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Sample records for absorption two-photon absorption

  1. Optimizing ultrashort laser pulse compression by two photon absorption

    NASA Astrophysics Data System (ADS)

    Welch, G.; Frisch, J.; Smith, S.; Glownia, J. M.; Fry, A.

    2016-02-01

    Demonstrated is an approach for relative optimization of ultrashort pulses using two-photon generated photocurrent in a GaAsP photodiode. Two-photon absorption is a nonlinear process, allowing for highly sensitive tuning of ultrashort laser systems.

  2. Full Quantum Analysis of Two-Photon Absorption Using Two-Photon Wave Function: Comparison of Two-Photon Absorption with One-Photon Absorption

    NASA Astrophysics Data System (ADS)

    Nakanishi, Toshihiro; Kobayashi, Hirokazu; Sugiyama, Kazuhiko; Kitano, Masao

    2009-10-01

    For dissipation-free photon-photon interaction at the single photon level, we analyze one-photon and two-photon transitions induced by photon pairs in three-level atoms using two-photon wave functions. We show that two-photon absorption can be substantially enhanced by adjusting the time correlation of photon pairs. We study two typical cases: a Gaussian wave function and a rectangular wave function. In the latter, we find that under special conditions one-photon transition is completely suppressed, while two-photon transition is maintained with a high probability.

  3. Two-photon absorption by a quantum dot pair

    NASA Astrophysics Data System (ADS)

    Scheibner, Michael; Economou, Sophia E.; Ponomarev, Ilya V.; Jennings, Cameron; Bracker, Allan S.; Gammon, Daniel

    2015-08-01

    The biexciton absorption spectrum of a pair of InAs/GaAs quantum dots is being studied by photoluminescence excitation spectroscopy. An absorption resonance with the characteristics of an instantaneous two-photon process reveals a coherent interdot two-photon transition. Pauli-selective tunneling is being used to demonstrate the transduction of the two-photon coherence into a nonlocal spin singlet state. The two-photon transition can be tuned spectrally by electric field, enabling amplification of its transition strength.

  4. The use of CNDO in spectroscopy. XV. Two photon absorption

    NASA Astrophysics Data System (ADS)

    Marchese, Francis T.; Seliskar, C. J.; Jaffé, H. H.

    1980-04-01

    Two-photon absorptivities have been calculated within the CNDO/S-CI molecular orbital framework of Del Bene and Jaffé utilizing the second order time dependent perturbation equations of Göppert-Mayer and polarization methods of McClain. Good agreement is found between this theory and experiment for transition energies, symmetries, and two-photon absorptivities for the following molecules: biphenyl, terphenyl, 2,2'-difluorobiphenyl, 2,2'-bipyridyl, phenanthrene, and the isoelectronic series: fluorene, carbazole, dibenzofuran.

  5. Two-photon absorption spectroscopy of rubrene single crystals

    NASA Astrophysics Data System (ADS)

    Irkhin, Pavel; Biaggio, Ivan

    2014-05-01

    We determine the wavelength dependence of the two-photon absorption cross section in rubrene single crystals both by direct measurement of nonlinear transmission and from the two-photon excitation spectrum of the photoluminescence. The peak two-photon absorption coefficient for b-polarized light was found to be (4.6±1)×10-11 m/W at a wavelength of 850±10 nm. It is 2.3 times larger for c-polarized light. The lowest energy two-photon excitation peak corresponds to an excited state energy of 2.92±0.04 eV and it is followed by a vibronic progression of higher energy peaks separated by ˜0.14 eV.

  6. Chromophore design for large two-photon absorption

    NASA Astrophysics Data System (ADS)

    Dudley, Christopher

    2014-11-01

    Conjugated oligothiophene chromophores are compared and studied for designing large linear and nonlinear absorption cross-sections. Optical properties of chromophores synthesized by the Naval Research Laboratory are modeled to construct a design factor of merit to predict and understand two-photon absorption (TPA) designs. Computer modeling to optimize parameters to produce photo active chromophores is conducted. Geometry, π-center (electron relay) and the electron donor or acceptor groups attached to the π-centers are considered for importance in TPA. This work could serve equally well as guide for quick back of the envelop research or industrial design verifications as well as an outline for introducing computation methods to students.

  7. Two-Photon Absorption in Organometallic Bromide Perovskites.

    PubMed

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P; Bakr, Osman M; Sargent, Edward H

    2015-09-22

    Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals' large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW(-1) at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  8. Synergistic Two-Photon Absorption Enhancement in Photosynthetic Light Harvesting

    NASA Astrophysics Data System (ADS)

    Chen, Kuo-Mei; Chen, Yu-Wei; Gao, Ting-Fong

    2012-06-01

    The grand scale fixation of solar energies into chemical substances by photosynthetic reactions of light-harvesting organisms provides Earth's other life forms a thriving environment. Scientific explorations in the past decades have unraveled the fundamental photophysical and photochemical processes in photosynthesis. Higher plants, green algae, and light-harvesting bacteria utilize organized pigment-protein complexes to harvest solar power efficiently and the resultant electronic excitations are funneled into a reaction center, where the first charge separation process takes place. Here we show experimental evidences that green algae (Chlorella vulgaris) in vivo display a synergistic two-photon absorption enhancement in their photosynthetic light harvesting. Their absorption coefficients at various wavelengths display dramatic dependence on the photon flux. This newly found phenomenon is attributed to a coherence-electronic-energy-transfer-mediated (CEETRAM) photon absorption process of light-harvesting pigment-protein complexes of green algae. Under the ambient light level, algae and higher plants can utilize this quantum mechanical mechanism to create two entangled electronic excitations adjacently in their light-harvesting networks. Concerted multiple electron transfer reactions in the reaction centers and oxygen evolving complexes can be implemented efficiently by the coherent motion of two entangled excitons from antennae to the charge separation reaction sites. To fabricate nanostructured, synthetic light-harvesting apparatus, the paramount role of the CEETRAM photon absorption mechanism should be seriously considered in the strategic guidelines.

  9. Temperature dependence of the two photon absorption in indium arsenide

    SciTech Connect

    Berryman, K.W.; Rella, C.W.

    1995-12-31

    Nonlinear optical processes in semiconductors have long been a source of interesting physics. Two photon absorption (TPA) is one such process, in which two photons provide the energy for the creation of an electron-hole pair. Researchers at other FEL centers have studied room temperature TPA in InSb, InAs, and HgCdTe. Working at the Stanford Picosecond FEL Center, we have extended and refined this work by measuring the temperature dependence of the TPA coefficient in InAs over the range from 80 to 350 K at four wavelengths: 4.5, 5.06, 6.01, and 6.3 microns. The measurements validate the functional dependence of recent band structure calculations with enough precision to discriminate parabolic from non-parabolic models, and to begin to observe smaller effects, such as contributions due to the split-off band. These experiments therefore serve as a strong independent test of the Kane band theory, as well as providing a starting point for detailed observations of other nonlinear absorption mechanisms.

  10. Two photon absorption in high power broad area laser diodes

    NASA Astrophysics Data System (ADS)

    Dogan, Mehmet; Michael, Christopher P.; Zheng, Yan; Zhu, Lin; Jacob, Jonah H.

    2014-03-01

    Recent advances in thermal management and improvements in fabrication and facet passivation enabled extracting unprecedented optical powers from laser diodes (LDs). However, even in the absence of thermal roll-over or catastrophic optical damage (COD), the maximum achievable power is limited by optical non-linear effects. Due to its non-linear nature, two-photon absorption (TPA) becomes one of the dominant factors that limit efficient extraction of laser power from LDs. In this paper, theoretical and experimental analysis of TPA in high-power broad area laser diodes (BALD) is presented. A phenomenological optical extraction model that incorporates TPA explains the reduction in optical extraction efficiency at high intensities in BALD bars with 100μm-wide emitters. The model includes two contributions associated with TPA: the straightforward absorption of laser photons and the subsequent single photon absorption by the holes and electrons generated by the TPA process. TPA is a fundamental limitation since it is inherent to the LD semiconductor material. Therefore scaling the LDs to high power requires designs that reduce the optical intensity by increasing the mode size.

  11. Exploring Entangled Two-Photon Absorption in Molecules

    NASA Astrophysics Data System (ADS)

    Caraher, John

    2014-05-01

    Goodson and colleagues have reported anomalously large cross-sections (of order σ =10-17 cm2) for the two-photon absorption of entangled photons in a number of molecules. This poster reports on attempts to replicate and expand upon their results for one of these, zinc tetraphenylporphyrin (Zn TPP) in chloroform solution. It will also discuss the interpretation of the Goodson group's experimental data, particularly their results regarding entanglement area and entanglement time (the spatial and temporal widths of the fourth-order coherence functions, respectively). Results of direct measurement of entanglement time (via a Hong-Ou-Mandel interferometer) for a laser and optical system essentially identical to the one used in Goodson's work will be presented and compared with their reported values. Supported by the DePauw University Faculty Development Committee.

  12. Two-Photon Absorption in Conjugated Energetic Molecules.

    PubMed

    Bjorgaard, Josiah A; Sifain, Andrew E; Nelson, Tammie; Myers, Thomas W; Veauthier, Jacqueline M; Chavez, David E; Scharff, R Jason; Tretiak, Sergei

    2016-07-01

    Time-dependent density functional theory (TD-DFT) was used to investigate the relationship between molecular structure and the one- and two-photon absorption (OPA and TPA, respectively) properties of novel and recently synthesized conjugated energetic molecules (CEMs). The molecular structures of CEMs can be strategically altered to influence the heat of formation and oxygen balance, two factors that can contribute to the sensitivity and strength of an explosive material. OPA and TPA are sensitive to changes in molecular structure as well, influencing the optical range of excitation. We found calculated vertical excitation energies to be in good agreement with experiment for most molecules. Peak TPA intensities were found to be significant and on the order of 10(2) GM. Natural transition orbitals for essential electronic states defining TPA peaks of relatively large intensity were used to examine the character of relevant transitions. Modification of molecular substituents, such as additional oxygen or other functional groups, produces significant changes in electronic structure, OPA, and TPA and improves oxygen balance. The results show that certain molecules are apt to undergo nonlinear absorption, opening the possibility for controlled, direct optical initiation of CEMs through photochemical pathways. PMID:27257984

  13. Two-Photon-Absorption Scheme for Optical Beam Tracking

    NASA Technical Reports Server (NTRS)

    Ortiz, Gerardo G.; Farr, William H.

    2011-01-01

    A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector material was demonstrated. This tracking scheme is part of the canonical architecture described in the preceding article. TPA is used to track a long-wavelength transmit laser while direct absorption on the same sensor simultaneously tracks a shorter-wavelength beacon. The TPA responsivity was measured for silicon using a PIN photodiode at a laser beacon wavelength of 1,550 nm. As expected, the responsivity shows a linear dependence with incident power level. The responsivity slope is 4.5 x 10(exp -7) A/W2. Also, optical beam spots from the 1,550-nm laser beacon were characterized on commercial charge coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) imagers with as little as 13.7 microWatts of optical power (see figure). This new tracker technology offers an innovative solution to reduce system complexity, improve transmit/receive isolation, improve optical efficiency, improve signal-to-noise ratio (SNR), and reduce cost for free-space optical communications transceivers.

  14. Frequency upconversion and two-photon absorption of salicylaldehyde azine 1

    NASA Astrophysics Data System (ADS)

    Souza, A. B.; Alencar, M. A. R. C.; Cardoso, S. H.; Valle, M. S.; Diniz, R.; Hickmann, J. M.

    2013-10-01

    Two-photon absorption and two-photon excitation fluorescence of salicylaldehyde azine 1 crystals were investigated. It was observed an intense visible fluorescence when this material was excited with a laser tuned at the near infrared region. Varying the laser intensity we characterized this phenomenon as a simultaneous two-photon laser absorption process. Using open aperture Z-scan measurements we characterized this two-photon absorption phenomenon and measured the value of the two-photon absorption cross-section of this molecule to be equal to 87 GM. Our results indicate that this is a promising organic material aiming nonlinear photonics applications.

  15. Effect of morphology and solvent on two-photon absorption of nano zinc oxide

    SciTech Connect

    Kavitha, M.K.; Haripadmam, P.C.; Gopinath, Pramod; Krishnan, Bindu; John, Honey

    2013-05-15

    Highlights: ► ZnO nanospheres and triangular structures synthesis by novel precipitation technique. ► The effect of precursor concentration on the size and shape of nano ZnO. ► Open aperture Z-scan measurements of the ZnO nanoparticle dispersions. ► Nanospheres exhibit higher two photon absorption coefficient than triangular nanostructures. ► Nanospheres dispersed in water exhibit higher two photon absorption coefficient than its dispersion in 2-propanol. - Abstract: In this paper, we report the effect of morphology and solvent on the two-photon absorption of nano zinc oxide. Zinc oxide nanoparticles in two different morphologies like nanospheres and triangular nanostructures are synthesized by novel precipitation technique and their two-photon absorption coefficient is measured using open aperture Z-scan technique. Experimental results show that the zinc oxide nanospheres exhibit higher two-photon absorption coefficient than the zinc oxide triangular nanostructures. The zinc oxide nanospheres dispersed in water exhibit higher two-photon absorption coefficient than that of its dispersion in 2-propanol. The zinc oxide nanospheres dispersed in water shows a decrease in two-photon absorption coefficient with an increase in on-axis irradiance. The result confirms the dependence of shape and solvent on the two-photon absorption of nano zinc oxide.

  16. Measurement of Two-Photon Absorption Cross Section of Metal Ions by a Mass Sedimentation Approach

    PubMed Central

    Ma, Zhuo-Chen; Chen, Qi-Dai; Han, Bing; Liu, Xue-Qing; Song, Jun-Feng; Sun, Hong-Bo

    2015-01-01

    The photo-reduction of metal ions in solution induced by femtosecond laser is an important and novel method for fabricating three-dimensional metal microstructures. However, the nonlinear absorption cross section of metal ions remains unknown because its measurement is difficult. In the present study, a method based on Two-Photon Excited Sedimentation (TPES) is proposed to measure the two-photon absorption cross section (TPACS) of metal ions in solution. The power-squared dependence of the amount of sediment on the excitation intensity was confirmed, revealing that 800 nm femtosecond laser induced reduction of metal ions was a two photon absorption process. We believe that the proposed method may be applied to measure the TPACS of several metal ions, thereby opening a new avenue towards future analysis of two-photon absorption materials. PMID:26657990

  17. Chirp measurement of large-bandwidth femtosecond optical pulses using two-photon absorption

    NASA Astrophysics Data System (ADS)

    Albrecht, T. F.; Seibert, K.; Kurz, H.

    1991-08-01

    We describe a novel method for accurate chirp measurement of broadband femtosecond pulses over their entire bandwidth based on two-photon absorption. These chirp measurements are applied for the optimization of a fiber-grating-prism pulse compressor.

  18. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  19. Non-degenerate two photon absorption enhancement for laser dyes by precise lock-in detection

    SciTech Connect

    Xue, B.; Katan, C.; Bjorgaard, J. A.; Kobayashi, T.

    2015-12-15

    This study demonstrates a measurement system for a non-degenerate two-photon absorption (NDTPA) spectrum. The NDTPA light sources are a white light super continuum beam (WLSC, 500 ∼ 720 nm) and a fundamental beam (798 nm) from a Ti:Sapphire laser. A reliable broadband NDTPA spectrum is acquired in a single-shot detection procedure using a 128-channel lock-in amplifier. The NDTPA spectra for several common laser dyes are measured. Two photon absorption cross section enhancements are found in the experiment and validated by theoretical calculation for all of the chromophores.

  20. Non-degenerate two photon absorption enhancement for laser dyes by precise lock-in detection

    NASA Astrophysics Data System (ADS)

    Xue, B.; Katan, C.; Bjorgaard, J. A.; Kobayashi, T.

    2015-12-01

    This study demonstrates a measurement system for a non-degenerate two-photon absorption (NDTPA) spectrum. The NDTPA light sources are a white light super continuum beam (WLSC, 500 ˜ 720 nm) and a fundamental beam (798 nm) from a Ti:Sapphire laser. A reliable broadband NDTPA spectrum is acquired in a single-shot detection procedure using a 128-channel lock-in amplifier. The NDTPA spectra for several common laser dyes are measured. Two photon absorption cross section enhancements are found in the experiment and validated by theoretical calculation for all of the chromophores.

  1. Non-resonant below-bandgap two-photon absorption in quantum dot solar cells

    SciTech Connect

    Li, Tian; Dagenais, Mario

    2015-04-27

    We study the optically nonlinear sub-bandgap photocurrent generation facilitated by an extended tailing distribution of states in an InAs/GaAs quantum dots (QDs) solar cell. The tailing states function as both the energy states for low energy photon absorption and the photocarriers extraction pathway. One of the biggest advantages of our method is that it can clearly differentiate the photocurrent due to one-photon absorption (1PA) process and two-photon absorption (2PA) process. Both 1PA and 2PA photocurrent generation efficiency in an InAs/GaAs QD device operated at 1550 nm have been quantitatively evaluated. A two-photon absorption coefficient β = 5.7 cm/GW is extracted.

  2. Spectroscopy of α,ω-dithienyl polyenes: evidence for two-photon absorption states from fluorescence studies

    NASA Astrophysics Data System (ADS)

    Natarajan, Lalgudi V.; Kirkpatrick, Sean M.; Sutherland, Richard L.; Sowards, Laura A.; Spangler, Charles W.; Fleitz, Paul A.; Cooper, Thomas M.

    1998-10-01

    The photophysics of a series (alpha) ,(omega) -dithienyl polyenes was studied. Both one photon excited fluorescence and fluorescence originating from two photon absorption states were investigated. There is strong evidence of two photon absorption from fluorescence studies in agreement with our earlier studies involving nonlinear absorption.

  3. Fluorescence upconversion properties of a class of improved pyridinium dyes induced by two-photon absorption

    NASA Astrophysics Data System (ADS)

    Xu, Guibao; Hu, Dawei; Zhao, Xian; Shao, Zongshu; Liu, Huijun; Tian, Yupeng

    2007-06-01

    We report the fluorescence upconversion properties of a class of improved pyridinium toluene- p-sulfonates having donor- π-acceptor (D- π-A) structure under two-photon excitation at 1064 nm. The experimental results show that both the two-photon excited (TPE) fluorescence lifetime and the two-photon pumped (TPP) energy upconversion efficiency were increased with the enhancement of electron-donating capability of the donor in the molecule. It is also indicated that an overlong alkyl group tends to result in a weakened molecular conjugation, leading to a decreased two-photon absorption (TPA) cross section. By choosing the donor, we can obtain a longest fluorescence lifetime of 837 ps, a highest energy upconversion efficiency of ˜6.1%, and a maximum TPA cross-section of 8.74×10 -48 cm 4 s/photon in these dyes.

  4. Two-photon absorption in gapped bilayer graphene with a tunable chemical potential.

    PubMed

    Brinkley, M K; Abergel, D S L; Clader, B D

    2016-09-14

    Despite the now vast body of two-dimensional materials under study, bilayer graphene remains unique in two ways: it hosts a simultaneously tunable band gap and electron density; and stems from simple fabrication methods. These two advantages underscore why bilayer graphene is critical as a material for optoelectronic applications. In the work that follows, we calculate the one- and two-photon absorption coefficients for degenerate interband absorption in a graphene bilayer hosting an asymmetry gap and adjustable chemical potential-all at finite temperature. Our analysis is comprehensive, characterizing one- and two-photon absorptive behavior over wide ranges of photon energy, gap, chemical potential, and thermal broadening. The two-photon absorption coefficient for bilayer graphene displays a rich structure as a function of photon energy and band gap due to the existence of multiple absorption pathways and the nontrivial dispersion of the low energy bands. This systematic work will prove integral to the design of bilayer-graphene-based nonlinear optical devices.

  5. Two-photon absorption in gapped bilayer graphene with a tunable chemical potential

    NASA Astrophysics Data System (ADS)

    Brinkley, M. K.; Abergel, D. S. L.; Clader, B. D.

    2016-09-01

    Despite the now vast body of two-dimensional materials under study, bilayer graphene remains unique in two ways: it hosts a simultaneously tunable band gap and electron density; and stems from simple fabrication methods. These two advantages underscore why bilayer graphene is critical as a material for optoelectronic applications. In the work that follows, we calculate the one- and two-photon absorption coefficients for degenerate interband absorption in a graphene bilayer hosting an asymmetry gap and adjustable chemical potential—all at finite temperature. Our analysis is comprehensive, characterizing one- and two-photon absorptive behavior over wide ranges of photon energy, gap, chemical potential, and thermal broadening. The two-photon absorption coefficient for bilayer graphene displays a rich structure as a function of photon energy and band gap due to the existence of multiple absorption pathways and the nontrivial dispersion of the low energy bands. This systematic work will prove integral to the design of bilayer-graphene-based nonlinear optical devices.

  6. Two-photon absorption and spectroscopy of the lowest two-photon transition in small donor-acceptor-substituted organic molecules

    NASA Astrophysics Data System (ADS)

    Beels, Marten T.; Biaggio, Ivan; Reekie, Tristan; Chiu, Melanie; Diederich, François

    2015-04-01

    We determine the dispersion of the third-order polarizability of small donor-acceptor substituted organic molecules using wavelength-dependent degenerate four-wave mixing experiments in solutions with varying concentrations. We find that donor-acceptor-substituted molecules that are characterized by extremely efficient off-resonant nonlinearities also have a correspondingly high two-photon absorption cross section. The width and shape of the first two-photon resonance for these noncentrosymmetric molecules follows what is expected from their longest wavelength absorption peak, and the observed two-photon absorption cross sections are record high when compared to the available literature data, the size of the molecule, and the fundamental limit for two-photon absorption to the lowest excited state, which is essentially determined by the number of conjugated electrons and the excited-state energies. The two-photon absorption of the smallest molecule, which only has 16 electrons in its conjugated system, is one order of magnitude larger than for the molecule called AF-50, a reference molecule for two-photon absorption [O.-K. Kim et al., Chem. Mater. 12, 284 (2000), 10.1021/cm990662r].

  7. Enhanced two-photon absorption in a hollow-core photonic-band-gap fiber

    SciTech Connect

    Saha, Kasturi; Venkataraman, Vivek; Londero, Pablo; Gaeta, Alexander L.

    2011-03-15

    We show that two-photon absorption (TPA) in rubidium atoms can be greatly enhanced by the use of a hollow-core photonic-band-gap fiber. We investigate off-resonant, degenerate Doppler-free TPA on the 5S{sub 1/2{yields}}5D{sub 5/2} transition and observe 1% absorption of a pump beam with a total power of only 1 mW in the fiber. These results are verified by measuring the amount of emitted blue fluorescence and are consistent with the theoretical predictions which indicate that transit-time effects play an important role in determining the two-photon absorption cross section in a confined geometry.

  8. Dynamics and two-photon absorption properties of chromophore functionalized semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Varaganti, Shankar; Gessesse, Mathias; Obare, Sherine O.; Ramakrishna, Guda

    2009-08-01

    Two photon absorption cross-sections and fluorescence dynamics of Riboflavin, Fluorescein 548, Coumarin 519 and Quinizarin adsorbed onto reactive (TiO2) and non-reactive (ZrO2) semiconductor nanoparticles have been investigated. These dye molecules are chosen because of their inherently different anchoring groups with which they can bind to semiconductor nanoparticles giving a handle to probe the influence of anchoring group as well as molecule-nanoparticle electronic coupling on the two-photon absorption and nonlinear optical properties. Two-photon excited fluorescence technique has been utilized to monitor the two photon absorption cross-sections and the dynamics of singlet states are followed with femto second fluorescence upconversion. Interesting cross-section trends have been observed where the TPA cross-section of chromophore on ZrO2 surface is similar or lower to that of the free dye while the cross-sections seem to be higher on the surface of reactive TiO2 nanoparticle surface. Fluorescence upconversion investigations were able to probe the electronic interactions of the chromophore with semiconductor nanoparticle and also the adsorption of the chromophores on the surface of the nanoparticle.

  9. One- and two-photon absorption of a spiropyran-merocyanine system: experimental and theoretical studies.

    PubMed

    Matczyszyn, Katarzyna; Olesiak-Banska, Joanna; Nakatani, Keitaro; Yu, Pei; Murugan, N Arul; Zaleśny, Robert; Roztoczyńska, Agnieszka; Bednarska, Joanna; Bartkowiak, Wojciech; Kongsted, Jacob; Ågren, Hans; Samoć, Marek

    2015-01-29

    We report on the nonlinear optical properties measurements and quantum-chemical calculations of a well-known photochromic system consisting of spiropyran and the merocyanine photoproduct. The study of nonlinear absorption and refraction properties of the molecules dissolved in chloroform were performed with the Z-scan technique, using femtosecond pulses in a wide range of wavelengths. Maxima in the two-photon absorption spectrum at 700 and 1050 nm were found for the merocyanine form, and the corresponding two-photon absorption cross section is 80 GM and 20 GM, respectively. The latter feature does not vanish completely in the nonlinear spectrum of the spiropyran form, possibly because of the existence of some photoconversion caused by the laser beam during the measurements. A nonlinear absorption peak at 900 nm is found in the spiropyran form with an effective cross section of about 20 GM; it is likely due to three-photon absorption or to absorption by some intermediate species. The experimental data are supported by calculations performed with the use of a hybrid quantum mechanics-molecular mechanics approach. PMID:25531561

  10. Confined optical-phonon-assisted cyclotron resonance in quantum wells via two-photon absorption process

    NASA Astrophysics Data System (ADS)

    Phuc, Huynh Vinh; Hien, Nguyen Dinh; Dinh, Le; Phong, Tran Cong

    2016-06-01

    The effect of confined phonons on the phonon-assisted cyclotron resonance (PACR) via both one and two photon absorption processes in a quantum well is theoretically studied. We consider cases when electrons are scattered by confined optical phonons described by the Fuchs-Kliewer slab, Ridley's guided, and Huang-Zhu models. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. It predicts resonant peaks caused by transitions between Landau levels and electric subband accompanied by confined phonons emission in the absorption spectrum. The MOAC and the full-width at half-maximum (FWHM) for the intra- and inter-subband transitions are given as functions of the magnetic field, temperature, and quantum well width. In narrow quantum wells, the phonon confinement becomes more important and should be taken into account in studying FWHM.

  11. Novel xenon calibration scheme for two-photon absorption laser induced fluorescence of hydrogen

    NASA Astrophysics Data System (ADS)

    Elliott, Drew; Scime, Earl; Short, Zachary

    2016-11-01

    Two photon absorption laser induced fluorescence (TALIF) measurements of neutral hydrogen and its isotopes are typically calibrated by performing TALIF measurements on krypton with the same diagnostic system and using the known ratio of the absorption cross sections [K. Niemi et al., J. Phys. D 34, 2330 (2001)]. Here we present the measurements of a new calibration method based on a ground state xenon scheme for which the fluorescent emission wavelength is nearly identical to that of hydrogen, thereby eliminating chromatic effects in the collection optics and simplifying detector calibration. We determine that the ratio of the TALIF cross sections of xenon and hydrogen is 0.024 ± 0.001.

  12. Non-degenerate two-photon absorption in silicon waveguides. Analytical and experimental study

    DOE PAGES

    Zhang, Yanbing; Husko, Chad; Lefrancois, Simon; Rey, Isabella H.; Krauss, Thomas F.; Schröder, Jochen; Eggleton, Benjamin J.

    2015-06-22

    We theoretically and experimentally investigate the nonlinear evolution of two optical pulses in a silicon waveguide. We provide an analytic solution for the weak probe wave undergoing non-degenerate two-photon absorption (TPA) from the strong pump. At larger pump intensities, we employ a numerical solution to study the interplay between TPA and photo-generated free carriers. We develop a simple and powerful approach to extract and separate out the distinct loss contributions of TPA and free-carrier absorption from readily available experimental data. Our analysis accounts accurately for experimental results in silicon photonic crystal waveguides.

  13. Accuracy of different DFT formalisms for prediction of two-photon absorption properties of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Nayyar, Iffat; Mikhailov, Ivan; Masunov, Artem

    2010-03-01

    The importance of organic molecules with large two-photon absorption (2PA) is realized for deep-tissue fluorescence microscopy, photodynamic therapy, three-dimensional microfabrication and optical data storage. Computer predictions provide understanding of structure/activity relationships and assist in the rational design of polymer materials as an alternative to trial and error methods. In this contribution, we compare various density functional theory (DFT) formalisms to predict two-photon absorption spectra in a series of large donor-acceptor substituted conjugated molecules. We conclude that the accuracy of a posteriori Tamm-Dancoff approximation [1] is close to the exact results obtained in Coupled Electronic Oscillators formalism [2]. Adjusting fraction of exact exchange in XC functionals allow for improved agreement with experiment. [1] Mikhailov, I.A.; Tafur, S.; Masunov, A.E., Phys. Rev. A 77, 01250 (2008) [2] Masunov, A.M.; Tretiak, S., J. Phys. Chem. B 108, 899 (2004)

  14. Synthesis of Photoresponsive Dual NIR Two-Photon Absorptive [60]Fullerene Triads and Tetrads

    PubMed Central

    Jeon, Seaho; Wang, Min; Tan, Loon-Seng; Cooper, Thomas; Hamblin, Michael R.; Chiang, Long Y.

    2013-01-01

    Broadband nonlinear optical (NLO) organic nanostructures exhibiting both ultrafast photoresponse and a large cross-section of two-photon absorption throughout a wide NIR spectrum may make them suitable for use as nonlinear biophotonic materials. We report here the synthesis and characterization of two C60-(antenna)x analogous compounds as branched triad C60(>DPAF-C18)(>CPAF-C2M) and tetrad C60(>DPAF-C18)(>CPAF-C2M)2 nanostructures. These compounds showed approximately equal extinction coefficients of optical absorption over 400–550 nm that corresponds to near-IR two-photon based excitation wavelengths at 780–1,100 nm. Accordingly, they may be utilized as potential precursor candidates to the active-core structures of photosensitizing nanodrugs for 2γ-PDT in the biological optical window of 800–1,050 nm. PMID:23941881

  15. Two-photon absorption induced by electric field gradient of optical near-field and its application to photolithography

    SciTech Connect

    Yamaguchi, Maiku; Kawazoe, Tadashi; Yatsui, Takashi; Nobusada, Katsuyuki

    2015-05-11

    An electric field gradient is an inherent property of the optical near-field (ONF). We investigated its effect on electron excitation in a quantum dot via model calculations combining a density matrix formalism and a classical Lorentz model. The electric field gradient of the ONF was found to cause two-photon absorption by an unusual mechanism. Furthermore, the absorption exhibits a nonmonotonic dependence on the spatial arrangement of the nanosystem, completely different from that of conventional two-photon absorption induced by an intense electric field. The present two-photon absorption process was verified in a previous experimental observation by reinterpreting the results of ONF photolithography.

