Martyshkin, D. V.; Fedorov, V. V.; Moskalev, I. S.; Camata, R. P.; Mirov, S. B.

    2011-02-01

    Middle infrared (mid-IR) chromium-doped zinc selenide (Cr:ZnSe) bulk lasers have attracted a lot of attention due to their unique combination of optical and laser properties facilitating a wide range of potential scientific, industrial, and medical applications. Utilization of thin film waveguide geometry enabling good thermal management and control of beam quality is a viable pathway for compact chip-integrated optical laser design. Cr:ZnSe thin films are also promising as saturable absorbers and mode-lockers of the cavities of solid state lasers operating over 1.3-2.1 μm. We recently reported the first successful demonstration of mid-IR Cr:ZnSe planar waveguide lasing at 2.6 μm under gain-switched short-pulse (5 ns) 1.56 μm excitation as well as the passive Q-switching of the cavity of a fiber-pumped Er:YAG laser operating at 1645 nm using a highly doped Cr:ZnSe thin film. PLD grown Cr:ZnSe waveguide were fabricated on sapphire substrates (Cr:ZnSe/sapphire) with chromium concentration of 1018-1019 cm-3. Further development of mid-IR lasing in the Cr:ZnSe planar waveguide under continuous wave excitation were investigated. In addition, deposition of Cr:ZnSe-based thin film structures on n-type GaAs substrates were also investigated for possible mid-IR electroluminescence.

  13. Portable vibration exciter

    NASA Technical Reports Server (NTRS)

    Beecher, L. C.; Williams, F. T.

    1970-01-01

    Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

  14. Excited charmed mesons

    SciTech Connect

    Butler, J.N.; Shukla, S.

    1995-05-01

    The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.

  15. Collective Autoionization in Multiply-Excited Systems: A novel ionization process observed in Helium Nanodroplets

    PubMed Central

    LaForge, A. C.; Drabbels, M.; Brauer, N. B.; Coreno, M.; Devetta, M.; Di Fraia, M.; Finetti, P.; Grazioli, C.; Katzy, R.; Lyamayev, V.; Mazza, T.; Mudrich, M.; O'Keeffe, P.; Ovcharenko, Y.; Piseri, P.; Plekan, O.; Prince, K. C.; Richter, R.; Stranges, S.; Callegari, C.; Möller, T.; Stienkemeier, F.

    2014-01-01

    Free electron lasers (FELs) offer the unprecedented capability to study reaction dynamics and image the structure of complex systems. When multiple photons are absorbed in complex systems, a plasma-like state is formed where many atoms are ionized on a femtosecond timescale. If multiphoton absorption is resonantly-enhanced, the system becomes electronically-excited prior to plasma formation, with subsequent decay paths which have been scarcely investigated to date. Here, we show using helium nanodroplets as an example that these systems can decay by a new type of process, named collective autoionization. In addition, we show that this process is surprisingly efficient, leading to ion abundances much greater than that of direct single-photon ionization. This novel collective ionization process is expected to be important in many other complex systems, e.g. macromolecules and nanoparticles, exposed to high intensity radiation fields. PMID:24406316

  16. Optical/IR from ground

    NASA Technical Reports Server (NTRS)

    Strom, Stephen; Sargent, Wallace L. W.; Wolff, Sidney; Ahearn, Michael F.; Angel, J. Roger; Beckwith, Steven V. W.; Carney, Bruce W.; Conti, Peter S.; Edwards, Suzan; Grasdalen, Gary

    1991-01-01

    Optical/infrared (O/IR) astronomy in the 1990's is reviewed. The following subject areas are included: research environment; science opportunities; technical development of the 1980's and opportunities for the 1990's; and ground-based O/IR astronomy outside the U.S. Recommendations are presented for: (1) large scale programs (Priority 1: a coordinated program for large O/IR telescopes); (2) medium scale programs (Priority 1: a coordinated program for high angular resolution; Priority 2: a new generation of 4-m class telescopes); (3) small scale programs (Priority 1: near-IR and optical all-sky surveys; Priority 2: a National Astrometric Facility); and (4) infrastructure issues (develop, purchase, and distribute optical CCDs and infrared arrays; a program to support large optics technology; a new generation of large filled aperture telescopes; a program to archive and disseminate astronomical databases; and a program for training new instrumentalists)

  17. Resonant tunneling IR detectors

    NASA Technical Reports Server (NTRS)

    Woodall, Jerry M.; Smith, T. P., III

    1990-01-01

    Researchers propose a novel semiconductor heterojunction photodetector which would have a very low dark current and would be voltage tunable. A schematic diagram of the device and its band structure are shown. The two crucial components of the device are a cathode (InGaAs) whose condition band edge is below the conduction band edge of the quantum wells and a resonant tunneling filter (GaAs-AlGaAs). In a standard resonant tunneling device the electrodes are made of the same material as the quantum wells, and this device becomes highly conducting when the quantum levels in the wells are aligned with the Fermi level in the negatively biased electrode. In contrast, the researchers device is essentially non-conducting under the same bias conditions. This is because the Fermi Level of the cathode (InGaAs) is still well below the quantum levels so that no resonant transport occurs and the barriers (AlGaAs) effectively block current flow through the device. However, if light with the same photon energy as the conduction-band discontinuity between the cathode and the quantum wells, E sub c3-E sub c1, is shone on the sample, free carriers will be excited to an energy corresponding to the lowest quantum level in the well closest to the cathode (hv plue E sub c1 = E sub o). These electrons will resonantly tunnel through the quantum wells and be collected as a photocurrent in the anode (GaAs). To improve the quantum efficiency, the cathode (InGaAs) should be very heavily doped and capped with a highly reflective metal ohmic contact. The thickness of the device should be tailored to optimize thin film interference effects and afford the maximum absorption of light. Because the device relies on resonant tunneling, its response should be very fast, and the small voltages needed to change the responsivity should allow for very high frequency modulation of the photocurrent. In addition, the device is tuned to a specific photon energy so that it can be designed to detect a fairly

  18. Acoustically excited heated jets. 1: Internal excitation

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

    1988-01-01

    The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.

  19. Excited state dependent electron transfer of a rhenium-dipyridophenazine complex intercalated between the base pairs of DNA: a time-resolved UV-visible and IR absorption investigation into the photophysics of fac-[Re(CO)3(F2dppz)(py)]+ bound to either [poly(dA-dT)]2 or [poly(dG-dC)]2.

    PubMed

    Cao, Qian; Creely, Caitriona M; Davies, E Stephen; Dyer, Joanne; Easun, Timothy L; Grills, David C; McGovern, David A; McMaster, Jonathan; Pitchford, Jonathan; Smith, Jayden A; Sun, Xue-Zhong; Kelly, John M; George, Michael W

    2011-08-01

    The transient species formed following excitation of fac-[Re(CO)(3)(F(2)dppz)(py)](+) (F(2)dppz = 11,12-difluorodipyrido[3,2-a:2',3'-c]phenazine) bound to double-stranded polynucleotides [poly(dA-dT)](2) or [poly(dG-dC)](2) have been studied by transient visible and infra-red spectroscopy in both the picosecond and nanosecond time domains. The latter technique has been used to monitor both the metal complex and the DNA by monitoring the regions 1900-2100 and 1500-1750 cm(-1) respectively. These data provide direct evidence for electron transfer from guanine to the excited state of the metal complex, which proceeds both on a sub-picosecond time scale and with a lifetime of 35 ps, possibly due to the involvement of two excited states. No electron transfer is found for the [poly(dA-dT)](2) complex, although characteristic changes are seen in the DNA-region TRIR consistent with changes in the binding of the bases in the intercalation site upon excitation of the dppz-complex. This journal is © The Royal Society of Chemistry and Owner Societies 2011

  20. Infrared/ultraviolet quadruple resonance spectroscopy to investigate structures of electronically excited states

    SciTech Connect

    Weiler, M.; Bartl, K.; Gerhards, M.

    2012-03-21

    Molecular beam investigations in combination with IR/UV spectroscopy offer the possibility to obtain structural information on isolated molecules and clusters. One of the demanding tasks is the discrimination of different isomers, e.g., by the use of isomer specific UV excitations. If this discrimination fails due to overlaying UV spectra of different isomers, IR/IR methods offer another possibility. Here, we present a new IR/UV/IR/UV quadruple resonance technique to distinguish between different isomers especially in the electronically excited state. Due to the IR spectra, structural changes and photochemical pathways in excited states can be assigned and identified. The method is applied to the dihydrated cluster of 3-hydroxyflavone which has been investigated as photochemically relevant system and proton wire model in the S{sub 1} state. By applying the new IR/UV/IR/UV technique, we are able to show experimentally that both in the electronic ground (S{sub 0}) and the electronically excited state (S{sub 1}) two isomers have to be assigned.

  1. Single photon excimer laser photodissociation of highly vibrationally excited polyatomic molecules

    SciTech Connect

    Tiee, J.J.; Wampler, F.B.; Rice, W.W.

    1980-01-01

    The ir + uv photodissociation of SF/sub 6/ has been performed using CO/sub 2/ and ArF lasers. The two-color photolysis significantly enhances the photodissociation process over ArF irradiation alone and is found to preserve the initial isotopic specificity of the ir excitation process.

  2. Nanoscale infrared (IR) spectroscopy and imaging of structural lipids in human stratum corneum using an atomic force microscope to directly detect absorbed light from a tunable IR laser source.

    PubMed

    Marcott, Curtis; Lo, Michael; Kjoller, Kevin; Domanov, Yegor; Balooch, Guive; Luengo, Gustavo S

    2013-06-01

    An atomic force microscope (AFM) and a tunable infrared (IR) laser source have been combined in a single instrument (AFM-IR) capable of producing ~200-nm spatial resolution IR spectra and absorption images. This new capability enables IR spectroscopic characterization of human stratum corneum at unprecendented levels. Samples of normal and delipidized stratum corneum were embedded, cross-sectioned and mounted on ZnSe prisms. A pulsed tunable IR laser source produces thermomechanical expansion upon absorption, which is detected through excitation of contact resonance modes in the AFM cantilever. In addition to reducing the total lipid content, the delipidization process damages the stratum corneum morphological structure. The delipidized stratum corneum shows substantially less long-chain CH2 -stretching IR absorption band intensity than normal skin. AFM-IR images that compare absorbances at 2930/cm (lipid) and 3290/cm (keratin) suggest that regions of higher lipid concentration are located at the perimeter of corneocytes in the normal stratum corneum.

  3. Modeling Turbine Blade Crack Detection in Sonic IR Imaging with a Method of Creating Flat Crack Surface in FEA (Preprint)

    DTIC Science & Technology

    2011-11-01

    and subsequent crack heating requires fundamental understanding of physical and thermal processes in complex geometries such as turbine blades...interaction of the sonic excitation and subsequent crack heating requires fundamental understanding of physical and thermal processes in complex...external ultrasound excitation as the results of applying this new method, guided by our experimental Sonic IR imaging study on the blade. Keywords

  4. Spectroscopic and Raman excitation profile studies of 3-benzoylpyridine

    NASA Astrophysics Data System (ADS)

    Sett, Pinaky; Datta, Shirsendu; Chowdhury, Joydeep; Ghosh, Manash; Mallick, Prabal Kumar

    2017-03-01

    In the present work IR, UV absorption and Raman spectra including Raman excitation profiles and structure of 3-benzoyl pyridine have been investigated. Detailed studies on the vibrational and electronic properties of the molecule have been carried out. All these studies are aided with valuable quantum chemical calculations. The structural changes encountered on excitation to the low lying excited states have been investigated. Theoretical profiles determined by the sum-over-states method based on pertinent Franck-Condon and Herzberg-Teller terms have satisfactorily simulated the experimentally measured relative Raman intensities and these are also in compliance with the structural changes and potential energy distributions.

  5. Multiple photon emission in heavy particle decays

    NASA Technical Reports Server (NTRS)

    Asakimori, K.; Burnett, T. H.; Cherry, M. L.; Christl, M. J.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.

    1994-01-01

    Cosmic ray interactions, at energies above 1 TeV/nucleon, in emulsion chambers flown on high altitude balloons have yielded two events showing apparent decays of a heavy particle into one charged particle and four photons. The photons converted into electron pairs very close to the decay vertex. Attempts to explain this decay topology with known particle decays are presented. Unless both events represent a b yields u transition, which is statistically unlikely, then other known decay modes for charmed or bottom particles do not account satisfactorily for these observations. This could indicate, possibly, a new decay channel.

  6. Bond strength and electronic structures of coherent Ir /Ir3Zr interfaces

    NASA Astrophysics Data System (ADS)

    Gong, H. R.; Liu, Yong; Tang, Hui Ping; Xiang, Chang Shu

    2008-05-01

    First principles calculation reveals that the coherent Ir /Ir3Zr interfaces possess high values of bond strength and that interface orientation and atomic configuration have important effects on interface bonding and interface energy. Calculation also shows that the interface dipole is formed in the Ir /Ir3Zr interface due to an unequal loss of the electrons from Ir and Ir3Zr atoms, and density of states suggests that a stronger covalent bonding is formed in the interface than corresponding Ir or Ir3Zr bulks, which results in the strengthening effect of the Ir3Zr precipitation in the Ir-base superalloys from experimental observations in the literature.

  7. Disordered dimer state in electron-doped Sr3Ir2O7

    NASA Astrophysics Data System (ADS)

    Hogan, Tom; Dally, Rebecca; Upton, Mary; Clancy, J. P.; Finkelstein, Kenneth; Kim, Young-June; Graf, M. J.; Wilson, Stephen D.

    2016-09-01

    Spin excitations are explored in the electron-doped spin-orbit Mott insulator (Sr1-xLax) 3Ir2O7 . As this bilayer square lattice system is doped into the metallic regime, long-range antiferromagnetism vanishes, yet a spectrum of gapped spin excitation remains. Excitation lifetimes are strongly damped with increasing carrier concentration, and the energy-integrated spectral weight becomes nearly momentum independent as static spin order is suppressed. Local magnetic moments, absent in the parent system, grow in metallic samples and approach values consistent with one J =1/2 impurity per electron doped. Our combined data suggest that the magnetic spectra of metallic (Sr1-xLax) 3Ir2O7 are best described by excitations out of a disordered dimer state.

  8. Near IR-emitting DNA-probes exploiting stepwise energy transfer processes.

    PubMed

    Bodi, Andras; Borbas, K Eszter; Bruce, James I

    2007-10-10

    The synthesis and characterisation of two new cyclen-based near IR-emitting lanthanide complexes is reported; the lanthanides are sensitised by rhodamine, which in turn is excited by energy transfer from a coumarin 2 moiety. The three lumophores function as an energy transfer cascade spanning the UV-visible-near IR region of the spectrum, resulting in large Stokes shifts. Double stranded DNA selectively switches one of the two energy transfer processes off, enabling luminescent DNA-sensing in the near IR region. The regioselective di-alkylation of the cyclen scaffold is explained with the help of DFT calculations.

  9. Non-Statistical Oligopeptide Fragmentation by IR Photons with λ=16-18 μm

    NASA Astrophysics Data System (ADS)

    Jungclas, Hartmut; Komarov, Viacheslav V.; Popova, Anna M.; Schmidt, Lothar

    2015-12-01

    In this article we analyse the vibration excitation and following dissociation of protonated oligopeptide molecules induced by IR photons with λ=16-18 μm. The analysis is based on our previous works in which we considered a specific non-statistical dissociation process in organic molecules containing substructures consisting of chained identical diatomic dipoles such as (CH2)n. Such dipole chains can serve as IR antennas for external radiation in the IR frequency range. The acquired vibration energy accumulated in IR antennas can be large enough to dissociate molecules within a femtosecond time interval by a non-statistical process, which is driven by a radiationless low-energy transport mechanism inside the peptide molecules. We point out in this article that the suggested IR-induced dissociation mechanism can be applied to obtain sequence information of protonated oligopeptides.

  10. Bis-cyclometalated Ir(III) complexes as efficient singlet oxygen sensitizers.

    PubMed

    Gao, Ruomei; Ho, David G; Hernandez, Billy; Selke, Matthias; Murphy, Drew; Djurovich, Peter I; Thompson, Mark E

    2002-12-18

    We report the singlet oxygen sensitization properties of a series of bis-cyclometalated Ir(III) complexes (i.e., (bt)2Ir(acac), (bsn)2Ir(acac), and (pq)2Ir(acac); bt = 2-phenylbenzothiazole, bsn = 2-(1-naphthyl)benzothiazole, pq = 2-phenylquinoline, and acac = acetylacetonate). Complexes with acetylacetonate ancillary ligands give singlet oxygen quantum yields near unity (PhiDelta = (0.7-1.0) +/- 0.1), whether exciting the ligand-based state or the lowest energy excited state (MLCT + 3LC). The singlet oxygen quenching rates for these beta-diketonate complexes were found to be small [(5 +/- 2) x 105 to (6 +/- 0.2) x 106 M-1 s-1], roughly 3 orders of magnitude slower than the corresponding phosphorescence quenching rate. Similar complexes were prepared with glycine or pyridine tethered to the Ir(III) center (i.e., (bsn)2Ir(gly) and (bt)2Ir(py)Cl; gly = glycine and py = pyridine). The glycine and pyridine derivatives give high singlet oxygen yields (PhiDelta = (0.7-1.0) +/- 0.1).

  11. Localized excitations in hydrogen-bonded molecular crystals

    NASA Astrophysics Data System (ADS)

    Alexander, D. M.; Krumhansl, J. A.

    1986-05-01

    Localized excitations analogous to the small Holstein polaron, to localized modes in alkali halides, and to localized excitonic states, are postulated for a set of internal vibrational modes in crystalline acetanilide. The theoretical framework in which one can describe the characteristics of the ir and Raman spectroscopy peaks associated with these localized states is adequately provided by the Davydov model (formally equivalent to the Holstein polaron model). The possible low-lying excitations arising from this model are determined using a variational approach. Hence, the contribution to the spectral function due to each type of excitation can be calculated. The internal modes of chief concern here are the amide-I (CO stretch) and the N-H stretch modes for which we demonstrate consistency of the theoretical model with the available ir data. Past theoretical approaches will be discussed and reasons why one should prefer one description over another will be examined.

  12. Giant spin gap and magnon localization in the disordered Heisenberg antiferromagnet Sr2Ir1-xRuxO4

    DOE PAGES

    Cao, Yue; Liu, X.; Xu, Wenhu; ...

    2017-03-06

    Here, we study the evolution of magnetic excitations in the disordered two-dimensional antiferromagnet Sr2Ir1–xRuxO4. The maximum energy of the magnetic excitation remains robust up to x = 0.77, with a gap opening at low dopings and increasing to over 150 meV at x = 0.77. At these higher Ru concentrations, the dispersive magnetic excitations in Sr2IrO4 are rendered essentially momentum independent. Up to a Ru concentration of x = 0.77, both experiments and first-principles calculations show the Ir Jeff = 1/2 state remains intact. The magnetic gap arises from the local interaction anisotropy in the proximity of the Ru disorder.more » Under the coherent potential approximation, we reproduce the experimental magnetic excitations using the disordered Heisenberg antiferromagnetic model with suppressed next-nearest-neighbor ferromagnetic coupling.« less

  13. Giant spin gap and magnon localization in the disordered Heisenberg antiferromagnet Sr2Ir1 -xRuxO4

    NASA Astrophysics Data System (ADS)

    Cao, Yue; Liu, X.; Xu, Wenhu; Yin, Wei-Guo; Meyers, D.; Kim, Jungho; Casa, Diego; Upton, M. H.; Gog, Thomas; Berlijn, Tom; Alvarez, Gonzalo; Yuan, Shujuan; Terzic, Jasminka; Tranquada, J. M.; Hill, John P.; Cao, Gang; Konik, Robert M.; Dean, M. P. M.

    2017-03-01

    We study the evolution of magnetic excitations in the disordered two-dimensional antiferromagnet Sr2Ir1 -xRuxO4 . The maximum energy of the magnetic excitation remains robust up to x =0.77 , with a gap opening at low dopings and increasing to over 150 meV at x =0.77 . At these higher Ru concentrations, the dispersive magnetic excitations in Sr2IrO4 are rendered essentially momentum independent. Up to a Ru concentration of x =0.77 , both experiments and first-principles calculations show the Ir Jeff=1 /2 state remains intact. The magnetic gap arises from the local interaction anisotropy in the proximity of the Ru disorder. Under the coherent potential approximation, we reproduce the experimental magnetic excitations using the disordered Heisenberg antiferromagnetic model with suppressed next-nearest-neighbor ferromagnetic coupling.

  14. Theoretical studies of Ir5Th and Ir5Ce nanoscale precipitates in Ir

    SciTech Connect

    Morris, James R; Averill, Frank; Cooper, Valentino R

    2014-01-01

    Experimentally, it is known that very small amounts of thorium and/or cerium added to iridium metal form a precipitate, Ir5Th / Ir5Ce, which improves the high temperature mechanical properties of the resulting alloys. We demonstrate that there are low-energy configurations for nano-scale precipitates of these phases in Ir, and that these coherent arrangements may assist in producing improved mechanical properties. One precipitate/matrix orientation gives a particularly low interfacial energy, and a low lattice misfit. Nanolayer precipitates with this orientation are found to be likely to form, with little driving force to coarsen. The predicted morphology of the precipitates and their orientation with the matrix phase provide a potential experiment that could be used to test these predictions.

  15. Sensitisation of Eu(III)- and Tb(III)-based luminescence by Ir(III) units in Ir/lanthanide dyads: evidence for parallel energy-transfer and electron-transfer based mechanisms.

    PubMed

    Sykes, Daniel; Cankut, Ahmet J; Ali, Noorshida Mohd; Stephenson, Andrew; Spall, Steven J P; Parker, Simon C; Weinstein, Julia A; Ward, Michael D

    2014-05-07

    A series of blue-luminescent Ir(III) complexes with a pendant binding site for lanthanide(III) ions has been synthesized and used to prepare Ir(III)/Ln(III) dyads (Ln = Eu, Tb, Gd). Photophysical studies were used to establish mechanisms of Ir→Ln (Ln = Tb, Eu) energy-transfer. In the Ir/Gd dyads, where direct Ir→Gd energy-transfer is not possible, significant quenching of Ir-based luminescence nonetheless occurred; this can be ascribed to photoinduced electron-transfer from the photo-excited Ir unit (*Ir, (3)MLCT/(3)LC excited state) to the pendant pyrazolyl-pyridine site which becomes a good electron-acceptor when coordinated to an electropositive Gd(III) centre. This electron transfer quenches the Ir-based luminescence, leading to formation of a charge-separated {Ir(4+)}˙-(pyrazolyl-pyridine)˙(-) state, which is short-lived possibly due to fast back electron-transfer (<20 ns). In the Ir/Tb and Ir/Eu dyads this electron-transfer pathway is again operative and leads to sensitisation of Eu-based and Tb-based emission using the energy liberated from the back electron-transfer process. In addition direct Dexter-type Ir→Ln (Ln = Tb, Eu) energy-transfer occurs on a similar timescale, meaning that there are two parallel mechanisms by which excitation energy can be transferred from *Ir to the Eu/Tb centre. Time-resolved luminescence measurements on the sensitised Eu-based emission showed both fast and slow rise-time components, associated with the PET-based and Dexter-based energy-transfer mechanisms respectively. In the Ir/Tb dyads, the Ir→Tb energy-transfer is only just thermodynamically favourable, leading to rapid Tb→Ir thermally-activated back energy-transfer and non-radiative deactivation to an extent that depends on the precise energy gap between the *Ir and Tb-based (5)D4 states. Thus, the sensitised Tb(iii)-based emission is weak and unusually short-lived due to back energy transfer, but nonetheless represents rare examples of Tb(III) sensitisation by

  16. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.

    1959-08-01

    A cavity excitation circuit is described for rapidly building up and maintaining high-level oscillations in a resonant cavity. The circuit overcomes oscillation buildup slowing effects such as ion locking in the cavity by providing for the selective application of an amplified accelerating drive signal to the main cavity exciting oscillator during oscillation buildup and a direct drive signal to the oscillator thereafter.

  17. Dust content in compact HII regions (NGC 7538-IRS1, IRS2, and IRS3)

    NASA Astrophysics Data System (ADS)

    Akabane, K.; Kuno, N.

    2005-02-01

    The luminosity of the central star of the compact HII regions of NGC 7538 was estimated from the solid angle of the IR sources subtended relative to the central star, and was found to be 5˜ 10 times as intense as that of IR sources. Under the single central star approximation, the luminosity gives a stellar UV photon rate NU(*) (s-1) of ˜3.0 × 1048, ˜1.5 × 1049, ˜5.1 × 1049, and ˜1.7 × 1047 for the compact HII regions of NGC 7538-IRS1(A/2), B, IRS2, and IRS3, respectively. NU (*) and the observed electron density, ne, provide the dust opacity of the ionizing photon, τSd, for the optical path out to the Strömgren sphere radius rS, assuming a gas with standard dust content. Ionizing photon opacity over the same optical path but with the actual dust content τSda is also derived from ri / rS, where ri is the radius of the ionized sphere, which is estimated from NU(*) and the observed volume emission measure ne2 (4 π ri3/3) (Spitzer \\cite{Spitzer1978}). An observational trend of γ NU(*) / 4π ri2 1/2 ˜ constant, where γ = τSda / τSd}, was obtained for the 4 compact HII regions of the NGC 7538(N). Fourteen selected compact HII regions from data catalogued by VLA observations were examined for this trend, and a similar result was obtained. A limit of γ as 15 ≥ γ ≥ 0.1 was given for the 14 selected sources. The size of the dust-depleted cavity of the NGC 7538(N) suggested by Chini et al. (\\cite{Chini1986}) coincides with that of the ionized sphere of the IRS2 of the region.

  18. Compact IR synchrotron beamline design.

    PubMed

    Moreno, Thierry

    2017-03-01

    Third-generation storage rings are massively evolving due to the very compact nature of the multi-bend achromat (MBA) lattice which allows amazing decreases of the horizontal electron beam emittance, but leaves very little place for infrared (IR) extraction mirrors to be placed, thus prohibiting traditional IR beamlines. In order to circumvent this apparent restriction, an optimized optical layout directly integrated inside a SOLEIL synchrotron dipole chamber that delivers intense and almost aberration-free beams in the near- to mid-IR domain (1-30 µm) is proposed and analyzed, and which can be integrated into space-restricted MBA rings. Since the optics and chamber are interdependent, the feasibility of this approach depends on a large part on the technical ability to assemble mechanically the optics inside the dipole chamber and control their resulting stability and thermo-mechanical deformation. Acquiring this expertise should allow dipole chambers to provide almost aberration-free IR synchrotron sources on current and `ultimate' MBA storage rings.

  19. IR Variability During a Shell Ejection of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Smith, Nathan

    2006-02-01

    Every 5.5 years, η Carinae experiences a dramatic ``spectroscopic event'' when high-excitation lines in its UV, optical, and IR spectrum disappear, and its hard X-ray and radio continuum flux crash. This periodicity has been attributed to a very eccentric binary system with a shell ejection occurring at periastron. Mid-IR images and spectra with T-ReCS are needed to measure changes in the current bolometric luminosity and to trace dust formation episodes. This will provide a direct estimate of the mass ejected. Near-IR emission lines trace related changes in the post-event wind and ionization changes in the circumstellar environment needed to test specific models for the cause of η Car's variability as it recovers from its recent ``event''. High resolution near-IR spectra with GNIRS will continue the important work of HST/STIS, investigating changes in the direct and reflected spectrum of the stellar wind, and ionization changes in the nebula. The complex kinematic structure of η Car's ejecta also holds important clues to its mass ejection history, and is essential for interpreting other data. Phoenix can provide a unique kinematic map of the complex density and time-variable ionization structure of η Car's nebula, which is our best example of the pre-explosion environment of very massive stars.

  20. Two-Step Processes and IR Recording in Photorefractive Crystals

    NASA Astrophysics Data System (ADS)

    Kraetzig, Eckhard; Buse, Karsten

    Two-step excitation processes have been used for hologram storage in photorefractive crystals. By this means the interference pattern can be formed with red or near-IR light and nondestructive readout of information is possible. Often shallow levels are involved in the holographic recording process in photorefractive crystals. The shallow levels can be populated by illumination with visible or UV pulses forming states with relatively long lifetimes, thus sensitizing the crystals for holographic recording with IR pulses. In LiNbO3 and LiTaO3 the most important shallow levels have been identified. They result from NbLi^5+ and TaLi^5+ antisite defects (Nb5+ or Ta5+ on Li+ site). The crystals can also be pre-illuminated with visible light from a cw argon laser or a xenon lamp and holograms can be recorded with red light from a laser diode. The sensitization process is possible for other photorefractive crystals, too. The holograms can be read nondestructively with IR light and can be erased with green light. The hologram lifetime is limited by electron tunneling or by an ionic conductivity. Lifetimes up to years can be achieved. Recording of components for telecommunication applications with IR light allows one to create reconfigurable and thus more versatile devices.

  1. The excitation of O2 in auroras

    NASA Technical Reports Server (NTRS)

    Cartwright, D. C.; Trajmar, S.; Williams, W., Jr.

    1972-01-01

    Newly measured electron impact cross sections for excitation of the a 1 Delta g and b 1 Sigma g+ electronic states of O2 were employed to predict the absolute volume emission rates from these states under auroral conditions. A secondary electron electron flux typical of an IBC II nighttime aurora was used and the most important quenching processes were included in the calculations. The new excitation cross sections for the a 1 Delta g and b 1 Sigma g+ states are more than an order of magnitude larger than previous estimates, and lead to correspondingly greater intensities in the atmospheric and IR-atmospheric band systems. The calculated intensity ratios of the volume emission rates of 7621 A and 1.27 microns to that for 3914 A are smaller than obtained from aircraft observations and recent rocket experiments.

  2. The excitation of O2 in auroras.

    NASA Technical Reports Server (NTRS)

    Cartwright, D. C.; Trajmar, S.; Williams, W.

    1972-01-01

    Newly measured electron impact cross sections for excitation of the a super 1 Delta sub g and b super 1 Sigma (plus) sub g electronic states of O2 have been employed to predict the absolute volume emission rates from these states under auroral conditions. A secondary electron flux typical of an IBC II nighttime aurora was used, and the most important quenching processes were included in the calculations. The new excitation cross sections for the a super 1 Delta sub g and b super 1 Sigma (plus) sub g states are more than an order of magnitude larger than previous estimates and lead to correspondingly greater intensities in the atmospheric and IR atmospheric band systems. The calculated intensity ratios of the volume emission rates of 7621 A and 1.27 micron to that for 3914 A are smaller than those obtained from aircraft observations and recent rocket experiments.

  3. 8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  4. IR OPTICS MEASUREMENT WITH LINEAR COUPLING'S ACTION-ANGLE PARAMETERIZATION.

    SciTech Connect

    LUO, Y.; BAI, M.; PILAT, R.; SATOGATA, T.; TRBOJEVIC, D.

    2005-05-16

    A parameterization of linear coupling in action-angle coordinates is convenient for analytical calculations and interpretation of turn-by-turn (TBT) beam position monitor (BPM) data. We demonstrate how to use this parameterization to extract the twiss and coupling parameters in interaction regions (IRs), using BPMs on each side of the long IR drift region. The example of TBT BPM analysis was acquired at the Relativistic Heavy Ion Collider (RHIC), using an AC dipole to excite a single eigenmode. Besides the full treatment, a fast estimate of beta*, the beta function at the interaction point (IP), is provided, along with the phase advance between these BPMs. We also calculate and measure the waist of the beta function and the local optics.

  5. X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

    DOE PAGES

    Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; ...

    2016-07-06

    We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (~6 to 300 K) and pressures (~0.1 to 17 GPa) studied. We have also investigated the electronic and magneticmore » excitations in single-crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high-resolution Ir L-3-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ~3-5 eV, spin-orbit excitations at ~ 0.5-1 eV, and broad low-lying excitations below ~0.15 eV. In single-crystal samples of "Eu-rich" Eu2Ir2O7 (found to possess an actual stoichiometry of Eu2.18Ir1.82O7.06) we observe highly damped magnetic excitations at ~45 meV, which display significant momentum dependence. Here, we compare these results with recent dynamical structure factor calculations« less

  6. X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

    SciTech Connect

    Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; Tian, Di; Kim, J.; Upton, M. H.; Casa, D.; Gog, T.; Islam, Z.; Jeon, Byung -Gu; Kim, Kee Hoon; Desgreniers, S.; Kim, Yong Baek; Julian, S. J.; Kim, Young -June

    2016-07-06

    We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (~6 to 300 K) and pressures (~0.1 to 17 GPa) studied. We have also investigated the electronic and magnetic excitations in single-crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high-resolution Ir L-3-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ~3-5 eV, spin-orbit excitations at ~ 0.5-1 eV, and broad low-lying excitations below ~0.15 eV. In single-crystal samples of "Eu-rich" Eu2Ir2O7 (found to possess an actual stoichiometry of Eu2.18Ir1.82O7.06) we observe highly damped magnetic excitations at ~45 meV, which display significant momentum dependence. Here, we compare these results with recent dynamical structure factor calculations

  7. X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

    SciTech Connect

    Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; Tian, Di; Kim, J.; Upton, M. H.; Casa, D.; Gog, T.; Islam, Z.; Jeon, Byung -Gu; Kim, Kee Hoon; Desgreniers, S.; Kim, Yong Baek; Julian, S. J.; Kim, Young -June

    2016-07-06

    We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (~6 to 300 K) and pressures (~0.1 to 17 GPa) studied. We have also investigated the electronic and magnetic excitations in single-crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high-resolution Ir L-3-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ~3-5 eV, spin-orbit excitations at ~ 0.5-1 eV, and broad low-lying excitations below ~0.15 eV. In single-crystal samples of "Eu-rich" Eu2Ir2O7 (found to possess an actual stoichiometry of Eu2.18Ir1.82O7.06) we observe highly damped magnetic excitations at ~45 meV, which display significant momentum dependence. Here, we compare these results with recent dynamical structure factor calculations

  8. Dust processing in photodissociation regions. Mid-IR emission modelling

    NASA Astrophysics Data System (ADS)

    Compiègne, M.; Abergel, A.; Verstraete, L.; Habart, E.

    2008-12-01

    Context: Mid-infrared spectroscopy of dense illuminated ridges (or photodissociation regions, PDRs) suggests dust evolution. Such evolution must be reflected in the gas physical properties through processes like photo-electric heating or H2 formation. Aims: With Spitzer Infrared Spectrograph (IRS) and ISOCAM data, we study the mid-IR emission of closeby, well known PDRs. Focusing on the band and continuum dust emissions, we follow their relative contributions and analyze their variations in terms of abundance of dust populations. Methods: In order to disentangle dust evolution and excitation effects, we use a dust emission model that we couple to radiative transfer. Our dust model reproduces extinction and emission of the standard interstellar medium that we represent with diffuse high galactic latitude clouds called Cirrus. We take the properties of dust in Cirrus as a reference to which we compare the dust emission from more excited regions, namely the Horsehead and the reflection nebula NGC 2023 North. Results: We show that in both regions, radiative transfer effects cannot account for the observed spectral variations. We interpret these variations in term of changes of the relative abundance between polycyclic aromatic hydrocarbons (PAHs, mid-IR band carriers) and very small grains (VSGs, mid-IR continuum carriers). Conclusions: We conclude that the PAH/VSG abundance ratio is 2.4 times smaller at the peak emission of the Horsehead nebula than in the Cirrus case. For NGC 2023 North where spectral evolution is observed across the northern PDR, we conclude that this ratio is ~5 times lower in the dense, cold zones of the PDR than in its diffuse illuminated part where dust properties seem to be the same as in Cirrus. We conclude that dust in PDRs seems to evolve from “dense” to “diffuse” properties at the small spatial scale of the dense illuminated ridge.

  9. The excitation mechanism of H2 in bipolar planetary nebulae

    NASA Astrophysics Data System (ADS)

    Marquez-Lugo, R. A.; Guerrero, M. A.; Ramos-Larios, G.; Miranda, L. F.

    2015-10-01

    We present near-IR K-band intermediate-dispersion spatially-resolved spectroscopic observations of a limited sample of bipolar planetary nebulae (PNe). The spectra have been used to determine the excitation mechanism of the H2 molecule using standard line ratios diagnostics. The H2 molecule is predominantly shock-excited in bipolar PNe with broad equatorial rings, whereas bipolar PNe with narrow equatorial waists present either UV excitation at their cores (e.g. Hb 12) or shock-excitation at their bipolar lobes (e.g. M1-92). The shock-excitation among bipolar PNe with ring is found to be correlated with emission in the H2 1-0 S(1) line brighter than Br γ. We have extended this investigation to other PNe with available near-IR spectroscopic observations. This confirms that bipolar PNe with equatorial rings are in average brighter in H2 than in Br γ and show dominant shock-excitation.

  10. Excitability dependent pattern formation

    NASA Astrophysics Data System (ADS)

    Prabhakara, Kaumudi; Gholami, Azam; Bodenschatz, Eberhard

    2014-03-01

    On starvation, the amoebae Dictyostelium discoideum emit the chemo-attractant cyclic adenosine monophosphate (cAMP) at specific frequencies. The neighboring amoebae sense cAMP through membrane receptors and produce their own cAMP. Soon the cells synchronize and move via chemotaxis along the gradient of cAMP. The response of the amoebae to the emission of cAMP is seen as spiral waves or target patterns under a dark field microscope. The causal reasons for the selection of one or the other patterns are still unclear. Here we present a possible explanation based on excitability. The excitability of the amoebae depends on the starvation time because the gene expression changes with starvation. Cells starved for longer times are more excitable. In this work, we mix cells of different excitabilities to study the dependence of the emergent patterns on the excitability. Preliminary results show a transition from spirals to target patterns for specific excitabilities. A phase map of the patterns for different combinations of excitability and number densities is obtained. We compare our findings with numerical simulations of existing theoretical models.