  16. Highly-efficient entangled two-photon absorption with the assistance of plasmon nanoantenna

    NASA Astrophysics Data System (ADS)

    Oka, Hisaki

    2015-06-01

    We propose an efficient reaction field for entangled photons utilizing a localized-surface-plasmon (LSP) nanoantenna system. The LSP nanoantenna system consists of two nanometals embedded in a microcavity. For two-photon absorption in a molecule as an example, we show that the excitation population is considerably enhanced by properly choosing the LSP-microcavity parameters. This huge enhancement is attributed to the synergistic effects of the LSP antenna effect and the enhancement effect by entangled photons.

  17. Ultrashort coherence times in partially polarized stationary optical beams measured by two-photon absorption.

    PubMed

    Shevchenko, Andriy; Roussey, Matthieu; Friberg, Ari T; Setälä, Tero

    2015-11-30

    We measure the recently introduced electromagnetic temporal degree of coherence of a stationary, partially polarized, classical optical beam. Instead of recording the visibility of intensity fringes, the spectrum, or the polarization characteristics, we introduce a novel technique based on two-photon absorption. Using a Michelson interferometer equipped with polarizers and a specific GaAs photocount tube, we obtain the two fundamental quantities pertaining to the fluctuations of light: the degree of coherence and the degree of polarization. We also show that the electromagnetic intensity-correlation measurements with two-photon absorption require that the polarization dynamics, i.e., the time evolution of the instantaneous polarization state, is properly taken into account. We apply the technique to unpolarized and polarized sources of amplified spontaneous emission (Gaussian statistics) and to a superposition of two independent, narrow-band laser beams of different mid frequencies (non-Gaussian statistics). For these two sources femtosecond-range coherence times are found that are in good agreement with the traditional spectral measurements. Although previously employed for laser pulses, two-photon absorption provides a new physical principle to study electromagnetic coherence phenomena in classical and quantum continuous-wave light at extremely short time scales.

  18. Ultrashort coherence times in partially polarized stationary optical beams measured by two-photon absorption.

    PubMed

    Shevchenko, Andriy; Roussey, Matthieu; Friberg, Ari T; Setälä, Tero

    2015-11-30

    We measure the recently introduced electromagnetic temporal degree of coherence of a stationary, partially polarized, classical optical beam. Instead of recording the visibility of intensity fringes, the spectrum, or the polarization characteristics, we introduce a novel technique based on two-photon absorption. Using a Michelson interferometer equipped with polarizers and a specific GaAs photocount tube, we obtain the two fundamental quantities pertaining to the fluctuations of light: the degree of coherence and the degree of polarization. We also show that the electromagnetic intensity-correlation measurements with two-photon absorption require that the polarization dynamics, i.e., the time evolution of the instantaneous polarization state, is properly taken into account. We apply the technique to unpolarized and polarized sources of amplified spontaneous emission (Gaussian statistics) and to a superposition of two independent, narrow-band laser beams of different mid frequencies (non-Gaussian statistics). For these two sources femtosecond-range coherence times are found that are in good agreement with the traditional spectral measurements. Although previously employed for laser pulses, two-photon absorption provides a new physical principle to study electromagnetic coherence phenomena in classical and quantum continuous-wave light at extremely short time scales. PMID:26698754

  19. On the Theory of the Ballistic Linear Photovoltaic Effect in Semiconductors of Tetrahedral Symmetry Under Two-Photon Absorption

    NASA Astrophysics Data System (ADS)

    Rasulov, R. Ya.; Rasulov, V. R.; Eshboltaev, I.

    2016-07-01

    The ballistic contribution to the current of linear photovoltaic effect under two-photon absorption of light is calculated and theoretically analyzed for the semiconductors of a tetrahedral symmetry with a complex band structure consisting of two closely spaced subbands. The transitions between the branches of one band in cases of the simultaneous absorption of two photons and successive absorption of two single photons are taken into account.

  20. One- and two-photon absorption in solution: The effects of a passive auxiliary beam

    SciTech Connect

    Ford, J. S.; Andrews, D. L.

    2014-07-21

    The efficiencies of one- and two-photon absorption by chromophores in solution may be significantly modified by a sufficiently intense beam of off-resonant light. A molecular analysis based on quantum electrodynamics (QED) fully accounts for this phenomenon of laser-modified absorption. A time-dependent perturbation-theory treatment describes the process in terms of stimulated forward Rayleigh-scattering of the auxiliary beam occurring simultaneously with the absorption interaction(s). Our formulation accommodates media modifications to the basic character of light-matter interactions, taking into account the refractive and dispersive properties of a solution-phase environment. This introduces the bulk refractive index of the solvent directly into the QED framework. The measurable electronic response of molecules freely rotating in solution is defined by an average of all orientations. We explicitly derive fixed-orientation and rotationally averaged calculations for the Fermi-rule rate of laser-modified one- and two-photon absorption. For a given beam polarization geometry, the solution-phase molecular response is expressible as a set of natural invariant scalars. These results reveal details of the dependence on the beam polarisations and on the rotationally averaged molecular response: we illustrate the breadth of variation available via geometric manipulation of beam polarization, and raise new possibilities for quantum weak measurements of laser states.

  1. Anisotropy of two-photon absorption and free-carrier effect in nonpolar GaN

    SciTech Connect

    Fang, Yu; Zhou, Feng; Yang, Junyi; Wu, Xingzhi; Xiao, Zhengguo; Li, Zhongguo; Song, Yinglin

    2015-03-30

    We reported a systematic study about the anisotropic optical nonlinearities in bulk m-plane and a-plane GaN crystals by Z-scan and pump-probe with phase object methods under picosecond at 532 nm. The two-photon absorption coefficient, which was measured as a function of polarization angle, exhibited oscillation curves with a period of π/2, indicating a highly polarized optical third-order nonlinearity in both nonpolar GaN samples. Furthermore, free-carrier absorption revealed stronger hole-related absorption for E⊥c than for E//c probe polarization. In contrast, free-carrier refraction was found almost isotropic due to electron-related refraction in the isotropic conduction bands.

  2. A Series of Imidazole Derivatives: Synthesis, Two-Photon Absorption, and Application for Bioimaging.

    PubMed

    Zhu, Yingzhong; Xiao, Lufei; Zhao, Meng; Zhou, Jiazheng; Zhang, Qiong; Wang, Hui; Li, Shengli; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

    2015-01-01

    A new series of D-π-A type imidazole derivatives have been synthesized and characterized. Two corresponding imidazolium salts (iodine and hexafluorophosphate) were prepared from the imidazole compound. Their electron-withdrawing ability can be largely tunable by salt formation reaction or ion exchange. UV-vis absorption and single-photon fluorescence spectra have been systematically investigated in different solvents. The two-photon cross sections (δ 2PA) of the imidazole derivatives are measured by two-photon excited fluorescence (2PEF) method. Compared with those of T-1 (107 GM) and T-3 (96 GM), T-2 (imidazolium iodine salt) has a large two-photon absorption (2PA) cross section value of 276 GM. Furthermore, the cytotoxicity and applications in bioimaging for the imidazole derivatives were carried out. The results showed that T-1 can be used as a lysosomal tracker with high stability and water solubility within pHs of 4-6, while T-2 and T-3 can be used as probes for cell cytoplasm. PMID:26579544

  3. Two-photon fluorescence absorption and emission spectra of dyes relevant for cell imaging.

    PubMed

    Bestvater, F; Spiess, E; Stobrawa, G; Hacker, M; Feurer, T; Porwol, T; Berchner-Pfannschmidt, U; Wotzlaw, C; Acker, H

    2002-11-01

    Two-photon absorption and emission spectra for fluorophores relevant in cell imaging were measured using a 45 fs Ti:sapphire laser, a continuously tuneable optical parametric amplifier for the excitation range 580-1150 nm and an optical multichannel analyser. The measurements included DNA stains, fluorescent dyes coupled to antibodies as well as organelle trackers, e.g. Alexa and Bodipy dyes, Cy2, Cy3, DAPI, Hoechst 33342, propidium iodide, FITC and rhodamine. In accordance with the two-photon excitation theory, the majority of the investigated fluorochromes did not reveal significant discrepancies between the two-photon and the one-photon emission spectra. However, a blue-shift of the absorption maxima ranging from a few nanometres up to considerably differing courses of the spectrum was found for most fluorochromes. The potential of non-linear laser scanning fluorescence microscopy is demonstrated here by visualizing multiple intracellular structures in living cells. Combined with 3D reconstruction techniques, this approach gives a deeper insight into the spatial relationships of subcellular organelles. PMID:12423261

  4. Describing Two-Photon Absorptivity of Fluorescent Proteins with a New Vibronic Coupling Mechanism

    PubMed Central

    Makarov, N. S.; Tillo, S. E.; Hughes, T. E.; Rebane, A.

    2012-01-01

    Fluorescent proteins (FPs) are widely used in two-photon microscopy as genetically-encoded probes. Understanding the physical basics of their two-photon absorption (2PA) properties is therefore crucial for creation of two-photon brighter mutants. On the other hand, it can give us better insight into molecular interactions of the FP chromophore with complex protein environment. It is known that, compared to one-photon absorption spectrum, where the pure electronic transition is the strongest, the 2PA spectrum of a number of FPs is dominated by a vibronic transition. The physical mechanism of such intensity redistribution is not understood. Here we present a new physical model that explains this effect through the “Herzberg-Teller”-type vibronic coupling of the difference between the permanent dipole moments in the ground and excited states (Δμ) to the bond-length-alternating coordinate. This model also enables us to quantitatively describe a large variability of the 2PA peak intensity in a series of red FPs with the same chromophore through the interference between the “Herzberg-Teller” and Franck-Condon terms. PMID:22224830

  5. Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

    SciTech Connect

    Garcia-Lechuga, M.; Fuentes, L. M.; Grützmacher, K.; Pérez, C. Rosa, M. I. de la

    2014-10-07

    We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed to resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.

  6. A Series of Imidazole Derivatives: Synthesis, Two-Photon Absorption, and Application for Bioimaging

    PubMed Central

    Zhu, Yingzhong; Xiao, Lufei; Zhao, Meng; Zhou, Jiazheng; Zhang, Qiong; Wang, Hui; Li, Shengli; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

    2015-01-01

    A new series of D-π-A type imidazole derivatives have been synthesized and characterized. Two corresponding imidazolium salts (iodine and hexafluorophosphate) were prepared from the imidazole compound. Their electron-withdrawing ability can be largely tunable by salt formation reaction or ion exchange. UV-vis absorption and single-photon fluorescence spectra have been systematically investigated in different solvents. The two-photon cross sections (δ2PA) of the imidazole derivatives are measured by two-photon excited fluorescence (2PEF) method. Compared with those of T-1 (107 GM) and T-3 (96 GM), T-2 (imidazolium iodine salt) has a large two-photon absorption (2PA) cross section value of 276 GM. Furthermore, the cytotoxicity and applications in bioimaging for the imidazole derivatives were carried out. The results showed that T-1 can be used as a lysosomal tracker with high stability and water solubility within pHs of 4–6, while T-2 and T-3 can be used as probes for cell cytoplasm. PMID:26579544

  7. Applications of Two-Photon Absorption in Medicine and Biology Enabled by Specially Designed Biological Molecules

    NASA Astrophysics Data System (ADS)

    Drobizhev, M.

    2008-05-01

    We quantitatively study how the two-photon absorption (2PA) properties of biological molecules depend on their structure. 2PA is advantageous over regular one-photon absorption because of deeper penetration and more localized excitation in biological tissues. However, 2PA cross sections of biological chromophores are usually rather small to be useful in real life applications. Using quantum-mechanical few-level description of molecular electronic states, we interpret our data and predict new structures with considerably increased 2PA cross sections. These new materials either synthesized or genetically engineered make 2PA-based techniques applicable in medicine and biology. We show how our new porphyrin photosensitizers with drastically enhanced 2PA (˜1000 times compared to regular porphyrins) can be used for in vivo two-photon-induced closing of blood vessels in Age-Related Macular Degeneration. The second example describes the application of fluorescent proteins in two-photon laser microscopy of biological cells. We demonstrate how the 2PA properties of fluorescent proteins can be considerably improved by smart mutations of the environment of chromophore inside the protein.

  8. Two-photon absorption and transient photothermal imaging of pigments in tissues

    NASA Astrophysics Data System (ADS)

    Ye, Tong; Fu, Dan; Matthews, Thomas E.; Hong, Lian; Simon, John D.; Warren, Warren S.

    2008-02-01

    As a main pigment in skin tissues, melanin plays an important role in photo-protecting skin from UV radiation. However, melanogenesis may be altered due to disease or environmental factors; for example, sun exposure may cause damage and mutation of melanocytes and induce melanoma. Imaging pigmentation changes may provide invaluable information to catch the malignant transformation in its early stage and in turn improve the prognosis of patients. We have demonstrated previously that transmission mode, two-photon, one- or two-color absorption microscopy could provide remarkable contrast in imaging melanin in skin. In this report we demonstrate significantly improved sensitivity, so that we are now able to image in epi-mode (or back reflection) in two-photon absorption. This improvement makes possible for us to characterize the different types of pigmentation on the skin in vivo at virtually any location. Another finding is that we can also image transient photothermal dynamics due to the light absorption of melanin. By carefully choosing excitation and probe wavelengths, we might be able to image melanin in different structures under different micro-environments in skin, which could provide useful photochemical and photophysical insights in understanding how pigments are involved in photoprotection and photodamage of cells.

  9. Ophthalmic drug delivery utilizing two-photon absorption: a novel approach to treat posterior capsule opacification

    NASA Astrophysics Data System (ADS)

    Kim, H.-C.; Träger, J.; Zorn, M.; Haberkorn, N.; Hampp, N.

    2007-07-01

    Intraocular lens (IOL) implantation is the standard technique to treat cataract. Despite recent progress in surgical procedures, posterior capsule opacification is one of the sill remaining postoperative complications of cataract surgery. We present a novel strategy to reduce the incidence of posterior capsule opacification. A drug delivery polymer suitable for manufacturing intraocular lenses has been developed which enables repeated drug release in a non-invasive and controlled manner. The therapeutic molecules are attached through a UV light sensitive linkage to the polymer backbone which is mainly responsible for the optical properties of the intraocular lenses. However, UV light can not trigger the release of drug from the polymer due to the high absorption of the cornea. We developed linkers which enable drug release by two-photon absorption induced cleavage of the linker structure. Since the two-photon absorption requires high photon densities, this does not occur in ambient light conditions in daily life, but is easily triggered by focused laser beams from a pulsed laser. In this proof-of-principle study we have employed a cyclobutane type linker and investigated the properties of the therapeutic system with the approved drugs 5-fluorouracil and chlorambucil. The controlled drug delivery was successfully demonstrated in vitro and additional cell tests confirmed that the device itself shows no cytotoxicity until photochemical activation. This presented concept can provide a powerful method in ophthalmic drug delivery.

  10. Conjugated polymers with pyrrole as the conjugated bridge: synthesis, characterization, and two-photon absorption properties.

    PubMed

    Li, Qianqian; Zhong, Cheng; Huang, Jing; Huang, Zhenli; Pei, Zhiguo; Liu, Jun; Qin, Jingui; Li, Zhen

    2011-07-14

    The synthesis, one- and two-photon absorption (2PA) and emission properties of two novel pyrrole-based conjugated polymers (P1 and P2) are reported. They emitted strong yellow-green and orange fluorescence with fluorescent quantum yields (Φ) of 46 and 33%, respectively. Their maximal 2PA cross sections (δ) measured by the two-photon-induced fluorescence method using femtosecond laser pulses in THF were 2392 and 1938 GM per repeating unit, respectively, indicating that the 2PA chromophores consisting of the triphenylamine with nonplanar structure as the donor and electron-rich pyrrole as the conjugated bridge could be the effective repeating units to enhance the δ values.

  11. Selective two-photon absorptive resonance femtosecond-laser electronic-excitation tagging velocimetry.

    PubMed

    Jiang, Naibo; Halls, Benjamin R; Stauffer, Hans U; Danehy, Paul M; Gord, James R; Roy, Sukesh

    2016-05-15

    Selective two-photon absorptive resonance femtosecond-laser electronic-excitation tagging (STARFLEET), a nonseeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and nonreactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25 nm 100 fs light. STARFLEET greatly reduces the per-pulse energy required (30 μJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and nonreactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities, and further demonstrate the significantly less intrusive nature of STARFLEET. PMID:27176968

  12. Broadband Two-Photon Absorption Characteristics of Highly Photostable Fluorenyl-Dicyanoethylenylated [60]Fullerene Dyads.

    PubMed

    Jeon, Seaho; Wang, Min; Ji, Wei; Tan, Loon-Seng; Cooper, Thomas; Chiang, Long Y

    2016-01-01

    We synthesized four C60-(light-harvesting antenna) dyads C60 (>CPAF-Cn) (n = 4, 9, 12, or 18) 1-Cn for the investigation of their broadband nonlinear absorption effect. Since we have previously demonstrated their high function as two-photon absorption (2PA) materials at 1000 nm, a different 2PA wavelength of 780 nm was applied in the study. The combined data taken at two different wavelength ranges substantiated the broadband characteristics of 1-Cn. We proposed that the observed broadband absorptions may be attributed by a partial π-conjugation between the C60 > cage and CPAF-Cn moieties, via endinitrile tautomeric resonance, giving a resonance state with enhanced molecular conjugation. This transient state could increase its 2PA and excited-state absorption at 800 nm. In addition, a trend of concentration-dependent 2PA cross-section (σ₂ ) and excited-state absorption magnitude was detected showing a higher σ value at a lower concentration that was correlated to increasing molecular separation with less aggregation for dyads C60(>CPAF-C18) and C60(>CPAF-C₉), as better 2PA and excited-state absorbers. PMID:27187350

  13. Exclusive-OR Encryption by Photoconduction and Two-Photon Absorption in Carbon Nanotubes.

    PubMed

    Torres-Torres, C; Rebollo, N R; Castañeda, L; Trejo-Valdez, M; Torres-Marínez, R

    2015-02-01

    A two-wave photoconductive system dependent on the nonlinear optical absorption in carbon nano-tubes is presented. Optical irradiation at 532 nm wavelength and 1 nanosecond pulse duration was employed for performing the experiments. A vectorial two-wave mixing configuration was used in order to measure the absorptive and refractive nonlinearities. A single-beam transmittance technique was carried out to evaluate the photoconductivity and also it allows us to confirm the participation of the nonlinear optical absorption displayed by the samples. A two-photon absorption effect was identified as the main physical mechanism associated to the third order absorptive nonlinearity. The exclusive disjunctive logic function was achieved by the optoelectronic response of an interferometric configuration. An ultrasonic spray pyrolysis processing route was utilized for the preparation of the samples. The morphology of the nanotubes was estimated by using scanning electronic microscopy. By combining the photoconductive response of two different carbon nanotubes thin film samples, a straightforward XOR encryption was performed. PMID:26353707

  14. Reduction of residual excess noise in class-A lasers using two-photon absorption.

    PubMed

    Audo, Kévin; Amili, Abdelkrim El; Baili, Ghaya; Dolfi, Daniel; Alouini, Mehdi

    2016-09-15

    We demonstrate experimentally a significant reduction of the remaining excess intensity noise in a class-A semi-conductor laser. This is obtained by inserting into the laser cavity a buffer reservoir mechanism based on two-photon absorption in GaAs. The excess noise peaks at the laser-free spectral range, induced by the beating between the lasing mode and the amplified spontaneous emission in the adjacent non-oscillating modes, is reduced by 20 dB, while preserving the class-A dynamical behavior of the laser cavity.

  15. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region.

    PubMed

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-01-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2-6 um) with a resonant TPA cross section of up to 10(11 )GM. The TPA peaks are tuned by the GQDs' size, edge and electron relaxation rate.

  16. Size-dependent two-photon absorption in circular graphene quantum dots.

    PubMed

    Feng, Xiaobo; Li, Xin; Li, Zhisong; Liu, Yingkai

    2016-02-01

    We investigate theoretically the size-dependence of two-photon absorption (TPA) for circular graphene quantum dots (GQDs) on the basis of electronic energy states obtained by solving the Dirac-Weyl equation analytically under infinite-mass boundary condition. The analytical expressions for TPA coefficient are derived with an arbitrary size-distribution and the transition selection rules are obtained. Results reveal that the intraband transitions in conduction band and valence band contribute much more to TPA than interband transitions. The energy spectrum and TPA peaks are tuned by the size of GQDs. PMID:26906856

  17. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region

    NASA Astrophysics Data System (ADS)

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-09-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2-6 um) with a resonant TPA cross section of up to 1011 GM. The TPA peaks are tuned by the GQDs’ size, edge and electron relaxation rate.

  18. Observation of two-photon induced three-photon absorption in chemically synthesized silver nanostructures

    NASA Astrophysics Data System (ADS)

    Biswas, S.; Kole, A. K.; Kumbhakar, P.

    2015-06-01

    In this work, we have reported nonlinear optical (NLO) properties of different nanostructures of Ag, namely spherical, nanopentagon, and nanowire, synthesized by single pot chemical technique. NLO properties are measured by open and closed aperture Z-scan techniques at 1064 nm Nd:YAG laser wavelength having pulsed duration of 10 ns. The synthesized Ag nanostructures are exhibiting the rarely reported two-photon induced three-photon absorption along-with self-defocusing nonlinear refraction. A plausible explanation of the observed NLO properties owing to shape variations has been presented. The materials are also exhibiting optical limiting effect making them suitable for applications in advanced photonic devices.

  19. Reduction of residual excess noise in class-A lasers using two-photon absorption.

    PubMed

    Audo, Kévin; Amili, Abdelkrim El; Baili, Ghaya; Dolfi, Daniel; Alouini, Mehdi

    2016-09-15

    We demonstrate experimentally a significant reduction of the remaining excess intensity noise in a class-A semi-conductor laser. This is obtained by inserting into the laser cavity a buffer reservoir mechanism based on two-photon absorption in GaAs. The excess noise peaks at the laser-free spectral range, induced by the beating between the lasing mode and the amplified spontaneous emission in the adjacent non-oscillating modes, is reduced by 20 dB, while preserving the class-A dynamical behavior of the laser cavity. PMID:27628366

  20. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region.

    PubMed

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-01-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2-6 um) with a resonant TPA cross section of up to 10(11 )GM. The TPA peaks are tuned by the GQDs' size, edge and electron relaxation rate. PMID:27629800

  1. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region

    PubMed Central

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-01-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2–6 um) with a resonant TPA cross section of up to 1011 GM. The TPA peaks are tuned by the GQDs’ size, edge and electron relaxation rate. PMID:27629800

  2. Dimerization and Isomerism Effects on Two-Photon Absorption of Tetraphenylethene Derivatives and Molecular Design for Two-Photon Absorption Materials.

    PubMed

    Wang, Fu-Qing; Zhao, Ke; Zhu, Mei-Yu; Wang, Chuan-Kui

    2016-09-15

    The two-photon absorption (TPA) properties of a new tetraphenylethene derivative and its covalent dimers have been calculated employing the density functional response theory. It is found that linear arrangement of branches can give rise to a cooperative TPA behavior. Partial planarity and linear arrangement are the possible reasons for the observed aggregation-induced TPA enhancement. On the basis of the model molecule, we have designed a series of tetraphenylethene derivatives which differ by donor moieties, connection modes, or central bridges after taking the structure-property relationship of TPA mechanism into account. The TPA spectra of the designed molecules have been calculated, and their TPA properties are analyzed at length. Our results suggest that the change of the connection mode of the carbazole group and the introduction of a vinylene or ethynylene linkage into a molecule can enhance TPA intensity greatly. It can be expected that all of the designed molecules could possess high TPA features. This research is helpful for the design of efficient TPA materials.

  3. Dimerization and Isomerism Effects on Two-Photon Absorption of Tetraphenylethene Derivatives and Molecular Design for Two-Photon Absorption Materials.

    PubMed

    Wang, Fu-Qing; Zhao, Ke; Zhu, Mei-Yu; Wang, Chuan-Kui

    2016-09-15

    The two-photon absorption (TPA) properties of a new tetraphenylethene derivative and its covalent dimers have been calculated employing the density functional response theory. It is found that linear arrangement of branches can give rise to a cooperative TPA behavior. Partial planarity and linear arrangement are the possible reasons for the observed aggregation-induced TPA enhancement. On the basis of the model molecule, we have designed a series of tetraphenylethene derivatives which differ by donor moieties, connection modes, or central bridges after taking the structure-property relationship of TPA mechanism into account. The TPA spectra of the designed molecules have been calculated, and their TPA properties are analyzed at length. Our results suggest that the change of the connection mode of the carbazole group and the introduction of a vinylene or ethynylene linkage into a molecule can enhance TPA intensity greatly. It can be expected that all of the designed molecules could possess high TPA features. This research is helpful for the design of efficient TPA materials. PMID:27564774

  4. Solvent dependence of two-photon absorption spectra of the enhanced green fluorescent protein (eGFP) chromophore

    NASA Astrophysics Data System (ADS)

    Hosoi, Haruko; Tayama, Ryo; Takeuchi, Satoshi; Tahara, Tahei

    2015-06-01

    Two-photon absorption spectra of 4‧-hydroxybenzylidene-2,3-dimethylimidazolinone, a model chromophore of enhanced green fluorescent protein (eGFP), were measured in various solvents. The two-photon absorption band of its anionic form is markedly blue-shifted from the corresponding one-photon absorption band in all solvents. Moreover, the magnitude of the blue shift varies largely depending on the solvent, which does not accord with the assignment of the two-photon absorption band to the transitions to the vibrationally excited S1 state. Our finding is readily rationalized by considering overlapping contributions of the S1 ← S0 and S2 ← S0 transitions, suggesting the involvement of the S2 state also in two-photon fluorescence of eGFP.

  5. Two-photon dichroic atomic vapor laser lock using electromagnetically induced transparency and absorption

    SciTech Connect

    Becerra, F. E.; Willis, R. T.; Rolston, S. L.; Orozco, L. A.

    2009-07-15

    We demonstrate a technique to lock the frequency of a laser to a transition between two excited states in Rb vapor using a two-photon process in the presence of a weak magnetic field. We use a ladder configuration from specific hyperfine sublevels of the 5S{sub 1/2}, 5P{sub 3/2}, and 5D{sub 5/2} levels. This atomic configuration can show electromagnetically induced transparency and absorption processes. The error signal comes from the difference in the transparency or absorption felt by the two orthogonal polarizations of the probe beam. A simplified model is in good quantitative agreement with the observed signals for the experimental parameters. We have used this technique to lock the frequency of the laser up to 1.5 GHz off atomic resonance.

  6. Synthesis and two-photon absorption spectrum of fluorenone-based molecules

    NASA Astrophysics Data System (ADS)

    Dipold, J.; Batista, R. J. M. B.; Fonseca, R. D.; Silva, D. L.; Moura, G. L. C.; dos Anjos, J. V.; Simas, A. M.; De Boni, L.; Mendonca, C. R.

    2016-09-01

    The two-photon absorption (2PA) of five symmetrical fluorenone-based molecules is studied by femtosecond wavelength-tunable Z-scan, as well as quantum-chemical calculations. The molecules are transparent for wavelengths greater than 500 nm and two main one-photon absorption bands are observed in the blue region; one weak, centered at 450 nm, and a stronger one at approximately 360 nm. We observed a strong 2PA band located around 720 nm with maxima 2PA cross-sections between 100 and 230 GM. Quantum chemical calculations employing the response function formalism were performed at the Density Function Theory level to support the interpretation of the experimental nonlinear spectra.

  7. Two Photon Absorption And Refraction in Bulk of the Semiconducting Materials

    SciTech Connect

    Kumari, Vinay; Kumar, Vinod; Malik, B. P.; Mohan, Devendra; Gaur, Arun

    2011-10-20

    Fast electronic detection systems have opened up a number of new fields like nonlinear optics, optical communication, coherent optics, optical bistability, two/four wave mixing. The interest in this field has been stimulated by the importance of multiphoton processes in many fundamental aspects of physics. It has proved to be an invaluable tool for determining the optical and electronic properties of the solids because of the fact that one gets the information about the bulk of the material rather than the surface one. In this paper we report, the measurement of the nonlinear absorption and refraction from the band gap to half-band gap region of bulk of semiconductors in the direct and indirect band gap crystals with nanosecond laser. The measured theoretical calculated values of two-photon absorption coefficients ({beta}) and nonlinear refraction n{sub 2}({omega}) of direct band gap crystal match the earlier reported theoretical predictions. By making use of these theoretical calculated values, we have estimated {beta} and n{sub 2}({omega}) in the case of indirect band gap crystals. Low value of absorption coefficient in case of indirect band gap crystals have been attributed to phonon assisted transition while reduction in nonlinear refraction is due to the rise in saturation taking place in the absorption.

  8. Two-Photon Absorption by H2 Molecules: Origin of the 2175A Astronomical Band?

    NASA Astrophysics Data System (ADS)

    Sorokin, Peter P.; Glownia, James H.

    2007-04-01

    The near UV spectra of OB stars are often dominated by a broad extinction band peaking at 2175A. Forty years after its discovery, the origin of this band remains unknown, although it is usually attributed to linear scattering or linear absorption by interstellar dust particles. Here we report that two-photon absorption by H2 molecules in gaseous clouds enveloping OB stars should lead to a strong band peaking near 2175A. We first show that if the product of the H2 density in the gaseous cloud times the emitted stellar VUV flux is sufficiently great, the threshold for stimulated Rayleigh scattering will be exceeded, resulting in the generation of intense, monochromatic VUV light at the rest frame frequencies of H2 B- and C-state resonance lines originating from levels J''=0 and J''=1 of X0. This coherently generated light must necessarily propagate radially inwards towards the photosphere of the illuminating OB star, and therefore cannot be detected externally. However, this same light effectively constitutes intense ``first step'' monochromatic radiation that should induce continuum photons emitted by the OB star near 2175A to be strongly absorbed as ``second steps'' in resonantly-enhanced H2 two-photon transitions to two well known doubly-excited dissociative states of H2. Archival UV and VUV spectra of 185 OB stars strongly support our nonlinear model for the 2175A band.