  11. Shaped Ir-Ni bimetallic nanoparticles for minimizing Ir utilization in oxygen evolution reaction.

    PubMed

    Lim, Jinkyu; Yang, Sungeun; Kim, Chanyeon; Roh, Chi-Woo; Kwon, Yongwoo; Kim, Yong-Tae; Lee, Hyunjoo

    2016-04-25

    Shaped Ir-Ni bimetallic nanoparticles were synthesized and used for electrocatalytic oxygen evolution reaction (OER). The obtained bimetallic nanoparticles showed significantly enhanced Ir mass activity and durability compared with Ir nanoparticles.

  12. Gold Corroles as Near-IR Phosphors for Oxygen Sensing.

    PubMed

    Lemon, Christopher M; Powers, David C; Brothers, Penelope J; Nocera, Daniel G

    2017-09-05

    The triplet state of gold(III) corroles is exploited for optical oxygen sensing. We report intense phosphorescence for gold(III) corroles in the near-IR, an optical window that is ideal for tissue transparency. Moreover, the triplet excited-state emission exhibits significant changes in intensity and lifetime over the 0-160 Torr O2 pressure range. This renders these compounds sensitive at biologically relevant pressures and overcomes the spectral limitations of palladium and platinum porphyrins for oxygen sensing in biology.

  13. 15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. 1 BEHIND. OVERHEAD CRANE DANGLES AT TOP OF PHOTO. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  14. Low-lying excited states and primary photoproducts of [Os3(CO)10(s-cis-L)] (L=cyclohexa-1,3-diene, buta-1,3-diene)] clusters studied by picosecond time-resolved UV/Vis and IR spectroscopy and by density functional theory.

    PubMed

    Vergeer, Frank W; Matousek, Pavel; Towrie, Michael; Costa, Paulo J; Calhorda, Maria J; Hartl, Frantisek

    2004-07-19

    Combined picosecond transient absorption and time-resolved infrared studies were performed, aimed at characterising low-lying excited states of the cluster [Os(3)(CO)(10)(s-cis-L)] (L=cyclohexa-1,3-diene, 1) and monitoring the formation of its photoproducts. Theoretical (DFT and TD-DFT) calculations on the closely related cluster with L=buta-1,3-diene (2') have revealed that the low-lying electronic transitions of these [Os(3)(CO)(10)(s-cis-1,3-diene)] clusters have a predominant sigma(core)pi*(CO) character. From the lowest sigmapi* excited state, cluster 1 undergoes fast Os-Os(1,3-diene) bond cleavage (tau=3.3 ps) resulting in the formation of a coordinatively unsaturated primary photoproduct (1 a) with a single CO bridge. A new insight into the structure of the transient has been obtained by DFT calculations. The cleaved Os-Os(1,3-diene) bond is bridged by the donor 1,3-diene ligand, compensating for the electron deficiency at the neighbouring Os centre. Because of the unequal distribution of the electron density in transient 1 a, a second CO bridge is formed in 20 ps in the photoproduct [Os(3)(CO)(8)(micro-CO)(2)(cyclohexa-1,3-diene)] (1 b). The latter compound, absorbing strongly around 630 nm, mainly regenerates the parent cluster with a lifetime of about 100 ns in hexane. Its structure, as suggested by the DFT calculations, again contains the 1,3-diene ligand coordinated in a bridging fashion. Photoproduct 1 b can therefore be assigned as a high-energy coordination isomer of the parent cluster with all Os-Os bonds bridged.

  15. A spectrophotometric study of IR Gem at outburst and quiescence

    NASA Technical Reports Server (NTRS)

    Feinswog, Laurie; Szkody, Paula; Garnavich, Peter

    1988-01-01

    Optical spectra with 2.5-A resolution obtained throughout the orbit of IR Gem during a five-day sequence beginning at an outburst state and ending at quiescence are compared with B magnitude and IUE spectra obtained throughout other quiescent-state orbits. No obvious second component is found in the emission lines. In contrast to previous results, little high-excitation He II 4686-A emission is noted, and no variation of the equivalent widths of the Balmer emission is found over the orbital cycle. The results suggest that large changes in the excitation level and in the modulation from a heated zone can take place during different quiescent states, possibly due to the interoutburst phase.

  16. Optimized IR synchrotron beamline design.

    PubMed

    Moreno, Thierry

    2015-09-01

    Synchrotron infrared beamlines are powerful tools on which to perform spectroscopy on microscopic length scales but require working with large bending-magnet source apertures in order to provide intense photon beams to the experiments. Many infrared beamlines use a single toroidal-shaped mirror to focus the source emission which generates, for large apertures, beams with significant geometrical aberrations resulting from the shape of the source and the beamline optics. In this paper, an optical layout optimized for synchrotron infrared beamlines, that removes almost totally the geometrical aberrations of the source, is presented and analyzed. This layout is already operational on the IR beamline of the Brazilian synchrotron. An infrared beamline design based on a SOLEIL bending-magnet source is given as an example, which could be useful for future IR beamline improvements at this facility.

  17. Ir/IrSi3/Si Schottky-Barrier Infrared Detector

    NASA Technical Reports Server (NTRS)

    Lin, True-Lon

    1991-01-01

    Quantum efficiency increased. Proposed Schottky-barrier infrared detector has double metallic layer of Ir and IrSi3 instead of single metallic layer of Ir, IrSi, or IrSi3. Offers advantages of both relatively high infrared absorption in thin film of Ir and stability and reproducibility of layer of IrSi3 in contact with Si. Also serves as barrier to chemical reactions between Ir overlayer and Si substrate. Detectors used to form focal-plane array integrated with charge-coupled-device-addressing and image-processing circuitry.

  18. Geomagnetic excitation of nutation

    NASA Astrophysics Data System (ADS)

    Ron, C.; Vondrák, J.

    2015-08-01

    We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.

  19. Excitation by rockets

    NASA Technical Reports Server (NTRS)

    Tammadge, C. E.

    1975-01-01

    Standard methods of excitation are not always practical when a single mode of known frequency requires investigation. This form of investigation is often required on a modified aircraft. A new method of excitation was developed and proved in flight, which consists of firing small rocket charges attached to the aircraft structure. Damping values at gradually increasing airspeeds are obtained, as in Stick Jerk tests, and flutter speeds predicted.

  20. High temperature Ir segregation in Ir-B ceramics: Effect of oxygen presence on stability of IrB2 and other Ir-B phases

    DOE PAGES

    Xie, Zhilin; Terracciano, Anthony C.; Cullen, David A.; ...

    2015-05-13

    The formation of IrB2, IrB1.35, IrB1.1 and IrB monoboride phases in the Ir–B ceramic nanopowder was confirmed during mechanochemical reaction between metallic Ir and elemental B powders. The Ir–B phases were analysed after 90 h of high energy ball milling and after annealing of the powder for 72 h at 1050°C in vacuo. The iridium monoboride (IrB) orthorhombic phase was synthesised experimentally for the first time and identified by powder X-ray diffraction. Additionally, the ReB2 type IrB2 hexagonal phase was also produced for the first time and identified by high resolution transmission electron microscope. Ir segregation along disordered domains ofmore » the boron lattice was found to occur during high temperature annealing. Furthermore, these nanodomains may have useful catalytic properties.« less

  1. Infrared spectroscopy of excited states and transients in photochemistry

    NASA Astrophysics Data System (ADS)

    Schaffner, Kurt; Grevels, Friedrich-Wilhelm

    Flash photolysis with time-resolved IR detection is used in investigations of the primary photoreactions of chromium, molybdenum, tungsten, manganese, iron, and osmium carbonyl complexes, and of the ensuing transformations of transient products in room temperature solution. The method bridges the gap to spectral data obtained at low temperatures. It provides information which has previously been inaccessible, such as detailed structural information, and kinetic data in cases where the UV-visible absorptions of the species of interest overlap. Finally, excited-state IR spectroscopy has now become feasible for many organic compounds with the most recent instrumental set-up which reaches a time resolution of ≥ 50 ns.

  2. Photon bunching reveals single-electron cathodoluminescence excitation efficiency in InGaN quantum wells

    NASA Astrophysics Data System (ADS)

    Meuret, Sophie; Coenen, Toon; Zeijlemaker, Hans; Latzel, Michael; Christiansen, Silke; Conesa-Boj, Sonia; Polman, Albert

    2017-07-01

    Cathodoluminescence spectroscopy is a key analysis technique in nanophotonics research and technology, yet many aspects of its fundamental excitation mechanisms are not well understood on the single-electron and single-photon level. Here, we determine the cathodoluminescence emission statistics of InGaN quantum wells embedded in GaN under 6-30-keV electron excitation and find that the light emission rate varies strongly from electron to electron. Strong photon bunching is observed for the InGaN quantum well emission at 2.77 eV due to the generation of multiple quantum well excitations by a single primary electron. The bunching effect, measured by the g(2 )(t ) autocorrelation function, decreases with increasing beam current in the range 3-350 pA. Under pulsed excitation (p =2 -100 ns ; 0.13-6 electrons per pulse), the bunching effect strongly increases. A model based on Monte Carlo simulations is developed that assumes a fraction γ of the primary electrons generates electron-hole pairs that create multiple photons in the quantum wells. At a fixed primary electron energy (10 keV) the model explains all g(2 ) measurements for different beam currents and pulse durations using a single value for γ =0.5 . At lower energies, when electrons cause mostly near-surface excitations, γ is reduced (γ =0.01 at 6 keV), which is explained by the presence of a AlGaN barrier layer that inhibits carrier diffusion to the buried quantum wells. The combination of g(2 ) measurements in pulsed and continuous mode with spectral analysis provides a powerful tool to study optoelectronic properties and may find application in many other optically active systems and devices.

  3. Diffraction-limited IR Microspectroscopy with IRENI

    Treesearch

    J. Sedlmair; B. Illman; M. Unger; C. Hirschmugl

    2012-01-01

    In a unique way, IRENI (Infrared environmental Imaging), operated at the Synchrotron Radiation Center in Madison, combines IR spectroscopy and IR imaging, revealing the chemical morphology of a sample. Most storage ring based IR confocal microscopes have to overcome a trade-off between spatial resolution versus...

  4. Using Graded Relevance Assessments in IR Evaluation.

    ERIC Educational Resources Information Center

    Kekalalainen, Jaana; Jarvelin, Kalervo

    2002-01-01

    Proposes evaluation methods based on the use of nondichotomous relevance judgements in information retrieval (IR) experiments. Argues that evaluation methods should credit IR methods for their ability to retrieve highly relevant documents. This is desirable from the user point of view in modern large IR environments. (Author/AEF)

  5. A COMPARATIVE ASTROCHEMICAL STUDY OF THE HIGH-MASS PROTOSTELLAR OBJECTS NGC 7538 IRS 9 AND IRS 1

    SciTech Connect

    Barentine, John C.; Lacy, John H.

    2012-10-01

    We report the results of a spectroscopic study of the high-mass protostellar object NGC 7538 IRS 9 and compare our observations to published data on the nearby object NGC 7538 IRS 1. Both objects originated in the same molecular cloud and appear to be at different points in their evolutionary histories, offering an unusual opportunity to study the temporal evolution of envelope chemistry in objects sharing a presumably identical starting composition. Observations were made with the Texas Echelon Cross Echelle Spectrograph, a sensitive, high spectral resolution (R {lambda}/{Delta}{lambda} {approx_equal} 100,000) mid-infrared grating spectrometer. Forty-six individual lines in vibrational modes of the molecules C{sub 2}H{sub 2}, CH{sub 4}, HCN, NH{sub 3}, and CO were detected, including two isotopologues ({sup 13}CO, {sup 12}C{sup 18}O) and one combination mode ({nu}{sub 4} + {nu}{sub 5} C{sub 2}H{sub 2}). Fitting synthetic spectra to the data yielded the Doppler shift, excitation temperature, Doppler b parameter, column density, and covering factor for each molecule observed; we also computed column density upper limits for lines and species not detected, such as HNCO and OCS. We find differences among spectra of the two objects likely attributable to their differing radiation and thermal environments. Temperatures and column densities for the two objects are generally consistent, while the larger line widths toward IRS 9 result in less saturated lines than those toward IRS 1. Finally, we compute an upper limit on the size of the continuum-emitting region ({approx}2000 AU) and use this constraint and our spectroscopy results to construct a schematic model of IRS 9.

  6. VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 - IRS5 region

    NASA Astrophysics Data System (ADS)

    Chen, Zhiwei; Nürnberger, Dieter E. A.; Chini, Rolf; Jiang, Zhibo; Fang, Min

    2015-06-01

    Aims: We investigate the surroundings of the hypercompact H ii region M 17 UC1 to probe the physical properties of the associated young stellar objects and the environment of massive star formation. Methods: We use diffraction-limited near-IR (VLT/NACO) and mid-IR (VLT/VISIR) images to reveal the different morphologies at various wavelengths. Likewise, we investigate the stellar and nebular content of the region with VLT/SINFONI integral field spectroscopy with a resolution R ˜ 1500 at H + K bands. Results: Five of the seven point sources in this region show L-band excess emission. A geometric match is found between the H2 emission and near-IR polarized light in the vicinity of IRS5A, and between the diffuse mid-IR emission and near-IR polarization north of UC1. The H2 emission is typical for dense photodissociation regions (PDRs), which are initially far-ultraviolet pumped and repopulated by collisional de-excitation. The spectral types of IRS5A and B273A are B3-B7 V/III and G4-G5 III, respectively. The observed infrared luminosity LIR in the range 1-20 μm is derived for three objects; we obtain 2.0 × 103 L⊙ for IRS5A, 13 L⊙ for IRS5C, and 10 L⊙ for B273A. Conclusions: IRS5 might be a young quadruple system. Its primary star IRS5A is confirmed to be a high-mass protostellar object (˜9 M⊙, ˜1 × 105 yrs); it might have terminated accretion due to the feedback from stellar activities (radiation pressure, outflow) and the expanding H ii region of M 17. The object UC1 might also have terminated accretion because of the expanding hypercompact H ii region, which it ionizes. The disk clearing process of the low-mass young stellar objects in this region might be accelerated by the expanding H ii region. The outflows driven by UC1 are running south-north with its northeastern side suppressed by the expanding ionization front of M 17; the blue-shifted outflow lobe of IRS5A is seen in two types of tracers along the same line of sight in the form of H2 emission

  7. Develop algorithms to improve detectability of defects in Sonic IR imaging NDE

    NASA Astrophysics Data System (ADS)

    Obeidat, Omar; Yu, Qiuye; Han, Xiaoyan

    2016-02-01

    Sonic Infrared (IR) technology is relative new in the NDE family. It is a fast, wide area imaging method. It combines ultrasound excitation and infrared imaging while the former to apply ultrasound energy thus induce friction heating in defects and the latter to capture the IR emission from the target. This technology can detect both surface and subsurface defects such as cracks and disbands/delaminations in various materials, metal/metal alloy or composites. However, certain defects may results in only very small IR signature be buried in noise or heating patterns. In such cases, to effectively extract the defect signals becomes critical in identifying the defects. In this paper, we will present algorithms which are developed to improve the detectability of defects in Sonic IR.

  8. IR susceptibility of naval ships using ShipIR/NTCS

    NASA Astrophysics Data System (ADS)

    Vaitekunas, David A.

    2010-04-01

    Methods of analysing the signature and susceptibility of naval platforms to infrared detection are described. An unclassified ShipIR destroyer model is used to illustrate the primary sources of infrared signature and detection: the exhaust system, solar-heating, and operating climate. The basic detection algorithm used by the Naval Threat Countermeasure Simulator (NTCS) component of ShipIR is described and used to analyse the effectiveness of various stealth technologies: stack suppression, low solar absorptive (LSA) paints, and Active Hull Cooling (AHC). Standard marine climate statistics are used to determine a minimum (5%), average (50%) and maximum (95%) signature condition for each operating region. The change in detection range of two wave-band sensors (3-5μm, 8-12 μm) operating at different altitudes (10m, 270m) in each of four climatic conditions is used to assess the effectiveness of each stealth solution, providing a more integral approach to infrared stealth design. These tools and methods form the basis on which future platform designs are being evaluated.

  9. Carbon nanotube IR detectors (SV)

    SciTech Connect

    Leonard, F. L.

    2012-03-01

    Sandia National Laboratories (Sandia) and Lockheed Martin Corporation (LMC) collaborated to (1) evaluate the potential of carbon nanotubes as channels in infrared (IR) photodetectors; (2) assemble and characterize carbon nanotube electronic devices and measure the photocurrent generated when exposed to infrared light;(3) compare the performance of the carbon nanotube devices with that of traditional devices; and (4) develop and numerically implement models of electronic transport and opto-electronic behavior of carbon nanotube infrared detectors. This work established a new paradigm for photodetectors.

  10. Moisture map by IR thermography

    NASA Astrophysics Data System (ADS)

    Grinzato, E.; Cadelano, G.; Bison, P.

    2010-10-01

    A new approach to moisture detection in buildings by an optical method is presented. Limits of classical and new methods are discussed. The state of the art about the use of IR thermography is illustrated as well. The new technique exploits characteristics of the materials and takes into account explicitly the heat and mass exchange between surface and environment. A set of experiments in controlled laboratory conditions on different materials is used to better understand the physical problem. The testing procedure and the data reduction are illustrated. A case study on a heritage building points up the features of this technique.

  11. IR Variability of Eta Carinae: The 2009 Event

    NASA Astrophysics Data System (ADS)

    Smith, Nathan

    2008-08-01

    Every 5.5 years, η Carinae experiences a dramatic ``spectroscopic event'' when high-excitation lines in its UV, optical, and IR spectrum disappear, and its hard X-ray and radio continuum flux crash. This periodicity has been attributed to an eccentric binary system with a shell ejection occurring at periastron, and the next periastron event will occur in January 2009. The last event in June/July 2003 was poorly observed because the star was very low in the sky, but this next event is perfectly suited for an intense ground-based monitoring campaign. Mid-IR images and spectra with T-ReCS provide a direct measure of changes in the current bolometric luminosity and a direct measure of the mass in dust formation episodes that may occur at periastron in the colliding wind shock. Near-IR emission lines trace related changes in the post-event wind and ionization changes in the circumstellar environment needed to test specific models for the cause of η Car's variability as it recovers from its recent ``event''. Because the nebular geometry is known very well from previous observations in this program, monitoring the changes in nebular ionization will yield a 3-D map of the changing asymmetric UV radiation field geometry in the binary system, and the first estimate of the orientation of its orbit.

  12. Gold-black as IR Absorber and Solar Cell Enhancer

    SciTech Connect

    Peale, Robert E.; Cleary, Justin W.; Ishimaru, Manabu; Smith, C. W.; Baillie, K.; Colwell, J. E.; Beck, Kenneth M.; Joly, Alan G.; Edwards, Oliver; Fredricksen, C. J.

    2010-03-01

    Infrared absorbance and visible/near-IR excited plasmon resonances are investigated in gold-black, a porous nano-structured conducting film. A two level full factorial optimization study with evaporation-chamber pressure, boat current, substrate temperature, and degree of polymer infusion (for hardening) was performed. Polymer infusion was found generally to reduce absorbance in the long wave IR but has little effect at THz wavelengths, although for samples with the highest absorbance there is a slight improvement in the absorbance figure of merit (FOM) in both wavelength regimes. The characteristic length scales of the structured films vary considerably as a function of deposition parameters, but the IR FOM is found to be only weakly correlated with these distributions, which are determined by wavelet analysis of scanning electron micrographs images. Initial investigations of gold-black by photoelectron emission microscopy (PEEM) reveal plasmon resonances, which have potential to enhance the efficiency of thin film solar cells. For films with different characteristic length scales, the plasmon resonances appear in portions of the film with similar length scales.

  13. Molecular Tectonics: Design of Enantiopure Luminescent Heterometallic Ir(III)-Cd(II) Coordination Network.

    PubMed

    Xu, Chaojie; Guenet, Aurélie; Kyritsakas, Nathalie; Planeix, Jean-Marc; Hosseini, Mir Wais

    2015-11-02

    With the aim of combining luminescence and chirality in heterometallic Ir(III)-Cd(II) coordination networks, synthetic strategies for the formation of new Ir(III)-based chiral metallatectons ([Ir(dFppy)2(1)][PF6]), both as a racemic mixture of Δ and Λ enantiomers (rac-[Ir(dFppy)2(1)][PF6]) and as enantiopure complexes (Δ-[Ir(dFppy)2(1)][PF6] and Λ-[Ir(dFppy)2(1)][PF6]), were developed. The final compounds were characterized both in solution and in the crystalline phase. Notably, their crystal structures were determined by single crystal X-ray diffraction, and their photophysical properties in solution and in the solid state were investigated. Combination of the cationic linear metallatecton with Cd(2+) iodide salt ([CdI3](-)), behaving as an anionic two-connecting node, leads to the formation of 1D chiral and neutral heterometallic Ir(III)-Cd(II) luminescent coordination networks both as a racemic mixture and as enantiomerically pure infinite architectures. The latter have been structurally studied in the solid state by X-ray diffraction both on single crystals and on microcrystalline powders. The infinite coordination networks display phosphorescence in the solid state at ca. 600 nm upon excitation at 400 nm.

  14. Coprates Chasma Landslides in IR

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Today's daytime IR image is of a portion of Coprates Chasma, part of Valles Marineris. As with yesterday's image, this image shows multiple large landslides.

    Image information: IR instrument. Latitude -8.2, Longitude 300.2 East (59.8 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  15. Xanthe Terra Landslide in IR

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    This is a daytime IR image of a chaos region within Xanthe Terra. As with earlier images, the landslide in this image is caused by the failure of steep slopes releasing material to form the landslide deposit.

    Image information: IR instrument. Latitude 3.1, Longitude 309.7 East (50.3 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  16. Xanthe Terra Landslide in IR

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    This is a daytime IR image of a chaos region within Xanthe Terra. As with earlier images, the landslide in this image is caused by the failure of steep slopes releasing material to form the landslide deposit.

    Image information: IR instrument. Latitude 3.1, Longitude 309.7 East (50.3 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. Coprates Chasma Landslides in IR

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Today's daytime IR image is of a portion of Coprates Chasma, part of Valles Marineris. As with yesterday's image, this image shows multiple large landslides.

    Image information: IR instrument. Latitude -8.2, Longitude 300.2 East (59.8 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. Excitation Methods for Bridge Structures

    SciTech Connect

    Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.

    1999-02-08

    This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.

  19. Peak-power dependence of rovibronic populations below the quasicontinuum during IR multiphoton absorption

    SciTech Connect

    Brenner, D M

    1981-01-01

    Experimental studies on IR multiphoton absorption and dissociation have generally provided insight only into the relationship of IR laser characteristics such as power, wavelength, and mode structure to the observables dissociation yields, average number of photons absorbed, and product energy distribution. As a result, theoretical modeling of absorption at levels below the quasicontinuum has been based on facts somewhat removed from the actual phenomenon of interest. The experiments presented here provide information on the unperturbed rotational/vibrational populations of levels subsequent to IR excitation at levels below 4000 cm/sup -1/ of energy. The experiment makes use of molecular beam techniques in conjunction with IR-visible double resonance. A CO/sub 2/ laser of known pulse duration prepares vibrationally excited thiophosgene, Cl/sub 2/C = S. The absorbing transition is 2 ..nu../sub 4/. A tunable nitrogen-pumped dye laser scans the visible excitation spectrum to probe the perturbed rotational-vibrational populations of the pumped mode. Because the electronic transition is electric dipole forbidden, combination hot bands having the appropriate quantum numbers of the ground state are used in the analysis.

  20. Spin waves and magnetic excitations

    SciTech Connect

    Borovik-Romanov, A.S.; Sinha, S.K.

    1988-01-01

    This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.

  1. M-M bond-stretching energy landscapes for M2(dimen)4(2+) (M = Rh, Ir; dimen = 1,8-diisocyanomenthane) complexes.

    PubMed

    Hunter, Bryan M; Villahermosa, Randy M; Exstrom, Christopher L; Hill, Michael G; Mann, Kent R; Gray, Harry B

    2012-06-18

    Isomers of Ir(2)(dimen)(4)(2+) (dimen = 1,8-diisocyanomenthane) exhibit different Ir-Ir bond distances in a 2:1 MTHF/EtCN solution (MTHF = 2-methyltetrahydrofuran). Variable-temperature absorption data suggest that the isomer with the shorter Ir-Ir distance is favored at room temperature [K = ∼8; ΔH° = -0.8 kcal/mol; ΔS° = 1.44 cal mol(-1) K(-1)]. We report calculations that shed light on M(2)(dimen)(4)(2+) (M = Rh, Ir) structural differences: (1) metal-metal interaction favors short distances; (2) ligand deformational-strain energy favors long distances; (3) out-of-plane (A(2u)) distortion promotes twisting of the ligand backbone at short metal-metal separations. Calculated potential-energy surfaces reveal a double minimum for Ir(2)(dimen)(4)(2+) (∼4.1 Å Ir-Ir with 0° twist angle and ∼3.6 Å Ir-Ir with ±12° twist angle) but not for the rhodium analogue (∼4.5 Å Rh-Rh with no twisting). Because both the ligand strain and A(2u) distortional energy are virtually identical for the two complexes, the strength of the metal-metal interaction is the determining factor. On the basis of the magnitude of this interaction, we obtain the following results: (1) a single-minimum (along the Ir-Ir coordinate), harmonic potential-energy surface for the triplet electronic excited state of Ir(2)(dimen)(4)(2+) (R(e,Ir-Ir) = 2.87 Å; F(Ir-Ir) = 0.99 mdyn Å(-1)); (2) a single-minimum, anharmonic surface for the ground state of Rh(2)(dimen)(4)(2+) (R(e,Rh-Rh) = 3.23 Å; F(Rh-Rh) = 0.09 mdyn Å(-1)); (3) a double-minimum (along the Ir-Ir coordinate) surface for the ground state of Ir(2)(dimen)(4)(2+) (R(e,Ir-Ir) = 3.23 Å; F(Ir-Ir) = 0.16 mdyn Å(-1)).

  2. Two-Photon-Excited Fluorescence-Encoded Infrared Spectroscopy.

    PubMed

    Mastron, Joseph N; Tokmakoff, Andrei

    2016-11-23

    We report on a method for performing ultrafast infrared (IR) vibrational spectroscopy using fluorescence detection. Vibrational dynamics on the ground electronic state driven by femtosecond mid-infrared pulses are detected by changes in fluorescence amplitude resulting from modulation of a two-photon visible transition by nuclear motion. We examine a series of coumarin dyes and study the signals as a function of solvent and excitation pulse parameters. The measured signal characterizes the relaxation of vibrational populations and coherences but yields different information than conventional IR transient absorption measurements. These differences result from the manner in which the ground-state dynamics are projected by the two-photon detection step. Extensions of this method can be adapted for a variety of increased-sensitivity IR measurements.

  3. Thermographic non-destructive testing using inductive thermal excitation

    NASA Astrophysics Data System (ADS)

    Safai, Morteza; Georgeson, Gary; Meredith, Kimberly

    2008-03-01

    This paper describes the utilization of induced radio frequency thermal excitation in conjunction with infrared (IR) imaging for the detection of discontinuities in embedded metal conductive mesh on composite structure. An electric current is inductively generated in the conductive media of the composite using a radio frequency coil held above the surface. As the generated current moves through the composite structure, any perturbation in the current flow caused by discontinuities in the grid or highly resistive areas becomes heated slightly above the surrounding. This small temperature variation is detected in real-time by means of an IR imaging system that includes an IR camera, a computer, and imaging software. The data is depicted as a thermogram on the computer monitor, and can be analyzed using specialized system software. From the detected thermal variations, one can determine electrical conductivity characteristics of the conductive composite layer.

  4. Positron excitation of neon

    NASA Technical Reports Server (NTRS)

    Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.

  5. Proteins of Excitable Membranes

    PubMed Central

    Nachmansohn, David

    1969-01-01

    Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment. PMID:19873642

  6. The Electric Dipole Moment of Iridium Monosilicide, IrSi

    NASA Astrophysics Data System (ADS)

    Le, Anh; Steimle, Timothy C.; Cheng, Lan; Stanton, John F.

    2013-06-01

    The optical spectrum of iridium monosilicide (IrSi) was recently observed using REMPI spectroscopy in the range 17200 to 23850 cm^{-1}. The observation was supported by an ab initio calculation which predicted a X^{2}Δ_{5/2} state. Here, we report on the analysis of the optical Stark effect for the X^{2}Δ_{5/2} and [16.0]1.5 (v=6) states. The (6,0)[16.0]1.5 - X^{2}Δ_{5/2} and the (7,0)[16.0]3.5- X^{2}Δ_{5/2} bands of IrSi have been recorded using high-resolution laser-induced fluorescence spectroscopy. The observed optical Stark shifts for the ^{193}IrSi and ^{191}IrSi isotopologues were analyzed to produce the electric dipole moments of -0.4139(64)D and 0.7821(63)D for the X^{2}Δ_{5/2} and [16.0]1.5 (v=6) states, respectively. The negative sign of electric dipole moment of the X^{2}Δ_{5/2} state is supported by high-level quantum-chemical calculations employing all-electron scalar-relativistic CCSD(T) method augmented with spin-orbit corrections as well as corrections due to full triple excitations. In particular, electron-correlation effects have been shown to be essential in the prediction of the negative sign of the dipole moment. A comparison with other iridium containing molecules will be made. Maria A. Garcia, Carolin Vietz, Fernando Ruipérez, Michael D. Morse, and Ivan Infante, Kimika Fakultatea, Euskal Herriko. J. Chem. Phys., (submitted)

  7. Dinuclear Ru/Ni, Ir/Ni, and Ir/Pt complexes with bridging phenanthroline-5,6-dithiolate: synthesis, structure, and electrochemical and photophysical behavior.

    PubMed

    Schallenberg, David; Neubauer, Antje; Erdmann, Elisa; Tänzler, Marco; Villinger, Alexander; Lochbrunner, Stefan; Seidel, Wolfram W

    2014-09-02

    We report the synthesis and full characterization of dinuclear complexes with the bridging ligand phenanthroline-5,6-dithiolate (phendt(2-)) featuring the [Ru(bpy)2](2+) or Ir(ppy)2](+) fragment at the diimine donor center and the [Ni(dppe)](2+) or [Pt(phen)](2+) complex moiety at the dithiolate group. The molecular structures of the mononuclear complexes [(C5H5)2Ti(S,S'-phendt)] and [(ppy)2Ir{N,N'-phendt-(C2H4CN)2}](PF6) as well as the dinuclear complex [(C5H5)(PPh3)Ru(phendt)Ni(dppe)](PF6) determined by X-ray diffraction (XRD) studies are compared. Photophysical studies with mononuclear [(bpy)2Ru{phendt-(C2H4CN)2}](2+) and [(ppy)2Ir{phendt-(C2H4CN)2}](+) as well as dinuclear [(bpy)2Ru(phendt)Ni(dppe)](2+) and [(ppy)2Ir(phendt)Ni(dppe)](+) uncovered an effective luminescence quenching in the dinuclear complexes. Lifetime measurements at room temperature, steady-state measurements at low temperature, electrochemical investigations, and DFT calculations provide evidence for a very efficient energy transfer from the Ru/Ir to the Ni complex moiety with a rate constant k > 5 × 10(9) s(-1). In comparison, the [Ru]phendt[Ni] complex displays a higher quenching efficiency with reduced excited state lifetime, whereas the [Ir]phendt[Ni] complex is characterized by an unaltered lifetime of the thermally equilibrated excited state.

  8. Energy transfer in a thin film of TPD fluorescent molecules doped with PtOEP and Ir(ppy)3 phosphorescent molecules

    NASA Astrophysics Data System (ADS)

    Tsuboi, T.; Murayama, H.; Penzkofer, A.

    2005-07-01

    A thin film of triphenylamine dimer, N,N‧-bis(3-methylphenyl)-N,N‧-bis(phenyl)-benzidine (TPD), doped with fac tris(2-phenylpyridine) iridium (Ir(ppy)3) and platinum octaethyl porphine (PtOEP) is characterized by photoluminescence emission measurements at several excitation wavelengths and photoluminescence excitation measurements at relevant emission wavelengths in the temperature range from 10 K to room temperature. The investigated film is a phosphorescent OLED material with singlet absorbing host (TPD) and triplet emitting guests [Ir(ppy)3 and PtOEP]. At short wavelength excitation simultaneous triple band emission from singlet TPD, triplet Ir(ppy)3 and TPD, and from triplet PtOEP is observed. Förster-type singlet-singlet state energy transfer from TPD to Ir(ppy)3 and PtOEP, intra-component intersystem crossing, and Dexter-type triplet-triplet energy transfer between the substituents are studied.

  9. IR spectral analysis for the diagnostics of crust earthquake precursors

    NASA Astrophysics Data System (ADS)

    Umarkhodgaev, R. M.; Liperovsky, V. A.; Mikhailin, V. V.; Meister, C.-V.; Naumov, D. Ju

    2012-04-01

    In regions of future earthquakes, a few days before the seismic shock, the emanation of radon and hydrogen is being observed, which causes clouds of increased ionisation in the atmosphere. In the present work the possible diagnostics of these clouds using infrared (IR) spectroscopy is considered, which may be important and useful for the general geophysical system of earthquake prediction and the observation of industrial emissions of radioactive materials into the atmosphere. Some possible physical processes are analysed, which cause, under the condition of additional ionisation in a pre-breakdown electrical field, emissions in the IR interval. In doing so, the transparency region of the IR spectrum at wavelengths of 7-15 μm is taken into account. This transparency region corresponds to spectral lines of small atmospheric constituents like CH4, CO2, N2O, NO2, NO, and O3. The possible intensities of the IR emissions observable in laboratories and in nature are estimated. The acceleration process of the electrons in the pre-breakdown electrical field before its adhesion to the molecules is analysed. The laboratory equipment for the investigation of the IR absorption spectrum is constructed for the cases of normal and decreased atmospheric pressures. The syntheses of ozone and nitrous oxides are performed in the barrier discharge. It is studied if the products of the syntheses may be used to model atmospheric processes where these components take part. Spectra of products of the syntheses in the wavelength region of 2-10 μm are observed and analysed. A device is created for the syntheses and accumulation of nitrous oxides. Experiments to observe the IR-spectra of ozone and nitrous oxides during the syntheses and during the further evolution of these molecules are performed. For the earthquake prediction, practically, the investigation of emission spectra is most important, but during the laboratory experiments, the radiation of the excited molecules is shifted by a

  10. Infrared multiphoton dissociation of acrolein. Time-resolved observation of CO ( v = 1) IR emission at 4.7 μm

    NASA Astrophysics Data System (ADS)

    Chowdhury, P. K.; Rama Rao, K. V. S.; Mittal, J. P.

    1994-02-01

    In contrast to the photochemistry of electronically excited acrolein producing vinyl and formyl radicals via CC bond rupture, multiphoton vibrationally excited molecules undergo concerted dissociation generating CO and ethylene. Vibrational excitation in the CO product is detected immediately following the CO 2 laser pulse by observing IR emission at 4.7 μm. The decay of the IR emission was studied as a function of acrolein pressure. A vibrational-vibrational relaxation rate constant of CO ( v=1) by acrolein is found to be 1240 ± 200 Torr -1 s -1.

  11. Photonic crystals and Bragg gratings for the mid-IR and terahertz spectral ranges

    SciTech Connect

    Usikova, A. A. Il’inskaya, N. D.; Matveev, B. A.; Shubina, T. V.; Kop’ev, P. S.

    2013-12-15

    A method for the fabrication of 2D periodic structures by contact optical photolithography with image inversion is reported. The optical properties of photonic crystals and Bragg gratings for mid-IR and terahertz emitters are considered. The possibility of raising the integral emission intensity of light-emitting diodes for the mid-IR spectral range is demonstrated. The requirements to gratings for the output of terahertz emission generated by surface plasmons excited in layers of narrow-gap degenerate semiconductors with an accumulation layer are determined.

  12. Further study of coupling materials on aluminum sample using sonic IR

    NASA Astrophysics Data System (ADS)

    Song, Yuyang; Han, Xiaoyan

    2012-05-01

    Sonic Infrared (IR) Imaging has been proving as a very promising NDE technology even though it has not been around for very long. This technology uses acoustic/ultrasound excitation externally and infrared imaging to identify defects in materials. Typically, coupling materials are employed between the sound transducer and a target. It has been shown that this coupling has shown importance in SonicIR. We have learned that coupling materials affect the vibration and heating in cracks. More systematic study has been done quantitatively by the authors over some selected coupling materials through experimental study on aluminum samples. In this paper, we present our results over this topic.

  13. Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

    SciTech Connect

    Danilov, P A; Zayarnyi, D A; Ionin, A A; Kudryashov, S I; Makarov, S V; Rudenko, A A; Saraeva, I N; Yurovskikh, V I; Lednev, V N; Pershin, S M

    2015-05-31

    The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fields and their applications)

  14. IR Thermography NDE of ISS Radiator Panels

    NASA Technical Reports Server (NTRS)

    Koshti, Ajay; Winfree, William; Morton, Richard; Wilson, Walter; Reynolds, Gary

    2010-01-01

    The presentation covers an active and a passive infrared (IR) thermography for detection of delaminations in the radiator panels used for the International Space Station (ISS) program. The passive radiator IR data was taken by a NASA astronaut in an extravehicular activity (EVA) using a modified FLIR EVA hand-held camera. The IR data could be successfully analyzed to detect gross facesheet disbonds. The technique used the internal hot fluid tube as the heat source in analyzing the IR data. Some non-flight ISS radiators were inspected using an active technique of IR flash thermography to detect disbond of face sheet with honeycomb core, and debonds in facesheet overlap areas. The surface temperature and radiated heat emission from flight radiators is stable during acquisition of the IR video data. This data was analyzed to detect locations of unexpected surface temperature gradients. The flash thermography data was analyzed using derivative analysis and contrast evolutions. Results of the inspection are provided.

  15. High-definition Fourier Transform Infrared (FT-IR) spectroscopic imaging of human tissue sections towards improving pathology.

    PubMed

    Sreedhar, Hari; Varma, Vishal K; Nguyen, Peter L; Davidson, Bennett; Akkina, Sanjeev; Guzman, Grace; Setty, Suman; Kajdacsy-Balla, Andre; Walsh, Michael J

    2015-01-21

    High-definition Fourier Transform Infrared (FT-IR) spectroscopic imaging is an emerging approach to obtain detailed images that have associated biochemical information. FT-IR imaging of tissue is based on the principle that different regions of the mid-infrared are absorbed by different chemical bonds (e.g., C=O, C-H, N-H) within cells or tissue that can then be related to the presence and composition of biomolecules (e.g., lipids, DNA, glycogen, protein, collagen). In an FT-IR image, every pixel within the image comprises an entire Infrared (IR) spectrum that can give information on the biochemical status of the cells that can then be exploited for cell-type or disease-type classification. In this paper, we show: how to obtain IR images from human tissues using an FT-IR system, how to modify existing instrumentation to allow for high-definition imaging capabilities, and how to visualize FT-IR images. We then present some applications of FT-IR for pathology using the liver and kidney as examples. FT-IR imaging holds exciting applications in providing a novel route to obtain biochemical information from cells and tissue in an entirely label-free non-perturbing route towards giving new insight into biomolecular changes as part of disease processes. Additionally, this biochemical information can potentially allow for objective and automated analysis of certain aspects of disease diagnosis.

  16. High-definition Fourier Transform Infrared (FT-IR) Spectroscopic Imaging of Human Tissue Sections towards Improving Pathology

    PubMed Central

    Nguyen, Peter L.; Davidson, Bennett; Akkina, Sanjeev; Guzman, Grace; Setty, Suman; Kajdacsy-Balla, Andre; Walsh, Michael J.

    2015-01-01

    High-definition Fourier Transform Infrared (FT-IR) spectroscopic imaging is an emerging approach to obtain detailed images that have associated biochemical information. FT-IR imaging of tissue is based on the principle that different regions of the mid-infrared are absorbed by different chemical bonds (e.g., C=O, C-H, N-H) within cells or tissue that can then be related to the presence and composition of biomolecules (e.g., lipids, DNA, glycogen, protein, collagen). In an FT-IR image, every pixel within the image comprises an entire Infrared (IR) spectrum that can give information on the biochemical status of the cells that can then be exploited for cell-type or disease-type classification. In this paper, we show: how to obtain IR images from human tissues using an FT-IR system, how to modify existing instrumentation to allow for high-definition imaging capabilities, and how to visualize FT-IR images. We then present some applications of FT-IR for pathology using the liver and kidney as examples. FT-IR imaging holds exciting applications in providing a novel route to obtain biochemical information from cells and tissue in an entirely label-free non-perturbing route towards giving new insight into biomolecular changes as part of disease processes. Additionally, this biochemical information can potentially allow for objective and automated analysis of certain aspects of disease diagnosis. PMID:25650759

  17. STIRAP on helium: Excitation to Rydberg states

    NASA Astrophysics Data System (ADS)

    Yuan, Deqian

    Research in optically induced transitions between dierent atomic levels has a long history. For transitions between states driven by a coherent optical eld, the theoretical eciency could be ideally high as 100% but there could be many factors preventing this. In the three state helium atom excitation process, i.e. 23S→33P→nL , the stimulated emission from intermediate state makes it hard to achieve ecient population transfer to the nal state through an intuitive excitation order. One technique to achieve a higher eciency is Stimulated Raman Adiabatic Passage (STIRAP) which is being studied and under research in our lab. Unlike traditional three level excitation processes, STIRAP actually uses a counter intuitive pulsed laser beams timing arrangement. The excitation objects are metastable helium atoms traveling in a vacuum system with a longitudinal velocity of ~ 1070 m/s. We are using a 389 nm UV laser to connect the 23S and the 33P state and a frequency tunable ~790 nm IR laser to connect the 33P state and the dierent Rydberg states. A third 1083 nm wavelength laser beam drives the 23S → 23P transition to transversely separate the residual metastable atoms and the Rydberg atoms for eciency measurements. The data is taken by a stainless steel detector in the vacuum system. As the Rydberg atoms will get ionized by blackbody radiation under room temperature, we can utilize this for their detection. An ion detector sitting on the eld plate is capable to collect the ion signals of the Rydberg atoms for detection. So far the whole system has not been ready for data collection and measurement, so here we are using data and results from previous theses for discussions. The highest transition frequency that has ever been achieved in our lab is around 70% after corrections.

  18. Fragmentation mechanism of UV-excited peptides in the gas phase

    SciTech Connect

    Zabuga, Aleksandra V. Kamrath, Michael Z.; Boyarkin, Oleg V.; Rizzo, Thomas R.

    2014-10-21

    We present evidence that following near-UV excitation, protonated tyrosine- or phenylalanine–containing peptides undergo intersystem crossing to produce a triplet species. This pathway competes with direct dissociation from the excited electronic state and with dissociation from the electronic ground state subsequent to internal conversion. We employ UV-IR double-resonance photofragment spectroscopy to record conformer-specific vibrational spectra of cold peptides pre-excited to their S{sub 1} electronic state. The absorption of tunable IR light by these electronically excited peptides leads to a drastic increase in fragmentation, selectively enhancing the loss of neutral phenylalanine or tyrosine side-chain, which are not the lowest dissociation channels in the ground electronic state. The recorded IR spectra evolve upon increasing the time delay between the UV and IR pulses, reflecting the dynamics of the intersystem crossing on a timescale of ∼80 ns and <10 ns for phenylalanine- and tyrosine-containing peptides, respectively. Once in the triplet state, phenylalanine-containing peptides may live for more than 100 ms, unless they absorb IR photons and undergo dissociation by the loss of an aromatic side-chain. We discuss the mechanism of this fragmentation channel and its possible implications for photofragment spectroscopy and peptide photostability.

  19. Epic changes in the IRS46 mid-infrared spectrum; an inner disk chemistry study

    NASA Astrophysics Data System (ADS)

    Lahuis, F.; Kamp, I.; Thi, W. F.; van Dishoeck, E. F.; Woitke, P.

    2011-05-01

    The Spitzer-IRS detection of highly abundant hot (Tex>400 K) molecular gas toward the low-mass star IRS 46 (Lahuis et al. 2006) was cause for great excitement. Strong absorption bands of gas-phase C_2H_2, HCN and CO_2 provided the first observational test of chemical models in the planet-forming zone of a circumstellar disk as well as a direct measure of the temperature and density in this zone. Subsequently, the same molecules have been observed in absorption toward the young star GV Tau (Gibb et al. 2007) and in emission (together with hot abundant H_2O and OH) toward a number of T Tauri stars (Carr & Najita 2008, Salyk et al. 2008, Pontoppidan et al. 2010). Follow-up Spitzer-IRS observations of IRS 46 at 5 epochs taken during 2008 and 2009 show dramatic changes of the mid-IR properties. The mid-IR continuum and the strength of hot water emission lines (detected in the newly reduced data) have increased (up to a factor of two) while the above mentioned absorption features have decreased (up to a factor of five) in strength (see figure below). At the same time GV Tau does not show any significant changes in flux or the strength of its molecular absorption bands. Starting with the parameters of the SED model as presented by Lahuis et al. (2006), we use the proptoplanetary disk model ProDiMo (Woitke et al. 2009, Kamp et al. 2010) to model the chemical composition of the inner few AU of the IRS 46 disk. In addition, the nature of the changes observed in the mid-IR spectra of IRS 46 are investigated using these models.

  20. HST WFC3/IR Calibration Updates

    NASA Astrophysics Data System (ADS)

    Durbin, Meredith; Brammer, Gabriel; Long, Knox S.; Pirzkal, Norbert; Ryan, Russell E.; McCullough, Peter R.; Baggett, Sylvia M.; Gosmeyer, Catherine; Bourque, Matthew; HST WFC3 Team

    2016-01-01

    We report on several improvements to the characterization, monitoring, and calibration of the HST WFC3/IR detector. The detector performance has remained overall stable since its installation during HST Servicing Mission 4 in 2009. We present an updated persistence model that takes into account effects of exposure time and spatial variations in persistence across the detector, new grism wavelength solutions and master sky images, and a new SPARS sample sequence. We also discuss the stability of the IR gain, the time evolution and photometric properties of IR "snowballs," and the effect of IR "blobs" on point-source photometry.

  1. Giant spin gap and magnon localization in the disordered Heisenberg antiferromagnet Sr2Ir1−xRuxO4

    DOE PAGES

    Cao, Yue; Liu, X.; Xu, Wenhu; ...

    2017-03-06

    Here, we study the evolution of magnetic excitations in the disordered two-dimensional antiferromagnet Sr2Ir1–xRuxO4. The maximum energy of the magnetic excitation remains robust up to x = 0.77, with a gap opening at low dopings and increasing to over 150 meV at x = 0.77. At these higher Ru concentrations, the dispersive magnetic excitations in Sr2IrO4 are rendered essentially momentum independent. Up to a Ru concentration of x = 0.77, both experiments and first-principles calculations show the Ir Jeff = 1/2 state remains intact. The magnetic gap arises from the local interaction anisotropy in the proximity of the Ru disorder.more » Under the coherent potential approximation, we reproduce the experimental magnetic excitations using the disordered Heisenberg antiferromagnetic model with suppressed next-nearest-neighbor ferromagnetic coupling.« less

  2. Experiments on excitation waves

    NASA Astrophysics Data System (ADS)

    Müller, S. C.

    Recent trends in the experimentation on chemical and biochemical excitation waves are presented. In the Belousov-Zhabotinsky reaction, which is the most suitable chemical laboratory system for the study of wave propagation in excitable medium, the efficient control of wave dynamics by electrical fields and by light illumination is illustrated. In particular, the effects of a feedback control are shown. Further new experiments in this system are concerned with three-dimensional topologies and boundary effects. Important biological applications are found in the aggregation of slime mould amoebae, in proton waves during oscillatory glycolysis, and in waves of spreading depression in neuronal tissue as studied by experiments in chicken retina. Numerical simulations with appropriate reaction-diffusion models complement a large number of these experimental findings.

  3. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

    The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.

  4. Atmospheric Entry Experiments at IRS

    NASA Astrophysics Data System (ADS)

    Auweter-Kurtz, M.; Endlich, P.; Herdrich, G.; Kurtz, H.; Laux, T.; Löhle, S.; Nazina, N.; Pidan, S.

    2002-01-01

    Entering the atmosphere of celestial bodies, spacecrafts encounter gases at velocities of several km/s, thereby being subjected to great heat loads. The thermal protection systems and the environment (plasma) have to be investigated by means of computational and ground facility based simulations. For more than a decade, plasma wind tunnels at IRS have been used for the investigation of TPS materials. Nevertheless, ground tests and computer simulations cannot re- place space flights completely. Particularly, entry mission phases encounter challenging problems, such as hypersonic aerothermodynamics. Concerning the TPS, radiation-cooled materials used for reuseable spacecrafts and ablator tech- nologies are of importance. Besides the mentioned technologies, there is the goal to manage guidance navigation, con- trol, landing technology and inflatable technologies such as ballutes that aim to keep vehicles in the atmosphere without landing. The requirement to save mass and energy for planned interplanetary missions such as Mars Society Balloon Mission, Mars Sample Return Mission, Mars Express or Venus Sample Return mission led to the need for manoeuvres like aerocapture, aero-breaking and hyperbolic entries. All three are characterized by very high kinetic vehicle energies to be dissipated by the manoeuvre. In this field flight data are rare. The importance of these manoeuvres and the need to increase the knowledge of required TPS designs and behavior during such mission phases point out the need of flight experiments. As result of the experience within the plasma diagnostic tool development and the plasma wind tunnel data base, flight experiments like the PYrometric RE-entry EXperiment PYREX were developed, fully qualified and successfully flown. Flight experiments such as the entry spectrometer RESPECT and PYREX on HOPE-X are in the conceptual phase. To increase knowledge in the scope of atmospheric manoeuvres and entries, data bases have to be created combining both

  5. Excitable scale free networks

    NASA Astrophysics Data System (ADS)

    Copelli, M.; Campos, P. R. A.

    2007-04-01

    When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.

  6. Harmonically excited orbital variations

    SciTech Connect

    Morgan, T.

    1985-08-06

    Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

  7. Northern Polar Spring in IR

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 12 March 2004

    The Odyssey spacecraft has completed a full Mars year of observations of the red planet. For the next several weeks the Image of the Day will look back over this first mars year. It will focus on four themes: 1) the poles - with the seasonal changes seen in the retreat and expansion of the caps; 2) craters - with a variety of morphologies relating to impact materials and later alteration, both infilling and exhumation; 3) channels - the clues to liquid surface flow; and 4) volcanic flow features. While some images have helped answer questions about the history of Mars, many have raised new questions that are still being investigated as Odyssey continues collecting data as it orbits Mars.

    Infrared images taken during the daytime exhibit both the morphological and thermophysical properties of the surface of Mars. Morphologic details are visible due to the effect of sun-facing slopes receiving more energy than antisun-facing slopes. This creates a warm (bright) slope and cool (dark) slope appearance that mimics the light and shadows of a visible wavelength image. Thermophysical properties are seen in that dust heats up more quickly than rocks. Thus dusty areas are bright and rocky areas are dark.

    This image was collected October 19, 2002 during the northern spring season. The top half of this daytime IR image shows the North Polar sand sea.

    Image information: IR instrument. Latitude 76.2, Longitude 226.8 East (133.2 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in

  8. Northern Polar Spring in IR

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 12 March 2004

    The Odyssey spacecraft has completed a full Mars year of observations of the red planet. For the next several weeks the Image of the Day will look back over this first mars year. It will focus on four themes: 1) the poles - with the seasonal changes seen in the retreat and expansion of the caps; 2) craters - with a variety of morphologies relating to impact materials and later alteration, both infilling and exhumation; 3) channels - the clues to liquid surface flow; and 4) volcanic flow features. While some images have helped answer questions about the history of Mars, many have raised new questions that are still being investigated as Odyssey continues collecting data as it orbits Mars.

    Infrared images taken during the daytime exhibit both the morphological and thermophysical properties of the surface of Mars. Morphologic details are visible due to the effect of sun-facing slopes receiving more energy than antisun-facing slopes. This creates a warm (bright) slope and cool (dark) slope appearance that mimics the light and shadows of a visible wavelength image. Thermophysical properties are seen in that dust heats up more quickly than rocks. Thus dusty areas are bright and rocky areas are dark.

    This image was collected October 19, 2002 during the northern spring season. The top half of this daytime IR image shows the North Polar sand sea.

    Image information: IR instrument. Latitude 76.2, Longitude 226.8 East (133.2 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in

  9. Pulse excitation of bolometer bridges

    NASA Technical Reports Server (NTRS)

    Rusk, S. J.

    1972-01-01

    Driving bolometer bridge by appropriately phased excitation pulses increases signal-to-noise ratio of bolometer sensor which operates on a chopped light beam. Method allows higher applied voltage than is possible by conventional ac or dc excitation.

  10. Apparatus for photon excited catalysis

    NASA Technical Reports Server (NTRS)

    Saffren, M. M. (Inventor)

    1977-01-01

    An apparatus is described for increasing the yield of photonically excited gas phase reactions by extracting excess energy from unstable, excited species by contacting the species with the surface of a finely divided solid.

  11. The Ionotropic Receptors IR21a and IR25a mediate cool sensing in Drosophila.

    PubMed

    Ni, Lina; Klein, Mason; Svec, Kathryn V; Budelli, Gonzalo; Chang, Elaine C; Ferrer, Anggie J; Benton, Richard; Samuel, Aravinthan Dt; Garrity, Paul A

    2016-04-29

    Animals rely on highly sensitive thermoreceptors to seek out optimal temperatures, but the molecular mechanisms of thermosensing are not well understood. The Dorsal Organ Cool Cells (DOCCs) of the Drosophila larva are a set of exceptionally thermosensitive neurons critical for larval cool avoidance. Here, we show that DOCC cool-sensing is mediated by Ionotropic Receptors (IRs), a family of sensory receptors widely studied in invertebrate chemical sensing. We find that two IRs, IR21a and IR25a, are required to mediate DOCC responses to cooling and are required for cool avoidance behavior. Furthermore, we find that ectopic expression of IR21a can confer cool-responsiveness in an Ir25a-dependent manner, suggesting an instructive role for IR21a in thermosensing. Together, these data show that IR family receptors can function together to mediate thermosensation of exquisite sensitivity.

  12. The Ionotropic Receptors IR21a and IR25a mediate cool sensing in Drosophila

    PubMed Central

    Ni, Lina; Klein, Mason; Svec, Kathryn V; Budelli, Gonzalo; Chang, Elaine C; Ferrer, Anggie J; Benton, Richard; Samuel, Aravinthan DT; Garrity, Paul A

    2016-01-01

    Animals rely on highly sensitive thermoreceptors to seek out optimal temperatures, but the molecular mechanisms of thermosensing are not well understood. The Dorsal Organ Cool Cells (DOCCs) of the Drosophila larva are a set of exceptionally thermosensitive neurons critical for larval cool avoidance. Here, we show that DOCC cool-sensing is mediated by Ionotropic Receptors (IRs), a family of sensory receptors widely studied in invertebrate chemical sensing. We find that two IRs, IR21a and IR25a, are required to mediate DOCC responses to cooling and are required for cool avoidance behavior. Furthermore, we find that ectopic expression of IR21a can confer cool-responsiveness in an Ir25a-dependent manner, suggesting an instructive role for IR21a in thermosensing. Together, these data show that IR family receptors can function together to mediate thermosensation of exquisite sensitivity. DOI: http://dx.doi.org/10.7554/eLife.13254.001 PMID:27126188

  13. Transient mid-IR study of electron dynamics in TiO2 conduction band.

    PubMed

    Sá, Jacinto; Friedli, Peter; Geiger, Richard; Lerch, Philippe; Rittmann-Frank, Mercedes H; Milne, Christopher J; Szlachetko, Jakub; Santomauro, Fabio G; van Bokhoven, Jeroen A; Chergui, Majed; Rossi, Michel J; Sigg, Hans

    2013-04-07

    The dynamics of TiO2 conduction band electrons were followed with a novel broadband synchrotron-based transient mid-IR spectroscopy setup. The lifetime of conduction band electrons was found to be dependent on the injection method used. Direct band gap excitation results in a lifetime of 2.5 ns, whereas indirect excitation at 532 nm via Ru-N719 dye followed by injection from the dye into TiO2 results in a lifetime of 5.9 ns.

  14. IR line scanner on UAV

    NASA Astrophysics Data System (ADS)

    Liu, Shi-chao; Qin, Jie-xin; Qi, Hong-xing; Xiao, Gong-hai

    2011-08-01

    This paper introduces the designing principle and method of the IR line scanner on UAV in three aspects of optical-mechanical system, electronics system and processing software. It makes the system achieve good results in practical application that there are many features in the system such as light weight, small size, low power assumption, wide field of view, high instantaneous field of view, high noise equivalent temperature difference, wirelessly controlled and so on. The entire system is designed as follows: Multi-element scanner is put into use for reducing the electrical noise bandwidth, and then improving SNR; Square split aperture scanner is put into use for solving the image ratation distortion, besides fit for large velocity to height ratio; DSP is put into use for non-uniformity correction and background nosie subtraction, and then improving the imagery quality; SD card is put into use as image data storage media instead of the hard disk; The image data is stored in SD card in FAT32 file system, easily playbacked by processing software on Windows and Linux operating system; wireless transceiver module is put into use for wirelessly controlled.

  15. Recent catalysis measurements at IRS

    NASA Astrophysics Data System (ADS)

    Massuti-Ballester, B.; Pidan, S.; Herdrich, G.; Fertig, M.

    2015-08-01

    At the Institute of Space Systems (IRS), experiments have been performed using the high enthalpy, inductively heated plasma generator (IPG) in plasma wind tunnel 3 (PWK3), in order to assess the catalytic behaviour of different materials. Utilising the Upwind Relaxation Algorithm for Non-equilibrium Flows of the University of Stuttgart (URANUS), a methodology for determining catalytic efficiencies by obtaining atomic recombination probabilities γ for high temperature materials, has been developed. This method eliminates the inherent uncertainties produced when using catalytic properties of previously tested materials to infer those of new materials. In this work, eight different candidates for the Thermal Protection System (TPS) of an entry vehicle have been studied, of which six are ceramic materials and the other two are metallic alloys. Thermochemical properties of these specimens are given for surface temperatures between 1000 and 2000 K in pure oxygen and pure nitrogen plasmas. The high enthalpies and relatively low pressure conditions in which these material samples have been tested in PWK3 are relevant for entry applications from Low Earth Orbit (LEO).

  16. IR detection with uncooled sensors

    NASA Astrophysics Data System (ADS)

    Tissot, J. L.

    2004-12-01

    The emergence of uncooled detectors has opened new opportunities for IR detection for both military and commercial applications. Development of such devices involves a lot of trade-offs between the different parameters that define the technological stack. These trade-offs explain the number of different architectures that are under worldwide development. The Laboratoire d'Electronique, de Technologies et d'Information (LETI) and ULIS have chosen to develop uncooled infrared sensor using a silicon technology. This silicon approach has the greatest potential for reducing infrared detector manufacturing cost. LETI and ULIS are now working to facilitate the infrared focal plane array (IRFPA) integration into equipment in order to address a very large market. Achievement of this goal needs the development of smart sensors with on-chip advanced functions and the decrease of manufacturing cost of IRFPA by decreasing the pixel pitch and simplifying the vacuum package. We present in this paper the new designs for readout circuit and packages that will be used for 384 × 288 and 160 × 120 arrays with a pitch of 35 μm and advanced results on 35 μm pixel pitch arrays. Thermographic application needs high stability infrared detector with a precise determination of the amount of absorbed infrared flux. Hence, infrared detector with internal temperature stabilized shield has been developed and characterized. The results will be presented.

  17. VIS-IR transmitting windows

    NASA Astrophysics Data System (ADS)

    Bayya, S. S.; Chin, G. D.; Villalobos, G.; Sanghera, J. S.; Aggarwal, I. D.

    2005-05-01

    The U.S. Naval Research Laboratory (NRL) has developed two unique materials with excellent properties for various military and commercial applications in the UV-Vis-IR wavelength range. These materials are: an amorphous Barium Gallo-Germanate (BGG) glass and a polycrystalline Magnesium Aluminate Spinel. The BGG glass is made using traditional glass melting techniques, and was developed as a low cost alternative to the currently used window materials. Large prototype windows have been fabricated for a Navy reconnaissance program. BGG windows have been successfully tested for environmental ruggedness (MIL-F-48616) and rain erosion durability up to 300 mph. BGG glass is currently under development and evaluation for High Energy Laser (HEL) applications. A new process has been developed to sinter spinel to clear transparency with very high yields. This process has been used to make various sizes and shapes (flats and domes) and is readily scalable to industrial sizes to produce large windows & domes for various applications. NRL has also developed modified BGG glasses, which are compatible with Spinel and ALON substrates for bonding.

  18. Jefferson Laboratory IR Demo project

    NASA Astrophysics Data System (ADS)

    Shinn, Michelle D.

    1997-05-01

    The Thomas Jefferson National Accelerator Facility (formerly known as CEBAF) has embarked on the construction of a 1 kW free-electron laser operating initially at 5 microns that is designed for laser-material interaction experiments and to explore the feasibility of scaling the system in power for Navy defense and industrial applications. The accelerator system for this IR demo includes a 10 MeV photocathode-based injector, a 32 MeV CEBAF-style superconducting radio-frequency linac, and single-pass transport that accelerates the beam from injector to wiggler, followed by energy-recovery deceleration to a dump. The initial optical configuration is a conventional near-concentric resonator with transmissive outcoupling. Following commissioning, the laser output will be extended to an operating range of 3-to-6.6 microns, and distributed to six labs in a user facility built with funds from the Commonwealth of Virginia. A description of the machine and facility and the project status are presented.

  19. Hydrogen intercalation under graphene on Ir(111)

    NASA Astrophysics Data System (ADS)

    Grånäs, Elin; Gerber, Timm; Schröder, Ulrike A.; Schulte, Karina; Andersen, Jesper N.; Michely, Thomas; Knudsen, Jan

    2016-09-01

    Using high resolution X-ray photoelectron spectroscopy and scanning tunneling microscopy we study the intercalation of hydrogen under graphene/Ir(111). The hydrogen intercalated graphene is characterized by a component in C 1s that is shifted -0.10 to -0.18 eV with respect to pristine graphene and a component in Ir 4f at 60.54 eV. The position of this Ir 4f component is identical to that of the Ir(111) surface layer with hydrogen atoms adsorbed, indicating that the atomic hydrogen adsorption site on bare Ir(111) and beneath graphene is the same. Based on co-existence of fully- and non-intercalated graphene, and the inability to intercalate a closed graphene film covering the entire Ir(111) surface, we conclude that hydrogen dissociatively adsorbs at bare Ir(111) patches, and subsequently diffuses rapidly under graphene. A likely entry point for the intercalating hydrogen atoms is identified to be where graphene crosses an underlying Ir(111) step.

  20. High temperature Ir segregation in Ir-B ceramics: Effect of oxygen presence on stability of IrB2 and other Ir-B phases

    SciTech Connect

    Xie, Zhilin; Terracciano, Anthony C.; Cullen, David A.; Blair, Richard G.; Orlovskaya, Nina

    2015-05-13

    The formation of IrB2, IrB1.35, IrB1.1 and IrB monoboride phases in the Ir–B ceramic nanopowder was confirmed during mechanochemical reaction between metallic Ir and elemental B powders. The Ir–B phases were analysed after 90 h of high energy ball milling and after annealing of the powder for 72 h at 1050°C in vacuo. The iridium monoboride (IrB) orthorhombic phase was synthesised experimentally for the first time and identified by powder X-ray diffraction. Additionally, the ReB2 type IrB2 hexagonal phase was also produced for the first time and identified by high resolution transmission electron microscope. Ir segregation along disordered domains of the boron lattice was found to occur during high temperature annealing. Furthermore, these nanodomains may have useful catalytic properties.

  1. Status Of Sofradir IR-CCD Detectors

    NASA Astrophysics Data System (ADS)

    Tribolet, Philippe; Radisson, Patrick

    1988-05-01

    The topics of this paper deal with the IR-CCD detectors manufactured by SOFRADIR the new French joint venture. Description of the IRCCD technology and the advantages of this approach are given. In conclusion, some IR-CCD typical results are given.

  2. Superluminal travel, UV/IR mixing, and turbulence in a (1+1)-dimensional world

    NASA Astrophysics Data System (ADS)

    Dubovsky, Sergei; Gorbenko, Victor

    2011-11-01

    We study renormalizable Lorentz invariant stable quantum field theories in two space-time dimensions with instantaneous causal structure (causal ordering induced by the light “cone” time ordering). These models provide a candidate UV completion of the two-dimensional ghost condensate. They exhibit a peculiar UV/IR mixing—energies of all excitations become arbitrarily small at high spatial momenta. We discuss several phenomena associated with this mixing. These include the impossibility to reach a thermal equilibrium and metastability of all excitations towards decay into short-wavelength modes resulting in an indefinite turbulent cascade. In spite of the UV/IR mixing in many cases the UV physics can still be decoupled from low-energy phenomena. However, a patient observer in the Lineland is able to produce arbitrarily heavy particles simply by waiting for a long enough time.

  3. Get excited: reappraising pre-performance anxiety as excitement.

    PubMed

    Brooks, Alison Wood

    2014-06-01

    Individuals often feel anxious in anticipation of tasks such as speaking in public or meeting with a boss. I find that an overwhelming majority of people believe trying to calm down is the best way to cope with pre-performance anxiety. However, across several studies involving karaoke singing, public speaking, and math performance, I investigate an alternative strategy: reappraising anxiety as excitement. Compared with those who attempt to calm down, individuals who reappraise their anxious arousal as excitement feel more excited and perform better. Individuals can reappraise anxiety as excitement using minimal strategies such as self-talk (e.g., saying "I am excited" out loud) or simple messages (e.g., "get excited"), which lead them to feel more excited, adopt an opportunity mind-set (as opposed to a threat mind-set), and improve their subsequent performance. These findings suggest the importance of arousal congruency during the emotional reappraisal process.

  4. The WFC3 IR "Blobs" Monitoring

    NASA Astrophysics Data System (ADS)

    Pirzkal, N.; Hilbert, B.

    2012-11-01

    We present new results on the WFC3 IR "Blobs" based on analysis of data acquired using the WFC3 IR channel from 2010 to 2012. In particular, we trace the date of appearance of each of the Blobs we identified in our deep IR sky flats. The number of Blobs identified in the WFC3 IR channel is now 40, and increase of a factor of 2 from our earlier 2010 ISR. We also discuss the color of the blobs, as measured using the F105W, F125W and F160W filters. We find Blobs to be more opaque to bluer light and their effect is therefore slightly stronger in the F105W and F125W filters when comparing these to the F160W filter. We find that the IR Blobs have appeared during somewhat discrete events and that there was a period a little over one year long when no new Blobs appeared.

  5. Inter-Valence-Subband/Conduction-Band-Transport IR Detectors

    NASA Technical Reports Server (NTRS)

    Ting, David; Gunapala, Sarath; Bandara, Sumith

    2004-01-01

    Infrared (IR) detectors characterized by a combination of (1) high-quantum-efficiency photoexcitation of inter-valence-subband transitions of charge carriers and (2) high-mobility conduction- band transport of the thus-excited charge carriers have been proposed in an effort to develop focal-plane arrays of such devices for infrared imaging. Like many prior quantum-well infrared photodetectors (QWIPs), the proposed devices would be made from semiconductor heterostructures. In order to obtain the combination of characteristics mentioned above, the proposed devices would be designed and fabricated in novel InAs/GaSb superlattice configurations that would exploit a phenomenon known in the semiconductor art as type-II broken-gap band offset.

  6. Search for Gluonic Excitations

    SciTech Connect

    Eugenio, Paul

    2007-10-26

    Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.

  7. Search for Gluonic Excitations

    SciTech Connect

    Paul Eugenio

    2007-10-01

    Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.

  8. Metastable Interactions: Dissociative Excitation.

    DTIC Science & Technology

    1985-05-01

    participate. The mercuric halide compounds HgBr2 , HgCl 2 , and HgI2 are of recent interest because of laser output achieved on the B2 E - X2 E transition in...the * respective mercuric halide radicals in the range of 400-600 nm. Population inversion has been obtained by photodissociation and electron impact...excitation in mixtures o the mercuric - halide compounds and the rare gases. Chang and -* Burnham (3) have noted Improved laser efficiency and improved

  9. SHOCK-EXCITED OSCILLATOR

    DOEpatents

    Creveling, R.

    1957-12-17

    S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.

  10. Spin liquid close to a quantum critical point in Na4Ir3O8

    NASA Astrophysics Data System (ADS)

    Singh, Yogesh; Tokiwa, Y.; Dong, J.; Gegenwart, P.

    2013-12-01

    Na4Ir3O8 is a candidate material for a three-dimensional quantum spin liquid on the hyperkagome lattice. We present thermodynamic measurements of heat capacity C and thermal conductivity κ on high-quality polycrystalline samples of Na4Ir3O8 down to T =500 and 75 mK, respectively. Absence of long-range magnetic order down to T =75 mK strongly supports claims of a spin-liquid ground state. The constant magnetic susceptibility χ below T ≈25 K and the presence of a small but finite linear-T term in C (T) suggest the presence of gapless spin excitations. Additionally, the magnetic Grüneisen ratio shows a divergence as T →0 K and a scaling behavior, which clearly demonstrates that Na4Ir3O8 is situated close to a zero-field QCP.

  11. Structural dynamics inside a functionalized metal–organic framework probed by ultrafast 2D IR spectroscopy

    DOE PAGES

    Nishida, Jun; Tamimi, Amr; Fei, Honghan; ...

    2014-12-15

    One key property of metal-organic frameworks (MOFs) are their structural elasticity. IHere we show that 2D IR spectroscopy with pulse-shaping techniques can probe the ultrafast structural fluctuations of MOFs. 2D IR data, obtained from a vibrational probe attached to the linkers of UiO-66 MOF in low concentration, revealed that the structural fluctuations have time constants of 7 and 670 ps with no solvent. Filling the MOF pores with dimethylformamide (DMF) slows the structural fluctuations by reducing the ability of the MOF to undergo deformations, and the dynamics of the DMF molecules are also greatly restricted. Finally, methodology advances were requiredmore » to remove the severe light scattering caused by the macroscopic-sized MOF particles, eliminate interfering oscillatory components from the 2D IR data, and address Förster vibrational excitation transfer.« less

  12. Near-IR fluorescence and reflectance confocal microscopy for imaging of quantum dots in mammalian skin

    PubMed Central

    Mortensen, Luke J.; Glazowski, Christopher E.; Zavislan, James M.; DeLouise, Lisa A.

    2011-01-01

    Understanding the skin penetration of nanoparticles (NPs) is an important concern due to the increasing presence of NPs in consumer products, including cosmetics. Technical challenges have slowed progress in evaluating skin barrier and NP factors that contribute to skin penetration risk. To limit sampling error and other problems associated with histological processing, many researchers are implementing whole tissue confocal or multiphoton microscopies. This work introduces a fluorescence and reflectance confocal microscopy system that utilizes near-IR excitation and emission to detect near-IR lead sulfide quantum dots (QDs) through ex vivo human epidermis. We provide a detailed prediction and experimental analysis of QD detection sensitivity and demonstrate detection of QD skin penetration in a barrier disrupted model. The unique properties of near-IR lead-based QDs will enable future studies that examine the impact of further barrier-disrupting agents on skin penetration of QDs and elucidate mechanistic insight into QD tissue interactions at the cellular level. PMID:21698023

  13. Spin waves and revised crystal structure of honeycomb iridate Na2IrO3.

    PubMed

    Choi, S K; Coldea, R; Kolmogorov, A N; Lancaster, T; Mazin, I I; Blundell, S J; Radaelli, P G; Singh, Yogesh; Gegenwart, P; Choi, K R; Cheong, S-W; Baker, P J; Stock, C; Taylor, J

    2012-03-23

    We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order. The onset of long-range magnetic order below T(N)=15.3  K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90° Ir-O-Ir bonds required for dominant Kitaev exchange.

  14. Excitability in Dictyostelium development

    NASA Astrophysics Data System (ADS)

    Schwab, David

    2013-03-01

    Discovering how populations of cells reliably develop into complex multi-cellular structures is a key challenge in modern developmental biology. This requires an understanding of how networks at the single-cell level, when combined with intercellular signaling and environmental cues, give rise to the collective behaviors observed in cellular populations. I will present work in collaboration with the Gregor lab, showing that the signal-relay response of starved cells of the amoebae Dictyostelium discoideum can be well modeled as an excitable system. This is in contrast to existing models of the network that postulate a feed-forward cascade. I then extend the signal-relay model to describe how spatial gradient sensing may be achieved via excitability. One potential advantage of relying on feedback for gradient sensing is in preventing ``cheaters'' that do not produce signals from taking over the population. I then combine these models of single-cell signaling and chemotaxis to perform large-scale agent-based simulations of aggregating populations. This allows direct study of how variations in single-cell dynamics modify population behavior. In order to further test this model, I use the results of a screen for mutant cell lines that exhibit altered collective patterns. Finally, I use an existing FRET movie database of starved cell populations at varying cell densities and dilution rates to study heterogeneity in repeated spatio-temporal activity patterns.

  15. Design of a mid-IR polarimeter for SOFIA

    NASA Astrophysics Data System (ADS)

    Packham, C.; Escuti, M.; Boreman, G.; Quijano, I.; Ginn, J. C.; Franklin, B.; Axon, D. J.; Hough, J. H.; Jones, T. J.; Roche, P. F.; Tamura, M.; Telesco, C. M.; Levenson, N.; Rodgers, J. M.; McGuire, J. P.

    2008-07-01

    Mid-infrared polarimetry remains an underexploited technique; where available it is limited in spectral coverage from the ground, and conspicuously absent from the Spitzer, JWST and Herschel instrument suites. The unique characteristics of SOFIA afford unprecedented spectral coverage and sensitivity in the mid-infrared waveband. We discuss the preliminary optical design for a 5-40μm spectro-polarimeter for use on SOFIA, the SOFIA Mid-InfraRed Polarimeter (SMIRPh). The design furthers the existing 5-40μm imaging and spectroscopic capabilities of SOFIA, and draws on experience gained through the University of Florida's mid-IR imagers, spectrometer and polarimeter designs of T-ReCS and CanariCam. We pay special attention to the challenges of obtaining polarimetric materials suitable at both these wavelengths and cryogenic temperatures. Finally, we (briefly) present an overview of science highlights that could be performed from a 5-40μm imaging- and spectro-polarimeter on SOFIA. Combined with the synergy between the possible future far-IR polarimeter, Hale, this instrument would provide the SOFIA community with unique and exciting science capabilities, leaving a unique scientific legacy.