  9. Two-photon absorption in CdSe colloidal quantum dots compared to organic molecules.

    PubMed

    Makarov, Nikolay S; Lau, Pick Chung; Olson, Christopher; Velizhanin, Kirill A; Solntsev, Kyril M; Kieu, Khanh; Kilina, Svetlana; Tretiak, Sergei; Norwood, Robert A; Peyghambarian, Nasser; Perry, Joseph W

    2014-12-23

    We discuss fundamental differences in electronic structure as reflected in one- and two-photon absorption spectra of semiconductor quantum dots and organic molecules by performing systematic experimental and theoretical studies of the size-dependent spectra of colloidal quantum dots. Quantum-chemical and effective-mass calculations are used to model the one- and two-photon absorption spectra and compare them with the experimental results. Currently, quantum-chemical calculations are limited to only small-sized quantum dots (nanoclusters) but allow one to study various environmental effects on the optical spectra such as solvation and various surface functionalizations. The effective-mass calculations, on the other hand, are applicable to the larger-sized quantum dots and can, in general, explain the observed trends but are insensitive to solvent and ligand effects. Careful comparison of the experimental and theoretical results allows for quantifying the range of applicability of theoretical methods used in this work. Our study shows that the small clusters can be in principle described in a manner similar to that used for organic molecules. In addition, there are several important factors (quality of passivation, nature of the ligands, and intraband/interband transitions) affecting optical properties of the nanoclusters. The larger-size quantum dots, on the other hand, behave similarly to bulk semiconductors, and can be well described in terms of the effective-mass models. PMID:25427158

  10. Size Dependence of Two-Photon Absorption in Semiconductor Quantum Dots

    SciTech Connect

    Dakovski, Georgi L.; Shan, Jie

    2013-01-01

    Quantum confinement plays an important role in the optical properties of semiconductor quantum dots (QDs). In this work, we combine experiment and modeling to systematically investigate the size dependence of the degenerate two-photon absorption (TPA) of below-band-gap radiation in CdSe QDs. The TPA coefficient β at 800 nm of CdSe QDs of varying radii was measured using femtosecond white-light transient absorption spectroscopy by probing the pump-induced bleaching at the first exciton transition energy. β was also calculated using a model based on the multiband effective-mass approximation. Satisfactory agreement between experiment and theory was obtained. Our findings show the evolution of the TPA in the QDs from that of atom-like to bulk-like with increasing the radius R. The TPA coefficient (or the volume normalized TPA cross-section) increases with radius approximately linearly in the strong confinement regime due to the rapid increase of the joint density of states for the two-photon allowed transitions, and saturates for R > 5 nm (the exciton Bohr radius), approaching that of bulk CdSe.

  11. Two-photon absorption induced drug delivery from polymeric intraocular lenses

    NASA Astrophysics Data System (ADS)

    Hampp, Norbert A.; Kim, Hee-Cheol; Kreiling, Stefan; Hesse, Lutz; Greiner, Andreas

    2003-10-01

    Secondary cataracts are quite often observed after implantation of polymeric intraocular lenses. The reason for this complication is that lens epithelial cells remain in the capsular bag when the natural lens is removed. They begin proliferation and cause secondary cataracts. It is not desireable to add cell toxic agents at the time of the implantation because wound healing is negatively affected. We have developed polymeric intraocular lenses which are equipped with a drug depot which may be released non-invasively through photochemical treatment. In the example presented the drug is 5-fluoruracil (5FU) which is covalently bound to the polymer. Deliberation of 5FU from the polymer is done photochemically. Since light is transmitted permanently through the artificial intraocular lens and wearing of special glasses by the patient should be omitted conventional photochemistry is not a suitable tool for the drug release. The polymer-5FU linkage is designed in a way that it has a high two-photon absorption cross-section. Two-photon absorption is used to selectively release 5FU from the lens. The one-photon reaction is blocked since the cornea does absorb UV light. The principle shown here is not limited to 5FU but may be applied to other drugs also.

  12. 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.

  13. 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.

  14. Elucidation of two photon absorption of ethylenediaminium (2,4-dinitrophenolate) crystals

    NASA Astrophysics Data System (ADS)

    Indumathi, C.; Sabari Girisun, T. C.; Anitha, K.; Cecil Raj, S. Alfred

    2016-10-01

    Optical quality single crystals of ethylenediaminium (2,4-dinitrophenolate) [EDA(2,4)DNP] were grown by solvent evaporation method for optical limiting applications against intense ultrashot pulse lasers. Single crystal XRD showed that the material crystallizes in monoclinic system with centric space group P21/C. The crystal packing diagram was elucidated for the first time in literature and it revealed six hydrogen bonds played a very important role in stabilizing the structure. A bifurcated hydrogen bond was also observed between ethylenediamminium and dinitrophenolate ions. The formation of charge transfer complex during the reaction of ethylenediamine and 2,4-dinitrophenol was strongly evident through the vibrational spectroscopic studies. TG-DTA and DSC curves indicate that the material exhibited strong decomposition at 224 °C. Ground state absorption analysis showed that the grown crystals possess absorption maxima in UV region (270 nm, 346 nm) and wide optical transmittance window (480-1200 nm) in the entire visible and NIR region. Measurement of two photon absorption (2PA) and optical limiting response by Z-scan technique under nanosecond pulse excitation was reported. Hence EDA(2,4)DNP with high 2PA coefficient (0.79 ± 0.04 × 10-10 m/W) and low limiting threshold (2.40 ± 0.05 × 1012 W/m2) will be a potential candidate for optical limiting applications like eye and sensor protection against short pulse lasers that are well spread in human interactive sectors.

  15. Revealing spectral features in two-photon absorption spectrum of Hoechst 33342: a combined experimental and quantum-chemical study.

    PubMed

    Olesiak-Banska, Joanna; Matczyszyn, Katarzyna; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Bartkowiak, Wojciech; Samoc, Marek

    2013-10-10

    We present the results of wide spectral range Z-scan measurements of the two-photon absorption (2PA) spectrum of the Hoechst 33342 dye. The strongest 2PA of the dye in aqueous solution is found at 575 nm, and the associated two-photon absorption cross section is 245 GM. A weak but clearly visible 2PA band at ∼850 nm is also observed, a feature that could not be anticipated from the one-photon absorption spectrum. On the basis of the results of hybrid quantum mechanics/molecular mechanics calculations, we put forward a notion that the long-wavelength feature observed in the two-photon absorption spectrum of Hoechst 33342 is due to the formation of dye aggregates. PMID:24016295

  16. Two-photon Absorption In Quantum Dots,quantum Dashes And Related Materials

    SciTech Connect

    Jain, Ravinder

    2009-08-31

    We have proposed the use of USQDs for various deep-tissue biological imaging applications, notably wavelength-multiplexed multicolor imaging and intra-nuclear studies such as those involving cell apoptosis, and have studied the issue of maximizing two-photon absorption-induced fluorescence (TPAF) signals from CdSe/ZnS USQDs to be used for this application. In particular, using 2 nm USQDs, we have shown that the TPAF signal at 780 nm is ~ 8 times that at 850 nm and 68 times that at 900 nm, two wavelengths that have been used in previous studies using CdSe/ZnS SQDs for deep-tissue imaging of biological studies via TPAF .

  17. Numerical approaches for predicting two-photon absorption induced single-event effects in semiconductors

    NASA Astrophysics Data System (ADS)

    Hales, Joel M.; Khachatrian, Ani; Roche, Nicolas J.; Buchner, Stephen; Warner, Jeffrey; McMorrow, Dale

    2016-05-01

    Two numerical approaches for determining the charge generated in semiconductors via two-photon absorption (2PA) under conditions relevant for laser-based single-event effects (SEE) experiments are presented. The first approach uses a simple analytical expression incorporating a small number of experimental/material parameters while the second approach employs a comprehensive beam propagation method that accounts for all the complex nonlinear optical (NLO) interactions present. The impact of the excitation conditions, device geometry, and specific NLO interactions on the resulting collected charge in silicon devices is also discussed. These approaches can provide value to the radiation-effects community by predicting the impacts that varying experimental parameters will have on 2PA SEE measurements.

  18. Position Isomerism on One and Two Photon Absorption in Multibranched Chromophores: A TDDFT Investigation.

    PubMed

    Katan, Claudine; Blanchard-Desce, Mireille; Tretiak, Sergei

    2010-11-01

    Recently, branching and click chemistry strategies have been combined to design a series of optically active chromophores built from triazole moieties. These triazole-based multipolar chromophores have been shown to be promising candidates for two-photon absorption (TPA) transparency optimization in perspective of optical limiting in the visible region. In this work, the nature of one- and two-photon absorption properties in a family of triazole-based chromophores has been investigated using hybrid time-dependent density functional theory (TD-DFT). We use recent extensions of TD-DFT to determine nonlinear optical responses and natural transition orbitals to analyze the underlying electronic processes. Our results are also interpreted in the framework of the Frenkel exciton model. In agreement with experimental data, we found that introducing a triazole moiety into multibranched chromophores substantially modifies their optical behavior due to changes in electronic delocalization and charge-transfer properties between donating end groups and the branching center that can be controlled by the triazole ring. Structural conformations via modulation of the torsion between phenyl and triazole rings significantly alter the excited state electronic structure. Moreover, isomer positioning also greatly influences both linear and nonlinear optical responses such as TPA. Our theoretical findings allow elucidation of these differences and contribute to the general understanding of structure-property relations. Consequently, the interplay of donor/acceptor strength, triazole regioisomerism, and branching are shown to provide flexible means allowing for precise tuning of both linear and nonlinear optical responses, thus opening new perspectives toward synergic TPA architectures. PMID:26617095

  19. Two-photon absorption cross section measurement in the gamma band system of nitric oxide

    SciTech Connect

    Burris, J.F. Jr.

    1982-01-01

    A dye laser with a single longitudinal mode and very stable spatial mode structure has been constructed. With this laser system a four-wave mixing experiment was done in the gamma bands of nitric oxide using two photon resonance. Another four-wave mixing experiment was done in nitrogen using coherent anti-Stokes Raman scattering (CARS) and the two signals ratioed. Using accurately known values of the Raman scattering cross section, the third order susceptibility in NO was determined without needing to know the spatial and temporal properties of the dye lasers. From this susceptibility, the two photon absorption cross section was calculated with the explicit dependence of sigma/sup (2)/ upon X/sup (3)/ shown. For the R/sub 22/ + S/sub 12/(J'' = 9 1/2) (A/sup 2/..sigma..+(v' = 0) -- X/sup 2/..pi..(v'' = 0)) line, sigma/sup (2)/ = (1.0 +/- 0.6) x 10/sup -38/cm/sup 4/g(2/sub 1/-Vertical Barsub f/ is the normalized lineshape. Branching ratios for the A/sup 2/..sigma..+(v' = n) ..-->.. X/sup 2/..omega..(v'' = n)(n = o,...9) transitions of NO were also measured, Franck-Condon factors calculated and the lifetime of the A state determined.

  20. Two-photon absorption-induced drug delivery from polymers for medical applications

    NASA Astrophysics Data System (ADS)

    Kim, Hee-Cheol; Kreiling, Stefan; Haertner, Sebastian; Hesse, Lutz; Greiner, Andreas; Hampp, Norbert A.

    2004-06-01

    Novel polymeric materials carrying a drug depot have been developed which are suitable for fabrication of photochemically modulated drug delivery devices. In order to avoid uncontrolled drug release the drug is covalently attached to the polymer backbone using a photo-active linker. Controlled drug release from the polymer can be accomplished either via single-photon excitation or by two-photon absorption (TPA). In particular the second possibility is of interest for applications where exposure to day light or UV light may not be omitted. One example are polymeric intraocular lenses (IOL), which are implanted instead of the opaque natural lens during cataract surgery. Secondary cataract formation is quite often observed after implantation of polymeric IOLs. In this study the well known cell toxic agent 5-fluorouracil (5FU) attached to a methylmethacrylate-based polymer was investigated as an IOL which can upon photochemical excitation release 5FU in order to treat or to prevent secondary cataract formation. The photochemical cleavage of the linker molecule was analyzed with single- and two-photon excitation. UV/VIS spectroscopy and HPLC analysis confirmed the release of 5FU form the polymer backbone. The diffusion of the drug precursor out from the polymer as well as the hydrolysis of the drug precursor which leads to 5FU formation were investigated in vitro.

  1. Molecular engineering of nanoscale quadrupolar chromophores for two-photon absorption

    NASA Astrophysics Data System (ADS)

    Porres, Laurent; Mongin, Olivier; Blanchard-Desce, Mireille H.; Ventelon, Lionel; Barzoukas, Marguerite; Moreaux, Laurent; Pons, Thomas; Mertz, Jerome

    2003-02-01

    Our aim has been the design of optimized NLO-phores with very high two-photon absorption (TPA) cross-sections (s2) in the red-NIR region, while maintaining high linear transparency and high fluorescence quantum yield. Our molecular engineering strategy is based on the push-push or pull-pull functionalization of semi-rigid nanoscale conjugated systems. The central building blocks were selected as rigid units that may assist quadrupolar intramolecular charge transfer by acting either as a (weak) donor or acceptor core. Quadrupolar molecules derived either from a phenyl unit, a rigidified biphenyl moiety or a fused bithiophene unit have been considered. Conjugated oligomers made of phenylene-vinylene and/or phenylene-ethynylene units were selected as connecting spacers between the core and the electroactive end groups to ensure effective electronic conjugation while maintaining suitable transparency/fluorescence. The TPA cross-sections were determined by investigating the two-photon-excited fluorescence properties using a Ti:sapphire laser delivering fs pulses. Both the nature of the end groups and of the core moiety play an important role in determining the TPA spectra. In addition, by adjusting the length and nature of the conjugated extensor, both amplification and spectral tuning of TPA cross-sections can be achieved. As a result, push-push fluorophores which demonstrate giant TPA cross-sections (up to 3000 GM) in the visible red, high fluorescence quantum yields and good transparency in the visible range have been obtained.

  2. Investigation of two-photon absorption properties in new A-D-A compounds emitting blue and yellow fluorescence

    NASA Astrophysics Data System (ADS)

    Jin, Fan; Cai, Zhi-Bin; Huang, Jiu-Qiang; Li, Sheng-Li; Tian, Yu-Peng

    2015-08-01

    Three new acceptor-donor-acceptor compounds (LBQ, DBQ, BYQ) were synthesized and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their photophysical properties were investigated including linear absorption, single-photon excited fluorescence, fluorescence quantum yield and two-photon absorption. These compounds in CH2Cl2 exhibit good fluorescence quantum yield which are 0.36, 0.26, and 0.25 and the largest two-photon absorption cross-section which are 48, 36, and 181 GM respectively. Under the excitation of Ti: sapphire laser with a pulse width of 140 fs, LBQ and DBQ emit blue two-photon excited fluorescence (TPEF), while BYQ emits bright yellow TPEF. BYQ has a good solubility in water and the σ can be as large as 130 GM, so it shows promising applications in many pharmaceutical and biological fields.

  3. Cross two photon absorption in a silicon photonic crystal waveguide fiber taper coupler with a physical junction

    SciTech Connect

    Sarkissian, Raymond O'Brien, John

    2015-01-21

    Cross two photon absorption in silicon is characterized using a tapered fiber photonic crystal silicon waveguide coupler. There is a physical junction between the tapered fiber and the waveguide constituting a stand-alone device. This device is used to obtain the spectrum for cross two photon absorption coefficient per unit volume of interaction between photons of nondegenerate energy. The corresponding Kerr coefficient per unit volume of interaction is also experimentally extracted. The thermal resistance of the device is also experimentally determined and the response time of the device is estimated for on-chip all-optical signal processing and data transfer between optical signals of different photon energies.

  4. Self-phase modulation and two-photon absorption imaging of cells and active neurons

    NASA Astrophysics Data System (ADS)

    Fischer, Martin C.; Liu, Henry; Piletic, Ivan R.; Ye, Tong; Yasuda, Ryohei; Warren, Warren S.

    2007-02-01

    Even though multi-photon fluorescence microscopy offers higher resolution and better penetration depth than traditional fluorescence microscopy, its use is restricted to the detection of molecules that fluoresce. Two-photon absorption (TPA) imaging can provide contrast in non-fluorescent molecules while retaining the high resolution and sectioning capabilities of nonlinear imaging modalities. In the long-wavelength water window, tissue TPA is dominated by the endogenous molecules melanin and hemoglobin with an almost complete absence of endogenous two-photon fluorescence. A complementary nonlinear contrast mechanism is self-phase modulation (SPM), which can provide intrinsic signatures that can depend on local tissue anisotropy, chemical environment, or other structural properties. We have developed a spectral hole refilling measurement technique for TPA and SPM measurements using shaped ultrafast laser pulses. Here we report on a microscopy setup to simultaneously acquire 3D, high-resolution TPA and SPM images. We have acquired data in mounted B16 melanoma cells with very modest laser power levels. We will also discuss the possible application of this measurement technique to neuronal imaging. Since SPM is sensitive to material structure we can expect SPM properties of neurons to change during neuronal firing. Using our hole-refilling technique we have now demonstrated strong novel intrinsic nonlinear signatures of neuronal activation in a hippocampal brain slice. The observed changes in nonlinear signal upon collective activation were up to factors of two, unlike other intrinsic optical signal changes on the percent level. These results show that TPA and SPM imaging can provide important novel functional contrast in tissue using very modest power levels suitable for in vivo applications.

  5. An Amphiphilic BODIPY-Porphyrin Conjugate: Intense Two-Photon Absorption and Rapid Cellular Uptake for Two-Photon-Induced Imaging and Photodynamic Therapy.

    PubMed

    Zhang, Tao; Lan, Rongfeng; Gong, Longlong; Wu, Baoyan; Wang, Yuzhi; Kwong, Daniel W J; Wong, Wai-Kwok; Wong, Ka-Leung; Xing, Da

    2015-11-01

    The new amphiphilic BODPY-porphyrin conjugate BZnPP and its precursor BZnPH were synthesised, and their linear and two-photon photophysical properties, together with their cellular uptake and photo-cytotoxicity, were studied. This amphiphilic conjugate consists of a hydrophobic BODIPY moiety and a hydrophilic tetra(ethylene glycol) chain bridging a cationic triphenylphosphonium group to an amphiphilic porphyrin ZnP through acetylide linkers at its meso positions. A large two-photon absorption cross-section (σ=1725 GM) and a high singlet oxygen quantum yield (0.52) were recorded. Intense linear- and two-photon-induced red emissions were also observed for both BZnPP and BZnPH. Further in vitro studies showed that BZnPP exhibited very efficient cellular uptake and strong photocytotoxic but weak dark cytotoxic properties towards human breast carcinoma MCF-7 cells. In summary, the two-photon-induced emission and the potent photo-cytotoxicity of BZnPP make it an efficacious dual-purpose tumour-imaging and photodynamic therapeutic agent in the tissue-transparent spectral windows.

  6. Colloidal quantum-dot-based silica gel glass: two-photon absorption, emission, and quenching mechanism.

    PubMed

    Li, Jingzhou; Dong, Hongxing; Zhang, Saifeng; Ma, Yunfei; Wang, Jun; Zhang, Long

    2016-09-28

    Two-photon (TP) three-dimensional solid matrices have potential applications in high density optical data reading and storage, infrared-pumped visible displays, lasers, etc. Such technologies will benefit greatly from the advantageous properties of TP materials including tunable emission wavelength, photostability, and simple chemical processing. Here, this ideal TP solid is made possible by using a facile sol-gel process to engineer colloid quantum dots into silica gel glass. Characterization using an open-aperture Z-scan technique shows that the solid matrices exhibited significant TP optical properties with a TP absorption coefficient of (9.41 ± 0.39) × 10(-2) cm GW(-1) and a third-order nonlinear figure of merit of (7.30 ± 0.30) × 10(-14) esu cm. In addition, the dependence of the TP properties on high-temperature thermal treatment is studied in detail to obtain a clear insight for practical applications. The results illustrate that the sample can maintain stable TP performance below the synthesis temperature of the CdTe/CdS colloidal quantum dots. Furthermore, the mechanisms for thermal quenching of photoluminescence under different temperature regimes are clarified as a function of the composition.

  7. Doppler-Free Two-Photon Absorption Spectroscopy of Naphthalene Assisted by AN Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Nishiyama, Akiko; Matsuba, Ayumi; Misono, Masatoshi

    2014-06-01

    Optical frequency combs are powerful tools for precise frequency measurements in various wavelength regions. The combs have been applied not only to metrology, but also to molecular spectroscopy. Recently, we studied high resolution spectroscopy of iodine molecule assisted by an optical frequency comb. In the study, the comb was used for frequency calibration of a scanning dye laser. In this study, we developed a frequency calibration scheme with a comb and an acousto-optic modulator to realize more precise frequency measurement in a wide frequency range. And the frequency calibration scheme was applied to Doppler-free two-photon absorption (DFTPA) spectroscopy of naphthalene. Naphthalene is one of the prototypical aromatic molecules, and its detailed structure and dynamics in excited states have been reported. We measured DFTPA spectra of A^1B1u(v4=1) ← X^1A_g(v=0) transition around 298 nm. A part of obtained spectra is shown in the figure. The spectral lines are rotationally resolved and the resolution is about 100 kHz. The horizontal axis was calibrated by the developed frequency calibration system employing the comb. The uncertainties of the calibrated frequencies were determined by the fluctuations of the comb modes which were stabilized to a GPS-disciplined clock. A. Nishiyama, D. Ishikawa, and M. Misono, J. Opt. Soc. Am. B 30, 2107 (2013).

  8. Colloidal quantum-dot-based silica gel glass: two-photon absorption, emission, and quenching mechanism.

    PubMed

    Li, Jingzhou; Dong, Hongxing; Zhang, Saifeng; Ma, Yunfei; Wang, Jun; Zhang, Long

    2016-09-28

    Two-photon (TP) three-dimensional solid matrices have potential applications in high density optical data reading and storage, infrared-pumped visible displays, lasers, etc. Such technologies will benefit greatly from the advantageous properties of TP materials including tunable emission wavelength, photostability, and simple chemical processing. Here, this ideal TP solid is made possible by using a facile sol-gel process to engineer colloid quantum dots into silica gel glass. Characterization using an open-aperture Z-scan technique shows that the solid matrices exhibited significant TP optical properties with a TP absorption coefficient of (9.41 ± 0.39) × 10(-2) cm GW(-1) and a third-order nonlinear figure of merit of (7.30 ± 0.30) × 10(-14) esu cm. In addition, the dependence of the TP properties on high-temperature thermal treatment is studied in detail to obtain a clear insight for practical applications. The results illustrate that the sample can maintain stable TP performance below the synthesis temperature of the CdTe/CdS colloidal quantum dots. Furthermore, the mechanisms for thermal quenching of photoluminescence under different temperature regimes are clarified as a function of the composition. PMID:27602563

  9. Two-photon absorption in 3-100 nm diameter Silicon nanocrystals in solution

    NASA Astrophysics Data System (ADS)

    Furey, Brandon; Downer, Michael; Yu, Yixuan; Korgel, Brian

    Silicon nanocrystals (nc-Si) exhibit efficient photoluminescence (PL) that has applications in non-toxic bio-imaging. Two-photon absorption (TPA) is an important process for exciting PL in the tissue transparency spectral window, but absolute TPA coefficients have not been measured as a continuous function of nc size or excitation wavelength. Previous TPA studies have focused on nc-Si embedded in an oxide matrix or on porous Si surfaces at selected discrete wavelengths. However, recently free standing, ligand-stabilized nc-Si with diameters ranging from 3 to 100 nm that are soluble in liquids, including water, and suitable for bio-imaging have become available. We will present calibrated TPA spectra for free standing nc-Si over a wide range of nc diameters, based on measurements with tunable femtosecond laser pulses. We will compare indirect TPA measurements based on collection and detection of PL with direct TPA measurements based on attenuation of the incident beam. Department of Physics.

  10. UV-induced two-photon absorption in BiB 3O 6 single crystals

    NASA Astrophysics Data System (ADS)

    Majchrowski, A.; Kisielewski, J.; Michalski, E.; Ozga, K.; Kityk, I. V.; Lukasiewicz, T.

    2005-06-01

    We show that BiB 3O 6 (BiBO) crystals, well known for their excellent second harmonic generation (SHG) properties, may also be of interest for third-order optical phenomena, particularly for two-photon absorption (TPA). Photoinduced TPA measurements were performed under illumination of excimer Xe-F laser ( λ = 217 nm) as a photoinducing (pumping) beam. It created a thin surface layer (about 85 nm) that was a source of the observed photoinduced TPA. Raman shifted Nd-YAG laser radiation ( λ = 1.9 μm) as well as its second and fourth harmonics ( λ = 950 and λ = 475 nm, respectively) were used as fundamental (probing) beams of the TPA. The highest values of the TPA β coefficient were achieved for a polarization of the pumping light directed along crystallographic axis b. Quantum chemical simulations indicate on substantial contribution of UV-induced electron-phonon anharmonicity to the observed TPA. The obtained values of TPA coefficients indicate a possibility of using BiBO crystals as UV-operated optical limiters in a wide spectral range.

  11. Experimental evidence and theoretical modeling of two-photon absorption dynamics in the reduction of intensity noise of solid-state Er:Yb lasers.

    PubMed

    El Amili, Abdelkrim; Kervella, Gaël; Alouini, Mehdi

    2013-04-01

    A theoretical and experimental investigation of the intensity noise reduction induced by two-photon absorption in a Er,Yb:Glass laser is reported. The time response of the two-photon absorption mechanism is shown to play an important role on the behavior of the intensity noise spectrum of the laser. A model including an additional rate equation for the two-photon-absorption losses is developed and allows the experimental observations to be predicted.

  12. Two-photon absorption of ligand-protected Ag15 nanoclusters. Towards a new class of nonlinear optics nanomaterials.

    PubMed

    Sanader, Željka; Krstić, Marjan; Russier-Antoine, Isabelle; Bertorelle, Franck; Dugourd, Philippe; Brevet, Pierre-François; Antoine, Rodolphe; Bonačić-Koutecký, Vlasta

    2016-05-14

    We report theoretical and experimental results on two-photon absorption (TPA) cross section of thiolated small silver cluster Ag15L11 exhibiting extraordinary large TPA in red. Our findings provide the responsible mechanism and allow proposing new classes of nanoclusters with large TPAs which are promising for biological and medical applications.

  13. Two-photon absorption-induced photoacoustic imaging of Rhodamine B dyed polyethylene spheres using a femtosecond laser.

    PubMed

    Langer, Gregor; Bouchal, Klaus-Dieter; Grün, Hubert; Burgholzer, Peter; Berer, Thomas

    2013-09-23

    In the present paper we demonstrate the possibility to image dyed solids, i.e. Rhodamine B dyed polyethylene spheres, by means of two-photon absorption-induced photoacoustic scanning microscopy. A two-photon luminescence image is recorded simultaneously with the photoacoustic image and we show that location and size of the photoacoustic and luminescence image match. In the experiments photoacoustic signals and luminescence signals are generated by pulses from a femtosecond laser. Photoacoustic signals are acquired with a hydrophone; luminescence signals with a spectrometer or an avalanche photo diode. In addition we derive the expected dependencies between excitation intensity and photoacoustic signal for single-photon absorption, two-photon absorption and for the combination of both. In order to verify our setup and evaluation method the theoretical predictions are compared with experimental results for liquid and solid specimens, i.e. a carbon fiber, Rhodamine B solution, silicon, and Rhodamine B dyed microspheres. The results suggest that the photoacoustic signals from the Rhodamine B dyed microspheres do indeed stem from two-photon absorption.

  14. Light up Live Cell Nuclear Envelope in Real-Time Using a Two-Photon Absorption and AIE Chromophore.

    PubMed

    Tian, Xiaohe; Wang, Hui; Guan, Lijuan; Zhang, Qiong; Zhou, Hongping; Li, Chunxia; Huang, Bei; Wu, Jieying; Tian, Yupeng

    2016-01-01

    In this letter, aggregation from two-photon absorption (2PA) molecules in living cells were firstly observed and the related aggregation induced emission (AIE) properties were investigated as a cell tracer for L ((Z)-3-(4-(Bis(4-ethoxyphenyl) amino)phenyl)-2-(4-amino-phenyl)- acrylonitrile cyano-substituted ) based on triphenylamine with D-π-A model. L was further used as a two-photon absorption (2PA, λex = 900, λem = 550 nm δ = 156 GM) live-cell marker for real-time, long-term cell growth and proliferation monitoring, with rapidly adhering whole intracellular membrane-rich system. Remarkably, different from existing organic AIE chromophores and other commercially available probes, L exhibited intense intracellular-AIE property with stable nuclear envelope (NE) staining under two-photon excited microscopy (TPEM) through detailed in cellulo studies.

  15. Temperature-dependent excitonic photoluminescence excited by two-photon absorption in perovskite CsPbBr_3 quantum dots

    NASA Astrophysics Data System (ADS)

    Wei, Ke; Xu, Zhongjie; Chen, Runze; Zheng, Xin; Cheng, Xiangai; Jiang, Tian

    2016-08-01

    Recently lead halide nanocrystals (quantum dots) have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) have been studied across a broad temperature range from 80K to 380K. Two-photon absorption has been investigated with absorption coefficient up to 0.085 cm/GW at room temperature. Moreover, the photoluminescence excited by two-photon absorption shows a linear blue-shift (0.25meV/K) below temperature of ~220K and turned steady with fluctuation below 1nm (4.4meV) for higher temperature up to 380K. These phenomena are distinctly different from general red-shift of semiconductor and can be explained by the competition between lattice expansion and electron-phonon couplling.Our results reveal the strong nonlinear absorption and temperature-independent chromaticity in a large temperature range from 220K to 380K in the CsPbX3 QDs, which will offer new opportunities in nonlinear photonics, light-harvesting and light-emitting devices.

  16. Study of the Effect of the Pulse Width of the Excitation Source on the Two-Photon Absorption and Two-Photon Circular Dichroism Spectra of Biaryl Derivatives.

    PubMed

    Vesga, Yuly; Hernandez, Florencio E

    2016-09-01

    Herein we report on the expanded theoretical calculations and the experimental measurements of the two-photon absorption (TPA) and two-photon circular dichroism (TPCD) spectra of a series of optically active biaryl derivatives (R-BINOL, R-VANOL, and R-VAPOL) using femtosecond pulses. The comparative analysis of the experimental TPCD spectra obtained with our tunable amplified femtosecond system with those previously measured in our group on the same series of compounds in the picosecond regime reveals a decrease in the amplitude of the signal and an improvement in matching with the theory in the former. These results can be explained based on the negligible contribution of excited state absorption (ESA) using femtosecond pulses compared to the picosecond regime. We show how ESA affects both the strength of the signal and the shape of the TPA and TPCD spectra. TPA and TPCD spectra were obtained using the double L-scan technique over a broad spectral range (450-750 nm) using 90 fs pulses at 50 Hz repetition rate produced by an amplified femtosecond system. The theoretical calculations were performed using modern analytical response theory within the time-dependent density functional theory (TD-DFT) approach using CAM-B3LYP and 6-311++G(d,p) basis sets. PMID:27525702

  17. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores.

    PubMed

    Katan, Claudine; Charlot, Marina; Mongin, Olivier; Le Droumaguet, Céline; Jouikov, Viatcheslav; Terenziani, Francesca; Badaeva, Ekaterina; Tretiak, Sergei; Blanchard-Desce, Mireille

    2010-03-11

    The aim of the present work is to demonstrate that combined spatial tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two model series of structurally related chromophores have been designed and investigated. One is based on rod-like quadrupolar chromophores bearing either two identical or different electron-donating (D) end groups and the other on three-branched octupolar chromophores built from a trigonal donating moiety bearing identical or different acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetrical chromophores compared to their symmetrical counterparts. In both types of systems (i.e., quadrupoles and octupoles), experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution (i.e., concerted intramolecular charge transfer) between the different D and A moieties within the multipolar structure. In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moiety due to fast excitation localization after excitation, prior to emission. Hence, control of emission characteristics (polarization and emission spectrum), can be achieved, in addition to localization, by controlled introduction of electronic dissymmetry (i.e., replacement of one of the D or A end-groups by a slightly stronger D' or A' unit). Interestingly, slight dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route allowing TPA enhancement in multipolar structures, due to

  18. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

    SciTech Connect

    Tretiak, Sergei

    2009-01-01

    The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D{prime} or A{prime} units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted

  19. Two-Photon Absorption Laser Induced Fluorescence Measurements of Neutral Density in Helicon Plasma

    NASA Astrophysics Data System (ADS)

    Galante, Matthew

    2013-10-01

    Neutral particles play a critical role in nearly all plasmas, from the pedestal region of a tokamak fusion plasma to industrial plasma processing systems. In fusion plasmas, neutrals at the edge serve as both a source of particles and also a sink of momentum and energy. Control of the edge plasma density in tokamaks is critical for the transition to H-mode plasmas and the role of neutrals in modifying the plasma rotation in the edge is an area of active research. However, few methods exist to make localized, direct neutral density measurements. We have developed a new diagnostic based on two-photon absorption laser induced fluorescence (TALIF). We use a high intensity (5 MW/cm2), narrow bandwidth (0.1 cm-1) laser to probe the ground state of neutral hydrogen, deuterium and krypton with spatial resolution better than 0.2 cm, a time resolution of 10 ns, and a measurement cadence of 20 Hz. In this talk I will describe proof-of-principle measurements in a helicon plasma source that demonstrate the TALIF diagnostic is capable of measuring neutral densities spanning four orders of magnitude; comparable to the edge neutral gradients predicted in the tokamak pedestal. The measurements are performed in hydrogen and deuterium plasmas and absolute calibration is accomplished through TALIF measurements in neutral krypton. The optical configuration employed is confocal, i.e., both light injection and collection are accomplished through a single optical port in the vacuum vessel. The wavelength resolution of the diagnostic is sufficient to separate hydrogen and deuterium spectra and I will present measurements from mixed hydrogen and deuterium plasmas that demonstrate isotopic abundance measurements are feasible with the TALIF system. Time and spatially resolved measurements also allow us to explore the effects of wall recycling and pulse repetition rates on the neutral density profile in the plasma source. Work supported in part by US DOE under DE-FC02-04ER54698.

  20. Two photon absorption laser induced fluorescence measurements of neutral density in a helicon plasmaa)

    NASA Astrophysics Data System (ADS)

    Galante, M. E.; Magee, R. M.; Scime, E. E.

    2014-05-01

    We have developed a new diagnostic based on two-photon absorption laser induced fluorescence (TALIF). We use a high intensity (5 MW/cm2), narrow bandwidth (0.1 cm-1) laser to probe the ground state of neutral hydrogen, deuterium and krypton with spatial resolution better than 0.2 cm, a time resolution of 10 ns, and a measurement cadence of 20 Hz. Here, we describe proof-of-principle measurements in a helicon plasma source that demonstrate the TALIF diagnostic is capable of measuring neutral densities spanning four orders of magnitude; comparable to the edge neutral gradients predicted in the DIII-D tokamak pedestal. The measurements are performed in hydrogen and deuterium plasmas and absolute calibration is accomplished through TALIF measurements in neutral krypton. The optical configuration employed is confocal, i.e., both light injection and collection are accomplished with a single lens through a single optical port in the vacuum vessel. The wavelength resolution of the diagnostic is sufficient to separate hydrogen and deuterium spectra and we present measurements from mixed hydrogen and deuterium plasmas that demonstrate isotopic abundance measurements are feasible. Time resolved measurements also allow us to explore the evolution of the neutral hydrogen density and temperature and effects of wall recycling. We find that the atomic neutral density grows rapidly at the initiation of the discharge, reaching the steady-state value within 1 ms. Additionally, we find that neutral hydrogen atoms are born with 0.08 eV temperatures, not 2 eV as is typically assumed.

  1. Two photon absorption laser induced fluorescence measurements of neutral density in a helicon plasma

    SciTech Connect

    Galante, M. E.; Magee, R. M.; Scime, E. E.

    2014-05-15

    We have developed a new diagnostic based on two-photon absorption laser induced fluorescence (TALIF). We use a high intensity (5 MW/cm{sup 2}), narrow bandwidth (0.1 cm{sup −1}) laser to probe the ground state of neutral hydrogen, deuterium and krypton with spatial resolution better than 0.2 cm, a time resolution of 10 ns, and a measurement cadence of 20 Hz. Here, we describe proof-of-principle measurements in a helicon plasma source that demonstrate the TALIF diagnostic is capable of measuring neutral densities spanning four orders of magnitude; comparable to the edge neutral gradients predicted in the DIII-D tokamak pedestal. The measurements are performed in hydrogen and deuterium plasmas and absolute calibration is accomplished through TALIF measurements in neutral krypton. The optical configuration employed is confocal, i.e., both light injection and collection are accomplished with a single lens through a single optical port in the vacuum vessel. The wavelength resolution of the diagnostic is sufficient to separate hydrogen and deuterium spectra and we present measurements from mixed hydrogen and deuterium plasmas that demonstrate isotopic abundance measurements are feasible. Time resolved measurements also allow us to explore the evolution of the neutral hydrogen density and temperature and effects of wall recycling. We find that the atomic neutral density grows rapidly at the initiation of the discharge, reaching the steady-state value within 1 ms. Additionally, we find that neutral hydrogen atoms are born with 0.08 eV temperatures, not 2 eV as is typically assumed.

  2. Off-Resonant Two-Photon Absorption Cross-Section Enhancement of an Organic Chromophore on Gold Nanorods

    PubMed Central

    Sivapalan, Sean T.; Vella, Jarrett H.; Yang, Timothy K.; Dalton, Matthew J.; Haley, Joy E.; Cooper, Thomas M.; Urbas, Augustine M.; Tan, Loon-Seng; Murphy, Catherine J.

    2013-01-01

    Surface-plasmon-initiated interference effects of polyelectrolyte-coated gold nanorods on the two-photon absorption of an organic chromophore were investigated. With polyelectrolyte bearing gold nanorods of 2,4,6 and 8 layers, the role of the plasmonic fields as function of distance on such effects was examined. An unusual distance dependence was found: enhancements in the two-photon cross-section were at a minimum at an intermediate distance, then rose again at a further distance. The observed values of enhancement were compared to theoretical predictions using finite element analysis and showed good agreementdue to constructive and destructive interference effects. PMID:23687561

  3. Polarization dependent two-photon absorption spectroscopy on a naturally occurring biomarker (curcumin) in solution: A theoretical-experimental study

    NASA Astrophysics Data System (ADS)

    Tiburcio-Moreno, Jose A.; Alvarado-Gil, J. J.; Diaz, Carlos; Echevarria, Lorenzo; Hernández, Florencio E.

    2013-09-01

    We report on the theoretical-experimental analysis of the two-photon absorption (TPA) and two-photon circular-linear dichroism (TPCLD) spectra of (1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin) in Tetrahydrofuran (THF) solution. The measurement of the full TPA spectrum of this molecule reveals a maximum TPA cross-section at 740 nm, i.e. more than 10 times larger than the maximum reported in the literature at 800 nm for the application of curcumin in bioimaging. The TPCLD spectrum exposes the symmetry of the main excited-states involved in the two-photon excitation process. TD-DFT calculations support the experimental results. These outcomes are expected to expand the application of natural-occurring dyes in bioimaging.

  4. Two-Photon Absorption and Time-Resolved Stimulated Emission Depletion Spectroscopy of a New Fluorenyl Derivative

    PubMed Central

    Bondar, Mykhailo V.; Morales, Alma R.; Yue, Xiling; Luchita, Gheorghe; Przhonska, Olga V.; Kachkovsky, Olexy D.

    2012-01-01

    The synthesis, comprehensive linear photophysical characterization, two-photon absorption (2PA), steady-state and time-resolved stimulated emission depletion properties of a new fluorene derivative, (E)-1-(2-(di-p-tolylamino)-9,9-diethyl-9H-fluoren-7-yl)-3-(thiophen-2-yl)prop-2-en-1-one (1), are reported. The primary linear spectral properties, including excitation anisotropy, fluorescence lifetimes, and photostability, were investigated in a number of aprotic solvents at room temperature. The degenerate 2PA spectra of 1 were obtained with an open aperture Z-scan and two-photon induced fluorescence methods, using a 1-kHz femtosecond laser system, and maximum 2PA cross-sections of ~400–600 GM were obtained. The nature of the electronic absorption processes in 1 was investigated by DFT-based quantum chemical methods implemented in the Gaussian 09 program. The one- and two-photon stimulated emission spectra of 1 were measured over a broad spectral range using a femtosecond pump probe–based fluorescence quenching technique, while a new methodology for time-resolved fluorescence emission spectroscopy is proposed. An effective application of 1 in fluorescence bioimaging was demonstrated via one- and two-photon fluorescence microscopy images of HCT 116 cells containing the dye encapsulated micelles. PMID:22887914

  5. Characterization of Photon-Counting Detector Responsivity for Non-Linear Two-Photon Absorption Process

    NASA Technical Reports Server (NTRS)

    Sburlan, S. E.; Farr, W. H.

    2011-01-01

    Sub-band absorption at 1550 nm has been demonstrated and characterized on silicon Geiger mode detectors which normally would be expected to have no response at this wavelength. We compare responsivity measurements to singlephoton absorption for wavelengths slightly above the bandgap wavelength of silicon (approx. 1100 microns). One application for this low efficiency sub-band absorption is in deep space optical communication systems where it is desirable to track a 1030 nm uplink beacon on the same flight terminal detector array that monitors a 1550 nm downlink signal for pointingcontrol. The currently observed absorption at 1550 nm provides 60-70 dB of isolation compared to the response at 1064 nm, which is desirable to avoid saturation of the detector by scattered light from the downlink laser.

  6. Optical limiting and dynamical two-photon absorption of porphyrin with ruthenium outlying complexes for a picosecond pulse train

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Jin; Sun, Yu-Ping; Wang, Chuan-Kui

    2016-01-01

    Propagation and nonlinear optical absorption of a picosecond pulse train in strong reverse saturable absorption (RSA) materials (free-based tetrapyridyl porphyrin H2TPyP with ruthenium (Ru) outlying complexes) are investigated by solving coupled rate equations and field intensity equation. Influence of outlying Ru groups on optical limiting (OL) properties is studied. Propagation of the front subpulses is mainly affected by linear transition between the ground state and the first excited singlet state, while intensity of the latter subpulses is attenuated by the excited state absorption (ESA). These two different absorption mechanisms result in asymmetric distribution of the transmitted pulse. It is shown that effective population transfer time from the ground state to the lowest triplet state and RSA play important roles in the OL performance and pulse shaping. Moreover, our results indicate that the porphyrins studied are ideal optical limiters because of their large ESA cross section and long lifetime of the lowest triplet state. Compounds with the presence of Ru group possess preferable power limiting ability. Ligand group attached to Ru also influences the nonlinear optical absorption of compounds. Special attention has been paid on dynamical two-photon absorption (TPA) cross section which depends crucially on the duration of the subpulse as well as time interval between subpulses. The present study provides a way to modulate nonlinear optical absorption properties of the medium by changing parameters of the pulse train.

  7. pH-Induced Modulation of One- and Two-Photon Absorption Properties in a Naphthalene-Based Molecular Probe.

    PubMed

    Murugan, N Arul; Kongsted, Jacob; Ågren, Hans

    2013-08-13

    Presently, there is a great demand for small probe molecules that can be used for two-photon excitation microscopy (TPM)-based monitoring of intracellular and intraorganelle activity and pH. The candidate molecules should ideally possess a large two-photon absorption cross section with optical properties sensitive to pH changes. In the present work, we investigate the potential of a methoxy napthalene (MONAP) derivative for its suitability to serve as a pH sensor using TPM. Using an integrated approach rooted in hybrid quantum mechanics/molecular mechanics, the structures, dynamics, and the one- and two-photon properties of the probe in dimethylformamide solvent are studied. It is found that the protonated form is responsible for the optical property of MONAP at moderately low pH, for which the calculated pH-induced red shift is in good agreement with experiments. A 2-fold increase in the two-photon absorption cross section in the IR region of the spectrum is predicted for the moderately low pH form of the probe, suggesting that this can be a potential probe for pH monitoring of living cells. We also propose some design principles aimed at obtaining control of the absorption spectral range of the probe by structural tuning. Our work indicates that the integrated approach employed is capable of capturing the pH-induced changes in structure and optical properties of organic molecular probes and that such in silico tools can be used to draw structure-property relationships to design novel molecular probes suitable for a specific application.

  8. Ultrashort Two-Photon-Absorption Laser-Induced Fluorescence in Nanosecond-Duration, Repetitively Pulsed Discharges

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob Brian

    Absolute number densities of atomic species produced by nanosecond duration, repetitively pulsed electric discharges are measured by two-photon absorption laser-induced fluorescence (TALIF). Relatively high plasma discharge pulse energies (=1 mJ/pulse) are used to generate atomic hydrogen, oxygen, and nitrogen in a variety of discharge conditions and geometries. Unique to this work is the development of femtosecond-laser-based TALIF (fs-TALIF). Fs-TALIF offers a number of advantages compared to more conventional ns-pulse-duration laser systems, including better accuracy of direct quenching measurements in challenging environments, significantly reduced photolytic interference including photo-dissociation and photo-ionization, higher signal and increased laser-pulse bandwidth, the ability to collect two-dimensional images of atomic species number densities with far greater spatial resolution compared with more conventional diagnostics, and much higher laser repetition rates allowing for more efficient and accurate measurements of atomic species number densities. In order to fully characterize the fs-TALIF diagnostic and compare it with conventional ns-TALIF, low pressure (100 Torr) ns-duration pulsed discharges are operated in mixtures of H2, O2, and N2 with different buffer gases including argon, helium, and nitrogen. These discharge conditions are used to demonstrate the capability for two-dimensional imaging measurements. The images produced are the first of their kind and offer quantitative insight into spatially and temporally resolved kinetics and transport in ns-pulsed discharge plasmas. The two-dimensional images make possible comparison with high-fidelity plasma kinetics models of the presented data. The comparison with the quasi-one-dimensional kinetic model show good spatial and temporal agreement. The same diagnostics are used at atmospheric pressure, when atomic oxygen fs-TALIF is performed in an atmospheric-pressure plasma jet (APPJ). Here, the

  9. A comparative study of one- and two-photon absorption properties of pyrene and perylene diimide derivatives.

    PubMed

    Liu, Xiao-Ting; Zhao, Yang; Ren, Ai-Min; Feng, Ji-Kang

    2011-06-01

    Two important classes of organic molecules, perylene diimide (PDI) and pyrene derivatives have been found to possess relatively excellent photophysical and photochemical properties and especially high two-photon absorption cross sections (δ(T)(max)). Herein, one-photon absorption (OPA) and two-photon absorption (TPA) properties of some novel PDI and pyrene derivatives were comparatively investigated by the density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods. The calculated results indicate that with respect to PDI derivatives, the maximum TPA cross-sections for pyrene compounds increase obviously, the maximum peaks of OPA and TPA spectra are blue-shifted, the ΔE(H-L) (energy gaps between the highest occupied orbital and the lowest unoccupied orbital) increase. The different π-conjugated bridges (fluorene and pyrene) and terminal groups have slight effect on the OPA properties. Nevertheless, the molecules bearing 1,6-disubstituted pyrene as the π-conjugated bridge display the largest δ(T)(max) in both series of compounds 3 and 4. Moreover, the δ(T)(max) values of molecules with benzothiazole-substituted terminal groups are larger than those of the molecules with diphenylamine, which is attributed to benzothiazole groups stabilizing the planarity of the branch parts, extending the conjugated length and increasing the π-electron delocalized extent. Furthermore, the molecular size has marked effect on OPA and TPA properties. It is worthy to mention that cruciform 8 displays the largest δ(T)(max) among all the studied molecules in the range of 600-1100 nm. This research could provide a better understanding for the origin of the linear and nonlinear optical properties, and it would be helpful to gain more information about designing two-photon absorption materials with large δ(T)(max).

  10. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    SciTech Connect

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  11. Selective Two-Photon Absorptive Resonance Femtosecond-Laser Electronic-Excitation Tagging (STARFLEET) Velocimetry in Flow and Combustion Diagnostics

    NASA Technical Reports Server (NTRS)

    Jiang, Naibo; Halls, Benjamin R.; Stauffer, Hans U.; Roy, Sukesh; Danehy, Paul M.; Gord, James R.

    2016-01-01

    Selective Two-Photon Absorptive Resonance Femtosecond-Laser Electronic-Excitation Tagging (STARFLEET), a non-seeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and non-reactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25-nm 100-fs light. STARFLEET greatly reduces the per-pulse energy required (30 µJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and non-reactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities and further demonstrate the significantly less-intrusive nature of STARFLEET.

  12. Two-photon solvatochromism II: experimental and theoretical study of solvent effects on the two-photon absorption spectrum of Reichardt's dye.

    PubMed

    Wielgus, Małgorzata; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Samoc, Marek; Bartkowiak, Wojciech

    2013-11-11

    In this study, we report on the influence of solvent on the two-photon absorption (2PA) spectra of Reichardt's dye (RD). The measurement of 2PA cross-sections is performed for three solvents (chloroform, dimethyl formamide, and dimethyl sulfoxide) using the Z-scan technique. The key finding of this study is the observation that the cross-section, corresponding to the 2PA of the intramolecular charge-transfer state, diminishes substantially upon increasing the solvent polarity. To unravel the solvent dependence of the 2PA cross-section, the electronic structure of RD is determined using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach, in which polarization between the solute and solvent is taken into account by using a self-consistent scheme in the solvent polarization. The two-state approximation proves to be adequate for the studied system, and allowed the observed solvent-polarity-induced decrease of the 2PA cross-section to be related to the decrease of the transition moment and the increase in the excitation energy. PMID:24106066

  13. Doppler-free two-photon absorption spectroscopy of rovibronic transition of naphthalene calibrated with an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Nishiyama, A.; Nakashima, K.; Matsuba, A.; Misono, M.

    2015-12-01

    We performed Doppler-free two-photon absorption spectroscopy of naphthalene using an optical frequency comb as a frequency reference. Rotationally resolved rovibronic spectra were observed, and absolute frequencies of the rovibronic transitions were determined with an uncertainty of several tens of kHz. The resolution and precision of our system are finer than the natural width of naphthalene. We assigned 1466 lines of the Q (Ka) Q (J) transition and calculated molecular constants. We attribute systematic spectral line shifts to the Coriolis interaction, and discuss the origin of the spectral linewidths.

  14. Effects of two-photon absorption on terahertz radiation generated by femtosecond-laser excited photoconductive antennas.

    PubMed

    Lee, Chao-Kuei; Yang, Chan-Shan; Lin, Sung-Hui; Huang, Shiuan-Hua; Wada, Osamu; Pan, Ci-Ling

    2011-11-21

    Terahertz (THz) radiation can be generated more efficiently from a low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) antenna by considering the two-photon absorption (TPA) induced photo-carrier in the photoconductor. A rate-equation-based approach using the Drude-Lorentz model taking into account the band-diagram of LT-GaAs is used for the theoretical analysis. The use of transform-limited pulses at the PC antenna is critical experimentally. Previously unnoticed THz pulse features and anomalously increasing THz radiation power rather than saturation were observed. These are in good agreement with the theoretical predictions. The interplay of intensity dependence and dynamics of generation of photoexcited carriers by single-photon absorption and TPA for THz emission is discussed. PMID:22109395

  15. Two-Photon Absorption Properties of Proquinoidal D-A-D and A-D-A Quadrupolar Chromophores

    PubMed Central

    Susumu, Kimihiro; Fisher, Jonathan A. N.; Zheng, Jieru

    2011-01-01

    We report the synthesis, one- and two-photon absorption spectroscopy, fluorescence, and electrochemical properties of a series of quadrupolar molecules that feature proquinoidal π-aromatic acceptors. These quadrupolar molecules possess either donor-acceptor-donor (D–A–D) or acceptor-donor-acceptor (A–D–A) electronic motifs, and feature 4-N,N-dihexylaminophenyl, 4-dodecyloxyphenyl, 4-(N,N-dihexylamino)benzo[c][1,2,5]thiadiazolyl or 2,5-dioctyloxyphenyl electron donor moieties and benzo[c][1,2,5]thiadiazole (BTD) or 6,7-bis(3’,7’-dimethyloctyl)[1,2,5]thiadiazolo[3,4-g]quinoxaline (TDQ) electron acceptor units. These conjugated structures are highly emissive in nonpolar solvents and exhibit large spectral red-shifts of their respective lowest energy absorption bands relative to analogous reference compounds that incorporate phenylene components in place of BTD and TDQ moieties. BTD-based D-A-D and A-D-A chromophores exhibit increasing fluorescence emission red-shifts, and a concomitant decrease of the fluorescence quantum yield (Φf) with increasing solvent polarity; these data indicate that electronic excitation augments benzothiadiazole electron density via an internal charge transfer mechanism. The BTD- and TDQ-containing structures exhibit blue-shifted two-photon absorption (TPA) spectra relative to their corresponding one-photon absorption (OPA) spectra, and display high TPA cross-sections (>100 GM) within these spectral windows. D-A-D and A-D-A structures that feature more extensive conjugation within this series of compounds exhibit larger TPA cross-sections consistent with computational simulation. Factors governing TPA properties of these quadrupolar chromophores are discussed within the context of a three-state model. PMID:21568299

  16. Understanding the two-photon absorption spectrum of PE2 platinum acetylide complex.

    PubMed

    Vivas, Marcelo G; De Boni, Leonardo; Cooper, Thomas M; Mendonca, Cleber R

    2014-07-31

    Herein, we report on the two-absorption cross-section spectrum of trans-Pt(PBu3)2 (C≡C-C6H4-C≡C-C6H5)2 (PE2) platinum acetylide complex employing the femtosecond wavelength-tunable Z-scan technique. The PE2 complex can be visualized as two branches containing two phenylacetylene units, each one linked by a platinum center, completely transparent in the visible region. Because of this structure, large delocalization of π-electrons allied to the strong intramolecular interaction between the branches is expected. The 2PA absorption spectrum was measured using the femtosecond wavelength-tunable Z-scan technique with low repetition rate (1 kHz), in order to obtain the 2PA spectrum without excited-state contributions. Our results reveal that PE2 in dichloromethane solution presents two 2PA allowed bands located at 570 and 710 nm, with cross section of about 320 and 45 GM, respectively. The first one is related to the strong intramolecular interaction between the molecule's branches due to the presence of platinum atom, while the second one is associated with the breaking of symmetry of the chromophore in solution due, most probably to a large twisting angle of the ligand's phenyl rings relative to the Pt core.

  17. A two photon absorption laser induced fluorescence diagnostic for fusion plasmasa)

    NASA Astrophysics Data System (ADS)

    Magee, R. M.; Galante, M. E.; McCarren, D.; Scime, E. E.; Boivin, R. L.; Brooks, N. H.; Groebner, R. J.; Hill, D. N.; Porter, G. D.

    2012-10-01

    The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm2), narrow bandwidth (0.1 cm-1) laser is injected into a hydrogen plasma to excite the Lyman β transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer α emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.

  18. A two photon absorption laser induced fluorescence diagnostic for fusion plasmas

    SciTech Connect

    Magee, R. M.; Galante, M. E.; McCarren, D.; Scime, E. E.; Boivin, R. L.; Brooks, N. H.; Groebner, R. J.; Hill, D. N.; Porter, G. D.

    2012-10-15

    The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm{sup 2}), narrow bandwidth (0.1 cm{sup -1}) laser is injected into a hydrogen plasma to excite the Lyman {beta} transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer {alpha} emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.

  19. Two-photon absorption spectra of a near-infrared 2-azaazulene polymethine dye: solvation and ground-state symmetry breaking.

    PubMed

    Hu, Honghua; Przhonska, Olga V; Terenziani, Francesca; Painelli, Anna; Fishman, Dmitry; Ensley, Trenton R; Reichert, Matthew; Webster, Scott; Bricks, Julia L; Kachkovski, Alexey D; Hagan, David J; Van Stryland, Eric W

    2013-05-28

    Polymethine dyes (PDs) with absorption bands in the near-infrared region undergo symmetry breaking in polar solvents. To investigate how symmetry breaking affects nonlinear optical responses of PDs, an extensive and challenging experimental characterization of a cationic 2-azaazulene polymethine dye, including linear absorption, fluorescence, two-photon absorption and excited-state absorption, has been performed in two solvents with different polarity. Based on this extensive set of experimental data, a three-electronic-state model, accounting for the coupling of electronic degrees of freedom to molecular vibrations and polar solvation, has been reliably parameterized and validated for this dye, fully rationalizing optical spectra in terms of spectral position, intensities and bandshapes. In low-polarity solvents where the dye is mainly in its symmetric form, a nominally forbidden two-photon absorption band is observed, due to a vibronic activation mechanism. Inhomogeneous broadening plays a major role in polar solvents: absorption spectra represent the weighted sum of contributions from states with a variable amount of symmetry breaking, leading to a complex evolution of linear and nonlinear optical spectra with solvent polarity. In more polar solvents, the dominant role of the asymmetric form leads to the activation of two-photon absorption as a result of the symmetry lowering. The subtle interplay between the two mechanisms for two-photon absorption activation, vibronic coupling and polar solvation, can be fully accounted for within the proposed microscopic model allowing a detailed interpretation of the optical spectra of PDs.

  20. Evaluation of the two-photon absorption characteristics of GaSb/GaAs quantum rings

    SciTech Connect

    Wagener, M. C.; Botha, J. R.; Carrington, P. J.; Krier, A.

    2014-07-28

    The optical parameters describing the sub-bandgap response of GaSb/GaAs quantum rings solar cells have been obtained from photocurrent measurements using a modulated pseudo-monochromatic light source in combination with a second, continuous photo-filling source. By controlling the charge state of the quantum rings, the photoemission cross-sections describing the two-photon sub-bandgap transitions could be determined independently. Temperature dependent photo-response measurements also revealed that the barrier for thermal hole emission from the quantum rings is significantly below the quantum ring localisation energy. The temperature dependence of the sub-bandgap photo-response of the solar cell is also described in terms of the photo- and thermal-emission characteristics of the quantum rings.

  1. New insights into two-photon absorption properties of functionalized aza-BODIPY dyes at telecommunication wavelengths: a theoretical study.

    PubMed

    Liu, Xiaoting; Zhang, Jilong; Li, Kai; Sun, Xiaobo; Wu, Zhijian; Ren, Aimin; Feng, Jikang

    2013-04-01

    Special attention has been paid to understanding the structural effect on electronic structure and absorption spectra for an extensive series of functionalized aza-BODIPY molecules. We have employed the quadratic response theory as well as a sum-over-states approach involving few intermediate states to calculate the two-photon cross section (δmax). The results suggest that chemical modifications on the aza-BODIPY core and peripheral moieties using various substituents can finely tune their linear and nonlinear optical properties. Therefore, some new fluorophores absorbing in the near infrared region and featuring considerably high δmax at telecommunication wavelengths are proposed, which are excellent candidates for nonlinear transmission and fluorescent labeling materials. The investigation contributes a useful starting point for further design of more effective aza-BODIPY dyes and can be valuable as a foundation for future experimental research and development.

  2. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    SciTech Connect

    Rana, Amit Kumar; Kumar, Yogendra; Arjunan, M.S.; Sen, Somaditya; Shirage, Parasharam M. E-mail: paras.shirage@gmail.com; J, Aneesh; Adarsh, K. V.

    2015-12-07

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  3. Two-photon-absorption DNA sensitization via solvated electron production: unraveling photochemical pathways by molecular modeling and simulation.

    PubMed

    Gattuso, Hugo; Dumont, Elise; Marazzi, Marco; Monari, Antonio

    2016-07-21

    DNA photosensitization is one of the physical processes behind photodynamic therapy techniques, i.e. the combined use of photoactive drugs and visible radiation for therapeutical purposes. In this contribution we report the analysis of the photophysical properties of a two-photon absorption dye together with its interaction with DNA. The linear and non-linear optical properties are modeled taking into account the complex environment including dynamic and vibrational effects. It is also clearly demonstrated that the excited state manifold may evolve toward spontaneous photoionization with the production of a solvated electron. In turn both the radical cation and the solvated electron may react with the DNA backbone to produce a strand break; hence we have characterized a phototherapeutic dye that absorbs in the infrared region and is able to work under hypoxidic conditions, i.e. a prodrug of great interest for the potential treatment of solid tumors. PMID:27345613

  4. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    NASA Astrophysics Data System (ADS)

    Rana, Amit Kumar; J, Aneesh; Kumar, Yogendra; M. S, Arjunan; Adarsh, K. V.; Sen, Somaditya; Shirage, Parasharam M.

    2015-12-01

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  5. High-accuracy reference standards for two-photon absorption in the 680-1050 nm wavelength range.