  16. Crystal-field splitting and correlation effect on the electronic structure of A2IrO3.

    PubMed

    Gretarsson, H; Clancy, J P; Liu, X; Hill, J P; Bozin, Emil; Singh, Yogesh; Manni, S; Gegenwart, P; Kim, Jungho; Said, A H; Casa, D; Gog, T; Upton, M H; Kim, Heung-Sik; Yu, J; Katukuri, Vamshi M; Hozoi, L; van den Brink, Jeroen; Kim, Young-June

    2013-02-15

    The electronic structure of the honeycomb lattice iridates Na(2)IrO(3) and Li(2)IrO(3) has been investigated using resonant inelastic x-ray scattering (RIXS). Crystal-field-split d-d excitations are resolved in the high-resolution RIXS spectra. In particular, the splitting due to noncubic crystal fields, derived from the splitting of j(eff)=3/2 states, is much smaller than the typical spin-orbit energy scale in iridates, validating the applicability of j(eff) physics in A(2)IrO(3). We also find excitonic enhancement of the particle-hole excitation gap around 0.4 eV, indicating that the nearest-neighbor Coulomb interaction could be large. These findings suggest that both Na(2)IrO(3) and Li(2)IrO(3) can be described as spin-orbit Mott insulators, similar to the square lattice iridate Sr(2)IrO(4).

  17. Visualizing Infrared (IR) Spectroscopy with Computer Animation

    NASA Technical Reports Server (NTRS)

    Abrams, Charles B.; Fine, Leonard W.

    1996-01-01

    IR Tutor, an interactive, animated infrared (IR) spectroscopy tutorial has been developed for Macintosh and IBM-compatible computers. Using unique color animation, complicated vibrational modes can be introduced to beginning students. Rules governing the appearance of IR absorption bands become obvious because the vibrational modes can be visualized. Each peak in the IR spectrum is highlighted, and the animation of the corresponding normal mode can be shown. Students can study each spectrum stepwise, or click on any individual peak to see its assignment. Important regions of each spectrum can be expanded and spectra can be overlaid for comparison. An introduction to the theory of IR spectroscopy is included, making the program a complete instructional package. Our own success in using this software for teaching and research in both academic and industrial environments will be described. IR Tutor consists of three sections: (1) The 'Introduction' is a review of basic principles of spectroscopy. (2) 'Theory' begins with the classical model of a simple diatomic molecule and is expanded to include larger molecules by introducing normal modes and group frequencies. (3) 'Interpretation' is the heart of the tutorial. Thirteen IR spectra are analyzed in detail, covering the most important functional groups. This section features color animation of each normal mode, full interactivity, overlay of related spectra, and expansion of important regions. This section can also be used as a reference.

  18. Detecting explosive substances by the IR spectrography

    NASA Astrophysics Data System (ADS)

    Kuula, J.; Rinta, Heikki J.; Pölönen, I.; Puupponen, H.-H.; Haukkamäki, Marko; Teräväinen, T.

    2014-05-01

    Fast and safe detection methods of explosive substances are needed both before and after actualized explosions. This article presents an experiment of the detection of three selected explosives by the ATR FTIR spectrometer and by three different IR hyperspectral imaging devices. The IR spectrometers give accurate analyzing results, whereas hyperspectral imagers can detect and analyze desired samples without touching the unidentified target at all. In the controlled explosion experiment TNT, dynamite and PENO were at first analyzed as pure substances with the ATR FTIR spectrometer and with VNIR, SWIR and MWIR cameras. After three controlled explosions also the residues of TNT, dynamite and PENO were analyzed with the same IR devices. The experiments were performed in arctic outdoor conditions and the residues were collected on ten different surfaces. In the measurements the spectra of all three explosives were received as pure substances with all four IR devices. Also the explosion residues of TNT were found on cotton with the IR spectrometer and with VNIR, SWIR and MWIR hyperspectral imagers. All measurements were made directly on the test materials which had been placed on the explosion site and were collected for the analysis after each blast. Measurements were made with the IR spectrometer also on diluted sample. Although further tests are suggested, the results indicate that the IR spectrography is a potential detection method for explosive subjects, both as pure substances and as post-blast residues.

  19. Visualizing Infrared (IR) Spectroscopy with Computer Animation

    NASA Technical Reports Server (NTRS)

    Abrams, Charles B.; Fine, Leonard W.

    1996-01-01

    IR Tutor, an interactive, animated infrared (IR) spectroscopy tutorial has been developed for Macintosh and IBM-compatible computers. Using unique color animation, complicated vibrational modes can be introduced to beginning students. Rules governing the appearance of IR absorption bands become obvious because the vibrational modes can be visualized. Each peak in the IR spectrum is highlighted, and the animation of the corresponding normal mode can be shown. Students can study each spectrum stepwise, or click on any individual peak to see its assignment. Important regions of each spectrum can be expanded and spectra can be overlaid for comparison. An introduction to the theory of IR spectroscopy is included, making the program a complete instructional package. Our own success in using this software for teaching and research in both academic and industrial environments will be described. IR Tutor consists of three sections: (1) The 'Introduction' is a review of basic principles of spectroscopy. (2) 'Theory' begins with the classical model of a simple diatomic molecule and is expanded to include larger molecules by introducing normal modes and group frequencies. (3) 'Interpretation' is the heart of the tutorial. Thirteen IR spectra are analyzed in detail, covering the most important functional groups. This section features color animation of each normal mode, full interactivity, overlay of related spectra, and expansion of important regions. This section can also be used as a reference.

  20. Quantifying Flaw Characteristics from IR NDE Data

    SciTech Connect

    Miller, W; Philips, N R; Burke, M W; Robbins, C L

    2003-02-14

    Work is presented which allows flaw characteristics to be quantified from the transient IR NDE signature. The goal of this effort was to accurately determine the type, size and depth of flaws revealed with IR NDE, using sonic IR as the example IR NDE technique. Typically an IR NDE experiment will result in a positive qualitative indication of a flaw such as a cold or hot spot in the image, but will not provide quantitative data thereby leaving the practitioner to make educated guesses as to the source of the signal. The technique presented here relies on comparing the transient IR signature to exact heat transfer analytical results for prototypical flaws, using the flaw characteristics as unknown fitting parameters. A nonlinear least squares algorithm is used to evaluate the fitting parameters, which then provide a direct measure of the flaw characteristics that can be mapped to the imaged surface for visual reference. The method uses temperature data for the heat transfer analysis, so radiometric calibration of the IR signal is required. The method provides quantitative data with a single thermal event (e.g. acoustic pulse or flash), as compared to phase-lock techniques that require many events. The work has been tested with numerical data but remains to be validated by experimental data, and that effort is underway.

  1. Detection of concealed and buried chemicals by using multifrequency excitations

    SciTech Connect

    Gao Yaohui; Chen, Meng-Ku; Yang, Chia-En; Chang, Yun-Ching; Yao, Jim; Cheng Jiping; Yin, Stuart; Hui Rongqing; Ruffin, Paul; Brantley, Christina; Edwards, Eugene; Luo, Claire

    2010-08-15

    In this paper, we present a new type of concealed and buried chemical detection system by stimulating and enhancing spectroscopic signatures with multifrequency excitations, which includes a low frequency gradient dc electric field, a high frequency microwave field, and higher frequency infrared (IR) radiations. Each excitation frequency plays a unique role. The microwave, which can penetrate into the underground and/or pass through the dielectric covers with low attenuation, could effectively transform its energy into the concealed and buried chemicals and increases its evaporation rate from the sample source. Subsequently, a gradient dc electric field, generated by a Van De Graaff generator, not only serves as a vapor accelerator for efficiently expediting the transportation process of the vapor release from the concealed and buried chemicals but also acts as a vapor concentrator for increasing the chemical concentrations in the detection area, which enables the trace level chemical detection. Finally, the stimulated and enhanced vapors on the surface are detected by the IR spectroscopic fingerprints. Our theoretical and experimental results demonstrate that more than sixfold increase in detection signal can be achieved by using this proposed technology. The proposed technology can also be used for standoff detection of concealed and buried chemicals by adding the remote IR and/or thermal spectroscopic and imaging detection systems.

  2. Basaltic Crater in Color IR

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 6, 2004 This image shows two representations of the same infra-red image near Nili Fosse in the the Isidis region of Mars. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations. In many cases craters trap sand in their topographic depressions, interrupting the sand's migration across the Martian surface. This image is particularly interesting because there appears to be more than 1 type of sand in the bottom of this crater and in the hummocky terrain near the bottom of the image. The pink/magenta areas are characteristic of a basaltic composition, but there are also orange areas that are likely caused by the presence of andesite. These two compositions, basalt and andesite, are some of the most common found on Mars.

    Image information: IR instrument. Latitude 24, Longitude 80.7 East (297.3 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip

  3. Basaltic Crater in Color IR

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 6, 2004 This image shows two representations of the same infra-red image near Nili Fosse in the the Isidis region of Mars. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations. In many cases craters trap sand in their topographic depressions, interrupting the sand's migration across the Martian surface. This image is particularly interesting because there appears to be more than 1 type of sand in the bottom of this crater and in the hummocky terrain near the bottom of the image. The pink/magenta areas are characteristic of a basaltic composition, but there are also orange areas that are likely caused by the presence of andesite. These two compositions, basalt and andesite, are some of the most common found on Mars.

    Image information: IR instrument. Latitude 24, Longitude 80.7 East (297.3 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip

  4. Atmospheric Effects in IR Color

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 3, 2004 This image shows two representations of the same infra-red image covering parts of Ius Chasma and Oudemans Crater. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

    This image is dominated by atmospheric effects. The pink/magenta colors inside the canyon show areas with a large amount of atmospheric dust. In the bottom half of the image, the patchy blue/cyan colors indicate the presence of water ice clouds out on the plains. Water ice clouds and high amounts of dust do not generally occur at the same place and time on Mars because the dust absorbs sunlight and heats the atmosphere. The more dust that is present, the warmer the atmosphere becomes, sublimating the water ice into water vapor and dissipating any clouds.

    Image information: IR instrument. Latitude -8.2, Longitude 267.9 East (92.1.West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is

  5. Melas Chasma in IR Color

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 11, 2004 This image shows two representations of the same infra-red image over Melas Chasma. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

    There is a distinct purple/blue layer present in the northern wall of the Chasma. Although this layer likely has a composition different than the surrounding areas, it is difficult to interpret its specific composition due to the high variability of sunlit and shaded surfaces in this area, which cause a wide range of temperatures to be present within each pixel of the image. It is possible that this layer has a unique composition due to differences in the volcanic or sedimentary environment at the time that the rock formed, or it could be a layer of magma injected between two previously existing rock layers. Another possibility is that the wall is mostly covered by dust and debris, and this portion contains the only exposed bedrock. The light blue colors present in many other areas of the Chasma are due to water ice clouds.

    Image information: IR instrument. Latitude -8.9, Longitude 282 East (78 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey

  6. Ice Clouds in Color IR

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 9, 2004 This image shows two representations of the same infra-red image in the Elysium region of Mars. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

    The light blue area in the center of this image is a very nice example of a water ice cloud. Water ice is frequently present in the Martian atmosphere as a thin haze. Clouds such as this one can be difficult to identify in a temperature image, but are easy to spot in the DCS images. In this case, the water ice is relatively confined and concentrated which may be due to the topography of the Elysium volcanic construct.

    Image information: IR instrument. Latitude 23.2, Longitude 150.1 East (209.9 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed

  7. Atmospheric Effects in IR Color

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 3, 2004 This image shows two representations of the same infra-red image covering parts of Ius Chasma and Oudemans Crater. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

    This image is dominated by atmospheric effects. The pink/magenta colors inside the canyon show areas with a large amount of atmospheric dust. In the bottom half of the image, the patchy blue/cyan colors indicate the presence of water ice clouds out on the plains. Water ice clouds and high amounts of dust do not generally occur at the same place and time on Mars because the dust absorbs sunlight and heats the atmosphere. The more dust that is present, the warmer the atmosphere becomes, sublimating the water ice into water vapor and dissipating any clouds.

    Image information: IR instrument. Latitude -8.2, Longitude 267.9 East (92.1.West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is

  8. Gale Crater in IR Color

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released August 4, 2004 This image shows two representations of the same infra-red image of Gale Crater. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

    In the bottom of the crater, surrounding the central mound, there are extensive basaltic sand deposits. The basaltic sand spectral signature combined with the warm surface (due to the low albedo of basaltic sand) produces a very strong pink/magenta color. This color signature contrasts with the green/yellow color of soil and dust in the top of the image, and the cyan color due to the presence of water ice clouds at the bottom of the image. This migrating sand may be producing the erosional features seen on the central mound.

    Image information: IR instrument. Latitude -4.4, Longitude 137.4 East (222.6 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University

  9. Plasma thruster development program at the IRS

    NASA Astrophysics Data System (ADS)

    Auweter-Kurtz, M.

    1992-08-01

    The current status of the plasma thruster development program at the Institute of Space Systems (IRS) of the University of Stuttgart is reviewed. Continuously running MPD thrusters up to the megawatt level are currently under development. The objective of this work at IRS is to identify and avoid critical regimes of operation and predict the performance of high-power MPD thrusters. The development program for thermal arcjets is more flight oriented. The discussion includes a description of the IRS facilities and highlights of the MPD thruster and thermal arcjet development programs.

  10. Monitoring Non-Adiabatic Dynamics of the RNA Base Uracil by UV-Pump-IR-Probe Spectroscopy

    PubMed Central

    Fingerhut, Benjamin P.; Dorfman, Konstantin E.; Mukamel, Shaul

    2013-01-01

    Resolving the excited state dynamics of DNA- and RNA- nucleobases has attracted considerably attention. UV irradiation of the isolated nucleobases leads to the population of an electronic excited state which is quenched by internal conversion mediated by conical intersections on an ultrafast timescale. We present non-adiabatic on-the-fly molecular dynamics simulations of the UV-pump-IR-probe signal of the pyrimidine nucleobase uracil using a novel semiclassical protocol which takes into account the path integral over the excited state vibrational dynamics and properly describes the joint temporal and spectral resolution of the technique. Simulations of vibrational motions of carbonyl fingerprint modes in the electronically excited states reveal clear signatures of different relaxation pathways on a timescale of hundreds of femtoseconds which arise from an ultrafast branching in the excited state. We show that the inherent temporal and spectral resolution of the technique is not purely instrumental but also depends on the vibrational fluctuation timescale. PMID:23914288

  11. FT-IR standoff detection of thermally excited emissions of trinitrotoluene (TNT) deposited on aluminum substrates.

    PubMed

    Castro-Suarez, John R; Pacheco-Londoño, Leonardo C; Vélez-Reyes, Miguel; Diem, Max; Tague, Thomas J; Hernandez-Rivera, Samuel P

    2013-02-01

    A standoff detection system was assembled by coupling a reflecting telescope to a Fourier transform infrared spectrometer equipped with a cryo-cooled mercury cadmium telluride detector and used for detection of solid-phase samples deposited on substrates. Samples of highly energetic materials were deposited on aluminum substrates and detected at several collector-target distances by performing passive-mode, remote, infrared detection measurements on the heated analytes. Aluminum plates were used as support material, and 2,4,6-Trinitrotoluene (TNT) was used as the target. For standoff detection experiments, the samples were placed at different distances (4 to 55 m). Several target surface temperatures were investigated. Partial least squares regression analysis was applied to the analysis of the intensities of the spectra obtained. Overall, standoff detection in passive mode was useful for quantifying TNT deposited on the aluminum plates with high confidence up to target-collector distances of 55 m.

  12. Helicity-dependent photocurrent in the resistive Ag/Pd films excited by IR laser radiation

    SciTech Connect

    Mikheev, G M; Saushin, A S; Vanyukov, V V

    2015-07-31

    It is shown that in resistive Ag/Pd films manufactured according to the thick-film technology, in the case of oblique incidence of laser radiation of nanosecond duration at a wavelengths of 1350 – 2100 nm, a photon-drag photocurrent arises in the direction perpendicular to the plane of incidence, dependent on the ellipticity and sign of circular polarisation of incident radiation. This photocurrent consists of the so-called circular and linear contributions, which are, respectively, dependent on and independent of the sign of circular polarisation. In this wavelength range, the amplitude of the circular contribution is many times greater than that of the linear contribution. The results allow the use of resistive Ag/Pd films for the development and manufacture of innovative sensors of the sign of circular polarisation of pulsed laser radiation, operating in a wide spectral range. (interaction of laser radiation with matter. laser plasma)

  13. Double photon excitation of high-Rydberg atoms as a long-lived submillimeter detector

    NASA Technical Reports Server (NTRS)

    Chutjian, A. N. (Inventor)

    1986-01-01

    A method and apparatus for detecting submillimeter or IR radiation is disclosed. A rare gas, such as xenon, is supplied at its ground state via a pressurized cylinder and an adjustable leak valve into a cryogenically cooled detection area. The ground state of xenon is double photon excited to a particularized level of the Rydberg series by a resonance lamp and a laser. The doubly excited gas is then further excited by the radiation to be measured. A field ionization and an ion measurement indicative of the radiation intensity is achieved.

  14. Observation of the interference between the intramolecular IR-visible and visible-IR processes in the doubly resonant sum frequency generation vibrational spectroscopy of Rhodamine 6G adsorbed at the air/water interface.

    PubMed

    Wu, Dan; Deng, Gang-Hua; Guo, Yuan; Wang, Hong-fei

    2009-05-28

    Using the picosecond visible light at 532.1 nm and infrared light at 2800-3100 cm(-1), we observed the interference between the intramolecular IR-visible and visible-IR processes in the doubly resonant sum frequency generation vibrational spectroscopy of Rhodamine 6G adsorbed at the air/water interface. The interference phenomenon exists for both the C-H stretching vibrations in the 2800-3100 cm(-1) region and the skeleton vibrations in the 1450-1700 cm(-1) region. The relative strength of the visible-IR process at different wavelengths is the result of the electronic structure of the molecule. This is the first direct observation of the visible-IR sum frequency generation process in the electronically excited state of a model molecular system.

  15. Length of excitable knots

    NASA Astrophysics Data System (ADS)

    Maucher, Fabian; Sutcliffe, Paul

    2017-07-01

    In this paper, we present extensive numerical simulations of an excitable medium to study the long-term dynamics of knotted vortex strings for all torus knots up to crossing number 11. We demonstrate that FitzHugh-Nagumo evolution preserves the knot topology for all the examples presented, thereby providing a field theory approach to the study of knots. Furthermore, the evolution yields a well-defined minimal length for each knot that is comparable to the ropelength of ideal knots. We highlight the role of the medium boundary in stabilizing the length of the knot and discuss the implications beyond torus knots. We also show that there is not a unique attractor within a given knot topology.

  16. CINE: Comet INfrared Excitation

    NASA Astrophysics Data System (ADS)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-08-01

    CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  17. PKC{delta}-mediated IRS-1 Ser24 phosphorylation negatively regulates IRS-1 function

    SciTech Connect

    Greene, Michael W. . E-mail: michael.greene@bassett.org; Ruhoff, Mary S.; Roth, Richard A.; Kim, Jeong-a; Quon, Michael J.; Krause, Jean A.

    2006-10-27

    The IRS-1 PH and PTB domains are essential for insulin-stimulated IRS-1 Tyr phosphorylation and insulin signaling, while Ser/Thr phosphorylation of IRS-1 disrupts these signaling events. To investigate consensus PKC phosphorylation sites in the PH-PTB domains of human IRS-1, we changed Ser24, Ser58, and Thr191 to Ala (3A) or Glu (3E), to block or mimic phosphorylation, respectively. The 3A mutant abrogated the inhibitory effect of PKC{delta} on insulin-stimulated IRS-1 Tyr phosphorylation, while reductions in insulin-stimulated IRS-1 Tyr phosphorylation, cellular proliferation, and Akt activation were observed with the 3E mutant. When single Glu mutants were tested, the Ser24 to Glu mutant had the greatest inhibitory effect on insulin-stimulated IRS-1 Tyr phosphorylation. PKC{delta}-mediated IRS-1 Ser24 phosphorylation was confirmed in cells with PKC{delta} catalytic domain mutants and by an RNAi method. Mechanistic studies revealed that IRS-1 with Ala and Glu point mutations at Ser24 impaired phosphatidylinositol-4,5-bisphosphate binding. In summary, our data are consistent with the hypothesis that Ser24 is a negative regulatory phosphorylation site in IRS-1.

  18. PKCdelta-mediated IRS-1 Ser24 phosphorylation negatively regulates IRS-1 function.

    PubMed

    Greene, Michael W; Ruhoff, Mary S; Roth, Richard A; Kim, Jeong-A; Quon, Michael J; Krause, Jean A

    2006-10-27

    The IRS-1 PH and PTB domains are essential for insulin-stimulated IRS-1 Tyr phosphorylation and insulin signaling, while Ser/Thr phosphorylation of IRS-1 disrupts these signaling events. To investigate consensus PKC phosphorylation sites in the PH-PTB domains of human IRS-1, we changed Ser24, Ser58, and Thr191 to Ala (3A) or Glu (3E), to block or mimic phosphorylation, respectively. The 3A mutant abrogated the inhibitory effect of PKCdelta on insulin-stimulated IRS-1 Tyr phosphorylation, while reductions in insulin-stimulated IRS-1 Tyr phosphorylation, cellular proliferation, and Akt activation were observed with the 3E mutant. When single Glu mutants were tested, the Ser24 to Glu mutant had the greatest inhibitory effect on insulin-stimulated IRS-1 Tyr phosphorylation. PKCdelta-mediated IRS-1 Ser24 phosphorylation was confirmed in cells with PKCdelta catalytic domain mutants and by an RNAi method. Mechanistic studies revealed that IRS-1 with Ala and Glu point mutations at Ser24 impaired phosphatidylinositol-4,5-bisphosphate binding. In summary, our data are consistent with the hypothesis that Ser24 is a negative regulatory phosphorylation site in IRS-1.

  19. Increasing Medical Student Exposure to IR through Integration of IR into the Gross Anatomy Course.

    PubMed

    DePietro, Daniel M; Kiefer, Ryan M; Redmond, Jonas W; Workman, Alan D; Nadolski, Gregory J; Gade, Terence P; Trerotola, Scott O; Hunt, Stephen J

    2017-10-01

    To compare medical student knowledge of and interest in interventional radiology (IR) before and after the integration of an IR lecture series within the gross anatomy course. Four elective IR lectures were scheduled to coincide with the relevant anatomy dissection curriculum. Anonymous surveys were distributed to 146 students before and after the lectures regarding students' knowledge of and interest in IR, responsibilities of an IR physician, and IR training pathways. Those who did not attend served as controls. Response rates were 67% (n = 98) in the prelecture group, 55% (n = 22) in the group who attended the lecture, and 28% (n = 30) in the control group. A total of 73% of the prelecture group reported little knowledge of IR compared with other specialties. This decreased to 27% in those who attended the lecture (P < .001). A total of 32% of those who attended believed they had more knowledge of IR than any other specialty, compared with 7% of controls (P value not significant) and 2% of the prelecture group (P < .001). Those in attendance could name a significantly greater number of IR procedures (mean, 1.82) than the prelecture group (mean, 0.57; P < .001). A total of 64% of those who attended would consider a career in IR, compared with 24% in the prelecture group and 33% in the control group (P < .05). A total of 68% of those who attended had knowledge of the IR residency, compared with 5% in the prelecture group and 33% in the control group (P < .05). Integration of IR education into the gross anatomy course proved to be a highly effective way of teaching preclinical students about IR and generating interest in the field. Copyright © 2017 SIR. All rights reserved.

  20. Peptide backbone orientation and dynamics in spider dragline silk and two-photon excitation in nuclear magnetic and quadrupole resonance

    NASA Astrophysics Data System (ADS)

    Eles, Philip Thomas

    2005-07-01

    In the first part of the dissertation, spider dragline silk is studied by solid state NMR techniques. The dependence of NMR frequency on molecular orientation is exploited using the DECODER experiment to determine the orientation of the protein backbone within the silk fibre. Practical experimental considerations require that the silk fibres be wound about a cylindrical axis perpendicular to the external magnetic field, complicating the reconstruction of the underlying orientation distribution and necess-itating the development of numerical techniques for this purpose. A two-component model of silk incorporating static b-sheets and polyglycine II helices adequately fits the NMR data and suggests that the b-sheets are well aligned along the silk axis (20 FWHM) while the helices are poorly aligned (68 FWHM). The effects of fibre strain, draw rate and hydration on orientation are measured. Measurements of the time-scale for peptide backbone motion indicate that when wet, a strain-dependent frac-tion of the poorly aligned component becomes mobile. This suggests a mechanism for the supercontraction of silk involving latent entropic springs that undergo a local strain-dependent phase transition, driving supercontraction. In the second part of this dissertation a novel method is developed for exciting NMR and nuclear quadrupole resonance (NQR) by rf irradiation at multiple frequencies that sum to (or differ by) the resonance frequency. This is fundamentally different than traditional NMR experiments where irradiation is applied on-resonance. With excitation outside the detection bandwidth, two-photon excitation allows for detection of free induction signals during excitation, completely eliminating receiver dead-time. A theoretical approach to describing two-photon excitation is developed based on average Hamiltonian theory. An intuition for two-photon excitation is gained by analogy to the coherent absorption of multiple photons requiring conservation of total energy and

  1. Occupational radiodermatitis from Ir192 exposure.

    PubMed

    Condé-Salazar, L; Guimaraens, D; Romero, L V

    1986-10-01

    3 cases of occupational radiodermatitis from Ir192 exposure in personnel handling a gamma ray projector in industrial radiography are presented. The diagnosis was confirmed histologically. The nature and use of the industrial machines are described.

  2. IR heating of the cometary atmosphere

    NASA Technical Reports Server (NTRS)

    Marconi, M. L.; Mendis, D. A.

    1986-01-01

    The transfer of radiation, solar and IR dust, in the cometary atmosphere is analyzed using a six-band radiative transfer model. The first five bands correlate with the strongest IR band of H2O and the sixth corresponds to the bulk of solar energy. The radiation field for each band is calculated as a function of the cometocentric distance using the three-stream approximation. It is observed that the mean intensity of the IR radiation field generated by the dust and the cometary nucleus drops from a very large value of about 40,000 erg/sq cm sec at the surface to 400 erg/sq cm sec at 7 km, rises to a peak value of 500 erg/sq cm sec at 100 km and then falls off monotonically. The causes of these changes in radiation field intensity are discussed. The effect of variation of the IR radiation field on the gas temperature is studied.

  3. Front interaction induces excitable behavior

    NASA Astrophysics Data System (ADS)

    Parra-Rivas, P.; Matías, M. A.; Colet, P.; Gelens, L.; Walgraef, D.; Gomila, D.

    2017-02-01

    Spatially extended systems can support local transient excitations in which just a part of the system is excited. The mechanisms reported so far are local excitability and excitation of a localized structure. Here we introduce an alternative mechanism based on the coexistence of two homogeneous stable states and spatial coupling. We show the existence of a threshold for perturbations of the homogeneous state. Subthreshold perturbations decay exponentially. Superthreshold perturbations induce the emergence of a long-lived structure formed by two back to back fronts that join the two homogeneous states. While in typical excitability the trajectory follows the remnants of a limit cycle, here reinjection is provided by front interaction, such that fronts slowly approach each other until eventually annihilating. This front-mediated mechanism shows that extended systems with no oscillatory regimes can display excitability.

  4. The repopulation of electronic states upon vibrational excitation of niobium carbide clusters

    NASA Astrophysics Data System (ADS)

    Chernyy, V.; Logemann, R.; Bakker, J. M.; Kirilyuk, A.

    2016-07-01

    We study the infrared (IR) resonant heating of neutral niobium carbide clusters probed through ultraviolet photoionization spectroscopy. The IR excitation not only changes the photoionization spectra for the photon energies above the ionization threshold, but also modulates ion yield for energies significantly below it. An attempt to describe the experimental spectra using either Fowler's theory or thermally populated vibrational states was not successful. However, the data can be fully modeled by vibrationally and rotationally broadened discrete electronic levels obtained from Density Functional Theory (DFT) calculations. The application of this method to spectra with different IR pulse energies not only yields information about the excited electronic states in the vicinity of the HOMO level, populated by manipulation of the vibrational coordinates of a cluster, but also can serve as an extra indicator for the cluster isomeric structure and corresponding DFT-calculated electronic levels.

  5. IR Optimization, DID and anti-DID

    SciTech Connect

    Seryi, Andrei; Maruyama, Takashi; Parker, Brett; /Brookhaven

    2006-02-03

    In this paper, we discuss optimization of the larger crossing angle Interaction Region of the Linear Collider, where specially shaped transverse field of the Detector Integrated Dipole can be reversed and adjusted to optimize trajectories of the low energy pairs, so that their majority would be directed into the extraction exit hole. This decreases the backscattering and makes background in 14mrad IR to be similar to background in 2mrad IR.

  6. Competing reaction channels in IR-laser-induced unimolecular reactions

    SciTech Connect

    Berman, M.R.

    1981-01-01

    The competing reaction channels in the unimolecular decomposition of two molecules, formaldehyde and tetralin were studied. A TEA CO/sub 2/ laser was used as the excitation source in all experiments. The dissociation of D/sub 2/CO was studied by infrared multiphoton dissociation (MPD) and the small-molecule nature of formaldehyde with regard to MPD was explored. The effect of collisions in MPD were probed by the pressure dependence of the MPD yield and ir fluorescence from multiphoton excited D/sub 2/CO. MPD yield shows a near cubic dependence in pure D/sub 2/CO which is reduced to a 1.7 power dependence when 15 torr of NO is added. The peak amplitude of 5 ..mu..m ir fluorescence from D/sub 2/CO is proportional to the square of the D/sub 2/CO pressure in pure D/sub 2/CO or in the presence of 50 torr of Ar. Results are explained in terms of bottlenecks to excitation at the v = 1 level which are overcome by a combination of vibrational energy transfer and rotational relaxation. The radical/molecule branching ratio in D/sub 2/CO MPD was 0.10 +- 0.02 at a fluence of 125 J/cm/sup 2/ at 946.0 cm/sup -1/. The barrier height to molecular dissociation was calculated to be 3.6 +- 2.0 kcal/mole below the radical threshold or 85.0 +- 3.0 kcal/mole above the ground state of D/sub 2/CO. In H/sub 2/CO, this corresponds to 2.5 +- 2.0 kcal/mole below the radical threshold or 83.8 +- 3.0 kcal/mole above the ground state. Comparison with uv data indicate that RRKM theory is an acceptable description of formaldehyde dissociation in the 5 to 10 torr pressure range. The unimolecular decomposition of tetralin was studied by MPD and SiF/sub 4/ - sensitized pyrolysis. Both techniques induce decomposition without the interference of catalytic surfaces. Ethylene loss is identified as the lowest energy reaction channel. Dehydrogenation is found to result from step-wise H atom loss. Isomerization via disproportionation is also identified as a primary reaction channel.

  7. IR diver vision for turbidity mitigation

    NASA Astrophysics Data System (ADS)

    Milam, Jerry A.

    2010-04-01

    Commercial, forensic, and military divers often encounter turbid conditions which reduce visibility to zero. Under such conditions, work must be performed completely blind. The darkness resulting from high levels of turbidity is complete, and can be dangerous as well as disorienting. Such darkness can even occur near the surface on a bright and sunny day. Artificial underwater lighting is of no use in such situations, as it only makes matters worse (similar to the use of high beam headlights in dense fog). Certain wavelengths of infrared (IR) light have the ability to penetrate this underwater "fog," and thus form the basis of the current development. Turbidity results from clay, silt, finely divided organic and inorganic matter, soluble colored organic compounds, plankton and microscopic organisms suspended in water. The IR Diver Vision system described herein consists of a standard commercial diving mask of any of several configurations whereby an IR light source, IR video camera, video display, and power source may be integrated within or attached to the mask. The IR light source wavelength is compatible with the spectral bandwidth of the video camera. The camera field-of-view (FOV) is matched to the video display in order to provide a unity magnification and hence prevent diver ocular fatigue. The IR video camera, video display, power source and controls are compatible with extended use in a submarine environment. Some such masks will incorporate tilt/heading sensors and video indicators. 3-D Imaging, Inc. has developed prototypes and has patents pending on such devices.

  8. Optically excited states in positronium

    NASA Technical Reports Server (NTRS)

    Howell, R. H.; Ziock, Klaus P.; Magnotta, F.; Dermer, Charles D.; Failor, R. A.; Jones, K. M.

    1990-01-01

    Optical excitation are reported of the 1 3S-2 3P transition in positronium, and a second excitation from n=2 to higher n states. The experiment used light from two pulsed dye lasers. Changes in the positronium annihilation rate during and after the laser pulse were used to deduce the excited state populations. The n=2 level was found to be saturable and excitable to a substantial fraction of n=2 positronium to higher levels. Preliminary spectroscopic measurements were performed on n=14 and n=15 positronium.

  9. Fission fragment excited laser system

    DOEpatents

    McArthur, David A.; Tollefsrud, Philip B.

    1976-01-01

    A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.

  10. Laser IR fragmentation of molecular clusters: the role of channels for energy input and relaxation, the influence of surroundings, and the dynamics of fragmentation

    NASA Astrophysics Data System (ADS)

    Makarov, G. N.

    2017-06-01

    The results of research into the infrared (IR) laser fragmentation of molecular clusters by resonant vibrational excitation of their constituent molecules are presented with special attention given to the role of cluster environment, the energy input and relaxation channels, and dynamical aspects. For this purpose, the results of experiments with free homogeneous and mixed molecular clusters and of experiments with clusters inside or on the surface of large inert gas clusters are analyzed, the laser excitation pulses varying in wavelength and duration. Data on the character and rate of cluster fragmentation, and on the intramolecular and intracluster vibrational energy relaxation times in clusters are discussed. Results of an investigation into the structure and dynamics of molecular clusters and atomic-molecular complexes obtained by IR photodissociation spectroscopy and the spectroscopy of photofragments are analyzed. Methods for generating heterogeneous molecular clusters, for size-selecting clusters. and for studying the IR dissociation and IR fragmentation of clusters are also briefly considered.

  11. Mapping Ultrafast Dynamics of Highly Excited H2by Attosecond VUV-Radiation

    NASA Astrophysics Data System (ADS)

    Weber, Thorsten; Sturm, Felix; Wright, Travis; Ray, Dipanwita; Shivaram, Niranjan; Slaughter, Daniel; Bocharova, Irina; Ranitovic, Predrag; Belkacem, Ali

    2016-05-01

    We show how attosecond vacuum ultraviolet (VUV) and femtosecond infrared (IR) radiation can be used to excite and map dynamics of a highly excited neutral hydrogen molecule. By using time-delayed, strong laser pulses and ion imaging, we map the dynamics of highly-excited, bound states of hydrogen molecules. Due to the large stretching amplitude of the B electronic state, excited by the 9th harmonic of the fundamental laser frequency, the effective ionization potential of the hydrogen molecular ion changes substantially as the nuclear wave packet (NWP) vibrates in the bound, B potential energy curve. Therefore, the probability of ionizing the neutrally-excited hydrogen molecule by the IR probe pulse changes as the NWP evolves in the B potential. We probe this dynamics by ionizing the vibrating molecule by means of time-delayed IR radiation, and identify the dissociation channels with 3D-momentum ion imaging. Supported by DOE under Contract No. DE-AC02-05CH11231.

  12. Pump-probe scheme to study the autoionization decay of optically-forbidden H2 doubly excited states.

    PubMed

    Rivière, P; Silva, R E F; Martín, F

    2012-11-26

    A pump-probe scheme is proposed to investigate the autoionization dynamics of the optically forbidden Q(1)(1)Σ(g)(+) doubly excited states of the H(2) molecule. The scheme consists of a pump that contains an attosecond pulse train (APT) and an infrared (IR) pulse, which is phase-locked with the APT, and an IR probe identical to the former IR pulse. The dynamical information is obtained by analyzing the electron kinetic energy spectra (EKE) and proton kinetic energy spectra (PKE) as a function of the time delay between the pump and the probe. The essential requirement for an efficient population of the Q(1)(1)Σ(g)(+) states is that they are resonantly coupled to both the dipole-allowed Q(1)(1)Σ(u)(+) doubly excited states and the ground state of H(2) by the combined effect of the APT + IR fields.

  13. Hyperhoneycomb iridate beta-Li2 IrO3 as a platform for Kitaev spin liquid

    NASA Astrophysics Data System (ADS)

    Takayama, Tomohiro

    Realization of quantum spin liquid has been a long-sought dream in condensed matter physics, where exotic excitations and unconventional superconductivity upon doping are expected. Honeycomb iridates recently emerged as a possible materialization of Kitaev spin liquid with frustrated `` bond - dependent ferromagnetic interaction ''. However, the real materials, α-Na2IrO3 and α-Li2IrO3, undergo antiferromagnetic ordering likely due to the presence of other dominant magnetic interactions and lattice distortion. We discovered a new form of Li2IrO3, β-Li2IrO3, which comprises a three-dimensional analogue of honeycomb lattice dubbed as ''hyperhoneycomb''. Each Ir4+ ion of the hyperhoneycomb lattice has three neighboring like ions rotated by 120° and thus the local structure is identical with 2D honeycomb, indicating that the hyperhoneycomb lattice is a new platform for Kitaev physics. β-Li2IrO3 diplays a spiral magnetic order below 38 K, which likely originates from dominance of ferromagnetic Kitaev interaction. We argure that β-Li2IrO3 locates in a close proximity to Kitaev spin liquid. We also discuss the spin liquid behavior observed in a new honeycomb iridate obtained by chemical modulation.

  14. The Excitable Membrane

    PubMed Central

    Offner, Franklin F.