    PubMed

    de Reguardati, Sophie; Pahapill, Juri; Mikhailov, Alexander; Stepanenko, Yuriy; Rebane, Aleksander

    2016-04-18

    Degenerate two-photon absorption (2PA) of a series of organic fluorophores is measured using femtosecond fluorescence excitation method in the wavelength range, λ2PA = 680-1050 nm, and ~100 MHz pulse repetition rate. The function of relative 2PA spectral shape is obtained with estimated accuracy 5%, and the absolute 2PA cross section is measured at selected wavelengths with the accuracy 8%. Significant improvement of the accuracy is achieved by means of rigorous evaluation of the quadratic dependence of the fluorescence signal on the incident photon flux in the whole wavelength range, by comparing results obtained from two independent experiments, as well as due to meticulous evaluation of critical experimental parameters, including the excitation spatial- and temporal pulse shape, laser power and sample geometry. Application of the reference standards in nonlinear transmittance measurements is discussed.

  6. Enhanced two-photon absorption and fluorescence upconversion in Thioflavin T micelle-type aggregates in glycerol/water solution

    NASA Astrophysics Data System (ADS)

    Donnelly, Julie; Vesga, Yuly; Hernandez, Florencio E.

    2016-09-01

    In this article, we report the systematic characterization of the two-photon absorption of ThT in different mixtures of glycerol/water solution. The relationships of TPA peak position and amplitude revealed a dependence on particle size suggesting that the curious trend observed in TPA with changing glycerol content can be attributed to the presence of micelle-type aggregates. Consequently, the relatively strong TPA cross-section (δTPA = 300 GM) obtained in 8.75% glycerol/water solutions could be attributed to the immobilization of dye molecules and the strong coupling of the molecular transition dipoles in micelle-type aggregates. This enhancement of TPA, in addition to the already reported significant fluorescence quantum yield of ThT attached to brain tissue, is expected to boost the application of this compound for in vitro and perhaps in vivo high resolution multiphoton bioimaging of amyloids in brain tissue.

  7. Antimony orthophosphate glasses with large nonlinear refractive indices, low two-photon absorption coefficients, and ultrafast response

    SciTech Connect

    Falcao-Filho, E.L.; Araujo, Cid B. de; Bosco, C.A.C.; Maciel, G.S.; Acioli, L.H.; Nalin, M.; Messaddeq, Y.

    2005-01-01

    Antimony glasses based on the composition Sb{sub 2}O{sub 3}-SbPO{sub 4} were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n{sub 2}, of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response (<100 fs) for all compositions. Enhancement of n{sub 2} was observed by adding lead oxide to the Sb{sub 2}O{sub 3}-SbPO{sub 4} composition. Large values of n{sub 2}{approx_equal}10{sup -14} cm{sup 2}/W and negligible two-photon absorption coefficients (smaller than 0.01 cm/GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications.

  8. Multi-mode interference revealed by two photon absorption in silicon rich SiO{sub 2} waveguides

    SciTech Connect

    Manna, S. E-mail: mattia.mancinelli@unitn.it; Ramiro-Manzano, F.; Mancinelli, M. E-mail: mattia.mancinelli@unitn.it; Turri, F.; Pavesi, L.; Ghulinyan, M.; Pucker, G.

    2015-02-16

    Photoluminescence (PL) from Si nanocrystals (NCs) excited by two-photon absorption (TPA) has been observed in Si nanocrystal-based waveguides fabricated by plasma enhanced chemical vapor deposition. The TPA excited photoluminescence emission resembles the one-photon excited photoluminescence arising from inter-band transitions in the quantum confined Si nanocrystals. By measuring the non-linear transmission of waveguides, a large TPA coefficient of β up to 10{sup −8 }cm/W has been measured at 1550 nm. These values of β depend on the Si NCs size and are two orders of magnitude larger than the bulk silicon value. Here, we propose to use the TPA excited visible PL emission as a tool to map the spatial intensity profile of the 1550 nm propagating optical modes in multimode waveguides. In this way, multimode interference has been revealed experimentally and confirmed through a finite element simulation.

  9. Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet

    NASA Astrophysics Data System (ADS)

    Conway, J.; Gogna, G. S.; Gaman, C.; Turner, M. M.; Daniels, S.

    2016-08-01

    Atomic oxygen number density [O] is measured in an air atmospheric pressure plasma jet (APPJ) using two-photon absorption laser induced fluorescence (TALIF). Gas flow is fixed at 8 slpm, the RF power coupled into the plasma jet varied between 5 W and 20 W, and the resulting changes in atomic oxygen density measured. Photolysis of molecular oxygen is employed to allow in situ calibration of the TALIF system. During calibration, O2 photo-dissociation and two-photon excitation of the resulting oxygen atoms are achieved within the same laser pulse. The atomic oxygen density produced by photolysis is time varying and spatially non-uniform which needs to be corrected for to calibrate the TALIF system for measurement of atomic oxygen density in plasma. Knowledge of the laser pulse intensity I 0(t), wavelength, and focal spot size allows correction factors to be determined using a rate equation model. Atomic oxygen is used for calibration and measurement, so the laser intensity can be increased outside the TALIF quadratic laser power dependence region without affecting the calibration reliability as the laser power dependence will still be the same for both. The atomic O density results obtained are not directly benchmarked against other known density measurement techniques. The results show that the plasma jet atomic oxygen content increases as the RF power coupled into the plasma increases.

  10. Two-photon absorption of fluorescent protein chromophores incorporating non-canonical amino acids: TD-DFT screening and classical dynamics.

    PubMed

    Alaraby Salem, M; Brown, Alex

    2015-10-14

    Two-photon spectroscopy of fluorescent proteins is a powerful bio-imaging tool characterized by deep tissue penetration and little damage. However, two-photon spectroscopy has lower sensitivity than one-photon microscopy alternatives and hence a protein with a large two-photon absorption cross-section is needed. We use time-dependent density functional theory (TD-DFT) at the B3LYP/6-31+G(d,p) level of theory to screen twenty-two possible chromophores that can be formed upon replacing the amino-acid Tyr66 that forms the green fluorescent protein (GFP) chromophore with a non-canonical amino acid. A proposed chromophore with a nitro substituent was found to have a large two-photon absorption cross-section (29 GM) compared to other fluorescent protein chromophores as determined at the same level of theory. Classical molecular dynamics are then performed on a nitro-modified fluorescent protein to test its stability and study the effect of the conformational flexibility of the chromophore on its two-photon absorption cross-section. The theoretical results show that the large cross-section is primarily due to the difference between the permanent dipole moments of the excited and ground states of the nitro-modified chromophore. This large difference is maintained through the various conformations assumed by the chromophore in the protein cavity. The nitro-derived protein appears to be very promising as a two-photon absorption probe.

  11. Two-Photon Absorption of Bacteriorhodopsin: Formation of a Red-Shifted Thermally Stable Photoproduct F620

    PubMed Central

    Fischer, Thorsten; Hampp, Norbert A.

    2005-01-01

    By means of high-intensity 532 nm laser pulses, a photochemical conversion of the initial B570 state of bacteriorhodopsin (BR) to a stable photoproduct absorbing maximally at ≈620 nm in BR suspensions and at ≈610 nm in BR films is induced. This state, which we named F620, is photochemically further converted to a group of three products with maximal absorptions in the wavelength range from 340 nm to 380 nm, which show identical spectral properties to the so-called P360 state reported in the literature. The photoconversion from B570 to F620 is most likely a resonant two-photon absorption induced step. The formation of F620 and P360 leads to a distinguished photo-induced permanent optical anisotropy in BR films. The spectral dependence of the photo-induced anisotropy and the anisotropy orientations at the educt (B570) and product (F620) wavelengths are strong indicators that F620 is formed in a direct photochemical step from B570. The chemical nature of the P360 products probably is that of a retro-retinal containing BR, but the structural characteristics of the F620 state are still unclear. The photo-induced permanent anisotropy induced by short laser pulses in BR films helps to better understand the photochemical pathways related to this transition, and it is interesting in view of potential applications as this feature is the molecular basis for permanent optical data storage using BR films. PMID:15894635

  12. Saturable absorption and two-photon absorption of 1,2,5-thiadiazolo[3,4-g]quinoxaline based derivatives with near-infrared fluorescence

    NASA Astrophysics Data System (ADS)

    Du, Yabing; Lin, Xiaodong; Jia, Tingjian; Dong, Jun

    2015-03-01

    Organic molecules with near-infrared (NIR) fluorescence are extremely interesting for the applications in nonlinear optical devices and bioimaging. However, such kind of materials have been relatively rarely studied. In this work, the nonlinear optical properties of 1,2,5-thiadiazolo[3,4-g]quinoxaline based derivatives with NIR fluorescence emission have been investigated for the first time. Under the excitation of femtosecond pulses at 532 nm, the chromophore with dithienyl as donor (TQ2) presents saturable absorption (SA) behavior, while no SA has been observed in the derivative with biphenyl (TQ1) as donor. Moreover, TQ2 exhibits much larger two-photon absorption (TPA) cross-sections with strong NIR fluorescence in the second biological window. The larger nonlinear optical properties of TQ2 is due to the introduction of stronger electron-donating group (dithienyl) and the resultant enhanced intramolecular charge transfer properties. At the end, TPA based optical limiting behaviors of the molecules are demonstrated in THF solutions, thanks to their large solubility and strong TPA.

  13. o-nitrobenzyl photolabile protecting groups with red-shifted absorption: syntheses and uncaging cross-sections for one- and two-photon excitation.

    PubMed

    Aujard, Isabelle; Benbrahim, Chouaha; Gouget, Marine; Ruel, Odile; Baudin, Jean-Bernard; Neveu, Pierre; Jullien, Ludovic

    2006-09-01

    We evaluated the o-nitrobenzyl platform for designing photolabile protecting groups with red-shifted absorption that could be photolyzed upon one- and two-photon excitation. Several synthetic pathways to build different conjugated o-nitrobenzyl backbones, as well as to vary the benzylic position, are reported. Relative to the reference 4,5-dimethoxy-2-nitrobenzyl group, several o-nitrobenzyl derivatives exhibit a large and red-shifted one-photon absorption within the near-UV range. Uncaging after one-photon excitation was studied by measuring UV-visible absorption and steady-state fluorescence emission on model caged ethers and esters. In the whole series investigated, the caged substrates were released cleanly upon photolysis. Quantum yields of uncaging after one-photon absorption lie within the 0.1-1 % range. We observed that these drop as the maximum wavelength absorption of the o-nitrobenzyl protecting group is increased. A new method based on fluorescence correlation spectroscopy (FCS) after two-photon excitation was used to measure the action uncaging cross section for two-photon excitation. The series of o-nitrobenzyl caged fluorescent coumarins investigated exhibit values within the 0.1-0.01 Goeppert-Mayer (GM) range. Such results are in line with the low quantum yields of uncaging associated with cross-sections of 1-50 GM for two-photon absorption. Although the cross-sections for one- and two-photon absorption of o-nitrobenzyl photolabile protecting groups can be readily improved, we emphasize the difficulty in enlarging the corresponding action uncaging cross-sections in view of the observed trend of their quantum yield of uncaging.

  14. o-nitrobenzyl photolabile protecting groups with red-shifted absorption: syntheses and uncaging cross-sections for one- and two-photon excitation.

    PubMed

    Aujard, Isabelle; Benbrahim, Chouaha; Gouget, Marine; Ruel, Odile; Baudin, Jean-Bernard; Neveu, Pierre; Jullien, Ludovic

    2006-09-01

    We evaluated the o-nitrobenzyl platform for designing photolabile protecting groups with red-shifted absorption that could be photolyzed upon one- and two-photon excitation. Several synthetic pathways to build different conjugated o-nitrobenzyl backbones, as well as to vary the benzylic position, are reported. Relative to the reference 4,5-dimethoxy-2-nitrobenzyl group, several o-nitrobenzyl derivatives exhibit a large and red-shifted one-photon absorption within the near-UV range. Uncaging after one-photon excitation was studied by measuring UV-visible absorption and steady-state fluorescence emission on model caged ethers and esters. In the whole series investigated, the caged substrates were released cleanly upon photolysis. Quantum yields of uncaging after one-photon absorption lie within the 0.1-1 % range. We observed that these drop as the maximum wavelength absorption of the o-nitrobenzyl protecting group is increased. A new method based on fluorescence correlation spectroscopy (FCS) after two-photon excitation was used to measure the action uncaging cross section for two-photon excitation. The series of o-nitrobenzyl caged fluorescent coumarins investigated exhibit values within the 0.1-0.01 Goeppert-Mayer (GM) range. Such results are in line with the low quantum yields of uncaging associated with cross-sections of 1-50 GM for two-photon absorption. Although the cross-sections for one- and two-photon absorption of o-nitrobenzyl photolabile protecting groups can be readily improved, we emphasize the difficulty in enlarging the corresponding action uncaging cross-sections in view of the observed trend of their quantum yield of uncaging. PMID:16763952

  15. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    PubMed

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. PMID:27607941

  16. Temperature-dependent excitonic photoluminescence excited by two-photon absorption in perovskite CsPbBr3 quantum dots.

    PubMed

    Wei, Ke; Xu, Zhongjie; Chen, Runze; Zheng, Xin; Cheng, Xiangai; Jiang, Tian

    2016-08-15

    Recently, lead halide perovskite quantum dots have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) has been studied at a broad temperature range, from 80 to 380 K. Two-photon absorption has been investigated and the absorption coefficient is up to 0.085 cm/GW at room temperature. Moreover, the PL spectrum excited by two-photon absorption shows a linear blue-shift (0.32 meV/K) below the temperature of 220 K. However, for higher temperatures, the PL peak approaches a roughly constant value and shows temperature-independent chromaticity up to 380 K. This behavior is distinct from the general red-shift for semiconductors and can be attributed to the result of thermal expansion, electron-phonon interaction and structural phase transition around 360 K. The strong nonlinear absorption and temperature-independent chromaticity of CsPbBr3 QDs observed in temperature range from 220 to 380 K will offer new opportunities in nonlinear photonics, light-harvesting, and light-emitting devices. PMID:27519098

  17. Prediction of two-photon absorption enhancement in red fluorescent protein chromophores made from non-canonical amino acids.

    PubMed

    Salem, M Alaraby; Twelves, Isaac; Brown, Alex

    2016-09-21

    Two-photon spectroscopy of fluorescent proteins is a powerful bio-imaging tool known for deep tissue penetration and little cellular damage. Being less sensitive than the one-photon microscopy alternatives, a protein with a large two-photon absorption (TPA) cross-section is needed. Here, we use time-dependent density functional theory (TD-DFT) at the B3LYP and CAM-B3LYP/6-31+G(d,p) levels of theory to screen twenty-two possible chromophores that can be formed upon replacing the amino-acid Tyr66 that forms the red fluorescent protein (RFP) chromophore with a non-canonical amino acid. The two-level model for TPA was used to assess the properties (i.e., transition dipole moment, permanent dipole moment difference, and the angle between them) leading to the TPA cross-sections determined via response theory. Computing TPA cross-sections with B3LYP and CAM-B3LYP yields similar overall trends. Results using both functionals agree that the RFP-derived model of the Gold Fluorescent Protein chromophore (Model 20) has the largest intrinsic TPA cross-section at the optimized geometry. TPA was further computed for selected chromophores following conformational changes: variation of both the dihedral angle of the acylimine moiety and the tilt and twist angles between the rings of the chromophore. The TPA cross-section assumed an oscillatory trend with the rotation of the acylimine dihedral, and the TPA is maximized in the planar conformation for almost all models. Model 21 (a hydroxyquinoline derivative) is shown to be comparable to Model 20 in terms of TPA cross-section. The conformational study on Model 21 shows that the acylimine angle has a much stronger effect on the TPA than its tilt and twist angles. Having an intrinsic TPA ability that is more than 7 times that of the native RFP chromophore, Models 20 and 21 appear to be very promising for future experimental investigation. PMID:27534378

  18. Prediction of two-photon absorption enhancement in red fluorescent protein chromophores made from non-canonical amino acids.

    PubMed

    Salem, M Alaraby; Twelves, Isaac; Brown, Alex

    2016-09-21

    Two-photon spectroscopy of fluorescent proteins is a powerful bio-imaging tool known for deep tissue penetration and little cellular damage. Being less sensitive than the one-photon microscopy alternatives, a protein with a large two-photon absorption (TPA) cross-section is needed. Here, we use time-dependent density functional theory (TD-DFT) at the B3LYP and CAM-B3LYP/6-31+G(d,p) levels of theory to screen twenty-two possible chromophores that can be formed upon replacing the amino-acid Tyr66 that forms the red fluorescent protein (RFP) chromophore with a non-canonical amino acid. The two-level model for TPA was used to assess the properties (i.e., transition dipole moment, permanent dipole moment difference, and the angle between them) leading to the TPA cross-sections determined via response theory. Computing TPA cross-sections with B3LYP and CAM-B3LYP yields similar overall trends. Results using both functionals agree that the RFP-derived model of the Gold Fluorescent Protein chromophore (Model 20) has the largest intrinsic TPA cross-section at the optimized geometry. TPA was further computed for selected chromophores following conformational changes: variation of both the dihedral angle of the acylimine moiety and the tilt and twist angles between the rings of the chromophore. The TPA cross-section assumed an oscillatory trend with the rotation of the acylimine dihedral, and the TPA is maximized in the planar conformation for almost all models. Model 21 (a hydroxyquinoline derivative) is shown to be comparable to Model 20 in terms of TPA cross-section. The conformational study on Model 21 shows that the acylimine angle has a much stronger effect on the TPA than its tilt and twist angles. Having an intrinsic TPA ability that is more than 7 times that of the native RFP chromophore, Models 20 and 21 appear to be very promising for future experimental investigation.

  19. Two-photon absorption properties of cationic 1,4-bis(styryl)benzene derivative and its inclusion complexes with cyclodextrins.

    PubMed

    Nag, Okhil Kumar; Nayak, Rati Ranjan; Lim, Chang Su; Kim, In Hong; Kyhm, Kwangseuk; Cho, Bong Rae; Woo, Han Young

    2010-07-29

    Two-photon absorption properties of 1,4-bis{4'-[N,N-bis(6''-trimethylammoniumhexyl)amino]styryl}benzene tetrabromide (C1) and its inclusion complexes (ICs) with cyclodextrins (CDs) have been studied. Upon complexation with CDs, the absorption spectra of C1 showed a slight red shift, whereas the emission spectra showed a blue shift with concomitant increase in the fluorescence quantum efficiency. A Stern-Volmer study using K(3)Fe(CN)(6) as a quencher revealed significant reduction in the photoinduced charge transfer quenching, in accord with the IC formation. Comparison of the spectroscopic results reveals that C1 forms increasingly more stable ICs in the order C1/beta-CD < C1/gamma-CD < C1/(3gamma:beta)-CD (gamma-CD/beta-CD 3:1, mole ratio). Moreover, the two-photon action cross section of C1 increased from 200 GM for C1 to 400 GM for C1/beta-CD, 460 GM for C1/gamma-CD, and 650 GM for C1/(3gamma:beta)-CD, respectively. Furthermore, the two-photon microscopy images of HeLa cells stained with C1 emitted strong two-photon excited fluorescence in the plasma membrane. These results provide a useful guideline for the development of efficient two-photon materials for bioimaging applications.

  20. Acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids with strong two-photon absorption and high singlet oxygen quantum yield.

    PubMed

    Ke, Hanzhong; Li, Wenbin; Zhang, Tao; Zhu, Xunjin; Tam, Hoi-Lam; Hou, Anxin; Kwong, Daniel W J; Wong, Wai-Kwok

    2012-04-21

    Several acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids, PZn-PcYb, PH(2)-PcYb and PPd-PcYb, have been prepared and characterized by (1)H and (31)P NMR, mass spectrometry, and UV-vis spectroscopy. Their photophysical and photochemical properties, especially the relative singlet oxygen ((1)O(2)) quantum yields and the two-photon absorption cross-section (σ(2)), were investigated. These three newly synthesized compounds exhibited very large σ(2) values and substantial (1)O(2) quantum yields upon photo-excitation, making them potential candidates as one- and two-photon photodynamic therapeutic agents.

  1. Application of the Z-scan technique to determine the optical Kerr coefficient and two-photon absorption coefficient of magnetite nanoparticles colloidal suspension

    NASA Astrophysics Data System (ADS)

    Vivacqua, Marco; Espinosa, Daniel; Martins Figueiredo Neto, Antônio

    2012-06-01

    We investigate the occurrence of the optical Kerr effect and two-photon absorption when an oil-based magnetic Fe3O4 nanoparticles colloidal suspension is illuminated with high intensity femtosecond laser pulses. The frequency of the pulses is controlled and the Z-scan technique is employed in our measurements of the nonlinear optical Kerr coefficient (n2) and two-photon absorption coefficient (β). From these values it was possible to calculate the real and imaginary parts of the third-order susceptibility. We observed that increasing the pulse frequency, additional physical processes take place, increasing artificially the absolute values of n2 and β. The experimental conditions are discussed to assure the obtention of reliable values of these nonlinear optical parameters, which may be useful in all-optical switching and optical power limiting applications.

  2. Merged beam laser design for reduction of gain-saturation and two-photon absorption in high power single mode semiconductor lasers.

    PubMed

    Lysevych, M; Tan, H H; Karouta, F; Fu, L; Jagadish, C

    2013-04-01

    In this paper we report a method to overcome the limitations of gain-saturation and two-photon absorption faced by developers of high power single mode InP-based lasers and semiconductor optical amplifiers (SOA) including those based on wide-waveguide or slab-coupled optical waveguide laser (SCOWL) technology. The method is based on Y-coupling design of the laser cavity. The reduction in gain-saturation and two-photon absorption in the merged beam laser structures (MBL) are obtained by reducing the intensity of electromagnetic field in the laser cavity. Standard ridge-waveguide lasers and MBLs were fabricated, tested and compared. Despite a slightly higher threshold current, the reduced gain-saturation in MBLs results in higher output power. The MBLs also produced a single spatial mode, as well as a strongly dominating single spectral mode which is the inherent feature of MBL-type cavity.

  3. Combining Ruthenium(II) Complexes with Metal-Organic Frameworks to Realize Effective Two-Photon Absorption for Singlet Oxygen Generation.

    PubMed

    Zhang, Wenxiang; Li, Bin; Ma, Heping; Zhang, Liming; Guan, Yunlong; Zhang, Yihe; Zhang, Xindan; Jing, Pengtao; Yue, Shumei

    2016-08-24

    Singlet oxygen ((1)O2), as a reactive oxygen species, has garnered serious attention in physical, chemical, and biological studies. In this paper, we designed and synthesized a new type of singlet-oxygen generation system by exchanging cationic ruthenium complexes (RCs) into anionic bio-MOF-1. The resulting bio-MOF-1&RCs can be used as effective photocatalysts for generation of singlet oxygen under both single-photon and two-photon excitation. Especially, the excellent two-photon absorption (TPA) behavior of bio-MOF-1&RCs aroused our interest greatly because their two-photon absorption band lies in the optical window of biological tissue. Here, we measured the ability of bio-MOF-1&RCs to generate (1)O2 by irradiation under both 490 and 800 nm wavelength light in DMF. 1,3-Diphenylisobenzofuran (DPBF) and 2',7'-dichlorofluorescein (DCFH) were used as typical (1)O2 traps to detect and evaluate the efficiency of generation of (1)O2 under single-photon and two-photon excitation, respectively. Results indicated that bio-MOF-1&[Ru(phen)3](2+) was able to effectively generate (1)O2 under both conditions. Our work creates a novel synergistic TPA system with the excellent photophysical properties of RCs and the unique microporous structure benefit of MOFs, which may open a new avenue for creation of a cancer treatment system with both photodynamic therapy and chemotherapy. PMID:27483010

  4. Biocompatible photoresistant far-red emitting, fluorescent polymer probes, with near-infrared two-photon absorption, for living cell and zebrafish embryo imaging.

    PubMed

    Adjili, Salim; Favier, Arnaud; Fargier, Guillaume; Thomas, Audrey; Massin, Julien; Monier, Karine; Favard, Cyril; Vanbelle, Christophe; Bruneau, Sylvia; Peyriéras, Nadine; Andraud, Chantal; Muriaux, Delphine; Charreyre, Marie-Thérèse

    2015-04-01

    Exogenous probes with far-red or near-infrared (NIR) two-photon absorption and fluorescence emission are highly desirable for deep tissue imaging while limiting autofluorescence. However, molecular probes exhibiting such properties are often hydrophobic. As an attractive alternative, we synthesized water-soluble polymer probes carrying multiple far-red fluorophores and demonstrated here their potential for live cell and zebrafish embryo imaging. First, at concentrations up to 10 μm, these polymer probes were not cytotoxic. They could efficiently label living HeLa cells, T lymphocytes and neurons at an optimal concentration of 0.5 μm. Moreover, they exhibited a high resistance to photobleaching in usual microscopy conditions. In addition, these polymer probes could be successfully used for in toto labeling and in vivo two-photon microscopy imaging of developing zebrafish embryos, with remarkable properties in terms of biocompatibility, internalization, diffusion, stability and wavelength emission range. The near-infrared two-photon absorption peak at 910 nm is particularly interesting since it does not excite the zebrafish endogenous fluorescence and is likely to enable long-term time-lapse imaging with limited photodamage.

  5. Determination of Two-Photon Absorption Cross-Section of Noble Gases for Calibration of Laser Spectroscopic Techniques

    SciTech Connect

    Rosa, M. I. de la; Perez, C.; Gruetzmacher, K.; Fuentes, L. M.

    2008-10-22

    The objective of our work is to apply two-photon polarization spectroscopy as a new calibration method for the determination of two-photon excitation cross-sections of noble gases, like Xe and Kr, which are commonly used for calibrations of MP-LIF techniques in other laboratories.

  6. Two photon absorption energy transfer in the light-harvesting complex of photosystem II (LHC-II) modified with organic boron dye.

    PubMed

    Chen, Li; Liu, Cheng; Hu, Rui; Feng, Jiao; Wang, Shuangqing; Li, Shayu; Yang, Chunhong; Yang, Guoqiang

    2014-07-15

    The plant light-harvesting complexes of photosystem II (LHC-II) play important roles in collecting solar energy and transferring the energy to the reaction centers of photosystems I and II. A two photon absorption compound, 4-(bromomethyl)-N-(4-(dimesitylboryl)phenyl)-N-phenylaniline (DMDP-CH2Br), was synthesized and covalently linked to the LHC-II in formation of a LHC-II-dye complex, which still maintained the biological activity of LHC-II system. Under irradiation with femtosecond laser pulses at 754 nm, the LHC-II-dye complex can absorb two photons of the laser light effectively compared with the wild type LHC-II. The absorbed excitation energy is then transferred to chlorophyll a with an obvious fluorescence enhancement. The results may be interesting and give potentials for developing hybrid photosystems.

  7. Two photon absorption energy transfer in the light-harvesting complex of photosystem II (LHC-II) modified with organic boron dye

    NASA Astrophysics Data System (ADS)

    Chen, Li; Liu, Cheng; Hu, Rui; Feng, Jiao; Wang, Shuangqing; Li, Shayu; Yang, Chunhong; Yang, Guoqiang

    2014-07-01

    The plant light-harvesting complexes of photosystem II (LHC-II) play important roles in collecting solar energy and transferring the energy to the reaction centers of photosystems I and II. A two photon absorption compound, 4-(bromomethyl)-N-(4-(dimesitylboryl)phenyl)-N-phenylaniline (DMDP-CH2Br), was synthesized and covalently linked to the LHC-II in formation of a LHC-II-dye complex, which still maintained the biological activity of LHC-II system. Under irradiation with femtosecond laser pulses at 754 nm, the LHC-II-dye complex can absorb two photons of the laser light effectively compared with the wild type LHC-II. The absorbed excitation energy is then transferred to chlorophyll a with an obvious fluorescence enhancement. The results may be interesting and give potentials for developing hybrid photosystems.

  8. Ultrafast all-optical logic OR gate based on two-photon absorption with a semiconductor optical amplifier-assisted delayed interferometer

    NASA Astrophysics Data System (ADS)

    Kotb, Amer

    2016-01-01

    The performance of an all-optical logic OR gate is numerically studied and simulated. This Boolean operation is realized by using a semiconductor optical amplifier (SOA) and a delayed interferometer (DI) based on two-photon absorption (TPA). The input pulse intensities are high enough so that the two-photon-induced phase change is larger than the regular gain-induced phase change. The study is carried out with the effect of the amplified spontaneous emission (ASE) taken into account in the simulation analysis. The dependence of the output quality factor ( Q-factor) on the data signals and SOA's parameters is also investigated and discussed. The achieved results show that the OR gate is capable of operating at a data speed of 250 Gb/s with logical correctness and proper Q-factor.

  9. N-annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption.

    PubMed

    Luo, Jie; Lee, Sangsu; Son, Minjung; Zheng, Bin; Huang, Kuo-Wei; Qi, Qingbiao; Zeng, Wangdong; Li, Gongqiang; Kim, Dongho; Wu, Jishan

    2015-02-23

    Fusion of two N-annulated perylene (NP) units with a fused porphyrin dimer along the S0-S1 electronic transition moment axis has resulted in new near-infrared (NIR) dyes 1 a/1 b with very intense absorption (ε>1.3×10(5) M(-1) cm(-1)) beyond 1250 nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10(-6) and 6.0×10(-6) for 1 a and 1 b, respectively. The NP-substituted porphyrin dimers 2 a/2 b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited-state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer-like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two-photon absorption cross-sections in the NIR region due to extended π-conjugation. Time-dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.

  10. Relation between bond-length alternation and two-photon absorption of a push pull conjugated molecules: a quantum-chemical study

    NASA Astrophysics Data System (ADS)

    Bartkowiak, W.; Zaleśny, R.; Leszczynski, J.

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ( δ) of a series of prototypical π-conjugated push-pull molecules are presented. The calculations of δ for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ( β and γ) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of δ on the BLA parameter was noticed.

  11. Enhanced photoluminescence due to two-photon enhanced three-photon absorption in Mn{sup 2+}-doped ZnS quantum dots

    SciTech Connect

    Subha, Radhu; Nalla, Venkatram; Ji, Wei; Feng, Xiaobo; Vijayan, C.

    2014-10-15

    In this work, we have investigated the multi-photon absorption induced photoluminescence in Mn{sup 2+}-doped ZnS quantum dots in the wavelength range 860 – 1050 nm (Near-Infrared Window I). The observed three-photon action cross-section has been compared with the theoretical prediction under four band approximation. An enhancement of four to five orders has been observed in the range from 970 to 1050 nm compared to the theoretical value, which is attributed to two-photon enhanced three-photon absorption. Transient lifetime measurements reveal a lifetime of 0.35 ± 0.3 ms, which is four to five orders higher than other conventional fluorescent probes.