    1972-01-01

    The model of the excitable membrane assumes common channels for Na+ and K+; the two ion species interact within the pores through their electrostatic forces. The electric field varies across the membrane and with time, as a result of ionic redistribution. Ionic flow is primarily controlled by energy barriers at the two interfaces and by Ca++ adsorption at the external interface. When the membrane is polarized, the high electric field at the external interface acting on the membrane fixed charge keeps the effective channel diameter small, so that only dihydrated ions can cross the interface. The higher energy required to partially dehydrate Na+ accounts for its lower permeability when polarized. Depolarized, the channel entrance can expand, permitting quadrihydrated ions to pass; the large initial Na+ flow is the result of the large concentration ratio across the interface. The effect at the internal interface is symmetric; Na+ crosses with greater difficulty when the membrane is depolarized. Na+ inactivation occurs when the ion distribution within the membrane has assumed its new steady-state value. Calculations based on parameters consistent with physicochemical data agree generally with a wide range of experiments. The model does not obey the two fundamental Hodgkin-Huxley (HH) postulates (independence principle, ion flow proportional to thermodynamic potential). In several instances the model predicts experimental results which are not predicted by the HH equations. ImagesFIGURE 12 PMID:4655662

  15. Double excitations in finite systems.

    PubMed

    Romaniello, P; Sangalli, D; Berger, J A; Sottile, F; Molinari, L G; Reining, L; Onida, G

    2009-01-28

    Time-dependent density-functional theory (TDDFT) is widely used in the study of linear response properties of finite systems. However, there are difficulties in properly describing excited states, which have double- and higher-excitation characters, which are particularly important in molecules with an open-shell ground state. These states would be described if the exact TDDFT kernel were used; however, within the adiabatic approximation to the exchange-correlation (xc) kernel, the calculated excitation energies have a strict single-excitation character and are fewer than the real ones. A frequency-dependent xc kernel could create extra poles in the response function, which would describe states with a multiple-excitation character. We introduce a frequency-dependent xc kernel, which can reproduce, within TDDFT, double excitations in finite systems. In order to achieve this, we use the Bethe-Salpeter equation with a dynamically screened Coulomb interaction W(omega), which can describe these excitations, and from this we obtain the xc kernel. Using a two-electron model system, we show that the frequency dependence of W does indeed introduce the double excitations that are instead absent in any static approximation of the electron-hole screening.

  16. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  17. Iridium Interfacial Stack - IrIS

    NASA Technical Reports Server (NTRS)

    Spry, David

    2012-01-01

    Iridium Interfacial Stack (IrIS) is the sputter deposition of high-purity tantalum silicide (TaSi2-400 nm)/platinum (Pt-200 nm)/iridium (Ir-200 nm)/platinum (Pt-200 nm) in an ultra-high vacuum system followed by a 600 C anneal in nitrogen for 30 minutes. IrIS simultaneously acts as both a bond metal and a diffusion barrier. This bondable metallization that also acts as a diffusion barrier can prevent oxygen from air and gold from the wire-bond from infiltrating silicon carbide (SiC) monolithically integrated circuits (ICs) operating above 500 C in air for over 1,000 hours. This TaSi2/Pt/Ir/Pt metallization is easily bonded for electrical connection to off-chip circuitry and does not require extra anneals or masking steps. There are two ways that IrIS can be used in SiC ICs for applications above 500 C: it can be put directly on a SiC ohmic contact metal, such as Ti, or be used as a bond metal residing on top of an interconnect metal. For simplicity, only the use as a bond metal is discussed. The layer thickness ratio of TaSi2 to the first Pt layer deposited thereon should be 2:1. This will allow Si from the TaSi2 to react with the Pt to form Pt2Si during the 600 C anneal carried out after all layers have been deposited. The Ir layer does not readily form a silicide at 600 C, and thereby prevents the Si from migrating into the top-most Pt layer during future anneals and high-temperature IC operation. The second (i.e., top-most) deposited Pt layer needs to be about 200 nm to enable easy wire bonding. The thickness of 200 nm for Ir was chosen for initial experiments; further optimization of the Ir layer thickness may be possible via further experimentation. Ir itself is not easily wire-bonded because of its hardness and much higher melting point than Pt. Below the iridium layer, the TaSi2 and Pt react and form desired Pt2Si during the post-deposition anneal while above the iridium layer remains pure Pt as desired to facilitate easy and strong wire-bonding to the Si

  18. Vibrational excitation induces double reaction.

    PubMed

    Huang, Kai; Leung, Lydie; Lim, Tingbin; Ning, Zhanyu; Polanyi, John C

    2014-12-23

    Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110). The energy of the incident electron was near the electronic excitation threshold of E0=1.0 eV required to induce this single-electron process. STM has been employed in the present work to study the reaction dynamics at the substantially lower incident electron energies of 0.3 eV, well below the electronic excitation threshold. The observed increase in reaction rate with current was found to be fourth-order, indicative of multistep reagent vibrational excitation, in contrast to the first-order rate dependence found earlier for electronic excitation. The change in mode of excitation was accompanied by altered reaction dynamics, evidenced by a different pattern of binding of the chemisorbed products to the copper surface. We have modeled these altered reaction dynamics by exciting normal modes of vibration that distort the C-I bonds of the physisorbed reagent. Using the same ab initio ground potential-energy surface as in the prior work on electronic excitation, but with only vibrational excitation of the physisorbed reagent in the asymmetric stretch mode of C-I bonds, we obtained the observed alteration in reaction dynamics.

  19. Molecular excitations: a new way to detect Dark Matter

    SciTech Connect

    Va'vra, J.

    2014-09-01

    We believe that the Dark Matter (DM) search should be expanded into the domain of detectors sensitive to molecular excitations, and so that we should create detectors which are more sensitive to collisions with very light WIMPs. In this paper we investigate in detail diatomic molecules, such as fused silica material with large OH-molecule content, and water molecules. Presently, we do not have suitable low-cost IR detectors to observe single photons, however some OH-molecular excitations extend to visible and UV wavelengths and can be measured by bialkali photocathodes. There are many other chemical substances with diatomic molecules, or more complex oil molecules, which could be also investigated. This idea invites searches in experiments having large target volumes of such materials coupled to a large array of single-photon detectors with bialkali or infrared-sensitive photocathodes.

  20. Narcissus analysis for cooled staring IR system

    NASA Astrophysics Data System (ADS)

    He, Feng-Yun; Cui, Ji-Cheng; Feng, Shu-Long; Zhang, Xin

    2007-12-01

    Narcissus can have a deleterious effect on image quality for cooled infrared imaging systems. Therefore, analysis of narcissus is important for designing both scanning and staring optics. Narcissus is generally assumed to be negligible in staring IR optical designs because the shading effects can be removed by calibration of the detector array data. However, the calibration usually decreases sensitiveness of the system and Narcissus variation may be noticeable for sensors when the conditions changes as follows: 1. warming and cooling the optical housing, 2. zooming optical elements, 3. movement of lenses for focus. In that case, it will result in shading and other image defects even after calibration. To minimize these effects, narcissus should be assessed and controlled during the design of staring array IR system. We provided a direct and fast method for analyzing the narcissus variation in the presence of software such as LightTools, TracePro and ASAP, and proposed the principles in optical design of staring IR systems to reduce narcissus. A cooled staring IR system with serious narcissus was estimated and reoptimized. Narcissus analysis of this IR system confirmed the efficiency of the analysis method.

  1. Spatially and frequency-resolved monitoring of intradie capacitive coupling by heterodyne excitation infrared lock-in thermography

    NASA Astrophysics Data System (ADS)

    León, J.; Perpiñà, X.; Altet, J.; Vellvehi, M.; Jordà, X.

    2013-02-01

    This paper combines the infrared lock-in thermography (IR-LIT) and heterodyne excitation techniques to detect high-frequency capacitive currents due to intradie electrical coupling between microelectronic devices or more complex systems. Modulating the excitation with the heterodyne approach, we drive devices or complex systems with high frequency electrical signals in such a way that they behave as low frequency heat sources, modulating their temperature field at a frequency detectable by an IR-LIT system. This approach is analytically studied and extended to a bi-dimensional scenario, showing that the thermal information at low frequency depends on the electrical characteristics of the sample at high frequency.

  2. Substantiation of the mechanism of biphoton nonresonance excitation of molecules of bacteriochlorophyll of purple bacteria by femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Borisov, A. Yu.

    2010-11-01

    In a series of published experimental works, there has been observed nonresonance biphoton excitation, by femtosecond IR pulses (1250-1500 nm) of molecules of bacteriochlorophyll-a and the pigment in the composition of light-absorbing natural "antenna" complexes of photosynthesizing purple bacteria. The authors of these works believe that IR quanta excite hypothetical forbidden levels of pigments of these bacteria in the dual frequency range of 625-750 nm. In this study, an alternative mechanism of intramolecular electron transport apparently responsible for this phenomenon is suggested and substantiated. The mechanism should manifest itself in powerful electric fields, which are achieved in the pulses of picofemtosecond lasers.

  3. Conformers of Kojic Acid and Their Near-IR-Induced Conversions: Long-Range Intramolecular Vibrational Energy Transfer.

    PubMed

    Halasa, Anna; Reva, Igor; Lapinski, Leszek; Rostkowska, Hanna; Fausto, Rui; Nowak, Maciej J

    2016-05-05

    Conformational transformations were investigated for molecules of kojic acid trapped in low-temperature argon and nitrogen matrixes. Two conformers, differing from each other by 120° rotation of the hydroxymethyl (-CH2OH) moiety, were found to be populated in freshly deposited matrixes, prior to any irradiation. Matrixes containing isolated monomers of kojic acid were irradiated with narrowband, tunable near-infrared (near-IR) laser light. Excitations at wavenumbers corresponding to the overtone of the stretching vibration of the OH bond of the hydroxymethyl group led to conversion of one of the observed conformers into another. The direction of this conformational transformation depended on the wavenumber (within the 7126-7115 cm(-1) range) used for irradiation. The same conformational photoconversion was also observed to occur upon narrowband irradiation at much lower wavenumbers (from the 6468-6447 cm(-1) range). Near-IR light from this range selectively excites overtone vibrations of the OH group directly attached to the heterocyclic ring. Such an observation provides a convincing evidence of a long-range vibrational energy transfer from the initially excited OH group (directly attached to the ring) to the remote hydroxymethyl fragment which changes its orientation. Structural changes, occurring in matrix-isolated molecules of kojic acid upon near-IR excitation, were monitored by FTIR spectroscopy.

  4. Tuning the Graphene on Ir(111) adsorption regime by Fe/Ir surface-alloying

    NASA Astrophysics Data System (ADS)

    Brede, Jens; Sławińska, Jagoda; Abadia, Mikel; Rogero, Celia; Ortega, J. Enrique; Piquero-Zulaica, Ignacio; Lobo-Checa, Jorge; Arnau, Andres; Iribas Cerdá, Jorge

    2017-03-01

    A combined scanning tunneling microscopy, x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, and density functional theory study of graphene on a Fe-Ir(111) alloy with variable Ir concentration is presented. Starting from an intercalated Fe layer between the graphene and Ir(111) surface we find that graphene-substrate interaction can be fine-tuned by Fe-Ir alloying at the interface. When a critical Ir-concentration close to 0.25 is reached in the Fe layer, the Dirac cone of graphene is largely restored and can thereafter be tuned across the Fermi level by further increasing the Ir content. Indeed, our study reveals an abrupt transition between a chemisorbed phase at small Ir concentrations and a physisorbed phase above the critical concentration. The latter phase is highly reminiscent of the graphene on the clean Ir(111) surface. Furthermore, the transition is accompanied by an inversion of the graphene’s induced magnetization due to the coupling with the Fe atoms from antiferromagnetic when chemisorbed to weakly ferromagnetic in the physisorption regime, with spin polarizations whose magnitude may be tuned with the amount of Fe content.

  5. Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling

    PubMed Central

    Lumbreras, Vicente; Bas, Esperanza; Gupta, Chhavi

    2014-01-01

    Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca2+ imaging. Both types of neurons responded consistently with robust intracellular Ca2+ ([Ca2+]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25–1 pps). Radiant exposures of ∼637 mJ/cm2 resulted in continual neuronal activation. Temperature or [Ca2+] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca2+ involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na+, K+, and Ca2+ plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca2+ cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca2+]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca2+ release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses. PMID:24920028

  6. Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling.

    PubMed

    Lumbreras, Vicente; Bas, Esperanza; Gupta, Chhavi; Rajguru, Suhrud M

    2014-09-15

    Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca(2+) imaging. Both types of neurons responded consistently with robust intracellular Ca(2+) ([Ca(2+)]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25-1 pps). Radiant exposures of ∼637 mJ/cm(2) resulted in continual neuronal activation. Temperature or [Ca(2+)] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca(2+) involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na(+), K(+), and Ca(2+) plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca(2+) cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca(2+)]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca(2+) release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses.

  7. Role of excited-state hydrogen detachment and hydrogen-transfer processes for the excited-state deactivation of an aromatic dipeptide: N-acetyl tryptophan methyl amide.

    PubMed

    Shemesh, Dorit; Sobolewski, Andrzej L; Domcke, Wolfgang

    2010-05-21

    The excited-state electronic potential-energy surfaces of the three conformers of the capped dipeptide N-acetyl tryptophan methyl amide (NATMA), for which UV and IR spectra have been reported by Dian et al. [J. Chem. Phys., 2003, 118, 2696], have been explored with ab initio electronic-structure methods. The results provide insight into the nonadiabatic electronic coupling mechanisms which are responsible for the pronounced and conformer-specific perturbations of the spectra, such as broad and congested UV spectra as well as the deletion of certain fundamentals in the IR spectrum of the S(1) state. It is shown that the photophysical dynamics of NATMA is governed by at least five excited singlet electronic states: the two spectroscopic (1)L(b) and (1)L(a) states and the dissociative (1)pisigma* state of the indole chromophore, as well as a locally-excited state and a charge-transfer state of the peptide backbone. For the conformer NATMA C, which exhibits a gamma-turn of the backbone, a potentially very efficient excited-state deactivation mechanism to the electronic ground state via three conical intersections has been revealed. The results confirm the important role of hydrogen bonds for rapid excited-state deactivation of peptides, which enhances their photostability.

  8. Intelligent multi-spectral IR image segmentation

    NASA Astrophysics Data System (ADS)

    Lu, Thomas; Luong, Andrew; Heim, Stephen; Patel, Maharshi; Chen, Kang; Chao, Tien-Hsin; Chow, Edward; Torres, Gilbert

    2017-05-01

    This article presents a neural network based multi-spectral image segmentation method. A neural network is trained on the selected features of both the objects and background in the longwave (LW) Infrared (IR) images. Multiple iterations of training are performed until the accuracy of the segmentation reaches satisfactory level. The segmentation boundary of the LW image is used to segment the midwave (MW) and shortwave (SW) IR images. A second neural network detects the local discontinuities and refines the accuracy of the local boundaries. This article compares the neural network based segmentation method to the Wavelet-threshold and Grab-Cut methods. Test results have shown increased accuracy and robustness of this segmentation scheme for multi-spectral IR images.

  9. IR signature management for the modern navy

    NASA Astrophysics Data System (ADS)

    Vaitekunas, David A.; Kim, Yoonsik

    2013-06-01

    A methodology for analysing the infrared (IR) signature and susceptibility of naval platforms using ShipIR/NTCS was presented by Vaitekunas (2010). This paper provides three key improvements: use of a larger climatic data set (N=100), a new target sub-image algorithm eliminating false detections from pixel-aliasing at the horizon, and a new seeker model interfacing with a line-by-line background clutter model. Existing commercial stealth technologies (exhaust stack suppression, low solar absorptive paints, extended hull film-cooling) are re-analysed using the new models and methods to produce a more rigorous and comprehensive analysis of their effectiveness based on the statistics of reduction in IR susceptibility. These methods and results combined with the cost of each stealth option should allow platform managers to select an appropriate level of infrared suppression and establish the design criteria for a new ship.

  10. Tunable mid IR plasmon in GZO nanocrystals.

    PubMed

    Hamza, M K; Bluet, J-M; Masenelli-Varlot, K; Canut, B; Boisron, O; Melinon, P; Masenelli, B

    2015-07-28

    Degenerate metal oxide nanoparticles are promising systems to expand the significant achievements of plasmonics into the infrared (IR) range. Among the possible candidates, Ga-doped ZnO nanocrystals are particularly suited for mid IR, considering their wide range of possible doping levels and thus of plasmon tuning. In the present work, we report on the tunable mid IR plasmon induced in degenerate Ga-doped ZnO nanocrystals. The nanocrystals are produced by a plasma expansion and exhibit unprotected surfaces. Tuning the Ga concentration allows tuning the localized surface plasmon resonance. Moreover, the plasmon resonance is characterized by a large damping. By comparing the plasmon of nanocrystal assemblies to that of nanoparticles dispersed in an alumina matrix, we investigate the possible origins of such damping. We demonstrate that it partially results from the self-organization of the naked particles and also from intrinsic inhomogeneity of dopants.

  11. Ir-induced activation of Au towards CO adsorption: Ir films deposited on Au{111}

    NASA Astrophysics Data System (ADS)

    Zhang, Tianfu; Driver, Stephen M.; Pratt, Stephanie J.; Jenkins, Stephen J.; King, David A.

    2016-06-01

    We have investigated the interaction of CO with Ir/Au{111} bimetallic surfaces, and the influence of morphology changes as Ir moves sub-surface into the Au bulk, using reflection-absorption infrared spectroscopy (RAIRS). The presence of Ir stabilises CO on exposed regions of the Au surface at temperatures up to around 200 K: we attribute this to low-coordinated Au sites, probably associated with lifting of the clean-surface 'herringbone' reconstruction by Ir deposition. The highest density of active Au sites is obtained after annealing the bimetallic surface to 500-600 K: we attribute this to morphology changes associated with the movement of Ir into bulk Au.

  12. The mid-IR and near-IR interferometry of AGNs: key results and their implications

    NASA Astrophysics Data System (ADS)

    Kishimoto, M.

    2015-09-01

    Infrared interferometry has been very productive in directly probing the structure of AGNs at sub-pc scales. With tens of objects already probed in the mid-IR and near-IR, I will summarize the key results and im- plications from this direct exploration. The Keck interferometry in the near-IR and VLTI in the mid-IR shaped the luminosity dependence of the torus size and structure, while the latter also revealed an equatorial structure at several Rsub (dust sublimation radius), and a polar-elongated region at a few tens of Rsub. Notably, this polar component seems to dominate the compact mid-IR flux. This component can persuasively be attributed to a polar outflow. However, interferometry, through emissivity estimations, also indicates that it is not a UV-optically-thin cloud but participating in the obscuration of the nucleus. I will discuss how to accommodate all these facts to build a consistent picture.

  13. Trapped Hydronium Radical Produced by Ultraviolet Excitation of Substituted Aromatic Molecule.

    PubMed

    Hernández, Federico J; Capello, Marcela C; Naito, Ayumi; Manita, Shun; Tsukada, Kohei; Miyazaki, Mitsuhiko; Fujii, Masaaki; Broquier, Michel; Gregoire, Gilles; Dedonder-Lardeux, Claude; Jouvet, Christophe; Pino, Gustavo A

    2015-12-24

    The gas phase structure and excited state dynamics of o-aminophenol-H2O complex have been investigated using REMPI, IR-UV hole-burning spectroscopy, and pump-probe experiments with picoseconds laser pulses. The IR-UV spectroscopy indicates that the isomer responsible for the excitation spectrum corresponds to an orientation of the OH bond away from the NH2 group. The water molecule acts as H-bond acceptor of the OH group of the chromophore. The complexation of o-aminophenol with one water molecule induced an enhancement in the excited state lifetime on the band origin. The variation of the excited state lifetime of the complex with the excess energy from 1.4 ± 0.1 ns for the 0-0 band to 0.24 ± 0.3 ns for the band at 0-0 + 120 cm(-1) is very similar to the variation observed in the phenol-NH3 system. This experimental result suggests that the excited state hydrogen transfer reaction is the dominant channel for the non radiative pathway. Indeed, excited state ab initio calculations demonstrate that H transfer leading to the formation of the H3O(•) radical within the complex is the main reactive pathway.

  14. Persistent Paramagnons Deep in the Metallic Phase of Sr2 -xLaxIrO4

    NASA Astrophysics Data System (ADS)

    Gretarsson, H.; Sung, N. H.; Porras, J.; Bertinshaw, J.; Dietl, C.; Bruin, Jan A. N.; Bangura, A. F.; Kim, Y. K.; Dinnebier, R.; Kim, Jungho; Al-Zein, A.; Moretti Sala, M.; Krisch, M.; Le Tacon, M.; Keimer, B.; Kim, B. J.

    2016-09-01

    We have studied the magnetic excitations of electron-doped Sr2 -xLax IrO4 (0 ≤x ≤0.10 ) using resonant inelastic x-ray scattering at the Ir L3 edge. The long-range magnetic order is rapidly lost with increasing x , but two-dimensional short-range order (SRO) and dispersive magnon excitations with nearly undiminished spectral weight persist well into the metallic part of the phase diagram. The magnons in the SRO phase are heavily damped and exhibit anisotropic softening. Their dispersions are well described by a pseudospin-1 /2 Heisenberg model with exchange interactions whose spatial range increases with doping. We also find a doping-independent high-energy magnetic continuum, which is not described by this model. The spin-orbit excitons arising from the pseudospin-3 /2 manifold of the Ir ions broaden substantially in the SRO phase, but remain largely separated from the low-energy magnons. Pseudospin-1 /2 models are therefore a good starting point for the theoretical description of the low-energy magnetic dynamics of doped iridates.

  15. Efficient Vibrational Energy Transfer through Covalent Bond in Indigo Carmine Revealed by Nonlinear IR Spectroscopy.

    PubMed

    He, Xuemei; Yu, Pengyun; Zhao, Juan; Wang, Jianping

    2017-09-28

    Ultrafast vibrational relaxation and structural dynamics of indigo carmine in dimethyl sulfoxide were examined using femtosecond pump-probe infrared and two-dimensional infrared (2D IR) spectroscopies. Using the intramolecularly hydrogen-bonded C═O and delocalized C═C stretching modes as infrared probes, local structural and dynamical variations of this blue dye molecule were observed. Energy relaxation of the vibrationally excited C═O stretching mode was found to occur through covalent bond to the delocalized aromatic vibrational modes on the time scale of a few picoseconds or less. Vibrational quantum beating was observed in magic-angle pump-probe, anisotropy, and 2D IR cross-peak dynamics, showing an oscillation period of ca. 1010 fs, which corresponds to the energy difference between the C═O and C═C transition frequency (33 cm(-1)). This confirms a resonant vibrational energy transfer happened between the two vibrators. However, a more efficient energy-accepting mode of the excited C═O stretching was believed to be a nearby combination and/or overtone mode that is more tightly connected to the C═O species. On the structural aspect, dynamical-time-dependent 2D IR spectra reveal an insignificant inhomogeneous contribution to time-correlation relaxation for both the C═O and C═C stretching modes, which is in agreement with the generally believed structural rigidity of such conjugated molecules.

  16. Interactions of low-energy electrons with Ir(ppy) 3 in the gas phase

    NASA Astrophysics Data System (ADS)

    Kukhta, A. V.; Kukhta, I. N.; Bagnich, S. A.; Kazakov, S. M.; Andreev, V. A.; Neyra, O. L.; Meza, E.

    2007-01-01

    The relative efficiency of excitation into singlet and triplet states in the region between 1.5 and 9 eV, their dependence on projectile electron energies for the scattering of monoenergetic electrons with tunable energies from 0 to 50 eV at an angle of 90°, for the widely known electroactive organic material tris(2-phenylpyridine)iridium (Ir(ppy) 3) in the gas phase are presented. Some direct singlet-triplet transitions in the region 2.5-2.8 eV and nearby 4.4 eV are observed. No intense singlet-triplet transitions can be observed in spite the presence of the heavy Ir atom; this is probably due to the charge transfer nature of the transition. The spectrum of singlet and the positions of triplet transitions are studied using density functional theory techniques. No essential differences between optical and electron impact excitation of Ir(ppy) 3 have been found, and phosphorescence can be observed mainly owing to intercombination singlet-triplet transitions.

  17. IR Spectroscopy of PAHs in Dense Clouds

    NASA Astrophysics Data System (ADS)

    Allamandola, Louis; Bernstein, Max; Mattioda, Andrew; Sandford, Scott

    2007-05-01

    Interstellar PAHs are likely to be a component of the ice mantles that form on dust grains in dense molecular clouds. PAHs frozen in grain mantles will produce IR absorption bands, not IR emission features. A couple of very weak absorption features in ground based spectra of a few objects embedded in dense clouds may be due to PAHs. Additionally spaceborne observations in the 5 to 8 ?m region, the region in which PAH spectroscopy is rich, reveal unidentified new bands and significant variation from object to object. It has not been possible to properly evaluate the contribution of PAH bands to these IR observations because the laboratory absorption spectra of PAHs condensed in realistic interstellar mixed-molecular ice analogs is lacking. This experimental data is necessary to interpret observations because, in ice mantles, the interaction of PAHs with the surrounding molecules effects PAH IR band positions, widths, profiles, and intrinsic strengths. Furthermore, PAHs are readily ionized in pure H2O ice, further altering the PAH spectrum. This laboratory proposal aims to remedy the situation by studying the IR spectroscopy of PAHs frozen in laboratory ice analogs that realistically reflect the composition of the interstellar ices observed in dense clouds. The purpose is to provide laboratory spectra which can be used to interpret IR observations. We will measure the spectra of these mixed molecular ices containing PAHs before and after ionization and determine the intrinsic band strengths of neutral and ionized PAHs in these ice analogs. This will enable a quantitative assessment of the role that PAHs can play in determining the 5-8 ?m spectrum of dense clouds and will directly address the following two fundamental questions associated with dense cloud spectroscopy and chemistry: 1- Can PAHs be detected in dense clouds? 2- Are PAH ions components of interstellar ice?

  18. Collapse of the Mott Gap and Emergence of a Nodal Liquid in Lightly Doped Sr(2)IrO(4).

    PubMed

    de la Torre, A; McKeown Walker, S; Bruno, F Y; Riccó, S; Wang, Z; Gutierrez Lezama, I; Scheerer, G; Giriat, G; Jaccard, D; Berthod, C; Kim, T K; Hoesch, M; Hunter, E C; Perry, R S; Tamai, A; Baumberger, F

    2015-10-23

    We report angle resolved photoemission experiments on the electron doped Heisenberg antiferromagnet (Sr(1-x)La(x))(2)IrO(4). For a doping level of x=0.05, we find an unusual metallic state with coherent nodal excitations and an antinodal pseudogap bearing strong similarities with underdoped cuprates. This state emerges from a rapid collapse of the Mott gap with doping resulting in a large underlying Fermi surface that is backfolded by a (π,π) reciprocal lattice vector which we attribute to the intrinsic structural distortion of Sr(2)IrO(4).

  19. IGF-IR Targeted Therapy: Past, Present and Future.

    PubMed

    Janssen, Joseph A M J L; Varewijck, Aimee J

    2014-01-01

    The IGF-I receptor (IGF-IR) has been studied as an anti-cancer target. However, monotherapy trials with IGF-IR targeted antibodies or with IGF-IR specific tyrosine kinase inhibitors have, overall, been very disappointing in the clinical setting. This review discusses potential reasons why IGF-I R targeted therapy fails to inhibit growth of human cancers. It has become clear that intracellular signaling pathways are highly interconnected and complex instead of being linear and simple. One of the most potent candidates for failure of IGF-IR targeted therapy is the insulin receptor isoform A (IR-A). Activation of the IR-A by insulin-like growth factor-II (IGF-II) bypasses the IGF-IR and its inhibition. Another factor may be that anti-cancer treatment may reduce IGF-IR expression. IGF-IR blocking drugs may also induce hyperglycemia and hyperinsulinemia, which may further stimulate cell growth. In addition, circulating IGF-IRs may reduce therapeutic effects of IGF-IR targeted therapy. Nevertheless, it is still possible that the IGF-IR may be a useful adjuvant or secondary target for the treatment of human cancers. Development of functional inhibitors that affect the IGF-IR and IR-A may be necessary to overcome resistance and to make IGF-IR targeted therapy successful. Drugs that modify alternative downstream effects of the IGF-IR, so called "biasing agonists," should also be considered.

  20. Femtosecond two-photon-excited fluorescence of melanin

    NASA Astrophysics Data System (ADS)

    Teuchner, Klaus; Mueller, Susanne; Freyer, Wolfgang; Leupold, Dieter; Altmeyer, Peter; Stuecker, Markus; Hoffmann, Klaus

    2003-02-01

    Spectral and time-resolved fluorescence studies of different eumelanins (natural, synthetic, enzymatic) in solution have been carried out by two-photon excitation at 800 nm, using 80 fs pulses with photon flux densities <= 1027 cm-2.s-1. Whereas all samples show monotonously decreasing absorption between near UV and near IR, their fluorescence behavior indicates strong heterogeneity. With respect to the also measured one-photon excited fluorescence (OPF) of melanin at 400 nm, the overall spectral shape of the two-photon excited fluorescence (TPF) is red-shifted. Both OPF and TPF exhibit three-exponential decay with a shortest component # 200 ps. As is also shown, the fluorescence properties of melanin are dependent on the micro-environment. This allows the hypothesis, that the process of malignant transformation in skin tissue could be reflected in the fluorescence, provided the melanin in skin is selectively excited. The latter is realized by the described stepwise absorption of two 800 nm photons. In this way, indeed characteristic differences between the TPF spectra of healthy tissue, nevus cell nevi and malignant melanoma have been found.

  1. Electronically Excited C2 from Laser Photodissociated C60

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Scott, Carl D.; Nikolaev, Pavel; Smalley, Richard E.

    1999-01-01

    Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C2 and, at early times, also from a black body continuum. The C2 radiation is observed only when C60 is excited by green (532 nm) and not with IR (1064 nm) laser radiation at energy densities of about 1.5 J/square cm. Transient measurements indicate that there are two characteristic periods of decay of radiation. The first period, lasting about 2 micro seconds, has a characteristic decay time of about 0.3 micro seconds. The second period, lasting at least 50 micro seconds, has a characteristic decay time of about 5 micro seconds. These characteristic times are thought to be associated with cooling of C60 molecules or nanosized carbon particles during the early period; and with electronically excited C2 that is a decomposition product of laser excited C60, C58, ... molecules during the later period.

  2. Noise analysis of spaceborne IR spatial interferometer

    NASA Technical Reports Server (NTRS)

    Wolfe, R. H., Jr.; Simpson, R. S.

    1976-01-01

    Analysis is performed to determine the relationship between the signal-to-noise ratio and the integration time for a spaceborne IR heterodyne spatial interferometer. The analysis includes consideration of the transformation of the interferogram to obtain the angular intensity distribution. The results presented show that for an IR source such as IRC + 10216, an integration time of 50 seconds per interferogram point will yield a signal-to-noise ratio greater than 10 dB in the angular intensity profile obtained from a 30-point transformation.

  3. FT-IR analysis of phosphorylated protein

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Yoshihashi, Sachiko S.; Chihara, Kunihiro; Awazu, Kunio

    2004-09-01

    Phosphorylation and dephosphorylation, which are the most remarkable posttranslational modifications, are considered to be important chemical reactions that control the activation of proteins. We examine the phosphorylation analysis method by measuring the infrared absorption peak of phosphate group that observed at about 1070cm-1 (9.4μm) with Fourier Transform Infrared Spectrometer (FT-IR). This study indicates that it is possible to identify a phosphorylation by measuring the infrared absorption peak of phosphate group observed at about 1070 cm-1 with FT-IR method. As long as target peptides have the same amino acid sequence, it is possible to identify the phosphorylated sites (threonine, serine and tyrosine).

  4. Photodissociation of Peroxynitric Acid in the Near-IR

    NASA Technical Reports Server (NTRS)

    Roehl, Coleen M.; Nizkorodov, Sergey A.; Zhang, Hui; Blake, Geoffrey A.; Wennberg, Paul O.

    2002-01-01

    Temperature-dependent near-IR photodissociation spectra were obtained for several vibrational overtone transitions of peroxynitric acid (HNO4) with a tunable OPO photolysis/OH laser-induced-fluorescence system. Band-integrated photodissociation cross-sections (definity integral of sigma(sub diss)), determined relative to that for the 3nu(sub 1), OH stretching overtone, were measured for three dissociative bands. Assuming unit quantum efficiency for photodissociation of 3nu(sub 1), we find 2nu(sub 1) + nu(sub 3)(8242/cm) = (1.21 x 10(exp -20) (independent of temperature), 2nu(sub 1) (6900/cm) = 4.09 x 10(exp 18) * e(sup (-826,5/T)) (295 K greater than T greater than 224 K), and nu(sub 1) + 2nu(sub 3) (6252/cm) = 1.87 x 10(exp -19) * e(sup (- 1410.7/T)) (278 K greater than T greater than 240 K) sq cm/molecule cm. The photodissociation cross-sections are independent of pressure over the range 2 to 40 Torr. Temperature-dependent quantum yields (phi) for these transitions were obtained using integrated absorption cross-sections (definity integral of sigma(sub abs)) of HNO4 overtone vibrations measured with a FTIR spectrometer. In the atmosphere, photodissociation in the infrared is dominated by excitation of the first overtone of the OH stretching vibration (2nu((sub 1)). Inclusion of all dissociative HNO4 overtone and combination transitions yields a daytime IR photolysis rate of approximately 1 x 10(esp -1)/s. This process significantly shortens the estimated lifetime of HNO4 in the upper troposphere and lower stratosphere.

  5. Pseudospin transport in the Jeff = 1/2 antiferromagnet Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Steckel, F.; Matsumoto, A.; Takayama, T.; Takagi, H.; Büchner, B.; Hess, C.

    2016-06-01

    Spin transport by itinerant electrons and collective excitations of localized spins with small relaxation rates is of eminent interest for both fundamental research and applications. Spin-orbit coupling (SOC) is not only considered a crucial origin for spin relaxation in spin transport, it recently emerged as the source of novel quantum phases such as topological insulators or SOC-induced Mott insulators with J eff = 1/2 pseudospins. Here we show that emergent pseudospin excitations in Sr2IrO4 give rise to significant heat transport despite this compound being a strong SOC-induced Mott insulator. The analysis of the heat conductivity reveals boundary-limited relaxation of the pseudospin excitations at low temperature. However, the relaxation rate dramatically increases upon heating towards room temperature due to thermally activated scattering off phonons. The comparison of this result with findings for cuprate analogs with S = 1/2 spin excitations suggests a radically stronger coupling of the J eff = 1/2 pseudospin excitations to the lattice.

  6. Calculation of Vibrational and Electronic Excited-State Absorption Spectra of Arsenic-Water Complexes Using Density Functional Theory

    DTIC Science & Technology

    2016-06-03

    provide interpretation of absorption spectra with respect to molecular structure for excitation by electromagnetic waves at frequencies within the...IR and UV-visible ranges. The absorption spectrum corresponding to excitation states of As-H2O complexes consisting of relatively small numbers of...As emphasized previously [17], the absorption spectrum of H2O clusters should be of significance for interpretation of absorption spectra

  7. High contrast reflectance imaging of simulated lesions on tooth occlusal surfaces at near-IR wavelengths.

    PubMed

    Fried, William A; Fried, Daniel; Chan, Kenneth H; Darling, Cynthia L

    2013-10-01

    In vivo and in vitro studies have shown that high contrast images of tooth demineralization can be acquired in the near-infrared (near-IR) without the interference of stain. The purpose of this study is to compare the lesion contrast in reflectance at near-IR wavelengths coincident with high water absorption with those in the visible, the near-IR at 1,300 nm and with fluorescence measurements for early lesions in occlusal surfaces. Twenty-four human molars were used in this in vitro study. Teeth were painted with an acid-resistant varnish, leaving a 4 × 4 mm window in the occlusal surface of each tooth exposed for demineralization. Artificial lesions were produced in the exposed windows after 1- and 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using near-IR reflectance at three wavelengths, 1,300, 1,460, and 1,600 nm using a high definition InGaAs camera. Visible light reflectance, and fluorescence with 405 nm excitation and detection at wavelengths greater than 500 nm were also used to acquire images for comparison. Crossed polarizers were used for reflectance measurements to reduce interference from specular reflectance. The contrast of both the 1- and 2-day lesions were significantly higher (P < 0.05) for near-IR reflectance imaging at 1,460 and 1,600 nm than it was for near-IR reflectance imaging at 1,300 nm, visible reflectance imaging, and fluorescence. The markedly higher contrast at 1,460 and 1,600 nm wavelengths, coincident with higher water absorption, suggest that these wavelengths are better suited than 1,300 nm for imaging early/shallow demineralization on tooth surfaces. © 2013 Wiley Periodicals, Inc.

  8. Photoexcited states of the harmonic honeycomb iridate γ -Li2IrO3

    NASA Astrophysics Data System (ADS)

    Hinton, J. P.; Patankar, S.; Thewalt, E.; Ruiz, A.; Lopez, G.; Breznay, N.; Vishwanath, A.; Analytis, J.; Orenstein, J.; Koralek, J. D.; Kimchi, I.

    2015-09-01

    We report equilibrium and nonequilibrium optical measurements on the recently synthesized "harmonic" honeycomb iridate γ -Li2IrO3 (LIO), as well as the layered honeycomb iridate Na2IrO3 (NIO). Using Fourier transform infrared microscopy we performed reflectance measurements on LIO, from which we obtained the optical conductivity below 2 eV. In addition, we measured the photoinduced changed in reflectance Δ R , as a function of time t , temperature T , and probe field polarization in both LIO and NIO. In LIO, Δ R (t ,T ) is anisotropic and comprises three T -dependent components. Two of these components are related to the onset of magnetic order and the third is related to a photoinduced population of metastable electronic excited states. In NIO, Δ R (t ,T ) has a single T -dependent component that is strikingly similar to the electronic excitation component of Δ R in LIO. Through analysis and comparison of Δ R (t ,T ) for two compounds, we extract information on the onset of magnetic correlations at and above the transition temperature in LIO, the bare spin-flip scattering rate in equilibrium, the lifetime of low-lying quasiparticle excitations, and the polarization dependence of optical transitions that are sensitive to magnetic order.