  12. Inhibition of the two-photon absorption response exhibited by a bilayer TiO2 film with embedded Au nanoparticles.

    PubMed

    Torres-Torres, D; Trejo-Valdez, M; Castañeda, L; Torres-Torres, C; Tamayo-Rivera, L; Fernández-Hernández, R C; Reyes-Esqueda, J A; Muñoz-Saldaña, J; Rangel-Rojo, R; Oliver, A

    2010-08-01

    We use two different synthesis approaches for the preparation of TiO(2) films in order to study their resulting third order optical nonlinearity, and its modification by the inclusion of Au nanoparticles in one of the samples. An ultrasonic spray pyrolysis method was used for preparing a TiO(2) film in which we found two-photon absorption as a dominant nonlinear effect for 532 nm and 26 ps pulses; and a purely electronic nonlinearity at 830 nm for 80 fs pulses. A strong optical Kerr effect and the inhibition of the nonlinear optical absorption in 532 nm can be obtained for the first sample if Au nanoparticles embedded in a second TiO(2) film prepared by a sol-gel technique are added to it. We used an optical Kerr gate, z-scan, a multi-wave mixing experiment and an input-output transmittance experiment for measuring the optical nonlinearities.

  13. Direct Observation of Degenerate Two-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films.

    PubMed

    Zhang, Saifeng; Dong, Ningning; McEvoy, Niall; O'Brien, Maria; Winters, Sinéad; Berner, Nina C; Yim, Chanyoung; Li, Yuanxin; Zhang, Xiaoyan; Chen, Zhanghai; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2015-07-28

    The optical nonlinearity of WS2 and MoS2 monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near-infrared range. The nonlinear absorption of few- and multilayer WS2 and MoS2 films and their dependences on excitation wavelength were studied. WS2 films with 1-3 layers exhibited a giant two-photon absorption (TPA) coefficient as high as (1.0 ± 0.8) × 10(4) cm/GW. TPA saturation was observed for the WS2 film with 1-3 layers and for the MoS2 film with 25-27 layers. The giant nonlinearity of WS2 and MoS2 films is attributed to a two-dimensional confinement, a giant exciton effect, and the band edge resonance of TPA. PMID:26135798

  14. Fabrication of PDMS (poly-dimethyl siloxane) molding and 3D structure by two-photon absorption induced by an ultrafast laser

    NASA Astrophysics Data System (ADS)

    Yi, Shin Wook; Lee, Seong Ku; Cho, Mi Jung; Kong, Hong Jin; Yang, Dong-Yol; Park, Sang-hu; Lim, Tae-woo; Kim, Ran Hee; Lee, Kwang-Sup

    2004-12-01

    Multi-photon absorption phenomena induced by ultra fast laser have been considered for many applications of microfabrications such as metal ablation, glass etching and photopolymerization. Among the applications, the photopolymerization by two-photon absorption (TPA) has been regarded as a new microfabricating method. It is possible to be used in photo mask correcting, diffractive optical element and micro machining. The TPA photopolymerization is made possible to fabricate a complicated three dimensional structure which the conventional photomask technology has not been able to make. Furthermore the TPA photopolymerization process applied to a two dimensional structure fabrication may take shorter time than the old process since the absence of etching and deposition processes. Recently we have made a simple 3D structure and applied the technique to PDMS(poly-dimethyl siloxane) molding.

  15. Investigation of free charge carrier dynamics in single-crystalline CVD diamond by two-photon absorption

    SciTech Connect

    Ivakin, E V; Kisialiou, I G; Ralchenko, V G; Bolshakov, A P; Ashkinazi, E E; Sharonov, G V

    2014-11-30

    By using the methods of transient gratings (TGs) and induced absorption, we have studied the kinetics of plasma of free charge carriers (FCCs) created by the action of a picosecond laser pulse in two high-purity diamond single crystals synthesised from the gas phase. The gratings with different spatial periods have been excited at the wavelengths of 266 or 213 nm (above and below the fundamental absorption edge in diamond) and probed with continuous-wave radiation in the visible region. At the moderate FCC concentrations (∼7 × 10{sup 17} cm{sup -3}), the coefficient of ambipolar diffusion and the carrier recombination time of two crystals are 20.3 and 18.9 cm{sup 2} s{sup -1} and 30 and 190 ns, respectively. The increase in the carrier concentration up to 5 × 10{sup 19} cm{sup -3} reduces the TG lifetime. We have determined the conditions under which the relaxation of the grating of carriers leads to the formation of a thermal grating, with the amplitude sufficient for its experimental observation. (interaction of laser radiation with matter. laser plasma)

  16. Theoretical investigation of the two-photon absorption properties of 3,6-bis(4-vinylpyridinium) carbazole derivatives--new biological fluorescent probes.

    PubMed

    Sun, Ying; Zhao, Yang; Liu, Xiao-Ting; Ren, Ai-Min; Feng, Ji-Kang; Yu, Xiao-Qiang

    2012-06-01

    The present study focuses on a series of carbazole derivatives, which are being investigated as potential two-photon fluorescent probes (TFP) for DNA detection and two-photon bioimaging. The geometric structures, electronic structures, and the one-photon (OPA) and two-photon (TPA) absorption properties of 3,6-bis(1-methyl-4-vinylpyridinium) carbazole (BMVC) derivatives, as well as their dications and diiodized derivatives, were studied using density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) method. The results showed that the TPA spectra of the diiodized BMVC derivatives and their dications are all found in the near-infrared region (NIR). At the same time, the diiodized BMVC derivatives presented larger TPA cross-sections than the neutral BMVC derivatives and the dications. These theoretically derived values were also in good agreement with their corresponding experimentally observed values, and they indicated that the diiodized BMVC may be the form of this TFP that combines with DNA. The diiodized BMVC derivatives and the dications have the potential to be excellent TPA materials, especially when used as TFPs in nucleic acid imaging applications.

  17. Calculations of nonlinear response properties using the intermediate state representation and the algebraic-diagrammatic construction polarization propagator approach: two-photon absorption spectra.

    PubMed

    Knippenberg, S; Rehn, D R; Wormit, M; Starcke, J H; Rusakova, I L; Trofimov, A B; Dreuw, A

    2012-02-14

    An earlier proposed approach to molecular response functions based on the intermediate state representation (ISR) of polarization propagator and algebraic-diagrammatic construction (ADC) approximations is for the first time employed for calculations of nonlinear response properties. The two-photon absorption (TPA) spectra are considered. The hierarchy of the first- and second-order ADC∕ISR computational schemes, ADC(1), ADC(2), ADC(2)-x, and ADC(3/2), is tested in applications to H(2)O, HF, and C(2)H(4) (ethylene). The calculated TPA spectra are compared with the results of coupled cluster (CC) models and time-dependent density-functional theory (TDDFT) calculations, using the results of the CC3 model as benchmarks. As a more realistic example, the TPA spectrum of C(8)H(10) (octatetraene) is calculated using the ADC(2)-x and ADC(2) methods. The results are compared with the results of TDDFT method and earlier calculations, as well as to the available experimental data. A prominent feature of octatetraene and other polyene molecules is the existence of low-lying excited states with increased double excitation character. We demonstrate that the two-photon absorption involving such states can be adequately studied using the ADC(2)-x scheme, explicitly accounting for interaction of doubly excited configurations. Observed peaks in the experimental TPA spectrum of octatetraene are assigned based on our calculations.

  18. Nonlinear refraction and two-photon absorption in dense 2Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3} glasses

    SciTech Connect

    Paramesh, Gadige; Varma, K. B. R.

    2012-06-05

    High density transparent glasses (7.86 g/cc) were fabricated in the 2Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3} (BBO) system. Optical band gap of the obtained glasses was found to be 2.6eV. The refractive index measured for these glasses was 2.25{+-}0.05 at {lambda}=543 nm. Nonlinear refraction and absorption studies were carried out on the BBO glasses using z-scan technique at {lambda}=532 nm of 10 ns pulse width. The nonlinear refractive index obtained was n{sub 2}=12.1x10{sup -14} cm{sup 2}/W and nonlinear absorption coefficient was {beta}=15.2 cm/GW. The n{sub 2} and {beta} values of the BBO glasses were large compared to the other reported high index bismuth based oxide glass systems in the literature. These were attributed to the high density, high linear refractive index, low band gap and two photon absorption associated with these glasses. The electronic origin of large nonlinearities was discussed based on bond-orbital theory.

  19. Solvent induced channel interference in the two-photon absorption process--a theoretical study with a generalized few-state-model in three dimensions.

    PubMed

    Alam, Md Mehboob; Chattopadhyaya, Mausumi; Chakrabarti, Swapan

    2012-01-21

    For the first time, we report the effect of interference between different optical channels on the two-photon absorption (TPA) process in three dimensions. We have employed response theory as well as a sum-over-states (SOS) approach involving few intermediate states to calculate the TPA parameters like transition probabilities (δ(TP)) and TPA tensor elements. In order to use the limited SOS approach, we have derived a new formula for a generalized few-state-model (GFSM) in three dimensions. Due to the presence of additional terms related to the angle between different transition moment vectors, the channel interference associated with the TPA process in 3D is significantly different and much more complicated than that in 1D and 2D cases. The entire study has been carried out on the two simplest Reichardt's dyes, namely 2- and 4-(pyridinium-1-yl)-phenolate (ortho- and para-betain) in gas phase, THF, CH(3)CN and water solvents. We have meticulously inspected the effect of the additional angle related terms on the overall TPA transition probabilities of the two 3D isomeric molecules studied and found that the interfering terms involved in the δ(TP) expression contribute both constructively and destructively as well to the overall δ(TP) value. Moreover, the interfering term has a more conspicuous role in determining the net δ(TP) associated with charge transfer transition in comparison to that of π-π* transition of the studied systems. Interestingly, our model calculations suggest that, for o- and p-betain, the quenching of destructive interference associated with a particular two-photon process can be done with high polarity solvents while the enhancement of constructive interference will be achieved in solvents having relatively small polarity. All the one- and two-photon parameters are evaluated using a range separated CAMB3LYP functional. PMID:22127437

  20. Benzothiazoles with tunable electron-withdrawing strength and reverse polarity: a route to triphenylamine-based chromophores with enhanced two-photon absorption.

    PubMed

    Hrobárik, Peter; Hrobáriková, Veronika; Sigmundová, Ivica; Zahradník, Pavol; Fakis, Mihalis; Polyzos, Ioannis; Persephonis, Peter

    2011-11-01

    A series of dipolar and octupolar triphenylamine-derived dyes containing a benzothiazole positioned in the matched or mismatched fashion have been designed and synthesized via palladium-catalyzed Sonogashira cross-coupling reactions. Linear and nonlinear optical properties of the designed molecules were tuned by an additional electron-withdrawing group (EWG) and by changing the relative positions of the donor and acceptor substituents on the heterocyclic ring. This allowed us to examine the effect of positional isomerism and extend the structure-property relationships useful in the engineering of novel heteroaromatic-based systems with enhanced two-photon absorption (TPA). The TPA cross-sections (δ(TPA)) in the target compounds dramatically increased with the branching of the triphenylamine core and with the strength of the auxiliary acceptor. In addition, a change from the commonly used polarity in push-pull benzothiazoles to a reverse one has been revealed as a particularly useful strategy (regioisomeric control) for enhancing TPA cross-sections and shifting the absorption and emission maxima to longer wavelengths. The maximum TPA cross-sections of the star-shaped three-branched triphenylamines are ∼500-2300 GM in the near-infrared region (740-810 nm); thereby the molecular weight normalized δ(TPA)/MW values of the best performing dyes within the series (2.0-2.4 GM·g(-1)·mol) are comparable to those of the most efficient TPA chromophores reported to date. The large TPA cross-sections combined with high emission quantum yields and large Stokes shifts make these compounds excellent candidates for various TPA applications, including two-photon fluorescence microscopy.

  1. Two-photon absorption properties of iron(II) and ruthenium(II) trischelate complexes of 2,2':4,4' ':4',4' ''-quaterpyridinium ligands.

    PubMed

    Coe, Benjamin J; Samoc, Marek; Samoc, Anna; Zhu, Lingyun; Yi, Yuanping; Shuai, Zhigang

    2007-01-25

    A series of RuII or FeII trischelate complex salts containing N-methyl/aryl-2,2':4,4' ':4',4' ''-quaterpyridinium ligands that has previously been subjected to quadratic nonlinear optical studies (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 13399) has now been investigated for two-photon absorbing behavior. Z-scan measurements using a 750 nm laser afford reasonably large two-photon absorption (2PA) cross-sections sigma2 of ca. 62-180 GM for the RuII complexes, but only very weak 2PA is observed for the FeII compounds. The excited-state and 2PA properties of the representative chromophore [RuII(Me2Qpy2+)3]8+ (Me2Qpy2+=N' ',N' ''-dimethyl-2,2':4,4' ':4',4' ''-quaterpyridinium) have also been investigated by using semiempirical intermediate neglect of differential overlap/multireference-determinant single and double configuration interaction computations with the optimized geometry obtained via density functional theory. The calculated sigma2 value of ca. 624 GM at 1.70 eV for this metal-to-ligand charge-transfer chromophore is about 10 times larger than that obtained from the Z-scan studies. PMID:17228896

  2. Large Femtosecond Two-Photon Absorption Cross-Sections of Fullerosome Vesicle Nanostructures Derived from Highly Photoresponsive Amphiphilic C60-Light-Harvesting Fluorene Dyad

    PubMed Central

    Wang, Min; Nalla, Venkatram; Jeon, Seaho; Mamidala, Venkatesh; Ji, Wei; Tan, Loon-Seng; Cooper, Thomas; Chiang, Long Y.

    2011-01-01

    We demonstrated ultrafast femtosecond nonlinear optical (NLO) absorption characteristics of bilayered fullerosome vesicle nanostructures derived from molecular self-assembly of amphiphilic oligo(ethylene glycolated) C60-(light-harvesting diphenylaminofluorene antenna). Fullerene conjugates were designed to enhance photoresponse in a femtosecond time scale by applying an isomerizable periconjugation linker between the C60 cage and diphenylaminofluorene antenna subunit in an intramolecular contact distance of only < 3.0 Å. Morphology of C60(>DPAF-EG12C1)-based fullerosome nanovesicles in H2O was characterized to consist of a bilayered shell with a sphere diameter of 20–70 nm and a chromophore shell-width of 9.0–10 nm, fitting well with a head-to-head packing configuration of the molecular length. At the estimated effective nanovesicle concentration as low as 5.5 × 10−8 MV (molecular molar concentration of 5.0 × 10−4 M) in H2O, two-photon absorption (2PA) phenomena were found to be the dominating photophysical events showing a large molar concentration-insensitive 2PA cross-section value equivalent to 8500 GM in a form of nanovesicles, on average. The observed NLO characteristics led to a sharp trend of efficient light-transmittance intensity reduction at the input laser intensity above 100 GW/cm2. PMID:22022620

  3. Two-dimensional organic molecules for two-photon absorption, aluminum alkyl complexes initiated polymerizations, and unimolecular living radical polymerization initiators

    NASA Astrophysics Data System (ADS)

    Bi, Xiangdong

    A study of structure-property relationship on two-photon absorbing chromophores showed that highly symmetric and conjugated molecular structures exhibited larger two-photon absorption cross-section in comparison to their counterparts with lower symmetry. A number of symmetric two-photon absorbing chromophores were developed. Measurements of their optical properties showed that cross-sections were further enhanced upon (i) attachment of electron donating groups, such as substituted amino groups, to the symmetric structures; (ii) extension of the conjugation length; and (iii) replacement of conjugated pi center with an sp3 hybridized nitrogen atom. Two-photon absorbing polymers and a dendritic structure of symmetric molecules were also synthesized and characterized. A series of bulky aluminum complexes were synthesized and characterized. For the first time, they were found to be active initiators towards the polymerization of acrylates. Coordination of methyl acrylate to aluminum complexes was observed by variable-temperature nuclear magnetic resonance spectroscopy. Adducts of methyl acrylate to aluminum complexes were isolated and characterized by both 1H and 13C nuclear magnetic resonance spectroscopy. The proposed mechanism involved a radical process where the radicals were produced by an assisted homolysis of the Al-alkyl bond. A kinetic study of the methyl acrylate polymerization initiated by bulky aluminum complex showed that the rate of polymerization was first-order with respect to the monomer concentration and half-order with respect to the concentration of aluminum initiator. Further investigation showed bulky aluminum complexes were also active in the initiation of the polymerization of styrene and some other monomers. A facile one-step synthesis of an unimolecular initiator, 2,3-dimethyl-4-phenyl-4-(2 ',2',6',6' -tetramethylpiperidinoxy)butanitrile, was developed for "living" radical polymerization study. A "living" polymerization of styrene was observed

  4. Novel 2,1,3-benzothiadiazole-based red-fluorescent dyes with enhanced two-photon absorption cross-sections.

    PubMed

    Kato, Shin-ichiro; Matsumoto, Taisuke; Shigeiwa, Motoyuki; Gorohmaru, Hideki; Maeda, Shuuichi; Ishi-i, Tsutomu; Mataka, Shuntaro

    2006-03-01

    This paper reports the two-photon absorbing and orange-red fluorescence emitting properties of a series of new 2,1,3-benzothiadiazole (BTD)-based D-pi-A-pi-D-type and star-burst-type fluorescent dyes. In the D-pi-A-pi-D-type dyes 1-6, a central BTD core was connected with two terminal N,N-disubstituted amino groups via various pi-conjugated spacers. The star-burst-type dyes 8 and 10 have a three-branched structure composed of a central core (benzene core in 8 and triphenylamine core in 10) and three triphenylamine-containing BTD branches. All the BTD-based dyes displayed intense orange-red color fluorescence in a region of 550-689 nm, which was obtained by single-photon excitation with good fluorescent quantum yield up to 0.98 as well as by two-photon excitation. Large two-photon absorption (TPA) cross-sections (110-800 GM) of these BTD dyes were evaluated by open aperture Z-scan technique with a femtosecond Ti/sapphire laser. The TPA cross-sections of D-pi-A-pi-D-type dyes 2-6 with a benzene, thiophene, ethene, ethyne, and styrene moiety, respectively, as an additional pi-conjugated spacer are about 1.5-2.5 times larger than that of 1c with only a benzene spacer. The TPA cross-sections significantly increased in three-branched star-burst-type BTDs 8 (780 GM) with a benzene core and 10 (800 GM) with a triphenylamine core, which are about 3-5 times larger than those of the corresponding one-dimensional sub-units 9 (170 GM) and 11 (230 GM), respectively. The ratios of sigma/e(pi) between three-branched and one-dimensional dyes were 6.5:3.8 (for 8 and 9) and 6.0:4.0 (for 10 and 11), which are larger than those predicted simply on the basis of the chromophore number density (1:1), according to a cooperative enhancement of the two-photon absorbing nature in the three-branched system.

  5. Two-photon absorption in SiO{sub 2}- and (SiO{sub 2} + GeO{sub 2})-based fibres at a wavelength of 349 nm

    SciTech Connect

    Chunaev, D S; Karasik, A Ya

    2014-06-30

    The nonlinear two-photon light absorption coefficients have been measured in an optical fibre with a quartz glass (SiO{sub 2}) core and in a fibre with a germanosilicate glass (SiO{sub 2} + GeO{sub 2}) core. The two-photon absorption coefficient β measured at a wavelength of 349 nm in the (SiO{sub 2} + GeO{sub 2})-based fibre (13.7 cm TW{sup -1}) multiply exceeds that for the pure quartz glass optical fibre (0.54 cm TW{sup -1}). (nonlinear optical phenomena)

  6. Solvent effects on static polarizability, static first hyperpolarizability and one- and two-photon absorption properties of functionalized triply twisted Möbius annulenes: a DFT study.

    PubMed

    Alam, Md Mehboob; Kundi, Varun; Thankachan, Pompozhi Protasis

    2016-08-21

    The present work aims to study solvent effects on the polarizability (α), static first hyperpolarizability (β) and one- and two-photon absorption (OPA and TPA) properties of a new class of molecules viz. triply twisted Möbius annulenes, recently studied by us in vacuum phase [Kundi et al., Phys. Chem. Chem. Phys., 2015, 17, 6827]. We have employed linear and quadratic response theories within the framework of time-dependent density functional theory with the CAM-B3LYP functional and a cc-pVDZ basis set to calculate different parameters. The microscopic details of the said properties have been studied using a two-state model (2SM) approach, which performs very well in the case of β and TPA of the first excited state of all the systems. However for the second excited state, the 2SM results are far from those of response theory. In fact, in comparison to response theory, 2SM predicts an opposite trend for the TP activity of some of the model systems, indicating a significant contribution from the other higher excited states. The anomaly between the 2SM approach and response theory has been resolved by incorporating three states in the calculations.

  7. Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Carter, C.

    2014-12-01

    Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

  8. Production mechanism of atomic nitrogen in atmospheric pressure pulsed corona discharge measured using two-photon absorption laser-induced fluorescence

    SciTech Connect

    Teramoto, Yoshiyuki; Ono, Ryo; Oda, Tetsuji

    2012-06-01

    To study the production mechanism of atomic nitrogen, the temporal profile and spatial distribution of atomic nitrogen are measured in atmospheric pressure pulsed positive corona discharge using two-photon absorption laser-induced fluorescence. The absolute atomic nitrogen density in the streamer filaments is estimated from decay rate of atomic nitrogen in N{sub 2} discharge. The results indicate that the absolute atomic nitrogen density is approximately constant against discharge energy. When the discharge voltage is 21.5 kV, production yield of atomic nitrogen produced by an N{sub 2} discharge pulse is estimated to be 2.9 - 9.8 Multiplication-Sign 10{sup 13} atoms and the energy efficiency of atomic nitrogen production is estimated to be about 1.8 - 6.1 Multiplication-Sign 10{sup 16} atoms/J. The energy efficiency of atomic nitrogen production in N{sub 2} discharge is constant against the discharge energy, while that in N{sub 2}/O{sub 2} discharge increases with discharge energy. In the N{sub 2}/O{sub 2} discharge, two-step process of N{sub 2} dissociation plays significant role for atomic nitrogen production.

  9. Red emissive AIE nanodots with high two-photon absorption efficiency at 1040 nm for deep-tissue in vivo imaging

    PubMed Central

    Wang, Yalun; Hu, Rongrong; Xi, Wang; Cai, Fuhong; Wang, Shaowei; Zhu, Zhenfeng; Bai, Rongpan; Qian, Jun

    2015-01-01

    Deep-tissue penetration is highly required in in vivo optical bioimaging. We synthesized a type of red emissive fluorophore BT with aggregation-induced emission (AIE) property. BT molecules were then encapsulated with amphiphilic polymers to form nanodots, and a large two-photon absorption (2PA) cross-section of 2.9 × 106 GM at 1040 nm was observed from each BT nanodot, which was much larger than those at the wavelengths of 770 to 860 nm. In addition, 1040 nm light was found to have better penetration and focusing capability than 800 nm light in biological tissue, according to the Monte Carlo simulation. The toxicity and tissue distribution of BT nanodots were studied, and they were found to have good biocompatibility. BT nanodots were then utilized for in vivo imaging of mouse ear and brain, and an imaging depth of 700 μm was obtained with the femtosecond (fs) excitation of 1040 nm. The red emissive AIE nanodots with high 2PA efficiency at 1040 nm would be useful for deep-tissue functional bioimaging in the future. PMID:26504629

  10. Solvent effects on static polarizability, static first hyperpolarizability and one- and two-photon absorption properties of functionalized triply twisted Möbius annulenes: a DFT study.

    PubMed

    Alam, Md Mehboob; Kundi, Varun; Thankachan, Pompozhi Protasis

    2016-08-21

    The present work aims to study solvent effects on the polarizability (α), static first hyperpolarizability (β) and one- and two-photon absorption (OPA and TPA) properties of a new class of molecules viz. triply twisted Möbius annulenes, recently studied by us in vacuum phase [Kundi et al., Phys. Chem. Chem. Phys., 2015, 17, 6827]. We have employed linear and quadratic response theories within the framework of time-dependent density functional theory with the CAM-B3LYP functional and a cc-pVDZ basis set to calculate different parameters. The microscopic details of the said properties have been studied using a two-state model (2SM) approach, which performs very well in the case of β and TPA of the first excited state of all the systems. However for the second excited state, the 2SM results are far from those of response theory. In fact, in comparison to response theory, 2SM predicts an opposite trend for the TP activity of some of the model systems, indicating a significant contribution from the other higher excited states. The anomaly between the 2SM approach and response theory has been resolved by incorporating three states in the calculations. PMID:27436622

  11. The two-photon absorptivity of rotational transitions in the A2 Sigma hyperon + (v prime = O) - X-2 pion (v prime prime = O) gamma band of nitric oxide

    NASA Technical Reports Server (NTRS)

    Gross, K. P.; Mckenzie, R. L.

    1982-01-01

    A predominantly single-mode pulsed dye laser system giving a well characterized spatial and temporal output suitable for absolute two-photon absorptivity measurements was used to study the NO gamma(0,0) S11 + R21 (J double prime = 7-1/2) transition. Using a calibrated induced-fluorescence technique, an absorptivity parameter of 2.8 + or - 1.4 x 10 to the minus 51st power cm to the 6th power was obtained. Relative strengths of other rotational transitions in the gamma(0,0) band were also measured and shown to compare well with predicted values in all cases except the O12 (J double prime = 10-1/2) transition.

  12. L(alpha)-induced two-photon absorption of visible light emitted from an O-type star by H2(+) ions located near the surface of the Stromgren sphere surrounding the star: A possible explanation for the diffuse interstellar absorption bands (DIDs)

    NASA Technical Reports Server (NTRS)

    Glownia, James H.; Sorokin, Peter P.

    1994-01-01

    In this paper, a new model is proposed to account for the DIB's (Diffuse Interstellar Bands). In this model, the DIB's result from a non-linear effect: resonantly-enhanced two-photon absorption of H(2+) ions located near the surface of the Stromgren sphere that surrounds an O- or B- type star. The strong light that is required to 'drive' the two-photon transition is provided by L(alpha) light emerging from the Stromgren sphere that bounds the H II region surrounding the star. A value of approximately 100 micro W/sq cm is estimated for the L(alpha) flux at the Stromgren radius, R(s), of a strong (O5) star. It is shown that a c.w. L(alpha) flux of this intensity should be sufficient to induce a few percent absorption for visible light radiated by the same star at a frequency (omega2) that completes an allowed two-photon transition, provided (1) the L(alpha) radiation happens to be nearly resonant with the frequency of a fully-allowed absorber transition that effectively represents the first step in the two-photon transition, and (2) an effective column density approximately 10(sup18)/sq cm of the absorber is present near the Stromgren sphere radius, R(sub s).

  13. Two-photon excitation and excited-state absorption cross sections for H2 E,F 1Sigma sub g (v=6) - Measurement and calculations

    NASA Astrophysics Data System (ADS)

    Buck, Jesse D.; Robie, Daniel C.; Hickman, A. P.; Bamford, Douglas J.; Bischel, William K.

    1989-04-01

    Observations of the E,F 1Sigma sub g (+) (v-prime=6)-to-B 1Sigma sub u (+) (v-double-prime=0) fluorescence transition at about 750 nm have been conducted to determine the absolute two-photon excitation cross section for the H2 E,F 1Sigma sub g (v-prime=6)-from-X 1Sigma sub g (v-double-prime=0) Q(1) transition at 193 nm. The 2.0 + or - 0.9 x 10 to the -36th cm exp 4 integrated two-photon excitation cross-section obtained is in good agreement with Huo and Jaffe's (1983) theoretical calculation result of 2.8 x 10 to the -36th cm exp 4.

  14. Two-photon absorption cross sections within equation-of-motion coupled-cluster formalism using resolution-of-the-identity and Cholesky decomposition representations: Theory, implementation, and benchmarks

    NASA Astrophysics Data System (ADS)

    Nanda, Kaushik D.; Krylov, Anna I.

    2015-02-01

    The equation-of-motion coupled-cluster (EOM-CC) methods provide a robust description of electronically excited states and their properties. Here, we present a formalism for two-photon absorption (2PA) cross sections for the equation-of-motion for excitation energies CC with single and double substitutions (EOM-CC for electronically excited states with single and double substitutions) wave functions. Rather than the response theory formulation, we employ the expectation-value approach which is commonly used within EOM-CC, configuration interaction, and algebraic diagrammatic construction frameworks. In addition to canonical implementation, we also exploit resolution-of-the-identity (RI) and Cholesky decomposition (CD) for the electron-repulsion integrals to reduce memory requirements and to increase parallel efficiency. The new methods are benchmarked against the CCSD and CC3 response theories for several small molecules. We found that the expectation-value 2PA cross sections are within 5% from the quadratic response CCSD values. The RI and CD approximations lead to small errors relative to the canonical implementation (less than 4%) while affording computational savings. RI/CD successfully address the well-known issue of large basis set requirements for 2PA cross sections calculations. The capabilities of the new code are illustrated by calculations of the 2PA cross sections for model chromophores of the photoactive yellow and green fluorescent proteins.

  15. Two-photon absorption cross sections within equation-of-motion coupled-cluster formalism using resolution-of-the-identity and Cholesky decomposition representations: Theory, implementation, and benchmarks

    SciTech Connect

    Nanda, Kaushik D.; Krylov, Anna I.

    2015-02-14

    The equation-of-motion coupled-cluster (EOM-CC) methods provide a robust description of electronically excited states and their properties. Here, we present a formalism for two-photon absorption (2PA) cross sections for the equation-of-motion for excitation energies CC with single and double substitutions (EOM-CC for electronically excited states with single and double substitutions) wave functions. Rather than the response theory formulation, we employ the expectation-value approach which is commonly used within EOM-CC, configuration interaction, and algebraic diagrammatic construction frameworks. In addition to canonical implementation, we also exploit resolution-of-the-identity (RI) and Cholesky decomposition (CD) for the electron-repulsion integrals to reduce memory requirements and to increase parallel efficiency. The new methods are benchmarked against the CCSD and CC3 response theories for several small molecules. We found that the expectation-value 2PA cross sections are within 5% from the quadratic response CCSD values. The RI and CD approximations lead to small errors relative to the canonical implementation (less than 4%) while affording computational savings. RI/CD successfully address the well-known issue of large basis set requirements for 2PA cross sections calculations. The capabilities of the new code are illustrated by calculations of the 2PA cross sections for model chromophores of the photoactive yellow and green fluorescent proteins.

  16. ABSORPTION ANALYZER

    DOEpatents

    Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

    1961-11-14

    A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

  17. Coherent Absorption of N00N States.

    PubMed

    Roger, Thomas; Restuccia, Sara; Lyons, Ashley; Giovannini, Daniel; Romero, Jacquiline; Jeffers, John; Padgett, Miles; Faccio, Daniele

    2016-07-01

    Recent results in deeply subwavelength thickness films demonstrate coherent control and logical gate operations with both classical and single-photon light sources. However, quantum processing and devices typically involve more than one photon and nontrivial input quantum states. Here we experimentally investigate two-photon N00N state coherent absorption in a multilayer graphene film. Depending on the N00N state input phase, it is possible to selectively choose between single- or two-photon absorption of the input state in the graphene film. These results demonstrate that coherent absorption in the quantum regime exhibits unique features, opening up applications in multiphoton spectroscopy and imaging. PMID:27447505

  18. Coherent Absorption of N00N States

    NASA Astrophysics Data System (ADS)

    Roger, Thomas; Restuccia, Sara; Lyons, Ashley; Giovannini, Daniel; Romero, Jacquiline; Jeffers, John; Padgett, Miles; Faccio, Daniele

    2016-07-01

    Recent results in deeply subwavelength thickness films demonstrate coherent control and logical gate operations with both classical and single-photon light sources. However, quantum processing and devices typically involve more than one photon and nontrivial input quantum states. Here we experimentally investigate two-photon N00N state coherent absorption in a multilayer graphene film. Depending on the N00N state input phase, it is possible to selectively choose between single- or two-photon absorption of the input state in the graphene film. These results demonstrate that coherent absorption in the quantum regime exhibits unique features, opening up applications in multiphoton spectroscopy and imaging.

  19. Two-photon excitation of aluminium phthalocyanines

    SciTech Connect

    Meshalkin, Yu P; Alfimov, E E; Makukha, V K; Vasil'ev, N E; Denisov, A N; Ogirenko, A P

    1999-12-31

    A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined. (lasers in medicine)

  20. Exciton absorption of entangled photons in semiconductor quantum wells

    NASA Astrophysics Data System (ADS)

    Rodriguez, Ferney; Guzman, David; Salazar, Luis; Quiroga, Luis; Condensed Matter Physics Group Team

    2013-03-01

    The dependence of the excitonic two-photon absorption on the quantum correlations (entanglement) of exciting biphotons by a semiconductor quantum well is studied. We show that entangled photon absorption can display very unusual features depending on space-time-polarization biphoton parameters and absorber density of states for both bound exciton states as well as for unbound electron-hole pairs. We report on the connection between biphoton entanglement, as quantified by the Schmidt number, and absorption by a semiconductor quantum well. Comparison between frequency-anti-correlated, unentangled and frequency-correlated biphoton absorption is addressed. We found that exciton oscillator strengths are highly increased when photons arrive almost simultaneously in an entangled state. Two-photon-absorption becomes a highly sensitive probe of photon quantum correlations when narrow semiconductor quantum wells are used as two-photon absorbers. Research funds from Facultad de Ciencias, Universidad de los Andes

  1. Solar absorption surface panel

    DOEpatents

    Santala, Teuvo J.

    1978-01-01

    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  2. Two-photon-induced singlet fission in rubrene single crystal.

    PubMed

    Ma, Lin; Galstyan, Gegham; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E; Gurzadyan, Gagik G

    2013-05-14

    The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm∕GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data. PMID:23676057

  3. Quantum Entanglement Molecular Absorption Spectrum Simulator

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Kojima, Jun

    2006-01-01

    Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

  4. Quasar Absorption Studies

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  5. Absorption heat pump system

    DOEpatents

    Grossman, G.

    1982-06-16

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  6. Absorption heat pump system

    DOEpatents

    Grossman, Gershon

    1984-01-01

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  7. Compounds affecting cholesterol absorption

    NASA Technical Reports Server (NTRS)

    Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)

    2004-01-01

    A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

  8. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2004-08-31

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  9. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2003-10-14

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  10. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  11. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, R.C.; Biermann, W.J.

    1989-05-09

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.

  12. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, Robert C.; Biermann, Wendell J.

    1989-01-01

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

  13. Absorption heat pump system

    DOEpatents

    Grossman, Gershon; Perez-Blanco, Horacio

    1984-01-01

    An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

  14. Polarization control of intermediate state absorption in resonance-mediated multi-photon absorption process

    NASA Astrophysics Data System (ADS)

    Xu, Shuwu; Huang, Yunxia; Yao, Yunhua; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong

    2015-07-01

    We theoretically and experimentally demonstrate the control of the intermediate state absorption in an (n + m) resonance-mediated multi-photon absorption process by the polarization-modulated femtosecond laser pulse. An analytical solution of the intermediate state absorption in a resonance-mediated multi-photon absorption process is obtained based on the time-dependent perturbation theory. Our theoretical results show that the control efficiency of the intermediate state absorption by the polarization modulation is independent of the laser intensity when the transition from the intermediate state to the final state is coupled by the single-photon absorption, but will be affected by the laser intensity when this transition is coupled by the non-resonant multi-photon absorption. These theoretical results are experimentally confirmed via a two-photon fluorescence control in (2 + 1) resonance-mediated three-photon absorption of Coumarin 480 dye and a single-photon fluorescence control in (1 + 2) resonance-mediated three-photon absorption of IR 125 dye.

  15. LASERS IN MEDICINE: Two-photon excitation of aluminium phthalocyanines

    NASA Astrophysics Data System (ADS)

    Meshalkin, Yu P.; Alfimov, E. E.; Vasil'ev, N. E.; Denisov, A. N.; Makukha, V. K.; Ogirenko, A. P.

    1999-12-01

    A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined.

  16. Lipids: Absorption and transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Due to the hydrophobic nature of lipids, dietary fat is handled differently than protein or carbohydrate with respect with digestion and absorption. Dietary fats are broken down throughout the gastrointestinal system. A unique group of enzymes and cofactors allows this process to proceed in an eff...

  17. Absorption driven focus shift

    NASA Astrophysics Data System (ADS)

    Harrop, N.; Wolf, S.; Maerten, O.; Dudek, K.; Ballach, S.; Kramer, R.

    2016-03-01

    Modern high brilliance near infrared lasers have seen a tremendous growth in applications throughout the world. Increased productivity has been achieved by higher laser power and increased brilliance of lasers. Positive impacts on the performance and costs of parts are opposed to threats on process stability and quality, namely shift of focus position over time. A high initial process quality will be reduced by contamination of optics, eventually leading to a focus shift or even destruction of the optics. Focus analysis at full power of multi-kilowatt high brilliance lasers is a very demanding task because of high power densities in the spot and the high power load on optical elements. With the newly developed high power projection optics, the High-Power Micro-Spot Monitor High Brilliance (HP-MSM-HB) is able to measure focus diameter as low as 20 μm at power levels up to 10 kW at very low internal focus shift. A main driving factor behind thermally induced focus shift is the absorption level of the optical element. A newly developed measuring system is designed to determine the relative absorption level in reference to a gold standard. Test results presented show a direct correlation between absorption levels and focus shift. The ability to determine the absorption level of optical elements as well as their performance at full processing power before they are put to use, enables a high level of quality assurance for optics manufacturers and processing head manufacturers alike.

  18. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

    A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

  19. Cholesterol Absorption and Metabolism.

    PubMed

    Howles, Philip N

    2016-01-01

    Inhibitors of cholesterol absorption have been sought for decades as a means to treat and prevent cardiovascular diseases (CVDs) associated with hypercholesterolemia. Ezetimibe is the one clear success story in this regard, and other compounds with similar efficacy continue to be sought. In the last decade, the laboratory mouse, with all its genetic power, has become the premier experimental model for discovering the mechanisms underlying cholesterol absorption and has become a critical tool for preclinical testing of potential pharmaceutical entities. This chapter briefly reviews the history of cholesterol absorption research and the various gene candidates that have come under consideration as drug targets. The most common and versatile method of measuring cholesterol absorption is described in detail along with important considerations when interpreting results, and an alternative method is also presented. In recent years, reverse cholesterol transport (RCT) has become an area of intense new interest for drug discovery since this process is now considered another key to reducing CVD risk. The ultimate measure of RCT is sterol excretion and a detailed description is given for measuring neutral and acidic fecal sterols and interpreting the results. PMID:27150091

  20. Ordering of azobenzenes by two-photon isomerization

    SciTech Connect

    Ishitobi, Hidekazu; Sekkat, Zouheir; Kawata, Satoshi

    2006-10-28

    We report on light induced orientation by two-photon isomerization of azobenzenes in films of polymer. The dynamics of isomerization and orientation by one-photon absorption and two-photon absorption (TPA) are similar, and TPA creates a degree of molecular orientation which is comparable to that achieved by single-photon isomerization, in agreement with the theoretical predictions of two-photon isomeric orientation.

  1. 69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER ...

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

    69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER UNDER CONSTRUCTION. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  2. Vaginal Absorption of Penicillin.

    PubMed

    Rock, J; Barker, R H; Bacon, W B

    1947-01-01

    Except during the last two months of pregnancy, penicillin is easily absorbed from cocoa butter suppositories in the vagina, ordinarily to give therapeutic blood levels for from 4 to 6 hours. Penicillin in the dosage used seems to have a good effect on vaginal infections. In nonpregnant women, during the ovulation phase, considered as including days 14 +/- 2 in the ordinary menstrual cycle of about 28 days, absorption seemed to be somewhat diminished. Higher levels were found in patients who were near the end of their menstrual cycles and in two patients who were menopausal. Patients who were very near term absorbed little or no penicillin, whereas patients 10 days post partum showed excellent absorption.

  3. Photothermal absorption correlation spectroscopy.

    PubMed

    Octeau, Vivien; Cognet, Laurent; Duchesne, Laurence; Lasne, David; Schaeffer, Nicolas; Fernig, David G; Lounis, Brahim

    2009-02-24

    Fluorescence correlation spectroscopy (FCS) is a popular technique, complementary to cell imaging for the investigation of dynamic processes in living cells. Based on fluorescence, this single molecule method suffers from artifacts originating from the poor fluorophore photophysics: photobleaching, blinking, and saturation. To circumvent these limitations we present here a new correlation method called photothermal absorption correlation spectroscopy (PhACS) which relies on the absorption properties of tiny nano-objects. PhACS is based on the photothermal heterodyne detection technique and measures akin FCS, the time correlation function of the detected signals. Application of this technique to the precise determination of the hydrodynamic sizes of different functionalized gold nanoparticles are presented, highlighting the potential of this method. PMID:19236070

  4. THE ABSORPTION OF ADRENALIN

    PubMed Central

    Lyon, D. Murray

    1923-01-01

    1. Adrenalin solution given subcutaneously is usually rapidly absorbed, probably by lymphatic channels. 2. The speed of this process may be influenced by the circulation rate. 3. The relative amounts of adrenalin at any moment unabsorbed at the site of inoculation, carried in the circulating fluids, and taken up by the reacting tissues can be calculated from figures extracted from the curve of the blood pressure changes. The relative rates of transference of adrenalin into the blood and from the circulation into the tissues can also be estimated. 4. When absorption takes place rapidly a large quantity of the drug comes into action at once and the maximum occurs early, the curve of blood pressure reaches a considerable height, and subsides quickly. When absorption is slow the apex appears later and does not reach so high a level. 5. The response to adrenalin bears a logarithmic relationship to the dose employed and a method of allowing for this is indicated. PMID:19868816

  5. Relic Neutrino Absorption Spectroscopy

    SciTech Connect

    Eberle, b

    2004-01-28

    Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 10{sup 21} eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasi-degenerate to optimize the dip, which implies m{sub {nu}} 0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.

  6. Corrosion Problems in Absorption Chillers

    ERIC Educational Resources Information Center

    Stetson, Bruce

    1978-01-01

    Absorption chillers use a lithium bromide solution as the medium of absorption and water as the refrigerant. Discussed are corrosion and related problems, tests and remedies, and cleaning procedures. (Author/MLF)

  7. Acoustic Absorption Characteristics of People.

    ERIC Educational Resources Information Center

    Kingsbury, H. F.; Wallace, W. J.

    1968-01-01

    The acoustic absorption characteristics of informally dressed college students in typical classroom seating are shown to differ substantially from data for formally dressed audiences in upholstered seating. Absorption data, expressed as sabins per person or absorption coefficient per square foot, shows that there is considerable variation between…

  8. Absorption heat pumps

    NASA Astrophysics Data System (ADS)

    Huhtinen, M.; Heikkilae, M.; Andersson, R.

    1987-03-01

    The aim of the study was to analyze the technical and economic feasibility of absorption heat pumps in Finland. The work was done as a case study: the technical and economic analyses have been carried out for six different cases, where in each the suitable size and type of the heat pump plant and the auxiliary components and connections were specified. The study also detailed the costs concerning the procurement, installation and test runs of the machinery, as well as the savings in energy costs incurred by the introduction of the plant. Conclusions were drawn of the economic viability of the applications studied. The following cases were analyzed: heat recovery from flue gases and productin of district heat in plants using peat, natural gas, and municipal wastes as a fuel. Heat recovery in the pulp and paper industry for the upgrading of pressure of secondary steam and for the heating of white liquor and combustion and drying the air. Heat recovery in a peat-fulled heat and power plant from flue gases that have been used for the drying of peat. According to the study, the absorption heat pump suits best to the production of district heat, when the heat source is the primary energy is steam produced by the boiler. Included in the flue as condensing is the purification of flue gases. Accordingly, benefit is gained on two levels in thick applications. In heat and power plants the use of absorption heat pumps is less economical, due to the fact that the steam used by the pump reduces the production of electricity, which is rated clearly higher than heat.

  9. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, Michael E.; Bien, Fritz; Bernstein, Lawrence S.

    1986-01-01

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.

  10. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, M.E.; Bien, F.; Bernstein, L.S.

    1986-12-09

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

  11. Modular total absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Karny, M.; Rykaczewski, K. P.; Fijałkowska, A.; Rasco, B. C.; Wolińska-Cichocka, M.; Grzywacz, R. K.; Goetz, K. C.; Miller, D.; Zganjar, E. F.

    2016-11-01

    The design and performance of the Modular Total Absorption Spectrometer built and commissioned at the Oak Ridge National Laboratory is presented. The active volume of the detector is approximately one ton of NaI(Tl), which results in very high full γ energy peak efficiency of 71% at 6 MeV and nearly flat efficiency of around 81.5% for low energy γ-rays between 300 keV and 1 MeV. In addition to the high peak efficiency, the modular construction of the detector permits the use of a γ-coincidence technique in data analysis as well as β-delayed neutron observation.

  12. Light absorption properties and absorption budget of Southeast Pacific waters

    NASA Astrophysics Data System (ADS)

    Bricaud, Annick; Babin, Marcel; Claustre, Hervé; Ras, JoséPhine; TièChe, Fanny

    2010-08-01

    Absorption coefficients of phytoplankton, nonalgal particles (NAPs), and colored dissolved organic matter (CDOM), and their relative contributions to total light absorption, are essential variables for bio-optical and biogeochemical models. However, their actual variations in the open ocean remain poorly documented, particularly for clear waters because of the difficulty in measuring very low absorption coefficients. The Biogeochemistry and Optics South Pacific Experiment (BIOSOPE) cruise investigated a large range of oceanic regimes, from mesotrophic waters around the Marquesas Islands to hyperoligotrophic waters in the subtropical gyre and eutrophic waters in the upwelling area off Chile. The spectral absorption coefficients of phytoplankton and NAPs were determined using the filter technique, while the CDOM absorption coefficients were measured using a 2 m capillary waveguide. Over the whole transect, the absorption coefficients of both dissolved and particulate components covered approximately two orders of magnitude; in the gyre, they were among the lowest ever reported for open ocean waters. In the oligotrophic and mesotrophic waters, absorption coefficients of phytoplankton and NAPs were notably lower than those measured in other oceanic areas with similar chlorophyll contents, indicating some deviation from the standard chlorophyll-absorption relationships. The contribution of absorption by NAPs to total particulate absorption showed large vertical and horizontal variations. CDOM absorption coefficients covaried with algal biomass, albeit with a high scatter. The spectral slopes of both NAP and CDOM absorption revealed structured spatial variability in relation with the trophic conditions. The relative contributions of each component to total nonwater absorption were (at a given wavelength) weakly variable over the transect, at least within the euphotic layer.

  13. The HI absorption "Zoo"

    NASA Astrophysics Data System (ADS)

    Geréb, K.; Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.

    2015-03-01

    We present an analysis of the H I 21 cm absorption in a sample of 101 flux-selected radio AGN (S1.4 GHz> 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). We detect H I absorption in 32 objects (30% of the sample). In a previous paper, we performed a spectral stacking analysis on the radio sources, while here we characterize the absorption spectra of the individual detections using the recently presented busy function. The H I absorption spectra show a broad variety of widths, shapes, and kinematical properties. The full width half maximum (FWHM) of the busy function fits of the detected H I lines lies in the range 32 km s-1absorption (FW20) lies in the range 63 km s-1 200 km s-1). We study the kinematical and radio source properties of each group, with the goal of identifying different morphological structures of H I. Narrow lines mostly lie at the systemic velocity and are likely produced by regularly rotating H I disks or gas clouds. More H I disks can be present among galaxies with lines of intermediate widths; however, the H I in these sources is more unsettled. We study the asymmetry parameter and blueshift/redshift distribution of the lines as a function of their width. We find a trend for which narrow profiles are also symmetric, while broad lines are the most asymmetric. Among the broadest lines, more lines appear blueshifted than redshifted, similarly to what was found by previous studies. Interestingly, symmetric broad lines are absent from the sample. We argue that if a profile is broad, it is also asymmetric and shifted relative to the systemic velocity because it is tracing unsettled H I gas. In particular, besides three of the broadest (up to FW20 = 825 km s-1

  14. Analyzing Water's Optical Absorption

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

  15. Percutaneous absorption in preterm infants.

    PubMed

    West, D P; Halket, J M; Harvey, D R; Hadgraft, J; Solomon, L M; Harper, J I

    1987-11-01

    The skin of preterm infants varies considerably in its level of maturity. To understand skin absorption in premature infants better, we report a technique for the assessment of percutaneous absorption at various gestational and postnatal ages using stable, isotope-labeled (13C6) benzoic acid. Our results indicate that in the preterm infant, this method detects enhanced skin absorption in the first postnatal days, which declines over three weeks to that expected of a full-term infant. This approach also indicates an inverse relationship between gestational age and skin absorption, as well as postnatal age and skin absorption. The reported technique is a safe and noninvasive method using a model skin penetrant for the study of percutaneous absorption in preterm infants from which basic data may be derived to add to our understanding of skin barrier function. PMID:3422856

  16. X-ray Absorption Spectroscopy

    SciTech Connect

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  17. Subgap Absorption in Conjugated Polymers

    DOE R&D Accomplishments Database

    Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

    1991-01-01

    Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

  18. Ultrafast multiphoton transient absorption of β-carotene

    NASA Astrophysics Data System (ADS)

    Buckup, Tiago; Weigel, Alexander; Hauer, Jürgen; Motzkus, Marcus

    2010-07-01

    Multiphoton spectroscopy is able to directly excite electronic states, which are one-photon forbidden. Under single photon conditions, such one-photon forbidden states are exclusively populated via internal relaxation. Hence, transient absorption with two-photon excitation has the potential of clarifying complex relaxation networks by using aimed excitation. In this work we exploited ultrafast two-photon spectroscopy to investigate the excitation of dark states of β-carotene in solution. After direct excitation of the vibronic manifold of S2Ag- from S 0 via two-photon transition, the characteristic internal conversion via hot-S 1 → S 1 → S 0 was observed in the respective spectral region. Additional slow dynamics in the blue-wing of excited-state absorption (ESA) and in the NIR were detected, which is not directly observable with one-photon excitation transient absorption. These features are associated here to resonant multiphoton processes, which lead simultaneously to ultrafast intersystem crossing between singlet and triplet systems as well as to excitation of doublet states. Furthermore, we identify a 340-400 fs relaxation component in the near-infrared region after two-photon resonant excitation and discuss the role of additional dark states ( 3Ag- and 1Bu-) in this process.

  19. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  20. Gas-absorption process

    DOEpatents

    Stephenson, Michael J.; Eby, Robert S.

    1978-01-01

    This invention is an improved gas-absorption process for the recovery of a desired component from a feed-gas mixture containing the same. In the preferred form of the invention, the process operations are conducted in a closed-loop system including a gas-liquid contacting column having upper, intermediate, and lower contacting zones. A liquid absorbent for the desired component is circulated through the loop, being passed downwardly through the column, regenerated, withdrawn from a reboiler, and then recycled to the column. A novel technique is employed to concentrate the desired component in a narrow section of the intermediate zone. This technique comprises maintaining the temperature of the liquid-phase input to the intermediate zone at a sufficiently lower value than that of the gas-phase input to the zone to effect condensation of a major part of the absorbent-vapor upflow to the section. This establishes a steep temperature gradient in the section. The stripping factors below this section are selected to ensure that virtually all of the gases in the downflowing absorbent from the section are desorbed. The stripping factors above the section are selected to ensure re-dissolution of the desired component but not the less-soluble diluent gases. As a result, a peak concentration of the desired component is established in the section, and gas rich in that component can be withdrawn therefrom. The new process provides important advantages. The chief advantage is that the process operations can be conducted in a single column in which the contacting zones operate at essentially the same pressure.

  1. Intestinal Folate Absorption

    PubMed Central

    Olinger, Edward J.; Bertino, Joseph R.; Binder, Henry J.

    1973-01-01

    These studies were designed to determine whether pteroylmonoglutamic acid (PGA) at physiologic concentrations is transported across the small intestine unaltered or is reduced and methylated to the circulating folate form (5-methyltetrahydrofolate [5-MeFH4]) during absorption. [3H]PGA was incubated in vitro on the mucosal side of rat jejunum. Of the folate transferred to the serosal side, the percent identified as 5-MeFH4 by DEAE-Sephadex chromtography was inversely related to the initial mucosa PGA concentration: at 7, 20, and 2,000 nM, 44%, 34%, and 2%, respectively, was converted to 5-MeFH4. In contrast, less than 4% of the folate transferred across ileal mucosa was 5-MeFH4 when the initial mucosa concentration was 20 nM. Specific activity of dihydrofolate (DHF) reductase, the enzyme responsible for converting PGA to tetrahydrofolic acid, was measured in villus homogenates and was significantly greater in the jejunum than in the ileum. 1,000 nM methotrexate (MTX), a DHF reductase inhibitor, markedly inhibited PGA conversion to 5-MeFH4 by the jejunum. Studies of transmural flux, initial rate of mucosal entry (influx) and mucosal accumulation (uptake) of folate were also performed. Although MTX did not alter the influx of PGA, MTX decreased jejunal mucosal uptake but increased transmural movement. Transmural folate movement across ileal mucosa was greater than across jejunal mucosa although mucosal uptake was greater in the jejunum than in the ileum. These results could explain previous studies which have failed to identify conversion of PGA to 5-MeFH4 when intestinal preparations have been exposed to higher and less physiologic concentrations of PGA. Further, these studies suggest that 5-MeFH4 may be retained by the jejunal mucosa. PMID:4727453

  2. Gastrointestinal citrate absorption in nephrolithiasis

    NASA Technical Reports Server (NTRS)

    Fegan, J.; Khan, R.; Poindexter, J.; Pak, C. Y.

    1992-01-01

    Gastrointestinal absorption of citrate was measured in stone patients with idiopathic hypocitraturia to determine if citrate malabsorption could account for low urinary citrate. Citrate absorption was measured directly from recovery of orally administered potassium citrate (40 mEq.) in the intestinal lavage fluid, using an intestinal washout technique. In 7 stone patients citrate absorption, serum citrate levels, peak citrate concentration in serum and area under the curve were not significantly different from those of 7 normal subjects. Citrate absorption was rapid and efficient in both groups, with 96 to 98% absorbed within 3 hours. The absorption of citrate was less efficient from a tablet preparation of potassium citrate than from a liquid preparation, probably due to a delayed release of citrate from wax matrix. However, citrate absorption from solid potassium citrate was still high at 91%, compared to 98% for a liquid preparation. Thus, hypocitraturia is unlikely to be due to an impaired gastrointestinal absorption of citrate in stone patients without overt bowel disease.

  3. Percutaneous absorption of Octopirox.

    PubMed

    Black, J G; Kamat, V B

    1988-01-01

    containing 1% Octopirox is 29,400, so that the possibility of systemic effects due to absorption through the skin is remote. PMID:3345970

  4. Resonant Absorption of Bessel Beams

    NASA Astrophysics Data System (ADS)

    Fan, J.; Parra, E.; Milchberg, H. M.

    1999-11-01

    We report the first observation of enhanced laser-plasma optical absorption in a subcritical density plasma resulting from spatial resonances, here in the laser breakdown of a gas with a Bessel beam. The enhancement in absorption is directly correlated to enhancements both in confinement of laser radiation to the plasma and in its heating. Under certain conditions, azimuthal asymmetry in the laser beam is essential for efficient gas breakdown. Simulations of this absorption consistently explain the experimental observations. This work is supported by the National Science Foundation (PHY-9515509) and the US Department of Energy (DEF G0297 ER 41039).

  5. Light absorption measurements: new techniques.

    PubMed

    Hänel, G; Busen, R; Hillenbrand, C; Schloss, R

    1982-02-01

    A new radiometer is described which simplifies measurement of the radiation supply of solar wavelengths. Two methods of measuring the radiant energy absorbed by aerosol particles are described: A photometric technique is used for particles collected on filters, and a calorimetric technique is used for in situ measurements. Data collected with the radiometer and the light absorption techniques yield the heating rate of the atmosphere due to light absorption by the particles. Sample measurements show substantial atmospheric temperature increases due to absorption, especially in industrial regions.

  6. Percutaneous nitroglycerin absorption in rats.

    PubMed

    Horhota, S T; Fung, H L

    1979-05-01

    Percutaneous nitroglycerin absorption was studied in shaved rats by monitoring unchanged plasma drug concentrations for up to 4 hr. Drug absorption from the neat liquid state or from an alcoholic solution was considerably poorer than that from a commercial ointment. This observation was unanticipated since the driving force for percutaneous drug absorption was assumed to be drug thermodynamics. Potential artifacts such as drug volatilization from the skin, reduction of surface area through droplet formation, and vehicle occlusion were investigated, but they did not appear to be responsible for the observed results. Two experimental aqueous nitroglycerin gels were prepared with polyethylene glycol 400. One gel contained just sufficient polyethylene glycol to solubilize the nitroglycerin; the other had excess polyethylene glycol to solubilize nitroglycerin far below saturation. Both gels gave extremely low plasma nitroglycerin levels. The composite data suggested that percutaneous nitroglycerin absorption is highly vehicle dependent and that this dependency cannot be explained by simple consideration of drug thermodynamic activity.

  7. Circadian Regulation of Macronutrient Absorption.

    PubMed

    Hussain, M Mahmood; Pan, Xiaoyue

    2015-12-01

    Various intestinal functions exhibit circadian rhythmicity. Disruptions in these rhythms as in shift workers and transcontinental travelers are associated with intestinal discomfort. Circadian rhythms are controlled at the molecular level by core clock and clock-controlled genes. These clock genes are expressed in intestinal cells, suggesting that they might participate in the circadian regulation of intestinal functions. A major function of the intestine is nutrient absorption. Here, we will review absorption of proteins, carbohydrates, and lipids and circadian regulation of various transporters involved in their absorption. A better understanding of circadian regulation of intestinal absorption might help control several metabolic disorders and attenuate intestinal discomfort associated with disruptions in sleep-wake cycles.

  8. Two-Photon Laser Scanning Microscopy

    NASA Astrophysics Data System (ADS)

    Nimmerjahn, A.; Theer, P.; Helmchen, F.

    Since its inception more than 15 years ago, two-photon laser scanning microscopy (2PLSM) has found widespread use in biological and medical research. Two-photon microscopy is based on simultaneous absorption of two photons by fluorophores and subsequent fluorescence emission, a process which under normal illumination conditions is highly improbable. Theoretically described around 1930 by Maria Göppert-Mayer [1], the first experimental demonstration of two-photon excitation had to await the invention of the laser, which produced sufficiently high light intensities to observe two-photon absorption events [2]. Only after the development of ultrafast lasers providing subpicosecond light pulses with high peak power intensities, however, two-photon-excited fluorescence became practical in a laser-scanning microscope [3]. Since then 2PLSM has developed into the method of choice for high-resolution imaging in living animals (reviewed in [4,5]). One of the main reasons is the low sensitivity of 2PLSM to light scattering, which enables imaging relatively deep inside biological tissue and direct observation of the dynamic behavior of cells in their native environment. In this chapter, we introduce the physical principles governing 2PLSM and briefly describe the key instrument components. We give an overview of fluorescence labeling techniques and how they are combined with 2PLSM for functional imaging and photomanipulation in living tissue. Finally, we discuss limitations and provide some future perspectives.

  9. Incomplete intestinal absorption of fructose.

    PubMed

    Kneepkens, C M; Vonk, R J; Fernandes, J

    1984-08-01

    Intestinal D-fructose absorption in 31 children was investigated using measurements of breath hydrogen. Twenty five children had no abdominal symptoms and six had functional bowel disorders. After ingestion of fructose (2 g/kg bodyweight), 22 children (71%) showed a breath hydrogen increase of more than 10 ppm over basal values, indicating incomplete absorption: the increase averaged 53 ppm, range 12 to 250 ppm. Four of these children experienced abdominal symptoms. Three of the six children with bowel disorders showed incomplete absorption. Seven children were tested again with an equal amount of glucose, and in three of them also of galactose, added to the fructose. The mean maximum breath hydrogen increases were 5 and 10 ppm, respectively, compared with 103 ppm after fructose alone. In one boy several tests were performed with various sugars; fructose was the only sugar incompletely absorbed, and the effect of glucose on fructose absorption was shown to be dependent on the amount added. It is concluded that children have a limited absorptive capacity for fructose. We speculate that the enhancing effect of glucose and galactose on fructose absorption may be due to activation of the fructose carrier. Apple juice in particular contains fructose in excess of glucose and could lead to abdominal symptoms in susceptible children.