  9. Ionotropic Glutamate Receptors IR64a and IR8a Form a Functional Odorant Receptor Complex In Vivo in Drosophila

    PubMed Central

    Blais, Steven; Park, Jin-Yong; Min, Soohong; Neubert, Thomas A.

    2013-01-01

    Drosophila olfactory sensory neurons express either odorant receptors or ionotropic glutamate receptors (IRs). The sensory neurons that express IR64a, a member of the IR family, send axonal projections to either the DC4 or DP1m glomeruli in the antennal lobe. DC4 neurons respond specifically to acids/protons, whereas DP1m neurons respond to a broad spectrum of odorants. The molecular composition of IR64a-containing receptor complexes in either DC4 or DP1m neurons is not known, however. Here, we immunoprecipitated the IR64a protein from lysates of fly antennal tissue and identified IR8a as a receptor subunit physically associated with IR64a by mass spectrometry. IR8a mutants and flies in which IR8a was knocked down by RNAi in IR64a+ neurons exhibited defects in acid-evoked physiological and behavioral responses. Furthermore, we found that the loss of IR8a caused a significant reduction in IR64a protein levels. When expressed in Xenopus oocytes, IR64a and IR8a formed a functional ion channel that allowed ligand-evoked cation currents. These findings provide direct evidence that IR8a is a subunit that forms a functional olfactory receptor with IR64a in vivo to mediate odor detection. PMID:23804096

  10. Ionotropic glutamate receptors IR64a and IR8a form a functional odorant receptor complex in vivo in Drosophila.

    PubMed

    Ai, Minrong; Blais, Steven; Park, Jin-Yong; Min, Soohong; Neubert, Thomas A; Suh, Greg S B

    2013-06-26

    Drosophila olfactory sensory neurons express either odorant receptors or ionotropic glutamate receptors (IRs). The sensory neurons that express IR64a, a member of the IR family, send axonal projections to either the DC4 or DP1m glomeruli in the antennal lobe. DC4 neurons respond specifically to acids/protons, whereas DP1m neurons respond to a broad spectrum of odorants. The molecular composition of IR64a-containing receptor complexes in either DC4 or DP1m neurons is not known, however. Here, we immunoprecipitated the IR64a protein from lysates of fly antennal tissue and identified IR8a as a receptor subunit physically associated with IR64a by mass spectrometry. IR8a mutants and flies in which IR8a was knocked down by RNAi in IR64a+ neurons exhibited defects in acid-evoked physiological and behavioral responses. Furthermore, we found that the loss of IR8a caused a significant reduction in IR64a protein levels. When expressed in Xenopus oocytes, IR64a and IR8a formed a functional ion channel that allowed ligand-evoked cation currents. These findings provide direct evidence that IR8a is a subunit that forms a functional olfactory receptor with IR64a in vivo to mediate odor detection.

  11. Visible-light-excited and europium-emissive nanoparticles for highly-luminescent bioimaging in vivo.

    PubMed

    Wu, Yongquan; Shi, Mei; Zhao, Lingzhi; Feng, Wei; Li, Fuyou; Huang, Chunhui

    2014-07-01

    Europium(III)-based material showing special milliseconds photoluminescence lifetime has been considered as an ideal time-gated luminescence probe for bioimaging, but is still limited in application in luminescent small-animal bioimaging in vivo. Here, a water-soluble, stable, highly-luminescent nanosystem, Ir-Eu-MSN (MSN = mesoporous silica nanoparticles, Ir-Eu = [Ir(dfppy)2(pic-OH)]3Eu·2H2O, dfppy = 2-(2,4-difluorophenyl)pyridine, pic-OH = 3-hydroxy-2-carboxypyridine), was developed by an in situ coordination reaction to form an insoluble dinuclear iridium(III) complex-sensitized-europium(III) emissive complex within mesoporous silica nanoparticles (MSNs) which had high loading efficiency. Compared with the usual approach of physical adsorption, this in-situ reaction strategy provided 20-fold the loading efficiency (43.2%) of the insoluble Ir-Eu complex in MSNs. These nanoparticles in solid state showed bright red luminescence with high quantum yield of 55.2%, and the excitation window extended up to 470 nm. These Ir-Eu-MSN nanoparticles were used for luminescence imaging in living cells under excitation at 458 nm with confocal microscopy, which was confirmed by flow cytometry. Furthermore, the Ir-Eu-MSN nanoparticles were successfully applied into high-contrast luminescent lymphatic imaging in vivo under low power density excitation of 5 mW cm(-2). This synthetic method provides a universal strategy of combining hydrophobic complexes with hydrophilic MSNs for in vivo bioimaging.

  12. Imaging of rotational wave-function in photodissociation of rovibrationally excited HCl molecules

    NASA Astrophysics Data System (ADS)

    Grygoryeva, K.; Rakovský, J.; Votava, O.; Fárník, M.

    2017-07-01

    We demonstrate a visualization of quantum mechanical phenomena with the velocity map imaging (VMI) technique, combining vibrationally mediated photodissociation (VMP) of a simple diatomic HCl with the VMI of its H-photofragments. Free HCl molecules were excited by a pump infrared (IR) laser pulse to particular rotational J levels of the v = 2 vibrational state, and subsequently a probe ultraviolet laser photodissociated the molecule at a fixed wavelength of 243.07 nm where also the H-fragments were ionized. The molecule was aligned by the IR excitation with respect to the IR laser polarization, and this alignment was reflected in the angular distribution of the H-photofragments. In particular, the highest degree of molecular alignment was achieved for the J =1 ←0 transition, which exclusively led to the population of a single rotational state with M = 0. The obtained images were analyzed for further details of the VMP dynamics, and different J states were studied as well. Additionally, we investigated the dynamic evolution of the excited states by changing the pump-probe laser pulse delay; the corresponding images reflected dephasing due to a coupling between the molecular angular momentum and nuclear spin. Our measurements confirmed previous observation using the time-of-flight technique by Sofikitis et al. [J. Chem. Phys. 127, 144307 (2007)]. We observed a partial recovery of the originally excited state after 60 ns in agreement with the previous observation.

  13. Coulomb excitations of monolayer germanene

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes.

  14. Coulomb excitations of monolayer germanene

    PubMed Central

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes. PMID:28091555

  15. Model for simulation of IR countermeasure effect on IR-seeker/missile

    NASA Astrophysics Data System (ADS)

    Berggren, Jan; Kihlen, Ralf G.

    2004-12-01

    TACSI (TACtical SImulation) is an existing simulator used as a tactical environment for manned simulators at Saab Aerosystems. TACSI can also be used as a stand-alone desktop development and simulation tool. TACSI simulates a large number of entities and functions such as platforms, sensors, weapons, signatures, communication, multisensor fusion, decision support etc. TACSI has a rule based pilot model and uses High Level Architecture (HLA) for interfacing with other simulation models. This model, a development of TACSI, simulates the flight dynamics, IR-signature and IR-seeker operation. The dynamic behaviour of the aircraft, the IRCM, the missile and the IR-seeker are modelled. The IR-contrast seen by the seeker through the atmosphere in front of the aircraft and the IRCM are spectrally and dynamically modelled. The seeker operation behaviour and function are also modelled. To implement this in a real-time simulation system simplifications are necessary. This paper describes the simplifications to model the IR-contrast and the seeker function. This model is used to analyse the effect of IR countermeasures (IRCM) on a missile IR-seeker.

  16. Systematic modeling for the insulin signaling network mediated by IRS(1) and IRS(2).

    PubMed

    Huang, Can; Wu, Ming; Du, Jun; Liu, Di; Chan, Christina

    2014-08-21

    The hepatic insulin signaling mediated by insulin receptor substrates IRS1 and IRS2 plays a central role in maintaining glucose homeostasis under different physiological conditions. Although functions of individual components in the signaling network have been extensively studied, our knowledge is still limited with regard to how the signals are integrated and coordinated in the complex network to render their functional roles. In this study, we construct systematic models for the insulin signaling network mediated by IRS1 and IRS2, through the integration of current knowledge in the literature into mathematical models of insulin signaling pathways. We hypothesize that the specificity of the IRS signaling mechanisms emerges from the wiring and kinetics of the entire network. A discrete dynamic model is first constructed to account for the numerous dynamic features in the system, i.e., complex feedback circuits, different regulatory time-scales and cross-talks between pathways. Our simulation shows that the wiring of the network determines different functions of IRS1 and IRS2. We further collate and reconstruct a kinetic model of the network as a system of ordinary differential equations to provide an informative model for predicting phenotypes. A sensitivity analysis is applied to identify essential regulators for the signaling process.

  17. Excitations of strange bottom baryons

    NASA Astrophysics Data System (ADS)

    Woloshyn, R. M.

    2016-09-01

    The ground-state and first-excited-state masses of Ωb and Ω_{bb} baryons are calculated in lattice QCD using dynamical 2 + 1 flavour gauge fields. A set of baryon operators employing different combinations of smeared quark fields was used in the framework of the variational method. Results for radial excitation energies were confirmed by carrying out a supplementary multiexponential fitting analysis. Comparison is made with quark model calculations.

  18. Collisional excitation of interstellar formaldehyde

    NASA Technical Reports Server (NTRS)

    Green, S.; Garrison, B. J.; Lester, W. A., Jr.; Miller, W. H.

    1978-01-01

    Previous calculations for rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Rates for para-H2CO have also been computed. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%. Excitation of formaldehyde by collisions with H2 molecules is also discussed.

  19. IR laser-induced protein crystal transformation

    PubMed Central

    Kiefersauer, Reiner; Grandl, Brigitte; Krapp, Stephan; Huber, Robert

    2014-01-01

    A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress. PMID:24816092

  20. IR "Snowballs": Long-Term Characterization

    NASA Astrophysics Data System (ADS)

    Durbin, M. J.; Bourque, M.; Baggett, S.

    2015-03-01

    We present a comprehensive analysis of the properties of the WFC3/IR anomalies known as "snowballs", using all in- ight WFC3/IR data through July 2014. The source of snowballs is unclear at present, but is hypothesized to be radionuclides in the detector or bonding material. Nearly 7400 unique snowball events have been identied from the search of 5 years of WFC3/IR images (over 6200 hours of exposure time), translating to a mean rate of about 1.2 snowballs per hour of IR exposure time. Typical snowballs a ect about 10 pixels and saturate 2-5 of those, and deposit about 200,000 to 500,000 electrons on the detector. We nd no trend over 5 years in the rates of snowball occurrences, consistent with the hypothesis that the uranium-238 decay chain is the source of snowballs. We also publish a table of all hitherto identied snowballs, available at http://www.stsci.edu/hst/wfc3/insperformance/anomalies/irsnowballtable.txt.

  1. Panel discussion: The future of IR astronomy

    NASA Technical Reports Server (NTRS)

    Caroff, Lawrence J.

    1995-01-01

    A panel discussion was held on the future of IR astronomy. The chairman gave a brief introduction to current planned programs for NASA and other space agencies, followed by short contributions from the six panel members on a variety of special topics. After that, a short question and answer session was held.

  2. IR-radiation detection by ultrasonic thermometry

    NASA Astrophysics Data System (ADS)

    Petrov, D. V.; Genin, D. E.; Korolkov, V. A.

    2017-05-01

    A method based on ultrasonic thermometry for detecting radiation in the IR range is described. The first results of experimental verification of this method are presented using the example of CO2-laser-radiation detection, and ways to improve its threshold sensitivity are described.

  3. Interactive Response Systems (IRS) Socrative Application Sample

    ERIC Educational Resources Information Center

    Aslan, Bilge; Seker, Hasan

    2017-01-01

    In globally developing education system, technology has made instructional improved in many ways. One of these improvements is the Interactive Response Systems (IRS) that are applied in classroom activities. Therefore, it is "smart" to focus on interactive response systems in learning environment. This study was conducted aiming to focus…

  4. Synchrotron IR spectromicroscopy: chemistry of living cells.

    PubMed

    Holman, Hoi-Ying N; Bechtel, Hans A; Hao, Zhao; Martin, Michael C

    2010-11-01

    Advanced analytical capabilities of synchrotron IR spectromicroscopy meet the demands of modern biological research for studying molecular reactions in individual living cells. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.).

  5. Wide-angle conformal IR transceiver

    NASA Astrophysics Data System (ADS)

    Liepmann, Till W.; Randall, Michael R.; Shapiro, Alan R.

    1993-08-01

    Accessing a large field-of-regard (FOR) from an aircraft-mounted infrared system imposes significant structural and aerodynamic penalties. A novel conformal infrared (IR) transceiver concept is presented which is currently under development. A trial design of this concept can access a 160 deg FOR without a gimbal mirror or 'fish eye' lens. A fiber optic bundle is used to allow a wide range of beamsteering technologies with small steering angles (i.e., +/- 5 degree(s)) to access the large FOR (+/- 80 deg) through a single, conformal aperture. The output lens size is less than a factor of three times larger than the input/output IR beam, yet provides near diffraction limited polychromatic collimation over the full FOR. The concept is applicable over a wide spectral band (ultraviolet to far IR), however, it is being developed for the mid-IR (2 - 6 micron) band. The challenging technical aspects of the fiber optics in this spectral band are discussed.

  6. Laser reflexotherapy in UV and IR wavelengths

    NASA Astrophysics Data System (ADS)

    Mokretsov, V. V.; Utz, Sergei R.; Vinichenko, N. V.; Barabanov, Alexander Y.; Tuchin, Valery V.

    1993-06-01

    The purpose of this work was the investigation of the effects of UV and IR laser irradiation on the central and regional hemodynamics of agricultural mechanization workers with border limited arterial hypertension, whose arterial pressure was within the limits from 140 to 90 mm of mercury column up to 159 and 94 mm mercury column.

  7. IR laser-induced protein crystal transformation

    SciTech Connect

    Kiefersauer, Reiner Grandl, Brigitte; Krapp, Stephan; Huber, Robert

    2014-05-01

    A novel method and the associated instrumentation for improving crystalline order (higher resolution of X-ray diffraction and reduced mosaicity) of protein crystals by precisely controlled heating is demonstrated. Crystal transformation is optically controlled by a video system. A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress.

  8. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  9. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  10. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  11. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  12. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  13. IR sensors and imagers in networked operations

    NASA Astrophysics Data System (ADS)

    Breiter, Rainer; Cabanski, Wolfgang

    2005-05-01

    "Network-centric Warfare" is a common slogan describing an overall concept of networked operation of sensors, information and weapons to gain command and control superiority. Referring to IR sensors, integration and fusion of different channels like day/night or SAR images or the ability to spread image data among various users are typical requirements. Looking for concrete implementations the German Army future infantryman IdZ is an example where a group of ten soldiers build a unit with every soldier equipped with a personal digital assistant (PDA) for information display, day photo camera and a high performance thermal imager for every unit. The challenge to allow networked operation among such a unit is bringing information together and distribution over a capable network. So also AIM's thermal reconnaissance and targeting sight HuntIR which was selected for the IdZ program provides this capabilities by an optional wireless interface. Besides the global approach of Network-centric Warfare network technology can also be an interesting solution for digital image data distribution and signal processing behind the FPA replacing analog video networks or specific point to point interfaces. The resulting architecture can provide capabilities of data fusion from e.g. IR dual-band or IR multicolor sensors. AIM has participated in a German/UK collaboration program to produce a demonstrator for day/IR video distribution via Gigabit Ethernet for vehicle applications. In this study Ethernet technology was chosen for network implementation and a set of electronics was developed for capturing video data of IR and day imagers and Gigabit Ethernet video distribution. The demonstrator setup follows the requirements of current and future vehicles having a set of day and night imager cameras and a crew station with several members. Replacing the analog video path by a digital video network also makes it easy to implement embedded training by simply feeding the network with

  14. Near-Infrared Imaging of Injured Tissue in Living Subjects using IR-820

    PubMed Central

    Prajapati, Suresh I; Martinez, Carlo O; Bahadur, Ali N; Wu, Isabel Q; Zheng, Wei; Lechleiter, James D; McManus, Linda M; Chisholm, Gary B; Michalek, Joel E; Shireman, Paula K; Keller, Charles

    2009-01-01

    The unprecedented increase in pre-clinical studies necessitates high-throughput, inexpensive and straightforward methods for evaluating diseased tissues. Near-infrared imaging of live subjects is a versatile, cost-effective technology that can be effectively used in a variety of pathological conditions. We have characterized an inexpensive optoelectronic chemical, IR-820, as an infrared blood pool contrast agent to detect and quantify diseased tissue in live animals. IR-820 has maximal excitation and emission wavelengths of 710 nm and 820 nm, respectively. IR-820 emission is significantly improved in vivo upon serum binding to albumin and elimination occurs predominantly via the gastrointestinal tract. We demonstrate the utility of this contrast agent for serially imaging of traumatized tissue (muscle), tissue following re-perfusion (e.g. stroke) and tumors. IR-820 can also be employed to map regional lymph nodes. This novel contrast agent is anticipated to be a useful and an inexpensive tool for screening a wide variety of preclinical models of human diseases. PMID:19344575

  15. projective variational study on low-temperature quantum magnetism in Na4Ir3O8

    NASA Astrophysics Data System (ADS)

    Shindou, Ryuichi

    2015-03-01

    Na4Ir3O8 is one of candidate materials of three-dimensional quantum spin liquid Mott isnulator, where Ir J=1/2 spin forms a hyperkagome lattice, a corner-sharing triangle network lattice with spin frustration. Due to lack of spatial inversion symmetries and heavy atom nature of Iridium, the system possesses larger anisotropic exchange interactions. In fact, preceding theories based on ab-initio band calculation show that Dzyaloshinskii-Moriya (DM) interaction is on order of 10 percent of isotropic exchange interaction, which could play vital role of highly competing grand state energetics in Na4Ir3O8. From transport experiments, the system is also known to be in weak Mott insulating regime, where charge fluctuation cause larger multiple-spin interactions. Employing variational analyses based on projective(fermionic) construction of many-body spin wavefunctions, we will reconsider possible quantum spin ground states in the hyperkagome antiferromagnetic Heisenberg model with anisotropic exchange and multiple-spin interactions of Na4Ir3O8. Starting from these states, we will discuss possible magnetic excitations and compare them with reported experiments.

  16. The structure and nature of NGC 2017 IRS. 1: High-resolution radio continuum maps

    NASA Technical Reports Server (NTRS)

    Smith, Howard A.; Beck, Sara C.

    1994-01-01

    We have observed the star formation cluster NGC 2071 IRS 1, 2, and 3, with 0.14 sec spatial resolution at 2 cm. The strong source IRS 1 breaks up into a bright peak sitting on a narrow line emission extending over about 400 AU, with three much weaker peaks. This ridge, which has a p.a. = 100 deg, is not aligned with any of the other structures that have previously been seen around IRS 1: its orientation is about 55 deg from the CO outflow direction, and 35 deg from a hypothetical disk direction. The spectral and spatial results, combined with earlier radio and infrared observations, indicate that most likely the radio and infrared emission from the exciting source, IRS 1, is produced by a dense wind hidden by at least 100 visual magnitudes of extinction; the extended ridge of emission comes from an optically thin H II region with characteristic dimensions of approximately AU and which may result from a clumpy distribution of local gas and dust.

  17. Redox Control of Cardiac Excitability

    PubMed Central

    Aggarwal, Nitin T.

    2013-01-01

    Abstract Reactive oxygen species (ROS) have been associated with various human diseases, and considerable attention has been paid to investigate their physiological effects. Various ROS are synthesized in the mitochondria and accumulate in the cytoplasm if the cellular antioxidant defense mechanism fails. The critical balance of this ROS synthesis and antioxidant defense systems is termed the redox system of the cell. Various cardiovascular diseases have also been affected by redox to different degrees. ROS have been indicated as both detrimental and protective, via different cellular pathways, for cardiac myocyte functions, electrophysiology, and pharmacology. Mostly, the ROS functions depend on the type and amount of ROS synthesized. While the literature clearly indicates ROS effects on cardiac contractility, their effects on cardiac excitability are relatively under appreciated. Cardiac excitability depends on the functions of various cardiac sarcolemal or mitochondrial ion channels carrying various depolarizing or repolarizing currents that also maintain cellular ionic homeostasis. ROS alter the functions of these ion channels to various degrees to determine excitability by affecting the cellular resting potential and the morphology of the cardiac action potential. Thus, redox balance regulates cardiac excitability, and under pathological regulation, may alter action potential propagation to cause arrhythmia. Understanding how redox affects cellular excitability may lead to potential prophylaxis or treatment for various arrhythmias. This review will focus on the studies of redox and cardiac excitation. Antioxid. Redox Signal. 18, 432–468. PMID:22897788

  18. Electron-excited molecule interactions

    SciTech Connect

    Christophorou, L.G. Tennessee Univ., Knoxville, TN . Dept. of Physics)

    1991-01-01

    In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10{sup 6} to 10{sup 7} times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs.

  19. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  20. ISO FAR-IR Spectroscopy of IR-Bright Galaxies and Ulirgs

    DTIC Science & Technology

    1999-01-01

    ISO FAR-IR SPECTROSCOPY OF IR-BRIGHT GALAXIES AND ULIRGS J. FISCHER AND M.L. LUHMAN Naval Research Laboratory, Washington, DC, USA S. SATYAPAL AND...flux ratios than in normal and less luminous IR-bright galaxies by an order of magnitude ( Luhman et al., 1998; 1999). This has been interpreted as an...line ratio is unexpectedly low (Fischer et al., 1997; Luhman et al., 1998). Implicit in this interpretation is the assumption that the [O I]145µm upper

  1. Growth and termination of a rutile IrO2(100) layer on Ir(111)

    NASA Astrophysics Data System (ADS)

    Rai, Rahul; Li, Tao; Liang, Zhu; Kim, Minkyu; Asthagiri, Aravind; Weaver, Jason F.

    2016-10-01

    We investigated the oxidation of Ir(111) by gas-phase oxygen atoms at temperatures between 500 and 625 K using temperature programmed desorption (TPD), low energy electron diffraction (LEED), low energy ion scattering spectroscopy (LEISS) and density functional theory (DFT) calculations. We find that a well-ordered surface oxide with (√ 3 × √ 3)R30° periodicity relative to Ir(111) develops prior to the formation of a rutile IrO2(100) layer. The IrO2(100) layer reaches a saturation thickness of about four oxide layers under the oxidation conditions employed, and decomposes during TPD to produce a single, sharp O2 desorption peak at 770 K. Favorable lattice matching at the oxide-metal interface is likely responsible for the preferential growth of the IrO2(100) facet during the initial oxidation of Ir(111), with the resulting coincidence lattice generating a clear (6 × 1) moiré pattern in LEED. Temperature programmed reaction spectroscopy (TPRS) experiments reveal that CO and H2O molecules bind only weakly on the IrO2(100) surface and LEISS measurements show that the oxide surface is highly enriched in O-atoms. These characteristics provide strong evidence that the rutile IrO2(100) layer is oxygen-terminated, and thus lacks reactive Ir atoms that can strongly bind molecular adsorbates. Oxygen binding energies predicted by DFT suggest that on-top O-atoms will remain adsorbed on IrO2(100) at temperatures up to 625 K, thus supporting the conclusion that the rutile IrO2 layer grown in our experiments is oxygen-terminated. As such, the appearance of only a single O2 TPD peak indicates that the singly coordinate, on-top O-atoms remain stable on the IrO2(100) surface up to temperatures at which the oxide layer begins to thermally decompose.

  2. Biological oxygen sensing via two-photon absorption by an Ir(III) complex using a femtosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Moritomo, Hiroki; Fujii, Akinari; Suzuki, Yasutaka; Yoshihara, Toshitada; Tobita, Seiji; Kawamata, Jun

    2016-09-01

    Near-infrared two-photon absorption of the phosphorescent Ir(III) complex (2,4-pentanedionato-κO 2,κO 4)bis[2-(6-phenanthridinyl-κN)benzo[b]thien-3-yl-κC]iridium (BTPHSA) was characterized. It exhibited a 800-1200 nm two-photon absorption band, and thus could be electronically excited by 1030-nm femtosecond Ti:sapphire and Yb-doped fiber lasers. By using BTPHSA, oxygen concentrations in human embryonic kidney 293 (HEK293) cells were imaged. These results demonstrate two-photon oxygen sensing of live tissues via easily operable excitation sources.

  3. Magnetic order and spin excitations in the Kitaev–Heisenberg model on a honeycomb lattice

    SciTech Connect

    Vladimirov, A. A.; Ihle, D.; Plakida, N. M.

    2016-06-15

    We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev–Heisenberg model proposed for A{sub 2}IrO{sub 3} (A = Li, Na) compounds. The spin-wave excitation spectrum, the sublattice magnetization, and the transition temperatures are calculated in the random phase approximation for four different ordered phases observed in the parameter space of the model: antiferromagnetic, stripe, ferromagnetic, and zigzag phases. The Néel temperature and temperature dependence of the sublattice magnetization are compared with the experimental data on Na{sub 2}IrO{sub 3}.

  4. Electronic photodissociation spectra and decay pathways of gas-phase IrBr{sub 6}{sup 2-}

    SciTech Connect

    Marcum, Jesse C.; Weber, J. Mathias

    2009-11-21

    We report photodissociation action spectra for the dianion IrBr{sub 6}{sup 2-} in the range of 1.08-5.6 eV. The photoproducts observed are IrBr{sub 6}{sup -}, IrBr{sub 5}{sup -}, IrBr{sub 4}{sup -} and Br{sup -}. Comparison of the action spectra to the aqueous absorption spectrum of K{sub 2}IrBr{sub 6} leads to the determination of solvatochromic shifts of between 0.02 and 0.16 eV in the visible region and approximately 0.3 eV in the ultraviolet. The fragmentation branching ratios vary greatly as a function of photon energy. This behavior can be attributed to differences in the fragmentation mechanisms as well as differences in the excited states that are accessed at different energies. Absorption in the visible region favors fragmentation into IrBr{sub 5}{sup -} and Br{sup -}, whereas a number of fragmentation channels and mechanisms are active in the ultraviolet region. These mechanisms include fragmentation as well as electron detachment and dissociative electron detachment.

  5. The Path to a UV/optical/IR Flagship: ATLAST and Its Predecessors

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Bolcar, Matthew R.; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Oegerle, William; Postman, Marc; Rioux, Norman; Stahl, H. Philip; Stapelfeldt, Karl

    2016-01-01

    The recently completed study for the Advanced Technology Large-Aperture Telescope (ATLAST) was the culmination of three years of work that built upon earlier engineering designs, science objectives, and sustained recommendations for technology investments. Since the mid-1980s, multiple teams of astronomers, technologists, and engineers have developed concepts for a large-aperture UV/optical/IR space observatory to follow the Hubble Space Telescope (HST). Especially over the past decade, technology advances and exciting scientific results has led to growing support for development in the 2020s of a large UVOIR space observatory. Here we summarize the history of major mission designs, scientific goals, key technology recommendations, community workshops and conferences, and recommendations to NASA for a major UV/optical/IR observatory to follow HST. We conclude with a capsule summary of the ATLAST reference design developed over the past three years.

  6. Powerful visible (530???770 nm) luminescence in Yb,Ho:GGG with IR diode pumping.

    PubMed

    Kir'yanov, Alexander; Aboites, V; Belovolov, A; Timoshechkin, M; Belovolov, M; Damzen, M; Minassian, A

    2002-08-12

    Powerful visible luminescence in a Gadolinium Gallium Garnet (GGG) crystal, co-activated with Yb3+ (~15 at.%) and Ho3+ (~0.1 at.%) ions, is investigated under CW laser diode pumping (lambda = 938 and 976 nm). The main visible emission band is observed in the green with its peak at lambda ~540 nm) and measured to be about 10% with respect to Yb3+ IR luminescence (lambda ~1000 nm). Red (lambda ~650 nm) and near-IR (lambda ~755 nm) emission bands are also observed but are weaker (about 3-5%). Analysis of the crystal absorption and luminescence spectra allows one to conclude that Yb3+ - Ho3+ stepwise up-conversion is the mechanism explaining the phenomenon. Ho3+ ions embedded in the crystal in small concentration are shown to form an effective reservoir for energy transferred from the excited Yb3+ subsystem and to be an efficient source of the visible emission.

  7. Laser action in chromium-activated forsterite for near infrared excitation

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Gayen, S. K.; Alfano, R. R.

    1988-01-01

    This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

  8. Laser action in chromium-activated forsterite for near infrared excitation

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Gayen, S. K.; Alfano, R. R.

    1988-01-01

    This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

  9. Performance seeking control excitation mode

    NASA Technical Reports Server (NTRS)

    Schkolnik, Gerard

    1995-01-01

    Flight testing of the performance seeking control (PSC) excitation mode was successfully completed at NASA Dryden on the F-15 highly integrated digital electronic control (HIDEC) aircraft. Although the excitation mode was not one of the original objectives of the PSC program, it was rapidly prototyped and implemented into the architecture of the PSC algorithm, allowing valuable and timely research data to be gathered. The primary flight test objective was to investigate the feasibility of a future measurement-based performance optimization algorithm. This future algorithm, called AdAPT, which stands for adaptive aircraft performance technology, generates and applies excitation inputs to selected control effectors. Fourier transformations are used to convert measured response and control effector data into frequency domain models which are mapped into state space models using multiterm frequency matching. Formal optimization principles are applied to produce an integrated, performance optimal effector suite. The key technical challenge of the measurement-based approach is the identification of the gradient of the performance index to the selected control effector. This concern was addressed by the excitation mode flight test. The AdAPT feasibility study utilized the PSC excitation mode to apply separate sinusoidal excitation trims to the controls - one aircraft, inlet first ramp (cowl), and one engine, throat area. Aircraft control and response data were recorded using on-board instrumentation and analyzed post-flight. Sensor noise characteristics, axial acceleration performance gradients, and repeatability were determined. Results were compared to pilot comments to assess the ride quality. Flight test results indicate that performance gradients were identified at all flight conditions, sensor noise levels were acceptable at the frequencies of interest, and excitations were generally not sensed by the pilot.

  10. Dealing confidently with IRS, Part II: IRS audit and postaudit procedures.

    PubMed

    Holub, S F; Walker, S R

    1978-11-01

    Preparation enables an administrator to control the hospital's participation in IRS audit procedures, to fulfill the requirements essential to the institution's tax-exempt status, and to choose the most appropriate alternative at the postaudit conference.

  11. Excitation with quantum light. I. Exciting a harmonic oscillator

    NASA Astrophysics Data System (ADS)

    Carreño, J. C. López; Laussy, F. P.

    2016-12-01

    We present a two-part study of the excitation of an optical target by quantum light. In this first part, we introduce the problematic and address the first case of interest, that of exciting the quantum harmonic oscillator, corresponding to, e.g., a single-mode passive cavity or a noninteracting bosonic field. We introduce a mapping of the Hilbert space that allows to chart usefully the accessible regions. We then consider the quantum excitation from single-photon sources in the form of a two-level system under various regimes of (classical) pumping: incoherent, coherent, and in the Mollow triplet regime. We close this first part with an overview of the material to be covered in the subsequent work.

  12. Photochemistry of 2-naphthoyl azide. An ultrafast time-resolved UV-vis and IR spectroscopic and computational study.

    PubMed

    Kubicki, Jacek; Zhang, Yunlong; Vyas, Shubham; Burdzinski, Gotard; Luk, Hoi Ling; Wang, Jin; Xue, Jiadan; Peng, Huo-Lei; Pritchina, Elena A; Sliwa, Michel; Buntinx, Guy; Gritsan, Nina P; Hadad, Christopher M; Platz, Matthew S

    2011-06-29

    The photochemistry of 2-naphthoyl azide was studied in various solvents by femtosecond time-resolved transient absorption spectroscopy with IR and UV-vis detection. The experimental findings were interpreted with the aid of computational studies. Using polar and nonpolar solvents, the formation and decay of the first singlet excited state (S(1)) was observed by both time-resolved techniques. Three processes are involved in the decay of the S(1) excited state of 2-naphthoyl azide: intersystem crossing, singlet nitrene formation, and isocyanate formation. The lifetime of the S(1) state decreases significantly as the solvent polarity increases. In all solvents studied, isocyanate formation correlates with the decay of the azide S(1) state. Nitrene formation correlates with the decay of the relaxed S(1) state only upon 350 nm excitation (S(0) → S(1) excitation). When S(n) (n ≥ 2) states are populated upon excitation (λ(ex) = 270 nm), most nitrene formation takes place within a few picoseconds through the hot S(1) and higher singlet excited states (S(n)) of 2-naphthoyl azide. The data correlate with the results of electron density difference calculations that predict nitrene formation from the higher-energy singlet excited states, in addition to the S(1) state. For all of these experiments, no recovery of the ground state was observed up to 3 ns after photolysis, which indicates that both internal conversion and fluorescence have very low efficiencies.

  13. Deep IR imaging of two gas-rich radio galaxies

    NASA Astrophysics Data System (ADS)

    Jackson, Neal

    1997-07-01

    We propose deep, high resolution continuum, line and polarization imaging of the two best candidates for recent mergers amongst the low-redshift radio galaxies: 3C 305 and 3C 293. Our primary aim is to obtain a deep IR image to locate the true nuclei and clarify the structure of the galaxies in order to test merger models, since our optical view is confused by dense dust lanes, scattering, and strong emission lines associated with the kpc-scale radio jets. The results will help assess popular models in which mergers trigger AGN activity. Our secondary aim is to image the shock-excited 1.64 micron Fe ii line to trace fast shocks and hence help understand the relationship between the radio jets and the {possibly collimated} ionizing continuum. These two galaxies provide a very rare opportunity to study the impact of the jets on their environment, because they are interacting directly with the cold interstellar medium {absent in normal elliptical radio galaxies}. The extended optical emission lines are already well studied, but interpretation has been hampered by confusion between shock- and photo-ionization. Our tertiary aim is to obtain 2 micron polarimetry to trace regions of electron scattering, to check the apparent 90degrees misalignment between the jet axis and that of the scattering ``cone'' in 3C 305, and to ensure location of even deeply-buried nuclei, either by picking up direct long- wavelength emission, or by locating the centre of the scattering pattern.

  14. Role of IRS1 and IRS2 in Modulating ErbB-induced Tumorigenesis

    DTIC Science & Technology

    2010-04-01

    cancer, BMS-754807, IGF, small molecule inhibitor 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF...IGF-IR signaling (Months 12-24) i) Correlate levels of IRSs with response to IGF-I and insulin in a large panel of breast cancer cell lines...i) Use transcriptomic profiling of a large panel of breast cancer cell lines to identify markers of sensitivity and resistance to an IGF-IR

  15. Spectrally resolved confocal microscopy using lanthanide centred near-IR emission.

    PubMed

    Liao, Zhiyu; Tropiano, Manuel; Mantulnikovs, Konstantins; Faulkner, Stephen; Vosch, Tom; Sørensen, Thomas Just

    2015-02-11

    The narrow, near infrared (NIR) emission from lanthanide ions has attracted great interest, particularly with regard to developing tools for bioimaging, where the long lifetimes of lanthanide excited states can be exploited to address problems arising from autofluorescence and sample transparency. Despite the promise of lanthanide-based probes for near-IR imaging, few reports on their use are present in the literature. Here, we demonstrate that images can be recorded by monitoring NIR emission from lanthanide complexes using detectors, optical elements and a microscope that were primarily designed for the visible part of the spectrum.

  16. Tax-deferred annuity plans: meeting the IRS audit challenge.

    PubMed

    Schussler, M

    1997-01-01

    A growing number of nonprofit organizations are being fined for violations of IRS regulations following IRS audits of their tax-deferred annuity (TDA) plans. To ensure that their organizations can withstand the scrutiny of an IRS audit, TDA plan administrators must ensure that plans meet IRS regulations and be prepared for IRS audits. Documentation--particularly of the TDA plan itself, and procedures related to salary reduction programs, compensation limits, excess deferrals and other excess contributions, loans, and distributions--must be comprehensive and in compliance with IRS regulations.

  17. Born Oppenheimer Molecular Dynamics calculation of the νO-H IR spectra for acetic acid cyclic dimers

    NASA Astrophysics Data System (ADS)

    El Amine Benmalti, Mohamed; Krallafa, Abdelghani; Gaigeot, Marie-Pierre

    2015-01-01

    Both ab initio molecular dynamics simulations based on the Born-Oppenheimer approach calculations and a quantum theoretical model are used in order to study the IR spectrum of the acetic acid dimer in the gas phase. The theoretical model is taking into account the strong anharmonic coupling, Davydov coupling, multiple Fermi resonances between the first harmonics of some bending modes and the first excited state of the symmetric combination of the two vO-H modes and the quantum direct and indirect relaxation. The IR spectra obtained from DFT-based molecular dynamics is compared with our theoretical lineshape and with experiment. Note that in a previous work we have shown that our approach reproduces satisfactorily the main futures of the IR experimental lineshapes of the acetic acid dimer [Mohamed el Amine Benmalti, Paul Blaise, H. T. Flakus, Olivier Henri-Rousseau, Chem Phys, 320(2006) 267-274.].

  18. Mid-IR Transition Metal Lasers (Postprint)

    DTIC Science & Technology

    2007-01-01

    alexandrite was demonstrated in 1979. [2] Cr4+ and Cr2+ infrared laser materials took even longer to be discovered. However, transition metal laser...already been mentioned. Other transition metal laser ions such as Cr3+ in alexandrite [19] and Ti3+ in YAlO3 [20] have excited state absorption (ESA...Washington, DC. 19. Shand, M.L., J.C. Walling, and R.C. Morris, Excited-state absorption in the pump region of alexandrite , Journal of Applied Physics

  19. New honeycomb iridium(V) oxides: NaIrO3 and Sr3CaIr2O9.

    PubMed

    Wallace, David C; McQueen, Tyrel M

    2015-12-21

    We report the structures and physical properties of two new iridates, NaIrO3 and Sr3CaIr2O9, both of which contain continuous two-dimensional honeycomb connectivity. NaIrO3 is produced by room temperature oxidative deintercalation of sodium from Na2IrO3, and contains edge-sharing IrO6 octahedra that form a planar honeycomb lattice. Sr3CaIr2O9, produced via conventional solid-state synthesis, hosts a buckled honeycomb lattice with novel corner-sharing connectivity between IrO6 octahedra. Both of these new compounds are comprised of Ir(5+) (5d(4)) and exhibit negligible magnetic susceptibility. They are thus platforms to investigate the origin of the nonmagnetic behavior exhibited by Ir(5+) oxides, and provide the first examples of a J = 0 state on a honeycomb lattice.

  20. Sadomasochism, sexual excitement, and perversion.

    PubMed

    Kernberg, O F

    1991-01-01

    Sadomasochism, an ingredient of infantile sexuality, is an essential part of normal sexual functioning and love relations, and of the very nature of sexual excitement. Sadomasochistic elements are also present in all sexual perversions. Sadomasochism starts out as the potential for erotic masochism in both sexes, and represents a very early capacity to link aggression with the libidinal elements of sexual excitement. Sexual excitement may be considered a basic affect that overcomes primitive splitting of love and hatred. Erotic desire is a more mature form of sexual excitement. Psychoanalytic exploration makes it possible to uncover the unconscious components of sexual excitement: wishes for symbiotic fusion and for aggressive penetration and intermingling; bisexual identifications; the desire to transgress oedipal prohibitions and the secretiveness of the primal scene, and to violate the boundaries of a teasing and withholding object. The relation between these wishes and the development of erotic idealization processes in both sexes is explored in the context of a critical review of the pertinent psychoanalytic literature.

  1. Signatures of spin-glass behaviour in PrIr2B2 and heavy fermion behaviour in PrIr2B2C.

    PubMed

    Anupam; Anand, V K; Hossain, Z; Adroja, D T; Geibel, C

    2011-09-21

    CEF-split singlet and the first excited state singlet is situated 15 K above the ground state. The Sommerfeld coefficient γ∼300 mJ mol(-1) K(-2) of PrIr(2)B(2)C is very high and reflects a heavy fermion behaviour in this compound. We believe that the heavy fermion state in PrIr(2)B(2)C has its origin in low lying crystal field excitations as has been observed in PrRh(2)B(2)C.

  2. Automated IR-weld seam control

    NASA Astrophysics Data System (ADS)

    Balle, Michel

    1990-03-01

    In 1975 the concept of visualizing, measuring and studying the thermal condition of welded seams was investigated by a laboratory of the French ministry of defense (at the request of a metal constructor). Gilbert Gaussorgues, the founding father of the company HGH was at the time in charge of the infrared laboratory in question, a department of the general administration of Armament in Toulon, France. His idea was to apply military IR-Technology to above mentioned welding application. Having developed a prototype, tests readily confirmed the validity of using IR-emission from the weld seam close to the actual moment of welding as an indicator of the quality of the fmal assembly. Nearly ten years later, in 1984, HGH decided, due to an increasing demand, to develop above preliminary tests to a complete product/application package designed specifically for welding process-control. The inspection oftubing and of the integrity welds of barrels with hazardous content, were the first applications.

  3. Theoretical IR spectra of ionized naphthalene

    NASA Technical Reports Server (NTRS)

    Pauzat, F.; Talbi, D.; Miller, M. D.; DeFrees, D. J.; Ellinger, Y.

    1992-01-01

    We report the results of a theoretical study of the effect of ionization on the IR spectrum of naphthalene, using ab initio molecular orbital theory. For that purpose we determined the structures, band frequencies, and intensities of neutral and positively ionized naphthalene. The calculated frequencies and intensities allowed an assignment of the most important bands appearing in the newly reported experimental spectrum of the positive ion. Agreement with the experimental spectrum is satisfactory enough to take into consideration the unexpected and important result that ionization significantly affects the intensities of most vibrations. A possible consequence on the interpretation of the IR interstellar emission, generally supposed to originate from polycyclic aromatic hydrocarbons (PAHs), is briefly presented.

  4. Infrared Measurements of Possible IR Filter Materials

    NASA Astrophysics Data System (ADS)

    Koller, Daniel; Ediss, G. A.; Mihaly, Laszlo; Carr, G. L.

    A Fourier Transform Infrared Spectrometer (FTS) was used to obtain the transmission spectra of candidate materials for use as infrared (IR) filters in cryogenic receivers. The data cover the range from 50 cm-1 (~1.5 THz), well below the peak of the 300 K black body spectrum, to 5000 cm-1 (~150 THz). Z-cut quartz, Goretex, Zitex G and Zitex A, High Density Polyethylene (HDPE), Teflon (PTFE), Fluorogold and Black Polyethylene were measured. The relative effectiveness of each material as a filter is determined by integrating the transmission spectrum multiplied by the Planck distribution to obtain a normalized attenuation for the mid-IR band. Measurements at both room temperature and 8 K are compared.

  5. Infrared Measurements of Possible IR Filter Materials

    SciTech Connect

    Koller,D.; Ediss, G.; Mihaly, L.; Carr, G.

    2006-01-01

    A Fourier Transform Infrared Spectrometer (FTS) was used to obtain the transmission spectra of candidate materials for use as infrared (IR) filters in cryogenic receivers. The data cover the range from 50 cm-1 ({approx}1.5 THz), well below the peak of the 300 K black body spectrum, to 5000 cm-1 ({approx}150 THz), Z-cut quartz, Gore-Tex, Zitex G and Zitex A, High Density Polyethylene (HDPE), Teflon (PTFE), Fluorogold and Black Polyethylene were measured. The relative effectiveness of each material as a filter is determined by integrating the transmission spectrum multiplied by the Planck distribution to obtain a normalized attenuation for the mid-IR band. Measurements at both room temperature and 8 K are compared.

  6. Flexible high-performance IR camera systems

    NASA Astrophysics Data System (ADS)

    Hoelter, Theodore R.; Petronio, Susan M.; Carralejo, Ronald J.; Frank, Jeffery D.; Graff, John H.

    1999-07-01

    Indigo Systems Corporation has developed a family of standard readout integrated circuits (ROIC) for use in IR focal plane arrays (FPAs) imaging systems. These standard ROICs are designed to provide a compete set of operating features for camera level FPA control, while also providing high performance capability with any of several detector materials. By creating a uniform electrical interface for FPAs, these standard ROICs simplify the task of FPA integration with imaging electronics and physical packages. This paper begins with a brief description of the features of four Indigo standard ROICs and continues with a description of the features, design, and measured performance of indium antimonide, quantum well IR photo- detectors and indium gallium arsenide imaging system built using the described standard ROICs.

  7. Theoretical IR spectra of ionized naphthalene

    NASA Technical Reports Server (NTRS)

    Pauzat, F.; Talbi, D.; Miller, M. D.; DeFrees, D. J.; Ellinger, Y.

    1992-01-01

    We report the results of a theoretical study of the effect of ionization on the IR spectrum of naphthalene, using ab initio molecular orbital theory. For that purpose we determined the structures, band frequencies, and intensities of neutral and positively ionized naphthalene. The calculated frequencies and intensities allowed an assignment of the most important bands appearing in the newly reported experimental spectrum of the positive ion. Agreement with the experimental spectrum is satisfactory enough to take into consideration the unexpected and important result that ionization significantly affects the intensities of most vibrations. A possible consequence on the interpretation of the IR interstellar emission, generally supposed to originate from polycyclic aromatic hydrocarbons (PAHs), is briefly presented.

  8. Applications of IR imagery to thermal evaluations

    NASA Astrophysics Data System (ADS)

    Bocchicchio, Richard L.

    1992-07-01

    Three successful applications of IR imagery to thermal measurements and analysis are presented: (1) turbo-prop engine exhaust heating measurements, (2) temperature measurements of the gun (a 20-mm cannon) port area, and (3) tailpipe bellows temperature measurements. IR measurements were made with a dual-band scanner system incorporating a shortwave scanner covering the 3- to 5.6-micron spectral band and a longwave scanner covering the 8- to 14-micron spectral band. The output of the electronics was fed to a computer that has been adapted to the imager display and analysis software. Real-time images were displayed continuously (approximately 25/sec) and were recorded on the internal hard disk every 4 to 5 sec or continuously on tape.

  9. Cooling and Infrared Emission due to Molecular Collisional Excitation in Astrophysical Environments

    NASA Astrophysics Data System (ADS)

    Stancil, Phillip

    2011-06-01

    Non-thermal popluations of molecules in a variety of astronomical environments, including photodissociation regions, X-ray dominated regions, and protoplanetary disks, are controlled by collisional excitation and quenching of their rovibrational levels. The important colliders are the dominant neutral species: H, He, and H2. Resulting emission lines are primary cooling transitions and can be observed by current and upcoming IR/submillimeter observatories including Spitzer, Herschel, SOFIA, and ALMA. Modeling these environments, however, requires large-scale computation of collisional excitation processes. The status, needs, and astrophysical applications for important molecular targets will be reviewed including H2, HD, CO, H2O, and NH3.

  10. Single-Photon Interference due to Motion in an Atomic Collective Excitation

    NASA Astrophysics Data System (ADS)

    Whiting, D. J.; Šibalić, N.; Keaveney, J.; Adams, C. S.; Hughes, I. G.

    2017-06-01

    We experimentally demonstrate the heralded generation of bichromatic single photons from an atomic collective spin excitation (CSE). The photon arrival times display collective quantum beats, a novel interference effect resulting from the relative motion of atoms in the CSE. A combination of velocity-selective excitation with strong laser dressing and the addition of a magnetic field allows for exquisite control of this collective beat phenomenon. The present experiment uses a diamond scheme with near-IR photons that can be extended to include telecommunications wavelengths or modified to allow storage and retrieval in an inverted-Y scheme.

  11. IRS1 and IRS2: molecular characterization, tissue expression and transcriptional regulation by insulin in yellow catfish Pelteobagrus fulvidraco.

    PubMed

    Zhuo, Mei-Qin; Pan, Ya-Xiong; Wu, Kun; Xu, Yi-Huan; Zhang, Li-Han; Luo, Zhi

    2017-04-01

    The insulin receptor substrate (IRS) proteins, in particular, IRS1 and IRS2, are the key downstream players of insulin signaling pathway and the regulation of lipid metabolism. In the present study, two genes of IRS (IRS1 and IRS2) were isolated and characterized from yellow catfish Pelteobagrus fulvidraco. Their molecular characterizations, tissue expressions, and transcriptional levels by insulin both in vivo and in vitro were determined. The validated complementary DNAs encoding for IRS1 and IRS2 were 3693 and 3177 bp in length, encoding proteins of 1230 and 1058 amino acid residues, respectively. Similarly to mammals, amino acid sequence alignment revealed that IRSs contained an N-terminal pleckstrin homology (PH) domain, a phosphotyrosine-binding (PTB) domain, and several C-terminal multiple sites of tyrosine phosphorylation. Both IRS1 and IRS2 were widely expressed across the ten tissues (liver, white muscle, spleen, brain, gill, mesenteric fat, anterior intestine, heart, mid-kidney, and ovary), but at the variable levels. Insulin injection at 1 μg/g in vivo significantly stimulated the messenger RNA (mRNA) expression of IRS2, but not IRS1 mRNA expression levels in the liver of yellow catfish after 48 h. In hepatocytes of yellow catfish, insulin incubation significantly stimulated the IRS1 (at a 1000 nM insulin group) and IRS2 (at both 100 and 1000 nM insulin groups) mRNA expressions, which indicated that IRS2 was more sensitive than IRS1 to insulin stimulation in the liver of yellow catfish, and IRS2 played a more important role in mediating insulin's effects on the liver metabolism. The present study serves to increase our understanding into the function of IRS in fish.

  12. New Cross Section Data for Production of the Therapeutic Radionuclides 64Cu, 140Nd, and 192Ir

    NASA Astrophysics Data System (ADS)

    Hilgers, K.; Qaim, S. M.; Coenen, H. H.

    2005-05-01

    For production of the therapeutic radionuclides 64Cu, 140Nd and 192Ir new cross section data are reported, all measured using the stacked-foil technique. In the case of 64Cu, the 66Zn(d,α)64Cu reaction was investigated radiochemically over the energy range of 5 to 14 MeV using highly enriched target material. From the measured excitation function the thick target yield of 64Cu was calculated as 6.6 MBq/μAṡh. A comparison with other production routes is given. For production of 140Nd, both natCe(3He,xn)140Nd and 141Pr(p,2n)140Nd processes were studied. For the 141Pr(p,2n)140Nd reaction the results are consistent with the literature data in the early rising part of the excitation function; at higher energies, however, our values differ considerably. The yields of 140Nd via these reactions amount to 22 and 128 MBq/μAṡh, respectively. The excitation function of the 192Os(p,n)192Ir reaction was measured from 6 to 20 MeV and the yield of 192Ir was calculated to be 0.16 MBq/μAṡh.

  13. Near-IR Photoluminescence of Pr/Cu/Sn Tridoped Phosphate Glass: Nonplasmonic Material System Versus Plasmonic Nanocomposite

    NASA Astrophysics Data System (ADS)

    Jiménez, José A.; Sendova, Mariana

    2015-04-01

    An optical spectroscopy study of Pr2O3, CuO, and SnO tridoped barium phosphate glass prepared by the melt-quenching technique has been carried out, emphasizing near-infrared (IR) emission properties. The material is studied in its nonplasmonic state (as synthesized) and plasmonic form (heat-treated), aiming to elucidate the effects of Cu nanoparticles. The data indicate that Cu+ ions and Sn centers are stabilized in the melt-quenched glass. Broad ultraviolet excitations of both species can lead to near-IR emission of Pr3+ ions via energy transfer. The plasmonic nanocomposite is produced upon heat treatment as Sn2+ reduces Cu+ to Cu0 atoms, ultimately precipitating as Cu nanoparticles sustaining the surface plasmon resonance. Consequently, depletion of primarily Cu+ modified the ultraviolet excitation properties for the sensitized near-IR Pr3+ emission. Further, suppression of the Pr3+ emission from near-IR emitting states 1D2 and 1G4 was observed in the Cu nanocomposite in accord with a "plasmonic diluent" role of the nanoparticles.

  14. Overview of IRS Plasma Wind Tunnel Facilities

    DTIC Science & Technology

    2000-04-01

    Saturn system with the 80- 30, 40, Cassini spacecraft, which was designed, built and 120 h launched by NASA [30]. During the entry into Titan’s i 60...launched in 1995, a ring reentry for landing in Cayenne and the re- first experiment was conducted to determine whether quired mass flow within the PWK... formation . In the IRS MPG facility continuous The operating times range typically from several operation with methane components up to 10%, as minutes to

  15. ARO Research Instrumentation Program - IR Spectrometer Procurement

    DTIC Science & Technology

    2015-11-01

    because chemical interactions at the electrode/electrolyte interface determine the type, rate, and efficiency of electron transfer processes that...changes in potential are lengthened significantly primarily due to ion-ion interactions, hydrogen bonding , et cetera that increase the viscosity. This...as C-C stretching and COH and CCH deformation vibrations are observed at 1000-1300 cm-1. The IR spectrum for processed yarn shows hydrogen bonding

  16. Broadband Near IR Laser Hazard Filters

    DTIC Science & Technology

    1992-09-10

    the first quarter of this program, we procured high quality gelatin and ammonium dichromate . It is well known that there are several kinds of...composition of gelatin, ammonium dichromate and water. We attempted to find the optimum coating thickness for 50 nm and 90 nm bandwidth range filters. Annual...fabrication is based on volume Bragg holography using photopolymers and dichromated gelatins. The successful performance of broad- band IR filters

  17. Medical Applications of IR Focal Plane Arrays

    DTIC Science & Technology

    2007-11-02

    vascular disorders, arthritis and rheumatism , pain (management and control), surgery, neonatology, oncology, tissue viability, emergency...specific areas of IR imaging uses are: neurology, vascular disorders, arthritis and rheumatism , pain management and control, tissue viability, oncological...Inflammatory Arthritis ", Clinics in Rheumatic Diseases- Piagnosis and Treatment, Vol.2, p.51-65, 1976 11. Balcerak,R., Jenkins,D.P., Diakides,N.A

  18. Methane Line Intensities: Near and Far IR

    NASA Astrophysics Data System (ADS)

    Brown, Linda R.; Devi, V. Malathy; Wishnow, Edward H.; Sung, Keeyoon; Crawford, Timothy J.; Mantz, Arlan W.; Smith, Mary Ann H.; Predoi-Cross, Adriana; Benner, D. Chris

    2014-11-01

    Accurate knowledge of line intensities is crucial input for radiance calculations to interpret atmospheric observations of planets and moons. We have therefore undertaken extensive laboratory studies to measure the methane spectrum line-by-line in order to improve theoretical quantum mechanical modeling for molecular spectroscopy databases (e. g. HITRAN and GEISA) used by planetary astronomers. Preliminary results will be presented for selected ro-vibrational transitions in both the near-IR (1.66 and 2.2 - 2.4 microns) and the far-IR (80 - 120 microns) regions. For this, we have recorded high-resolution spectra (instrumental resolving power: 1,300,000 (NIR) and 10,000 (FIR)) with the Bruker 125HR Fourier transform spectrometer at JPL using isotopically-enriched 12CH4 and 13CH4, as well as normal methane samples. For the NIR wavelengths, three different absorption cells have been employed to achieve sample temperatures ranging from 78 K to 299 K: 1) a White cell set to a path length of 13.09 m for room temperature data, 2) a single-pass 0.2038 m cold cell and 3) a new coolable Herriott cell with a fixed 20.941 m optical path and configured for the first time to a FT-IR spectrometer. For the Far-IR, another coolable absorption chamber set to a 52 m optical path has been used. These new experiments and intensity measurements will be presented and discussed.Part of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, the University of California, Berkeley, Connecticut College, and NASA Langley under contracts and grants with the National Aeronautics and Space Administration. A. Predoi-Cross and her research group have been supported by the National Science and Engineering Research Council of Canada.

  19. Advances in handheld FT-IR instrumentation

    NASA Astrophysics Data System (ADS)

    Arnó, Josep; Cardillo, Len; Judge, Kevin; Frayer, Maxim; Frunzi, Michael; Hetherington, Paul; Levy, Dustin; Oberndorfer, Kyle; Perec, Walter; Sauer, Terry; Stein, John; Zuidema, Eric

    2012-06-01

    FT-IR spectroscopy is the technology of choice to identify solid and liquid phase unknown samples. The challenges of ConOps (Concepts of Operation) in emergency response and military field applications require a significant redesign of the stationary FT-IR bench-top instruments typically used in laboratories. Specifically, field portable units require high levels of resistance against mechanical shock and chemical attack, ease of use in restrictive gear, quick and easy interpretation of results, and reduced size. In the last 20 years, FT-IR instruments have been re-engineered to fit in small suitcases for field portable use and recently further miniaturized for handheld operation. This article introduces the advances resulting from a project designed to overcome the challenges associated with miniaturizing FT-IR instruments. The project team developed a disturbance-corrected permanently aligned cube corner interferometer for improved robustness and optimized opto-mechanical design to maximize optical throughput and signal-to-noise ratios. Thermal management and heat flow were thoroughly modeled and studied to isolate sensitive components from heat sources and provide the widest temperature operation range. Similarly, extensive research on mechanical designs and compensation techniques to protect against shock and vibration will be discussed. A user interface was carefully created for military and emergency response applications to provide actionable information in a visual, intuitive format. Similar to the HazMatID family of products, state-of-the-art algorithms were used to quickly identify the chemical composition of complex samples based on the spectral information. This article includes an overview of the design considerations, tests results, and performance validation of the mechanical ruggedness, spectral, and thermal performance.

  20. Symbolic fusion of MMW and IR imagery

    NASA Astrophysics Data System (ADS)

    Eggleston, Peter A.; Kohl, Charles A.

    1988-01-01

    This paper describes the software architecture used to construct a multisensor knowledge-based Autonomous Target Recognizer (ATR). An Intermediate Symbolic Representation (SR) of processed data is employed to provide a very powerful method of associative access over data events and their features, thereby supporting data fusion algorithms at the symbolic level. This architecture supports data fusion from multiple sensors, and its operation is described here using MMW range and IR intensity data.

  1. Symbolic Fusion Of MMW And IR Imagery

    NASA Astrophysics Data System (ADS)

    Eggleston, Peter A.; Kohl, Charles A.

    1989-01-01

    This paper describes the software architecture used to construct a multi-sensor knowledge-based Autonomous Target Recognizer (ATR). An Intermediate Symbolic Representation (ISR) of processed data is employed to provide a very powerful method of associative access over data events and their features, thereby supporting data fusion algorithms at the symbolic level. This architecture supports data fusion from multiple sensors, and its operation is described here using MMW range and IR intensity data.

  2. Ir spectra of preparations of ozonized pyrocatechin

    NASA Astrophysics Data System (ADS)

    Khovratovich, N. N.; Novikova, T. M.; Khmel'Nitskii, A. I.; Cherenkevich, S. N.; Loban, V. A.

    1998-03-01

    We investigate IR spectra of the solid phase of products obtained at different stages in the process of ozonizing aqueous solutions of pyrocatechin. We found that melanin structures are formed in the process of pyrocatechin ozonization. The existence of intra- and intermolecular interactions in the melanin preparations formed, leading to the formation of molecular associates, is shown. Thorough treatment of preparations with ozone leads to destruction of polymer systems and formation of water-soluble products of acid type.

  3. CUBISM: CUbe Builder for IRS Spectra Maps

    NASA Astrophysics Data System (ADS)

    Sings Irs Team; Smith, J. D.; Armus, Lee; Bot, Caroline; Buckalew, Brent; Dale, Danny; Helou, George; Jarrett, Tom; Roussel, Helene; Sheth, Kartik

    2011-11-01

    CUBISM, written in IDL, constructs spectral cubes, maps, and arbitrary aperture 1D spectral extractions from sets of mapping mode spectra taken with Spitzer's IRS spectrograph. CUBISM is optimized for non-sparse maps of extended objects, e.g. the nearby galaxy sample of SINGS, but can be used with data from any spectral mapping AOR (primarily validated for maps which are designed as suggested by the mapping HOWTO).

  4. Modeling excitable systems: Reentrant tachycardia

    NASA Astrophysics Data System (ADS)

    Lancaster, Jarrett L.; Hellen, Edward H.; Leise, Esther M.

    2010-01-01

    Excitable membranes are an important type of nonlinear dynamical system, and their study can be used to provide a connection between physical and biological circuits. We discuss two models of excitable membranes important in cardiac and neural tissues. One model is based on the Fitzhugh-Nagumo equations, and the other is based on a three-transistor excitable circuit. We construct a circuit that simulates reentrant tachycardia and its treatment by surgical ablation. This project is appropriate for advanced undergraduates as a laboratory capstone project or as a senior thesis or honors project and can also be a collaborative project, with one student responsible for the computational predictions and another for the circuit construction and measurements.

  5. Recurrent Excitation in Neocortical Circuits

    NASA Astrophysics Data System (ADS)

    Douglas, Rodney J.; Koch, Christof; Mahowald, Misha; Martin, Kevan A. C.; Suarez, Humbert H.

    1995-08-01

    The majority of synapses in the mammalian cortex originate from cortical neurons. Indeed, the largest input to cortical cells comes from neighboring excitatory cells. However, most models of cortical development and processing do not reflect the anatomy and physiology of feedback excitation and are restricted to serial feedforward excitation. This report describes how populations of neurons in cat visual cortex can use excitatory feedback, characterized as an effective "network conductance," to amplify their feedforward input signals and demonstrates how neuronal discharge can be kept proportional to stimulus strength despite strong, recurrent connections that threaten to cause runaway excitation. These principles are incorporated into models of cortical direction and orientation selectivity that emphasize the basic design principles of cortical architectures.

  6. Stochastic excitation of stellar oscillations

    NASA Astrophysics Data System (ADS)

    Samadi, Reza

    2001-05-01

    Since more than about thirty years, solar oscillations are thought to be excited stochastically by the turbulent motions in the solar convective zone. It is currently believed that oscillations of stars lower than 2 solar masses - which possess an upper convective zone - are excited stochastically by turbulent convection in their outer layers. Providing that accurate measurements of the oscillation amplitudes and damping rates are available it is possible to evaluate the power injected into the modes and thus - by comparison with the observations - to constrain current theories. A recent theoretical work (Samadi & Goupil, 2001; Samadi et al., 2001) supplements and reinforces the theory of stochastic excitation of star vibrations. This process was generalized to a global description of the turbulent state of their convective zone. The comparison between observation and theory, thus generalized, will allow to better know the turbulent spectrum of stars, and this in particular thanks to the COROT mission.

  7. Excitation optimization for damage detection

    SciTech Connect

    Bement, Matthew T; Bewley, Thomas R

    2009-01-01

    A technique is developed to answer the important question: 'Given limited system response measurements and ever-present physical limits on the level of excitation, what excitation should be provided to a system to make damage most detectable?' Specifically, a method is presented for optimizing excitations that maximize the sensitivity of output measurements to perturbations in damage-related parameters estimated with an extended Kalman filter. This optimization is carried out in a computationally efficient manner using adjoint-based optimization and causes the innovations term in the extended Kalman filter to be larger in the presence of estimation errors, which leads to a better estimate of the damage-related parameters in question. The technique is demonstrated numerically on a nonlinear 2 DOF system, where a significant improvement in the damage-related parameter estimation is observed.

  8. Modeling Dead OH/IR stars

    NASA Astrophysics Data System (ADS)

    Lorenz-Martins, S.; Ortiz, R.; Khouri, T.; de Araujo, F. X.

    2007-11-01

    OH/IR stars present several OH maser emission lines which are formed in the outer regions of their circumstellar dust envelopes. These stars can be recognized at large distances, based only on radio and infrared observations. They can therefore be used as kinematic tracers in galaxies. The emission at 1612 MHz is the strongest line and presents a double profile (Δv = 20--50 km/s), although in the planetary nebulae phase this line is sometimes no longer detected. In this work we calculate radiative transfer models to describe the dust envelopes of a sample of OH/IR stars. In this sample, the maser emission at 1612 MHz has disappeared. We also included some OH/IR stars in which this maser emission was recently detected. The results show that the physical parameters of the dust envelopes of almost the whole sample are those expected for normal oxygen-rich AGB stars. However, three sources have a different pattern: they present a double-peaked energy dustribution which may be due to an evolved dust envelope.

  9. Choices for Tissue Visualization with IR Microspectroscopy

    SciTech Connect

    Gough,K.; Rak, M.; Bookatz, A.; Del Bigio, M.; Mai, S.; Westaway, D.

    2005-01-01

    In this paper, we address some of the issues associated with infrared (IR) imaging, with reference to our work on brain tissue from the TgCRND8 mouse, a transgenic model of Alzheimer's disease (AD). AD is the most common cause of dementia in the aging population. One of the characteristic hallmarks of this chronic neurodegenerative disorder is the accumulation of plaques in the brain, usually visualized with histochemistry and immunostaining. Although these methods are extremely useful, they illustrate only certain aspects of the sample, require a great amount of tissue processing, and are highly dependent on experimental protocols and reagent quality. IR imaging provides information on multiple components, with a minimal amount of sample processing. However, in order to interpret the data successfully, the issues of spectral acquisition parameters, pre-processing, and spectral artifacts need to be considered. The methods commonly used to process the data, such as uni- and bi-variate spectral analysis, and multivariate methods, such as hierarchical cluster analysis, and some issues concerning the use of second derivatives of IR spectra are discussed.

  10. Illumination analysis of LAPAN's IR micro bolometer

    NASA Astrophysics Data System (ADS)

    Bustanul, A.; Irwan, P.; Andi M., T.

    2016-10-01

    We have since 2 years ago been doing a research in term of an IR Micrometer Bolometer which aims to fulfill our office, LAPAN, desire to put it as one of payloads into LAPAN's next micro satellite project, either at LAPAN A4 or at LAPAN A5. Due to the lack of experience on the subject, everything had been initiated by spectral radiance analysis adjusted by catastrophes sources in Indonesia, mainly wild fire (forest fire) and active volcano. Based on the result of the appropriate spectral radiance wavelength, 3.8 - 4 μm, and field of view (FOV), we, then, went through the further analysis, optical analysis. Focusing in illumination matter, the process was done by using Zemax software. Optical pass Interference and Stray light were two things that become our concern throughout the work. They could also be an evaluation of the performance optimization of illumination analysis of our optical design. The results, graphs, show that our design performance is close diffraction limited and the image blur of the geometrical produced by Lapan's IR Micro Bolometer lenses is in the pixel area range. Therefore, our optical design performance is relatively good and will produce image with high quality. In this paper, the Illumination analysis and process of LAPAN's Infra Red (IR) Micro Bolometer is presented.

  11. Calculation of molecular excitation rates

    NASA Technical Reports Server (NTRS)

    Flynn, George

    1993-01-01

    State-to-state collisional excitation rates for interstellar molecules observed by radio astronomers continue to be required to interpret observed line intensities in terms of local temperatures and densities. A problem of particular interest is collisional excitation of water which is important for modeling the observed interstellar masers. In earlier work supported by a different NASA Grant, excitation of water in collisions with He atoms was studied; after many years of successively more refined calculations that problem now seems to be well understood, and discrepancies with earlier experimental data for related (pressure broadening) phenomena are believed to reflect experimental errors. Because of interstellar abundances, excitation by H2, the dominant interstellar species, is much more important than excitation by He, although it has been argued that rates for excitation by these are similar. Under the current grant theoretical study of this problem has begun which is greatly complicated by the additional degrees of freedom which must be included both in determining the interaction potential and also in the molecular scattering calculation. We have now computed the interaction forces for nearly a thousand molecular geometries and are close to having an acceptable global fit to these points which is necessary for the molecular dynamics calculations. Also, extensive modifications have been made to the molecular scattering code, MOLSCAT. These included coding the rotational basis sets and coupling matrix elements required for collisions of an asymmetric top with a linear rotor. A new method for numerical solution of the coupled equations has been incorporated. Because of the long-ranged nature of the water-hydrogen interaction it is necessary to integrate the equations to rather large intermolecular separations, and the integration methods previously available in MOLSCAT are not ideal for such cases. However, the method used by Alexander in his HIBRIDON code is

  12. Excited-to-excited-state scattering using weak measurements

    NASA Astrophysics Data System (ADS)

    U, Satya Sainadh; Narayanan, Andal

    2015-11-01

    Weak measurements are a subset of measurement processes in quantum mechanics wherein the system, which is being measured, interacts very weakly with the measuring apparatus. Measurement values of observables undergoing a weak interaction and their amplification are concepts that have sharpened our understanding of interaction processes in quantum mechanics. Recent experiments show that naturally occurring processes such as resonance fluorescence from excited states of an atom can exhibit weak value amplification effect. In this paper we theoretically analyze the process of elastic resonance fluorescence from a V -type three-level atomic system, using the well-known Weiskopff-Wigner (WW) theory of spontaneous emission. Within this theory we show that a weak interaction regime can be identified and for suitable choices of initial and final excited states the mean scattering time between these states show an amplification effect during interaction with the vacuum bath modes of the electromagnetic field. We thus show that a system-bath interaction can show weak value amplification. Using our theory we reproduce the published experimental results carried out in such a system. More importantly, our theory can calculate scattering time scales in elastic resonance scattering between multiple excited states of a single atom or between common excited state configurations of interacting multiatom systems.

  13. Time-resolved observation of interatomic excitation-energy transfer in argon dimers.

    PubMed

    Mizuno, Tomoya; Cörlin, Philipp; Miteva, Tsveta; Gokhberg, Kirill; Kuleff, Alexander; Cederbaum, Lorenz S; Pfeifer, Thomas; Fischer, Andreas; Moshammer, Robert

    2017-03-14

    The ultrafast transfer of excitation energy from one atom to its neighbor is observed in singly charged argon dimers in a time-resolved extreme ultraviolet (XUV)-pump IR-probe experiment. In the pump step, bound 3s-hole states in the dimer are populated by single XUV-photon ionization. The excitation-energy transfer at avoided crossings of the potential-energy curves leads to dissociation of the dimer, which is experimentally observed by further ionization with a time-delayed IR-probe pulse. From the measured pump-probe delay-dependent kinetic-energy release of coincident Ar(+) + Ar(+) ions, we conclude that the transfer of energy occurs on a time scale of about 800fs. This mechanism represents a fast relaxation process below the energy threshold for interatomic Coulombic decay.

  14. Autoresonant Excitation of Antiproton Plasmas

    NASA Astrophysics Data System (ADS)

    Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Butler, E.; Carpenter, P. T.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hurt, J. L.; Hydomako, R.; Jonsell, S.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.

    2011-01-01

    We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.

  15. Directional excitation without breaking reciprocity

    NASA Astrophysics Data System (ADS)

    Ramezani, Hamidreza; Dubois, Marc; Wang, Yuan; Shen, Y. Ron; Zhang, Xiang

    2016-09-01

    We propose a mechanism for directional excitation without breaking reciprocity. This is achieved by embedding an impedance matched parity-time symmetric potential in a three-port system. The amplitude distribution within the gain and loss regions is strongly influenced by the direction of the incoming field. Consequently, the excitation of the third port is contingent on the direction of incidence while transmission in the main channel is immune. Our design improves the four-port directional coupler scheme, as there is no need to implement an anechoic termination to one of the ports.

  16. Decentralized nonlinear optimal excitation control

    SciTech Connect

    Lu, Q.; Sun, Y.; Xu, Z.; Mochizuki, T.

    1996-11-01

    A design method to lay emphasis on differential geometric approach for decentralized nonlinear optimal excitation control of multimachine systems is suggested in this paper. The control law achieved is implemented via purely local measurements. Moreover, it is independent of the parameters of power networks. Simulations are performed on a six-machine system. It has been demonstrated that the nonlinear optimal excitation control could adapt to the conditions under large disturbances. Besides, this paper has verified that the optimal control in the sense of LQR principle for the linearized system is equivalent to an optimal control in the sense of a quasi-quadratic performance index for the primitive nonlinear control system.

  17. Ngc7538 Irs1 - A Highly Collimated Ionized Wind Source Powered By Accretion

    NASA Astrophysics Data System (ADS)

    Sandell, Goran H. L.; Wright, M.; Goss, W.; Corder, S.

    2009-01-01

    Recent images show that NGC7538 IRS1 is not a conventional Ultracompact or Hypercompact HII region, but is completely wind-excited (other broad recombination line hypercompact HII regions may be similar to IRS1). NGC 7538 IRS1 is a well studied young high-mass star (L 2 10^5 L_Sun).VLA images at 6 and 2 cm (Cambell 1984; ApJ, 282, L27) showed a compact bipolar core (lobe separation 0.2") with more extended faint lobes. Recombination line observations (Gaume et al. 1995, ApJ, 438, 776) show extremely wide line profiles indicating substantial mass motion of the ionized gas. We re-analyzed high angular resolution VLA archive data from 6 cm to 7 mm, and measured the flux from the compact core and the extended (1.5 - 2") bipolar lobes. We find that the compact core has a spectral index, alpha 0.6, which could be explained by an optically thick hypercompact core with a density gradient. However, the size of the core shrinks with increasing frequency; from 0.24" at 6 cm to 0.1" at 7 mm, consistent with that expected for a collimated jet (Reynolds 1986, ApJ, 304, 713). If we do a crude size correction so that we compare emission from the optically thick inner part of the jet for a set of 2 cm and 7 mm observations we get alpha 1.6, i.e. close to the optically thick value. BIMA and CARMA continuum observations at 3 mm show some dust excess, while. HCO+ J=1-0 observations combined with FCRAO single dish data show a clear inverse P Cygni profile towards IRS1. These observations confirm that IRS1 is heavily accreting with an accretion rate 2 10^-4 M_Sun/year, sufficient to quench the formation of an HII region.

  18. IR decoys modeling method based on particle system

    NASA Astrophysics Data System (ADS)

    Liu, Jun-yu; Wu, Kai-feng; Dong, Yan-bing

    2016-10-01

    Due to the complexity in combustion processes of IR decoys, it is difficult to describe its infrared radiation characteristics by deterministic model. In this work, the IR decoys simulation based on particle system was found. The measured date of the IR decoy is used to analyze the typical characteristic of the IR decoy. A semi-empirical model of the IR decoy motion law has been set up based on friction factors and a IR decoys simulation model has been build up based on particle system. The infrared imaging characteristic and time varying characteristic of the IR decoy were simulated by making use of the particle feature such as lifetime, speed and color. The dynamic IR decoys simulation is realized with the VC++6.0 and OpenGL.

  19. Monitoring Persistence in WFC3/IR after scanned grism observations

    NASA Astrophysics Data System (ADS)

    Sabbi, Elena

    2013-10-01

    This is a calibration program designed to put full frame IR darks exposures immediately following ALL visits with WFC3/IR spatially scanned spectra. This will allow us to measure the persistence and its early decay characteristics.

  20. Is the ``IR Coincidence'' Just That?

    NASA Astrophysics Data System (ADS)

    Nowak, Michael A.; Wilms, Jörn; Heinz, Sebastian; Pooley, Guy; Pottschmidt, Katja; Corbel, Stephane

    2005-06-01

    Previous work by Motch et al. suggested that in the low/hard state of GX 339-4 the soft X-ray power law extrapolated backward in energy agrees with the IR flux level. Corbel & Fender later showed that the typical hard-state radio power law extrapolated forward in energy meets the backward-extrapolated X-ray power law at an IR spectral break, which was explicitly observed twice in GX 339-4. This IR coincidence has been cited as further evidence that synchrotron radiation from a jet might make a significant contribution to the observed X-rays in hard-state black hole systems. We quantitatively explore this hypothesis with a series of simultaneous radio/X-ray observations of GX 339-4, taken during its 1997, 1999, and 2002 hard states. We fit these spectra, in detector space, with a simple, but remarkably successful, doubly broken power-law model that indeed requires an IR spectral break. For these observations, the break position and the integrated radio/IR flux have stronger dependences upon the X-ray flux than the simplest jet model predictions. If one allows for a softening of the X-ray power law with increasing flux, then the jet model can agree with the observed correlation. We also find evidence that the radio flux-X-ray flux correlation previously observed in the 1997 and 1999 GX 339-4 hard states shows a parallel track for the 2002 hard state. The slope of the 2002 correlation is consistent with observations taken in prior hard states; however, the radio amplitude is reduced. We then examine the radio flux-X-ray flux correlation in Cyg X-1 through the use of 15 GHz radio data obtained with the Ryle radio telescope and Rossi X-Ray Timing Explorer data from the All-Sky Monitor and pointed observations. We again find evidence of parallel tracks, and here they are associated with ``failed transitions,'' or the beginning of a transition, to the soft state. We also find that for Cyg X-1 the radio flux is more fundamentally correlated with the hard, rather than the

  1. Is the `IR Coincidence' Just That?

    NASA Astrophysics Data System (ADS)

    Nowak, M.

    2005-09-01

    Previous work by Motch (1985) suggested that in the low/hard state of GX 339-4 the soft X-ray power-law extrapolated backward in energy agrees with the IR flux level. Corbel & Fender (2002) later showed that the typical hard state radio power-law extrapolated forward in energy meets the backward extrapolated X-ray power-law at an IR spectral break, which was explicitly observed twice in GX 339-4. This `IR coincidence' has been cited as further evidence that synchrotron radiation from a jet might make a significant contribution to the observed X-rays in hard state black hole systems. We quantitatively explore this hypothesis with a series of simultaneous radio/X-ray observations of GX 339-4, taken during its 1997, 1999, and 2002 hard states. We fit these spectra, in detector space, with a simple, but remarkably successful, doubly broken power-law model that indeed requires an IR spectral break. For these observations, the break position and the integrated radio/IR flux have stronger dependences upon the X-ray flux than the simplest jet model predictions. If one allows for a softening of the X-ray power law with increasing flux, then the jet model can agree with the observed correlation. We also find evidence that the radio flux/X-ray flux correlation previously observed in the 1997 and 1999 GX 339-4 hard states shows a `parallel track' for the 2002 hard state. The slope of the 2002 correlation is consistent with observations taken in prior hard states; however, the radio amplitude is reduced. We then examine the radio flux/X-ray flux correlation in Cyg X-1 through the use of 15 GHz radio data, obtained with the Ryle radio telescope, and Rossi X-ray Timing Explorer data, from the All Sky Monitor and pointed observations. We again find evidence of `parallel tracks', and here they are associated with `failed transitions' to, or the beginning of a transition to, the soft state. We also find that for Cyg X-1 the radio flux is more fundamentally correlated with the hard

  2. Photochemical dynamics of all-trans retinal protonated Schiff-base in solution: Excitation wavelength dependence

    NASA Astrophysics Data System (ADS)

    Bismuth, Oshrat; Friedman, Noga; Sheves, Mordechai; Ruhman, Sanford

    2007-11-01

    Photochemistry of protonated all-trans retinal Schiff-base (RPSB), the active chromophore in bacteriorhodopsin (BR) and sensory rhodopsins has been investigated with femtosecond multichannel pump probe spectroscopy at two excitation wavelengths. In a recent study of an RPSB analogue which mimics the opsin shift in BR, significant excitation wavelength dependence of the transient spectra was observed and assigned to structural inhomogeneity in the ground state. Our aim is to determine if similar inhomogeneity is manifest also in the native RPSB in solution which is the archtypical model for appreciating the apoproteins effect on retinal protein photochemistry. Significant differences in transient spectra collected after 390 and 480 nm excitation are observed and are likewise assigned to ground state structural inhomogeneity. For both excitation wavelengths the stimulated emission band extends well beyond 900 nm, much deeper than previously reported in the near IR. The shallowness of this feature and a newly revealed dip in its intensity near 760 nm are attributed to an overlapping excited state absorption, as reported for BR. This assignment identifies the documented RPSB excited state absorption band which peaks at 500 nm as the counterpart of the 460 nm absorption feature reported for the reactive excited state of BR coined I 460. Implications of this assignment, and possible mechanisms for inhomogeneous broadening of the electronic absorption spectrum of RPSB in solution are discussed.

  3. HOMA1-IR and HOMA2-IR indexes in identifying insulin resistance and metabolic syndrome: Brazilian Metabolic Syndrome Study (BRAMS).

    PubMed

    Geloneze, Bruno; Vasques, Ana Carolina Junqueira; Stabe, Christiane França Camargo; Pareja, José Carlos; Rosado, Lina Enriqueta Frandsen Paez de Lima; Queiroz, Elaine Cristina de; Tambascia, Marcos Antonio

    2009-03-01

    To investigate cut-off values for HOMA1-IR and HOMA2-IR to identify insulin resistance (IR) and metabolic syndrome (MS), and to assess the association of the indexes with components of the MS. Nondiabetic subjects from the Brazilian Metabolic Syndrome Study were studied (n = 1,203, 18 to 78 years). The cut-off values for IR were determined from the 90th percentile in the healthy group (n = 297) and, for MS, a ROC curve was generated for the total sample. In the healthy group, HOMA-IR indexes were associated with central obesity, triglycerides and total cholesterol (p < 0.001). The cut-off values for IR were: HOMA1-IR > 2.7 and HOMA2-IR > 1.8; and, for MS were: HOMA1-IR > 2.3 (sensitivity: 76.8%; specificity: 66.7%) and HOMA2-IR > 1.4 (sensitivity: 79.2%; specificity: 61.2%). The cut-off values identified for HOMA1-IR and HOMA2-IR indexes have a clinical and epidemiological application for identifying IR and MS in Westernized admixtured multi-ethnic populations.

  4. Structure and elementary properties of the new Ir hollandite Rb{sub 0.17}IrO{sub 2}

    SciTech Connect

    Schoop, Leslie M.; Krizan, Jason W.; Gibson, Quinn D.; Cava, R.J.

    2014-01-15

    We report the synthesis and structural characterization of the new Ir holladite, Rb{sub 0.17}IrO{sub 2}. Rb{sub 0.17}IrO{sub 2} crystallizes in the tetragonal hollandite structure. In contrast to the previously reported monoclinic Ir hollandite K{sub 0.25}IrO{sub 2}, we do not observe a difference in Ir–O bond lengths in Rb{sub 0.17}IrO{sub 2} and thus find Ir in an average oxidation state of + 3.83. We also report and compare the electronic and magnetic properties of Rb{sub 0.17}IrO{sub 2} and K{sub 0.25}IrO{sub 2}, finding that they are both metallic and Pauli paramagnets further supporting that the electrons are delocalized in the Ir 5d states. - Graphical abstract: Crystal structure of Rb{sub 0.17}IrO{sub 2} (right), and the SEM image of Rb{sub 0.17}IrO{sub 2}, showing the growth of thin needles (left). Display Omitted - Highlights: • New iridium hollandite. • Naturally grows in very thin wires. • Elementary physical properties of Ir holladites reported for the first time metallic conductor and paramagnetic.

  5. Studies of Highly Excited Atoms.

    DTIC Science & Technology

    1986-04-02

    much smaller than the laser linewidth . We note that calculations show that a simlar resonance condition does not occur for the 16d state ir FIG. S. Plot...approximately 2 GHz (see Fig. 5) which is comparable shown here the large cross sections and narro . linewidth "- to the width of the previously observed...collison of two Rydherg atoms. We have extensively measured the linewidths and the collision cross sections and have determined their dependence on

  6. Expression of insulin receptor (IR) A and B isoforms, IGF-IR, and IR/IGF-IR hybrid receptors in vascular smooth muscle cells and their role in cell migration in atherosclerosis.

    PubMed

    Beneit, N; Fernández-García, C E; Martín-Ventura, J L; Perdomo, L; Escribano, Ó; Michel, J B; García-Gómez, G; Fernández, S; Díaz-Castroverde, S; Egido, J; Gómez-Hernández, A; Benito, M

    2016-12-01

    Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) is a major contributor to the development of atherosclerotic process. In a previous work, we demonstrated that the insulin receptor isoform A (IRA) and its association with the insulin-like growth factor-I receptor (IGF-IR) confer a proliferative advantage to VSMCs. However, the role of IR and IGF-IR in VSMC migration remains poorly understood. Wound healing assays were performed in VSMCs bearing IR (IRLoxP(+/+) VSMCs), or not (IR(-/-) VSMCs), expressing IRA (IRA VSMCs) or expressing IRB (IRB VSMCs). To study the role of IR isoforms and IGF-IR in experimental atherosclerosis, we used ApoE(-/-) mice at 8, 12, 18 and 24 weeks of age. Finally, we analyzed the mRNA expression of total IR, IRB isoform, IGF-IR and IGFs by qRT-PCR in the medial layer of human aortas. IGF-I strongly induced migration of the four cell lines through IGF-IR. In contrast, insulin and IGF-II only caused a significant increase of IRA VSMC migration which might be favored by the formation of IRA/IGF-IR receptors. Additionally, a specific IGF-IR inhibitor, picropodophyllin, completely abolished insulin- and IGF-II-induced migration in IRB, but not in IRA VSMCs. A significant increase of IRA and IGF-IR, and VSMC migration were observed in fibrous plaques from 24-week-old ApoE(-/-) mice. Finally, we observed a marked increase of IGF-IR, IGF-I and IGF-II in media from fatty streaks as compared with both healthy aortas and fibrolipidic lesions, favoring the ability of medial VSMCs to migrate into the intima. Our data suggest that overexpression of IGF-IR or IRA isoform, as homodimers or as part of IRA/IGF-IR hybrid receptors, confers a stronger migratory capability to VSMCs as might occur in early stages of atherosclerotic process.

  7. Laser-based excitation and diagnostics of planar fractures

    NASA Astrophysics Data System (ADS)

    Blum, T. E.; Van Wijk, K.; Snieder, R.; Willis, M. E.

    2011-12-01

    Faults are of interest not only to earth science, but also at different scales in the non-destructive testing (NDT) community. Remote sensing of faults is of interest to both communities, with the idea of inverting for the fracture properties in a non-invasive way. Alternatively, the wave field directly excited at the fracture is of interest to both communities because the waves thus radiated are equivalent to those emitted by acoustic emissions or micro-earthquakes. Much can be learned from recording of elastic waves excited at the the fracture. Based on technology developed for NDT, we use laser ultrasonics in the laboratory to excite and detect elastic waves, in order to determine the properties of fractures or faults in laboratory rock and synthetic samples. We show examples of wave propagation in a clear Poly(methyl methacrylate) cylinder. By focusing a high power infrared (IR) laser inside the cylinder we create a visible single disk-shaped fracture near the center of the sample. The laser generates a short pulse (~20 ns) of infrared light that is absorbed by the sample material at the focal point and is converted into heat. The sudden thermal expansion generates stress and forms a fracture parallel to the cylindrical axis. We excite elastic waves at the surface of the sample using the same high-power pulsed laser, but at a much lower energy setting, and with an unfocused beam. We measure the direct and scattered wave field from the fracture with a laser interferometer, and also excite the fracture directly with a fraction of the source laser energy impinging directly on the fracture. A comparison of the direct excitation and the elastic scattered wavefields, including studies of the tip diffractions from the fracture, shows strong agreement. The measured tip diffractions carry information about the stress concentration near the crack tips, which is crucial for understanding rupture processes. This novel laboratory technique allows us to measure the source

  8. TAX ADMINISTRATION: IRS Undercover Operations Management Oversight Should Be Strengthened.

    DTIC Science & Technology

    1992-04-01

    stemmed from concerns with IRS’ management of an undercover operation, called Project Layoff , carried out in 1984 and 1985 during which IRS agents... Layoff more specifically in a separate report. An undercover operation is a potentially risky investigative technique. IRS’ Criminal Investigation

  9. IR Cards: Inquiry-Based Introduction to Infrared Spectroscopy

    ERIC Educational Resources Information Center

    Bennett, Jacqueline; Forster, Tabetha

    2010-01-01

    As infrared spectroscopy (IR) is frequently used in undergraduate organic chemistry courses, an inductive introduction to IR spectroscopy that uses index cards printed with spectra, structures, and chemical names is described. Groups of students are given an alphabetized deck of these "IR cards" to sort into functional groups. The students then…

  10. Arbitrage Rebate Compliance: Recent IRS Scrutiny of School Districts.

    ERIC Educational Resources Information Center

    Given, Lynda K.; Gurrola, George E.; Richardson, James R.

    2002-01-01

    Describes rules and procedures school districts must follow to comply with IRS arbitrage and rebate rules and exceptions on profits derived from investing yields of tax-exempt bonds in a higher yielding account. Describes consequences of noncompliance and seven ways to be prepared for an IRS audit--for example, answering the IRS promptly. (PKP)

  11. IR Cards: Inquiry-Based Introduction to Infrared Spectroscopy

    ERIC Educational Resources Information Center

    Bennett, Jacqueline; Forster, Tabetha

    2010-01-01

    As infrared spectroscopy (IR) is frequently used in undergraduate organic chemistry courses, an inductive introduction to IR spectroscopy that uses index cards printed with spectra, structures, and chemical names is described. Groups of students are given an alphabetized deck of these "IR cards" to sort into functional groups. The students then…

  12. OHANA: Eta Carinae's Variability in the Near-IR

    NASA Astrophysics Data System (ADS)

    Mehner, Andrea; de Wit, Willem-Jan; Rivinius, Thomas; Rivinius

    2015-01-01

    Near-IR photometry of η Car since 1972 revealed a long-term trend towards hotter temperatures and a cycloidal behavior of its near-IR colors around periastron passages. Both effects are likely triggered by the companion. We used VLTI AMBER observations from 2004-2014 to investigate η Car's variabilities in the near-IR.

  13. Launch Excitement with Water Rockets

    ERIC Educational Resources Information Center

    Sanchez, Juan Carlos; Penick, John

    2007-01-01

    Explosions and fires--these are what many students are waiting for in science classes. And when they do occur, students pay attention. While we can't entertain our students with continual mayhem, we can catch their attention and cater to their desires for excitement by saying, "Let's make rockets." In this activity, students make simple, reusable…

  14. Elementary Excitations in Quantum Liquids.

    ERIC Educational Resources Information Center

    Pines, David

    1981-01-01

    Discusses elementary excitations and their role in condensed matter physics, focusing on quantum plasma, helium liquids, and superconductors. Considers research primarily conducted in the 1950s and concludes with a brief survey of some closely related further developments. (Author/JN)

  15. Pseudorandom selective excitation in NMR

    NASA Astrophysics Data System (ADS)

    Walls, Jamie D.; Coomes, Alexandra

    2011-09-01

    In this work, average Hamiltonian theory is used to study selective excitation under a series of small flip-angle θ-pulses θ ≪ {π}/{3} applied either periodically [corresponding to the DANTE pulse sequence] or aperiodically to a spin-1/2 system. First, an average Hamiltonian description of the DANTE pulse sequence is developed that is valid for frequencies either at or very far from integer multiples of {1}/{τ}, where τ is the interpulse delay. For aperiodic excitation, a single resonance, νsel, can be selectively excited if the θ-pulse phases are modulated in concert with the interpulse delays. The conditions where average Hamiltonian theory can be accurately applied to describe the dynamics under aperiodic selective pulses, which are referred to as pseudorandom-DANTE or p-DANTE sequences, are similar to those found for the DANTE sequence. Signal averaging over different p-DANTE sequences improves the apparent selectivity at νsel by reducing the excitations at other frequencies. Experimental demonstrations of p-DANTE sequences and comparisons with the theory are presented.

  16. Exciting cytoskeleton-membrane waves

    NASA Astrophysics Data System (ADS)

    Shlomovitz, R.; Gov, N. S.

    2008-10-01

    Propagating waves on the surface of cells, over many micrometers, involve active forces. We investigate here the mechanical excitation of such waves when the membrane is perturbed by an external oscillatory force. The external perturbation may trigger the propagation of such waves away from the force application. This scheme is then suggested as a method to probe the properties of the excitable medium of the cell, and learn about the mechanisms that drive the wave propagation. We then apply these ideas to a specific model of active cellular membrane waves, demonstrating how the response of the system to the external perturbation depends on the properties of the model. The most outstanding feature that we find is that the excited waves exhibit a resonance phenomenon at the frequency corresponding to the tendency of the system to develop a linear instability. Mechanical excitation of membrane waves in cells at different frequencies can therefore be used to characterize the properties of the mechanism underlying the existence of these waves.

  17. Communicating the Excitement of Science

    ScienceCinema

    Michael Turner

    2016-07-12

    In this talk (which will include some exciting science) I will discuss some lessons I have learned about communicating science to scientists (in my own field and others), students, the public, the press, and policy makers in giving 500+ colloquia and seminars, 300+ public lectures and many informal presentations (including cocktail parties).

  18. Predictions for Excited Strange Baryons

    SciTech Connect

    Fernando, Ishara P.; Goity, Jose L.

    2016-04-01

    An assessment is made of predictions for excited hyperon masses which follow from flavor symmetry and consistency with a 1/N c expansion of QCD. Such predictions are based on presently established baryonic resonances. Low lying hyperon resonances which do not seem to fit into the proposed scheme are discussed.

  19. Pattern Formation in Excitable Media

    NASA Astrophysics Data System (ADS)

    Mikhailov, Alexander S.

    1997-03-01

    In this talk I give a short review of the history and the current state of theoretical research on spiral wave patterns in excitable media. I start with the theoretical model of wave propagation in excitable media proposed in 1946 by Wiener and Rosenblueth(N. Wiener and A. Rosenblueth, The mathematical formulation of the problem of conduction of impulses in a network of connected excitable elements, specifically in cardiac muscle, Arch. Inst. Cardiol. Mexico 16 (1946) 205). This model describes spiral waves rotating around obstacles. I show how, by taking additionally into account curvature effects and gradual recovery of the medium after passage of an excitation wave, the model is generalized to describe freely rotating spiral waves and the breakup which produces spirals. In the context of this kinematic model, complex dynamics of spiral waves, i.e. their meandering, drift and resonance, is discussed. Instabilities of spiral waves in confined geometries, i.e. inside a circular region and on a sphere, are analyzed. At the end, I show how spiral waves in such systems can be efficiently controlled by application of a delayed global feedback. The talk is based on the review paper(A. S. Mikhailov, V. A. Davydov, and V. S. Zykov, Complex dynamics of spiral waves and motion of curves, Physica D 70 (1994) 1) and the monograph(A. S. Mikhailov, Foundations of Synergetics I, 2nd revised edition (Springer, Berlin, 1994)).

  20. Elementary Excitations in Quantum Liquids.

    ERIC Educational Resources Information Center

    Pines, David

    1981-01-01

    Discusses elementary excitations and their role in condensed matter physics, focusing on quantum plasma, helium liquids, and superconductors. Considers research primarily conducted in the 1950s and concludes with a brief survey of some closely related further developments. (Author/JN)

  1. Launch Excitement with Water Rockets

    ERIC Educational Resources Information Center

    Sanchez, Juan Carlos; Penick, John

    2007-01-01

    Explosions and fires--these are what many students are waiting for in science classes. And when they do occur, students pay attention. While we can't entertain our students with continual mayhem, we can catch their attention and cater to their desires for excitement by saying, "Let's make rockets." In this activity, students make simple, reusable…

  2. Excitation processes in cometary comae

    NASA Astrophysics Data System (ADS)

    Singh, P. D.

    The excitation of cometary NH and S2 molecules is discussed. Particular attention is given to emission bands due to a specific S2 transition in the range of 2829-3058 A observed in the UV spectra of comet IRAS Araki-Alcock (1983). It is suggested that photodissociation and dissociative electron recombination processes may be sources of metastable nitrogen atoms in comets.

  3. Perceptual Load Alters Visual Excitability

    ERIC Educational Resources Information Center

    Carmel, David; Thorne, Jeremy D.; Rees, Geraint; Lavie, Nilli

    2011-01-01

    Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load…

  4. Dynamics of excited molecular states

    NASA Astrophysics Data System (ADS)

    Meyer, Hans-Dieter

    2005-01-01

    The photo-excitation or photo-ionization of a polyatomic molecule is typically accompanied by a strong excitation of the vibrational modes. In particular when a conical intersection of the electronic potential energy surfaces involved lies within or close to the Frank-Condon zone, the nuclear motion becomes very complicated, often chaotic, and the spectra become irregular and dense. An accurate simulation of the dynamics of such excited molecules requires firstly that the multi-dimensional and multi-state potential energy surface - or a reliable model thereof - can be determined. Secondly, the multi-dimensional quantum dynamics have to be solved. This is a very difficult task, because of the high dimensionality of the problem (6 to 30 degrees of freedom, say). The multi-configuration time-dependent Hartree (MCTDH) method has proven to be very useful for the study of such problems. In fact, an accurate treatment of the quantal dynamics of molecules like the allene cation (C3 H+4, 15D), the butatriene cation (C4 H+4, 18D), or the pyrazine molecule (C4N2H4, 24D) in their full dimensionality, is - up to date - only possible with MCTDH. (The acronym n D denotes the dimensionality.) The construction of the vibronic model Hamiltonian and the MCTDH method will be briefly discussed. After this, the excited state dynamics of the butatriene and pyrazine molecules will be discussed.

  5. Fast excitation variable period wiggler

    SciTech Connect

    van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.

    1991-01-01

    The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced field reflectors,'' is discussed and experimental results obtained with short wiggler models are presented.

  6. Fast excitation variable period wiggler

    SciTech Connect

    van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.

    1991-12-31

    The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced ``field reflectors,`` is discussed and experimental results obtained with short wiggler models are presented.

  7. Communicating the Excitement of Science

    SciTech Connect

    Michael Turner

    2009-06-05

    In this talk (which will include some exciting science) I will discuss some lessons I have learned about communicating science to scientists (in my own field and others), students, the public, the press, and policy makers in giving 500+ colloquia and seminars, 300+ public lectures and many informal presentations (including cocktail parties).

  8. Effects of Multiple Photon Scattering in Deciduous Tree Canopies

    DTIC Science & Technology

    2009-12-01

    SCATTERING IN DECIDUOUS TREE CANOPIES 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62204F 6. AUTHOR(S...where mh 18= , 16132.0 −= mLm , and 85.0=hzm . Note that the value for mL corresponds to our own experimental results, as will be described in Section 4

  9. Detection of chemical explosives using multiple photon signatures.

    PubMed

    Loschke, K W; Dunn, W L

    2010-01-01

    A template-matching procedure is being investigated for rapid detection of improvised explosive devices at standoff distances. Photon-scattered and photon-induced positron annihilation radiation responses are being studied as a part of a signature-based radiation scanning approach. Back-streaming radiation responses, called signatures, are compared to templates, which are collections of the same signatures if the interrogated volume contained a significant amount of explosive. Experiments have been conducted that show that explosive surrogates (fertilizers) can be distinguished from several inert materials. Copyright 2009 Elsevier Ltd. All rights reserved.

  10. Molecular tectonics: heterometallic (Ir,Cu) grid-type coordination networks based on cyclometallated Ir(III) chiral metallatectons.

    PubMed

    Xu, Chaojie; Guenet, Aurélie; Kyritsakas, Nathalie; Planeix, Jean-Marc; Hosseini, Mir Wais

    2015-10-11

    A chiral-at-metal Ir(III) organometallic metallatecton was synthesised as a racemic mixture and as enantiopure complexes and combined with Cu(II) to afford a heterobimetallic (Ir,Cu) grid-type 2D coordination network.

  11. Letter : NIR FT-Raman microspectroscopy of fluid inclusions: Comparisons with VIS Raman and FT-IR microspectroscopies

    NASA Astrophysics Data System (ADS)

    Pironon, J.; Sawatzki, J.; Dubessy, J.

    1991-12-01

    The first Raman spectra of hydrocarbon inclusions using Fourier transform (FT) Raman microspectroscopy were obtained with a 1064 nm laser excitation in the near-infrared range (NIR FT-Raman). Some inclusions reveal the typical CH vibrational bands of organic compounds, but most of the inclusions that are fluorescent during visible Raman microspectroscopy (514 nm excitation) are still fluorescent in the NIR range. These Raman spectra are presented and compared to the conventional visible (VIS) Raman and FT-IR spectra. For spectra obtained on the same nonfluorescent inclusion, the signal/background ratio is lower in NIR FT-Raman than in VIS Raman. This ratio should be improved by application of more sensitive detectors. The increase of the power density (laser power/impact laser area) could be a future improvement in the limit of thermal background excitation and pyrolysis of the oils trapped in inclusions.

  12. Synthesis and photophysical properties of Ir(iii)/Re(i) dyads: control of Ir→Re photoinduced energy transfer.

    PubMed

    Saad, Suad T; Metherell, Alexander J; Baggaley, Elizabeth; Ward, Michael D

    2016-07-28

    A series of dinuclear Ir(iii)/Re(i) complexes has been prepared based on a family of symmetrical bridging ligands containing two bidentate N,N'-chelating pyrazolyl-pyridine termini, connected by a central aromatic or aliphatic spacer. The Ir(iii) termini are based on {Ir(F2ppy)2}(+) units (where F2ppy is the cyclometallating anion of a fluorinated phenylpyridine) and the Re(i) termini are based on {Re(CO)3Cl} units. Both types of terminus are luminescent, with the Ir-based unit showing characteristic strong, structured phosphorescence in the blue region (maximum 452 nm) with a triplet excited state energy of 22 200 cm(-1) and the Re-based unit showing much weaker and lower-energy phosphorescence (maximum 530 nm) with a triplet excited state energy of 21 300 cm(-1). The energy gradient between the two excited states allows for partial Ir→Re photoinduced energy-transfer, with substantial (but incomplete) quenching of the higher-energy Ir-based emission component and sensitised emission - evidenced by an obvious grow-in component - on the lower-energy Re-based emission. The Ir→Re energy-transfer rate constants vary over the range 1-8 × 10(7) s(-1) depending on the bridging ligand: there is no simple correlation between bridging ligand structure and energy-transfer rate, possibly because this will depend substantially on the conformation of these flexible molecules in solution. To test the role of ligand conformation further, we investigated a complex in which the bridging chain is a (CH2CH2O)6 unit whose conformation is known to be solvent-polarity dependent, with such chains adopting an open, elongated conformation in water and more compact, folded conformations in organic solvents. There was a clear link between the rate and extent of Ir→Re energy-transfer which reduced in polar solvents as the chain became elongated and the Ir/Re separation was larger; and increased in less polar solvents as the chain adopted a more compact conformation and the Ir

  13. Near-IR imaging toward a puzzling young stellar object precessing jet

    NASA Astrophysics Data System (ADS)

    Paron, S.; Fariña, C.; Ortega, M. E.

    2016-10-01

    Aims: The study of jets that are related to stellar objects in formation is important because it enables us to understand the history of how the stars have built up their mass. Many studies currently examine jets towards low-mass young stellar objects, while equivalent studies toward massive or intermediate-mass young stellar objects are rare. In a previous study, based on 12CO J = 3-2 and public near-IR data, we found highly misaligned molecular outflows toward the infrared point source UGPS J185808.46+010041.8 (IRS) and some infrared features suggesting the existence of a precessing jet. Methods: Using near-IR data acquired with Gemini-NIRI at the JHKs broad- and narrowbands centered on the emission lines of [FeII], H2 1-0 S(1), H2 2-1 S(1), Brγ, and CO 2-0 (bh), we studied the circumstellar environment of IRS with an angular resolution between 0.̋35 and 0.̋45. Results: The emission in the JHKs broadbands shows in great detail a cone-shaped nebula extending to the north-northeast of the point source, which appears to be attached to it by a jet-like structure. In the three bands the nebula is resolved in a twisted-shaped feature composed of two arc-like features and a bow-shock-like structure seen mainly in the Ks band, which strongly suggests the presence of a precessing jet. An analysis of proper motions based on our Gemini observations and UKIDSS data additionally supports the precession scenario. We present one of the best-resolved cone-like nebula that is most likely related to a precessing jet up to date. The analysis of the observed near-IR lines shows that the H2 is collisionally excited, and the spatially coincidence of the [FeII] and H2 emissions in the closer arc-like feature suggests that this region is affected by a J shock. The second arc-like feature presents H2 emission without [FeII], which suggests a nondissociated C shock or a less energetic J shock. The H2 1-0 S(1) continuum-subtracted image reveals several knots and filaments at a larger

  14. Mechanism of pain relief by low-power infrared irradiation: ATP is an IR-target molecule in nociceptive neurons.

    PubMed

    Yachnev, Igor L; Plakhova, Vera B; Podzorova, Svetlana A; Shelykh, Tatiana N; Rogachevsky, Ilya V; Krylov, Boris V

    2012-01-01

    Effects of infrared (IR) radiation generated by a low-power CO2-laser on the membrane of cultured dissociated nociceptive neurons of newborn rat spinal ganglia were investigated using the whole-cell patch-clamp method. Low-power IR radiation diminished the voltage sensitivity of activation gating machinery of slow sodium channels (Na(v)1.8). Ouabain known to block both transducer and pumping functions of Na+,K+-ATPase eliminated IR irradiation effects. The molecular mechanism of interaction of CO2-laser radiation with sensory membrane was proposed. The primary event of this interaction is the process of energy absorption by ATP molecules. The transfer of vibrational energy from Na+,K+- ATPase-bound and vibrationally excited ATP molecules to Na+,K+-ATPase activates this enzyme and converts it into a signal transducer. This effect leads to a decrease in the voltage sensitivity of Na(v)1.8 channels. The effect of IR-radiation was elucidated by the combined application of a very sensitive patch-clamp method and an optical facility with a controlled CO2-laser. As a result, the mechanism of interaction of non-thermal low-power IR radiation with the nociceptive neuron membrane is suggested.

  15. ToO IRS Observations of Novae

    NASA Astrophysics Data System (ADS)

    Woodward, Charles; Black, John; Bode, Michael; Evans, Aneuryn; Geballe, Thomas; Gehrz, Robert; Greenhouse, Matthew; Hauschildt, Peter; Helton, Andrew; Krautter, Joachim; Liller, William; Lyke, James; Lynch, David; Rudy, Richard; Salama, Alberto; Schwarz, Greg; Shore, Steve; Starrfield, Sumner; Truran, Jim; Vanlandingham, Karen; Wagner, R. Mark

    2006-05-01

    Stars are the engines of energy production and chemical evolution in our Universe. They deposit radiative and mechanical energy into their environments and enrich the ambient interstellar medium with elements synthesized in their interiors and dust grains condensed in their atmospheres. Classical novae (CN) contribute to this cycle of chemical enrichment through explosive nucleosynthesis and the violent ejection of material dredged from the white dwarf progenitor and mixed with the accreted surface layers. Using Spitzer (+IRS), we propose a 25.8 hrs no-impact ToO program to study (in temporal detail) the evolutionary stages of CN by targeting 4 Galactic and 2 Magellanic Cloud (MC) novae. Spitzer is a unique facility that enables us to investigate aspects of the CN phenomenon including the in situ formation and astromineralogy of nova dust, the elemental abundances resulting from thermonuclear runaway, the correlation of ejecta masses with progenitor type, the bolometric luminosities of the outburst, and the kinematics and structure of the ejected envelopes. Synoptic, high signal-to-noise IRS spectra permit: 1) determination of the grain size distribution and mineral composition of nova dust; 2) estimation of chemical abundances of nova ejecta from coronal and other emission line spectroscopy; 3) measurement of the density and masses of the ejecta; 4) characterization of the geometry and structure of ejected shells at early stages during which the initial mixing of the chemical abundances can be studied in detail; and 5) exploration of the characteristics of CN in low metallicity systems (MC) at mid- to far-IR wavelengths. Observations of CN with Spitzer will be complemented by extensive ground-based, as well as space-based (e.g., Chandra, Swift, XMM-Newton), DDT and ToO programs led by team CoIs.

  16. High-fidelity synthetic IR imaging model

    NASA Astrophysics Data System (ADS)

    Wegener, Michael; Drake, Richard

    2000-07-01

    This paper describes a High Fidelity Synthetic IR Imaging Model which attempts to generate accurate static images as would be seen by a defined IR sensor given the target type and the atmospheric conditions. The model attempts to be quite general in its accommodation of physical processes yet maintain radiometric accuracy. Its main application are to assist in the validation of real-time IR scene generation software, and as a tool which can be used for range performance studies of electro-optical systems. The software model allows facet modeling of targets including temperature profiles and material properties. LOWTRAN/MODTRAN is used to provide atmospheric data for transmittance and self-radiation. Optical systems are described in terms of their transmittance and point spread function, both as functions of wavelength, and a self radiation term having temperature and material properties. At each wavelength desired the model generates descriptions of the flux distribution falling on the focal plane of the sensor system. The flux from different sources is added together to form the total flux distribution on the focal plane. Pixels on the focal plane are modeled by groups of facets with associated material properties allowing the shape and wavelength sensitivity to be expressed. The raw pixel output is obtained by integrating the flux distribution over the component facets and across wavelengths. Following non-uniformity modeling a convolution is applied which models readout smearing. Bandlimited noise is then added. The model is also able to generate and apply a matched filter to the output image. The model is designed to use common commercial software tools such as Multigen for target modeling and Open GL for the rendering. The model currently executes on Silicon Graphics hardware.

  17. Understanding Preprocedure Patient Flow in IR.

    PubMed

    Zafar, Abdul Mueed; Suri, Rajeev; Nguyen, Tran Khanh; Petrash, Carson Cope; Fazal, Zanira

    2016-08-01

    To quantify preprocedural patient flow in interventional radiology (IR) and to identify potential contributors to preprocedural delays. An administrative dataset was used to compute time intervals required for various preprocedural patient-flow processes. These time intervals were compared across on-time/delayed cases and inpatient/outpatient cases by Mann-Whitney U test. Spearman ρ was used to assess any correlation of the rank of a procedure on a given day and the procedure duration to the preprocedure time. A linear-regression model of preprocedure time was used to further explore potential contributing factors. Any identified reason(s) for delay were collated. P < .05 was considered statistically significant. Of the total 1,091 cases, 65.8% (n = 718) were delayed. Significantly more outpatient cases started late compared with inpatient cases (81.4% vs 45.0%; P < .001, χ(2) test). The multivariate linear regression model showed outpatient status, length of delay in arrival, and longer procedure times to be significantly associated with longer preprocedure times. Late arrival of patients (65.9%), unavailability of physicians (18.4%), and unavailability of procedure room (13.0%) were the three most frequently identified reasons for delay. The delay was multifactorial in 29.6% of cases (n = 213). Objective measurement of preprocedural IR patient flow demonstrated considerable waste and highlighted high-yield areas of possible improvement. A data-driven approach may aid efficient delivery of IR care. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

  18. Band Excitation Kelvin probe force microscopy utilizing photothermal excitation

    DOE PAGES

    Collins, Liam; Jesse, Stephen; Balke, Nina; ...

    2015-03-13

    A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standardmore » ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.« less

  19. Band Excitation Kelvin probe force microscopy utilizing photothermal excitation

    SciTech Connect

    Collins, Liam; Jesse, Stephen; Balke, Nina; Rodriguez, Brian J.; Kalinin, Sergei; Li, Qian

    2015-03-13

    A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standard ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.

  20. Stabilizing Ir(001) Epitaxy on Yttria-Stabilized Zirconia Using a Thin Ir Seed Layer Grown by Pulsed Laser Deposition

    SciTech Connect

    Fan, Lisha; Jacobs, Christopher B.; Rouleau, Christopher M.; Eres, Gyula

    2016-11-18

    In this paper, we demonstrate the reproducible epitaxial growth of 100 nm thick Ir(001) films on a heteroepitaxial stack consisting of 5 nm Ir and 100 nm yttria-stabilized zirconia (YSZ) grown on Si(001) substrates. It is shown that a 5 nm thick Ir layer grown by pulsed laser deposition in the same chamber as the YSZ film without breaking the vacuum is the key to stabilizing Ir(001) epitaxial growth. Growth of the Ir seed layer with pure (001) orientation occurs only in a narrow growth temperature window from 550 to 750 °C, and the fraction of Ir(111) increases at substrate temperatures outside of this window. The Ir seed layer prevents exposure of the YSZ film to air during sample transfer and enables highly reproducible Ir(001) heteroepitaxy on YSZ buffered Si(001). In contrast, if Ir is grown directly on a bare YSZ layer that was exposed to ambient conditions, the films are prone to change orientation to (111). These results reveal that preserving the chemical and structural purity of the YSZ surface is imperative for achieving Ir(001) epitaxy. The narrow range of the mosaic spread values from eight experiments demonstrates the high yield and high reproducibility of Ir(001) heteroepitaxy by this approach. Lastly, the improved Ir(001) epitaxial growth method is of great significance for integrating a variety of technologically important materials such as diamond, graphene, and functional oxides on a Si platform.