  10. Incomplete intestinal absorption of fructose.

    PubMed Central

    Kneepkens, C M; Vonk, R J; Fernandes, J

    1984-01-01

    Intestinal D-fructose absorption in 31 children was investigated using measurements of breath hydrogen. Twenty five children had no abdominal symptoms and six had functional bowel disorders. After ingestion of fructose (2 g/kg bodyweight), 22 children (71%) showed a breath hydrogen increase of more than 10 ppm over basal values, indicating incomplete absorption: the increase averaged 53 ppm, range 12 to 250 ppm. Four of these children experienced abdominal symptoms. Three of the six children with bowel disorders showed incomplete absorption. Seven children were tested again with an equal amount of glucose, and in three of them also of galactose, added to the fructose. The mean maximum breath hydrogen increases were 5 and 10 ppm, respectively, compared with 103 ppm after fructose alone. In one boy several tests were performed with various sugars; fructose was the only sugar incompletely absorbed, and the effect of glucose on fructose absorption was shown to be dependent on the amount added. It is concluded that children have a limited absorptive capacity for fructose. We speculate that the enhancing effect of glucose and galactose on fructose absorption may be due to activation of the fructose carrier. Apple juice in particular contains fructose in excess of glucose and could lead to abdominal symptoms in susceptible children. PMID:6476870

  11. Broadband optical limiting and nonlinear optical absorption properties of a novel hyperbranched conjugated polymer

    NASA Astrophysics Data System (ADS)

    Li, Chao; Liu, Chunling; Li, Quanshui; Gong, Qihuang

    2004-12-01

    The nonlinear transmittance of a novel hyperbranched conjugated polymer named DMA-HPV has been measured in CHCl 3 solution using a nanosecond optical parametric oscillator. DMA-HPV shows excellent optical limiting performance in the visible region from 490 to 610 nm. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its huge and broadband nonlinear optical absorption.

  12. Modulation of ganciclovir intestinal absorption in presence of absorption enhancers.

    PubMed

    Shah, Pranav; Jogani, Viral; Mishra, Pushpa; Mishra, Anil Kumar; Bagchi, Tamishraha; Misra, Ambikanandan

    2007-10-01

    The purpose of this investigation was to study the influences of absorption enhancers in increasing oral bioavailability of Ganciclovir (GAN) by assessing the transepithelial permeation across cell monolayers in vitro and bioavailability in rats in vivo. The permeation of GAN across Caco-2 and MDCK cell monolayers in the absence/presence of dimethyl-beta-cyclodextrin (DMbetaCD), chitosan hydrochloride (CH), sodium lauryl sulphate (SLS), and their combinations was studied for a 2-h period. GAN was administered to rats in absence/presence of absorption enhancers and drug contents in plasma were estimated. We found that the apparent permeability coefficient (Papp) of GAN in absence of absorption enhancers (control) were 0.261 +/- 0.072 x 10(-6) and 0.486 +/- 0.063 x 10(-6) cm/s in Caco-2 and MDCK cell monolayers, respectively, whereas in the presence of DMbetaCD, CH, SLS, and their combinations, Papp of GAN increased by 5- to 25-fold and 7- to 33-fold as compared to control in Caco-2 and MDCK cell monolayers, respectively. However, in rats, the maximum enhancement in bioavailability of GAN during coadministration of these absorption enhancers was only fivefold compared to GAN control. To conclude, the absorption enhancers-DMbetaCD, CH, SLS, and their combinations demonstrated significant improvement in transepithelial permeation and bioavailability of GAN.

  13. Converting Sabine absorption coefficients to random incidence absorption coefficients.

    PubMed

    Jeong, Cheol-Ho

    2013-06-01

    Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a sample and non-uniform intensity in the reverberation chambers under test. In this study, conversion methods from Sabine absorption coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations are suggested: An optimization method for the surface impedances for locally reacting absorbers, the flow resistivity for extendedly reacting absorbers, and the flow resistance for fabrics. With four porous type absorbers, the conversion methods are validated. For absorbers backed by a rigid wall, the surface impedance optimization produces the best results, while the flow resistivity optimization also yields reasonable results. The flow resistivity and flow resistance optimization for extendedly reacting absorbers are also found to be successful. However, the theoretical conversion factors based on Miki's model do not guarantee reliable estimations, particularly at frequencies below 250 Hz and beyond 2500 Hz.

  14. Fat-soluble vitamin intestinal absorption: absorption sites in the intestine and interactions for absorption.

    PubMed

    Goncalves, Aurélie; Roi, Stéphanie; Nowicki, Marion; Dhaussy, Amélie; Huertas, Alain; Amiot, Marie-Josèphe; Reboul, Emmanuelle

    2015-04-01

    The interactions occurring at the intestinal level between the fat-soluble vitamins A, D, E and K (FSVs) are poorly documented. We first determined each FSV absorption profile along the duodenal-colonic axis of mouse intestine to clarify their respective absorption sites. We then investigated the interactions between FSVs during their uptake by Caco-2 cells. Our data show that vitamin A was mostly absorbed in the mouse proximal intestine, while vitamin D was absorbed in the median intestine, and vitamin E and K in the distal intestine. Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E. These results should be taken into account, especially for supplement formulation, to optimise FSV absorption.

  15. Sound absorption in metallic foams

    NASA Astrophysics Data System (ADS)

    Lu, T. J.; Hess, Audrey; Ashby, M. F.

    1999-06-01

    The sound absorption capacity of one type of aluminum alloy foams—trade name Alporas—is studied experimentally. The foam in its as-received cast form contains closed porosities, and hence does not absorb sound well. To make the foam more transparent to air motion, techniques based on either rolling or hole drilling are used. Under rolling, the faces of some of the cells break to form small sharp-edged cracks as observed from a scanning electronic microscope. These cracks become passage ways for the in-and-out movement of air particles, resulting in sound absorption improvement. The best performance is nevertheless achieved via hole drilling where nearly all of the sound can be absorbed at selected frequencies. Combining rolling with hole drilling does not appear to lend additional benefits for sound absorption. Image analysis is carried out to characterize the changes in cell morphologies due to rolling/compression, and the drop in elastic modulus due to the formation of cracks is recorded. The effects of varying the relative foam density and panel thickness on sound absorption are measured, and optimal relative density and thickness of the panel are identified. Analytical models are used to explain the measured increase in sound absorption due to rolling and/or drilling. Sound absorbed by viscous flow across small cracks appears to dominate over that dissipated via other mechanisms.

  16. Harnessing the electromagnetic absorptions of metamaterials for positive applications

    NASA Astrophysics Data System (ADS)

    Xiang, Yuanjiang; Zou, Yanhong; Luo, Hailu; Dai, Xiaoyu; Wen, Shuangchun; Fan, Dianyuan

    2010-08-01

    Absorption or loss is inevitable for the metal-based metamaterials (MMs) due to the intrinsic loss of the metal, and constitutes a major hurdle to the practical realization of most applications such as a sub-wavelength lens. Thus, to reduce the losses becomes one of the major challenges in the MM field. However, the inevitable loss can also be harnessed to take a positive role in the applications of MMs such as stealth technology or other types of cloaking devices. In this presentation, after a brief review of the advances in MMs-based absorbers, we present several schemes to fulfill the desired electromagnetic absorption properties, both linear and nonlinear. For linear absorption, we have experimentally demonstrated that the absorption performance of an ordinary microwave absorbing material can be evidently improved by using the electric resonance resulting from an array of subwavelength metallic circuit elements. For nonlinear absorption, we show theoretically that the active linear magnetic permeability induces a nonlinear absorption, similar to the two-photon absorption (TPA), of electric field in a lossy MM with a Kerr-type nonlinear polarization.

  17. Enhanced absorption cycle computer model

    NASA Astrophysics Data System (ADS)

    Grossman, G.; Wilk, M.

    1993-09-01

    Absorption heat pumps have received renewed and increasing attention in the past two decades. The rising cost of electricity has made the particular features of this heat-powered cycle attractive for both residential and industrial applications. Solar-powered absorption chillers, gas-fired domestic heat pumps, and waste-heat-powered industrial temperature boosters are a few of the applications recently subjected to intensive research and development. The absorption heat pump research community has begun to search for both advanced cycles in various multistage configurations and new working fluid combinations with potential for enhanced performance and reliability. The development of working absorption systems has created a need for reliable and effective system simulations. A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components and property subroutines containing thermodynamic properties of the working fluids. The user conveys to the computer an image of his cycle by specifying the different subunits and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system, and the heat duty at each unit, from which the coefficient of performance (COP) may be determined. This report describes the code and its operation, including improvements introduced into the present version. Simulation results are described for LiBr-H2O triple-effect cycles, LiCl-H2O solar-powered open absorption cycles, and NH3-H2O single-effect and generator-absorber heat exchange cycles. An appendix contains the user's manual.

  18. Absorption-heat-pump system

    DOEpatents

    Grossman, G.; Perez-Blanco, H.

    1983-06-16

    An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

  19. Diabetic lipohypertrophy delays insulin absorption.

    PubMed

    Young, R J; Hannan, W J; Frier, B M; Steel, J M; Duncan, L J

    1984-01-01

    The effect of lipohypertrophy at injection sites on insulin absorption has been studied in 12 insulin-dependent diabetic patients. The clearance of 125I-insulin from sites with lipohypertrophy was significantly slower than from complementary nonhypertrophied sites (% clearance in 3 h, 43.8 +/- 3.5 +/- SEM) control; 35.3 +/- 3.9 lipohypertrophy, P less than 0.05). The degree of the effect was variable but sufficient in several patients to be of clinical importance. Injection-site lipohypertrophy is another factor that modifies the absorption of subcutaneously injected insulin.

  20. Solar powered absorption air conditioning

    NASA Astrophysics Data System (ADS)

    Vardon, J. M.

    1980-04-01

    Artificial means of providing or removing heat from the building are discussed along with the problem of the appropriate building design and construction for a suitable heat climate inside the building. The use of a lithium bromide-water absorption chiller, powered by a hot water store heated by an array of stationary flat collectors, is analyzed. An iterative method of predicting the cooling output from a LiBr-water absorption refrigeration plant having variable heat input is described and a model allowing investigation of the performance of a solar collector and thermal storage system is developed.

  1. Transient absorption spectroscopy of laser shocked explosives

    SciTech Connect

    Mcgrane, Shawn D; Dang, Nhan C; Whitley, Von H; Bolome, Cindy A; Moore, D S

    2010-01-01

    Transient absorption spectra from 390-890 nm of laser shocked RDX, PETN, sapphire, and polyvinylnitrate (PVN) at sub-nanosecond time scales are reported. RDX shows a nearly linear increase in absorption with time after shock at {approx}23 GPa. PETN is similar, but with smaller total absorption. A broad visible absorption in sapphire begins nearly immediately upon shock loading but does not build over time. PVN exhibits thin film interference in the absorption spectra along with increased absorption with time. The absorptions in RDX and PETN are suggested to originate in chemical reactions happening on picosecond time scales at these shock stresses, although further diagnostics are required to prove this interpretation.

  2. Nonlinear absorption and photoluminescence emission in nanocomposite films of Fuchsine Basic dye-polymer system

    NASA Astrophysics Data System (ADS)

    Sreekumar, G.; Louie Frobel, P. G.; Sreeja, S.; Suresh, S. R.; Mayadevi, S.; Muneera, C. I.; Suchand Sandeep, C. S.; Philip, Reji; Mukharjee, Chandrachur

    2011-04-01

    Fuchsine Basic dye-polyvinyl alcohol composite films were fabricated and their structure, nonlinear absorption as well as linear absorption and photoluminescence properties were investigated. Switchover from saturable absorption to two-photon assisted excited state absorption with increase in intensity was observed in the open aperture Z-scan study (Nd:YAG, 532 nm, 7 ns). The effective two-photon absorption coefficient β was found to be several orders higher than that reported for rhodamine B. The dye-polymer films were characterized as nanocomposites with dye microdomains encapsulated between molecules of the amorphous polymer and having average surface roughness as low as ≈0.46 nm. The samples also exhibited intense photoluminescence emission when excited with 534 nm radiation.

  3. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  4. Concentration-modulated absorption spectroscopy.

    PubMed

    Langley, A J; Beaman, R A; Baran, J; Davies, A N; Jones, W J

    1985-07-01

    Concentration modulation is demonstrated to be a technique capable of markedly extending sensitivity limits in absorption spectroscopy. The gain generated relates in such a manner to sample transmittance that for the first reported time direct spectroscopic concentration measurements become possible. When concentration modulation is used with picosecond lasers, state lifetimes can be determined to a limit of approximately 20 psec.

  5. Ultraviolet and Light Absorption Spectrometry.

    ERIC Educational Resources Information Center

    Hargis, L. G.; Howell, J. A.

    1984-01-01

    Reviews developments in ultraviolet and light absorption spectrometry from December 1981 through November 1983, focusing on the chemistry involved in developing suitable reagents, absorbing systems, and methods of determination, and on physical aspects of the procedures. Includes lists of spectrophotometric methods for metals, non-metals, and…

  6. Migrant labor absorption in Malaysia.

    PubMed

    Nayagam, J

    1992-01-01

    The use of migrant workers to ease labor shortages caused by rapid industrialization in Malaysia during the twentieth century is examined. "This paper will focus on: (1) the extent, composition and distribution of migrant workers; (2) the labor shortage and absorption of migrant workers; and (3) the role of migrant workers in the government's economic restructuring process."

  7. Migrant labor absorption in Malaysia.

    PubMed

    Nayagam, J

    1992-01-01

    The use of migrant workers to ease labor shortages caused by rapid industrialization in Malaysia during the twentieth century is examined. "This paper will focus on: (1) the extent, composition and distribution of migrant workers; (2) the labor shortage and absorption of migrant workers; and (3) the role of migrant workers in the government's economic restructuring process." PMID:12285766

  8. Phenoxyethanol absorption by polyvinyl chloride.

    PubMed

    Lee, M G

    1984-12-01

    Phenoxyethanol was found to be absorbed by polyvinyl chloride administration sets during continuous irrigation therapy. Depending upon the conditions of administration up to 20% loss of potency could occur. Absorption of the drug by the rigid plastic luer-lock fitting of the set caused softening and decreased rigidity of the plastic.

  9. Slow light and saturable absorption

    NASA Astrophysics Data System (ADS)

    Selden, A. C.

    2009-06-01

    Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er3+:Y2SiO5, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained.

  10. Nebular Hydrogen Absorption in the Ejecta of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.; Ishibashi, K.; Davidson, K.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    Space Telescope Imaging Spectrograph (STIS) observations of Eta Carinae and immediate ejecta reveal narrow Balmer absorption lines in addition to the nebular-scattered broad P-Cygni absorptions. The narrow absorption correlates with apparent disk structure that separates the two Homunculus lobes. We trace these features about half way up the Northern lobe until the scattered stellar Balmer line doppler-shifts redward beyond the nebular absorption feature. Three-dimensional data cubes, made by mapping the Homunculus at Balmer alpha and Balmer beta with the 52 x 0.1 arcsecond aperture and about 5000 spectral resolving power, demonstrate that the absorption feature changes slowly in velocity with nebular position. We have monitored the stellar Balmer alpha line profile of the central source over the past four years. The equivalent width of the nebular absorption feature changes considerably between observations. The changes do not correlate with measured brightness of Eta Carinae. Likely clumps of neutral hydrogen with a scale size comparable to the stellar disk diameter are passing through the intervening light path on the timescales less than several months. The excitation mechanism involves Lyman alpha radiation (possibly the Lyman series plus Lyman continuum) and collisions leading to populating the 2S metastable state. Before the electron can jump to the ground state by two photon emission (lifetime about 1/8 second), a stellar Balmer photon is absorbed and the electron shifts to an NP level. We see the absorption feature in higher Balmer lines, and but not in Paschen lines. Indeed we see narrow nebular Paschen emission lines. At present, we do not completely understand the details of the absorption. Better understanding should lead to improved insight of the unique conditions around Eta Carinae that leads to these absorptions.

  11. Nonlinear absorption coefficient of pulsed laser deposited MgZnO thin film

    SciTech Connect

    Agrawal, Arpana Dar, Tanveer A.; Solanki, Ravi; Sen, Pratima; Phase, D. M.

    2015-06-24

    We report the imaginary part of 3{sup rd} order nonlinear susceptibility and the nonlinear absorption coefficient of Mg doped ZnO thin film using standard Z-scan technique. The origin of nonlinear absorption is attributed to the two photon absorption followed by the free carrier absorption because of the presence of oxygen vacancy defects. We have also confirmed the experimental results with the theoretical results obtained by considering the steady state response of a two level atom with the monochromatic field models.

  12. Landing gear energy absorption system

    NASA Technical Reports Server (NTRS)

    Hansen, Christopher P. (Inventor)

    1994-01-01

    A landing pad system is described for absorbing horizontal and vertical impact forces upon engagement with a landing surface where circumferentially arranged landing struts respectively have a clevis which receives a slidable rod member and where the upper portion of a slidable rod member is coupled to the clevis by friction washers which are force fit onto the rod member to provide for controlled constant force energy absorption when the rod member moves relative to the clevis. The lower end of the friction rod is pivotally attached by a ball and socket to a support plate where the support plate is arranged to slide in a transverse direction relative to a housing which contains an energy absorption material for absorbing energy in a transverse direction.

  13. Photodetector with enhanced light absorption

    DOEpatents

    Kane, James

    1985-01-01

    A photodetector including a light transmissive electrically conducting layer having a textured surface with a semiconductor body thereon. This layer traps incident light thereby enhancing the absorption of light by the semiconductor body. A photodetector comprising a textured light transmissive electrically conducting layer of SnO.sub.2 and a body of hydrogenated amorphous silicon has a conversion efficiency about fifty percent greater than that of comparative cells. The invention also includes a method of fabricating the photodetector of the invention.

  14. Two-photon photovoltaic effect in gallium arsenide.

    PubMed

    Ma, Jichi; Chiles, Jeff; Sharma, Yagya D; Krishna, Sanjay; Fathpour, Sasan

    2014-09-15

    The two-photon photovoltaic effect is demonstrated in gallium arsenide at 976 and 1550 nm wavelengths. A waveguide-photodiode biased in its fourth quadrant harvests electrical power from the optical energy lost to two-photon absorption. The experimental results are in good agreement with simulations based on nonlinear wave propagation in waveguides and the drift-diffusion model of carrier transport in semiconductors. Power efficiency of up to 8% is theoretically predicted in optimized devices.

  15. Multicolor two-photon tissue imaging by wavelength mixing.

    PubMed

    Mahou, Pierre; Zimmerley, Maxwell; Loulier, Karine; Matho, Katherine S; Labroille, Guillaume; Morin, Xavier; Supatto, Willy; Livet, Jean; Débarre, Delphine; Beaurepaire, Emmanuel

    2012-08-01

    We achieve simultaneous two-photon excitation of three chromophores with distinct absorption spectra using synchronized pulses from a femtosecond laser and an optical parametric oscillator. The two beams generate separate multiphoton processes, and their spatiotemporal overlap provides an additional two-photon excitation route, with submicrometer overlay of the color channels. We report volume and live multicolor imaging of 'Brainbow'-labeled tissues as well as simultaneous three-color fluorescence and third-harmonic imaging of fly embryos. PMID:22772730

  16. Multicolor two-photon tissue imaging by wavelength mixing.

    PubMed

    Mahou, Pierre; Zimmerley, Maxwell; Loulier, Karine; Matho, Katherine S; Labroille, Guillaume; Morin, Xavier; Supatto, Willy; Livet, Jean; Débarre, Delphine; Beaurepaire, Emmanuel

    2012-07-08

    We achieve simultaneous two-photon excitation of three chromophores with distinct absorption spectra using synchronized pulses from a femtosecond laser and an optical parametric oscillator. The two beams generate separate multiphoton processes, and their spatiotemporal overlap provides an additional two-photon excitation route, with submicrometer overlay of the color channels. We report volume and live multicolor imaging of 'Brainbow'-labeled tissues as well as simultaneous three-color fluorescence and third-harmonic imaging of fly embryos.

  17. Two-photon photovoltaic effect in gallium arsenide.

    PubMed

    Ma, Jichi; Chiles, Jeff; Sharma, Yagya D; Krishna, Sanjay; Fathpour, Sasan

    2014-09-15

    The two-photon photovoltaic effect is demonstrated in gallium arsenide at 976 and 1550 nm wavelengths. A waveguide-photodiode biased in its fourth quadrant harvests electrical power from the optical energy lost to two-photon absorption. The experimental results are in good agreement with simulations based on nonlinear wave propagation in waveguides and the drift-diffusion model of carrier transport in semiconductors. Power efficiency of up to 8% is theoretically predicted in optimized devices. PMID:26466255

  18. Absorption, Creativity, Peak Experiences, Empathy, and Psychoticism.

    ERIC Educational Resources Information Center

    Mathes, Eugene W.; And Others

    Tellegen and Atkinson suggested that the trait of absorption may play a part in meditative skill, creativity, capacity for peak experiences, and empathy. Although the absorption-meditative skill relationship has been confirmed, other predictions have not been tested. Tellegen and Atkinson's Absorption Scale was completed by undergraduates in four…

  19. Nonlinear absorption and transmission properties of Ge, Te and InAs using tuneable IR FEL

    SciTech Connect

    Amirmadhi, F.; Becker, K.; Brau, C.A.

    1995-12-31

    Nonlinear absorption properties of Ge, Te and InAs are being investigated using the transmission of FEL optical pulses through these semiconductors (z-scan method). Wavelength, intensity and macropulse dependence are used to differentiate between two-photon and free-carrier absorption properties of these materials. Macropulse dependence is resolved by using a Pockles Cell to chop the 4-{mu}s macropulse down to 100 ns. Results of these experiments will be presented and discussed.

  20. Advanced regenerative absorption refrigeration cycles

    DOEpatents

    Dao, Kim

    1990-01-01

    Multi-effect regenerative absorption cycles which provide a high coefficient of performance (COP) at relatively high input temperatures. An absorber-coupled double-effect regenerative cycle (ADR cycle) (10) is provided having a single-effect absorption cycle (SEA cycle) (11) as a topping subcycle and a single-effect regenerative absorption cycle (1R cycle) (12) as a bottoming subcycle. The SEA cycle (11) includes a boiler (13), a condenser (21), an expansion device (28), an evaporator (31), and an absorber (40), all operatively connected together. The 1R cycle (12) includes a multistage boiler (48), a multi-stage resorber (51), a multisection regenerator (49) and also uses the condenser (21), expansion device (28) and evaporator (31) of the SEA topping subcycle (11), all operatively connected together. External heat is applied to the SEA boiler (13) for operation up to about 500 degrees F., with most of the high pressure vapor going to the condenser (21) and evaporator (31) being generated by the regenerator (49). The substantially adiabatic and isothermal functioning of the SER subcycle (12) provides a high COP. For higher input temperatures of up to 700 degrees F., another SEA cycle (111) is used as a topping subcycle, with the absorber (140) of the topping subcycle being heat coupled to the boiler (13) of an ADR cycle (10). The 1R cycle (12) itself is an improvement in that all resorber stages (50b-f) have a portion of their output pumped to boiling conduits (71a-f) through the regenerator (49), which conduits are connected to and at the same pressure as the highest pressure stage (48a) of the 1R multistage boiler (48).

  1. Carbon Dioxide Absorption Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    2002-01-01

    A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.

  2. NEUTRON ABSORPTION AND SHIELDING DEVICE

    DOEpatents

    Axelrad, I.R.

    1960-06-21

    A neutron absorption and shielding device is described which is adapted for mounting in a radiation shielding wall surrounding a radioactive area through which instrumentation leads and the like may safely pass without permitting gamma or neutron radiation to pass to the exterior. The shielding device comprises a container having at least one nonrectilinear tube or passageway means extending therethrough, which is adapted to contain instrumentation leads or the like, a layer of a substance capable of absorbing gamma rays, and a solid resinous composition adapted to attenuate fast-moving neutrons and capture slow- moving or thermal neutrons.

  3. Effective absorption in cladding-pumped fibers

    NASA Astrophysics Data System (ADS)

    Zervas, Michalis N.; Marshall, Andy; Kim, Jaesun

    2011-02-01

    We investigate experimentally and theoretically the wavelength dependence of the pump absorption along Yb3+-doped fibers, for cladding-pumped single as well as coupled multimode (GTWaveTM) fibers. We show that significant spectral absorption distortions occur along the length with the 976nm absorption peak affected the most. We have developed a novel theoretical approach, based on coupled mode theory, to explain the observed effects. We have also investigated the mode mixing requirements in order to improve the absorption spectral distribution along the increase the overall absorption efficiency and discuss the implications on fiber laser performance.

  4. Infrared absorption mechanisms of black silicon

    NASA Astrophysics Data System (ADS)

    Cheng, Zhengxi; Chen, Yongping; Ma, Bin

    2014-09-01

    Black silicon has a wide spectrum of non-spectral characteristics high absorption from visible to long wave infrared band .Based on semi-empirical impurity band model, free carrier absorption, radiation transitions between the valence band and the impurity band, radiation transitions between the impurity band and the conduction band were calculated, and absorption coefficients for each process were got. The results showed that the transitions from valence band to the impurity band induced absorption in the near-infrared waveband, but it has a rapid decay with wavelength. In the shortwave mid-wave and long-wave IR bands, transitions from the impurity band to the conduction band caused a huge absorption, and the absorption coefficient was slowly decreased with increasing wavelength. The free carrier absorption dominates in long-wave band. The calculation results agreed well with the test results of plant black silicon in magnitude and trends.

  5. Study on Nonlinear Absorption Effect of Nanosecond Pulse Laser Irradiation for GaAs.

    PubMed

    Sun, Wenjun; Liu, Zhongyang; Zhou, Haijiao

    2016-04-01

    In order to research nonlinear absorption effect of pulse laser irradiation for GaAs, a physical model of Gaussian distribution pulse laser irradiation for semiconductor material was established by software COMSOL Multiphysics. The thermal effects of semiconductor material GaAs was analyzed under irradiation of nanosecond pulse laser with wavelength of 1064 nm. The radial and transverse temperature distribution of semiconductor material GaAs was calculated under irradiation of nanosecond pulse laser with different power density by solving the thermal conduction equations. The contribution of one-photon absorption, two-photon absorption and free carrier absorption to temperature of GaAs material were discussed. The results show that when the pulse laser power density rises to 10(10) W/cm2, free carrier absorption played a leading role and it was more than that of one-photon absorption of material. The temperature contribution of two-photon absorption and free carrier absorption could be ignored at laser power density lower than 10(8) W/cm2. The result is basically consistent with relevant experiments, which shows that physical model constructed is valid. PMID:27451733

  6. Study on Nonlinear Absorption Effect of Nanosecond Pulse Laser Irradiation for GaAs.

    PubMed

    Sun, Wenjun; Liu, Zhongyang; Zhou, Haijiao

    2016-04-01

    In order to research nonlinear absorption effect of pulse laser irradiation for GaAs, a physical model of Gaussian distribution pulse laser irradiation for semiconductor material was established by software COMSOL Multiphysics. The thermal effects of semiconductor material GaAs was analyzed under irradiation of nanosecond pulse laser with wavelength of 1064 nm. The radial and transverse temperature distribution of semiconductor material GaAs was calculated under irradiation of nanosecond pulse laser with different power density by solving the thermal conduction equations. The contribution of one-photon absorption, two-photon absorption and free carrier absorption to temperature of GaAs material were discussed. The results show that when the pulse laser power density rises to 10(10) W/cm2, free carrier absorption played a leading role and it was more than that of one-photon absorption of material. The temperature contribution of two-photon absorption and free carrier absorption could be ignored at laser power density lower than 10(8) W/cm2. The result is basically consistent with relevant experiments, which shows that physical model constructed is valid.

  7. Energy absorption of composite materials

    NASA Technical Reports Server (NTRS)

    Farley, G. L.

    1983-01-01

    Results of a study on the energy absorption characteristics of selected composite material systems are presented and the results compared with aluminum. Composite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphite/epoxy (Gr/E), Kevlar (TM)/epoxy (K/E) and glass/epoxy (Gl/E). Chamfering and notching one end of the composite tube specimen reduced the peak load at initial failure without altering the sustained crushing load, and prevented catastrophic failure. Static compression and vertical impact tests were performed on 128 tubes. The results varied significantly as a function of material type and ply orientation. In general, the Gr/E tubes absorbed more energy than the Gl/E or K/E tubes for the same ply orientation. The 0/ + or - 15 Gr/E tubes absorbed more energy than the aluminum tubes. Gr/E and Gl/E tubes failed in a brittle mode and had negligible post crushing integrity, whereas the K/E tubes failed in an accordian buckling mode similar to the aluminum tubes. The energy absorption and post crushing integrity of hybrid composite tubes were not significantly better than that of the single material tubes.

  8. Percutaneous absorption of selenium sulfide

    SciTech Connect

    Farley, J.; Skelly, E.M.; Weber, C.B.

    1986-01-01

    The purpose of this study was to determine selenium levels in the urine of Tinea patients before and after overnight application of a 2.5% selenium sulfide lotion. Selenium was measured by atomic absorption spectroscopy (AAS). Hydride generation and carbon rod atomization were studied. It was concluded from this study that selenium is absorbed through intact skin. Selenium is then excreted, at least partially, in urine, for at least a week following treatment. The data show that absorption and excretion of selenium vary on an individual basis. Selenium levels in urine following a single application of selenium sulfide lotion do not indicate that toxic amounts of selenium are being absorbed. Repeated treatments with SeS/sub 2/ result in selenium concentrations in urine which are significantly higher than normal. Significant matrix effects are observed in the carbon rod atomization of urine samples for selenium determinations, even in the presence of a matrix modifier such as nickel. The method of standard additions is required to obtain accurate results in the direct determination of selenium in urine by carbon rod AAS.

  9. Iron Absorption in Drosophila melanogaster

    PubMed Central

    Mandilaras, Konstantinos; Pathmanathan, Tharse; Missirlis, Fanis

    2013-01-01

    The way in which Drosophila melanogaster acquires iron from the diet remains poorly understood despite iron absorption being of vital significance for larval growth. To describe the process of organismal iron absorption, consideration needs to be given to cellular iron import, storage, export and how intestinal epithelial cells sense and respond to iron availability. Here we review studies on the Divalent Metal Transporter-1 homolog Malvolio (iron import), the recent discovery that Multicopper Oxidase-1 has ferroxidase activity (iron export) and the role of ferritin in the process of iron acquisition (iron storage). We also describe what is known about iron regulation in insect cells. We then draw upon knowledge from mammalian iron homeostasis to identify candidate genes in flies. Questions arise from the lack of conservation in Drosophila for key mammalian players, such as ferroportin, hepcidin and all the components of the hemochromatosis-related pathway. Drosophila and other insects also lack erythropoiesis. Thus, systemic iron regulation is likely to be conveyed by different signaling pathways and tissue requirements. The significance of regulating intestinal iron uptake is inferred from reports linking Drosophila developmental, immune, heat-shock and behavioral responses to iron sequestration. PMID:23686013

  10. Multi-photon absorption limits to heralded single photon sources

    PubMed Central

    Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; De Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

    2013-01-01

    Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

  11. Multi-photon absorption limits to heralded single photon sources

    NASA Astrophysics Data System (ADS)

    Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; de Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

    2013-11-01

    Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources.

  12. Fraunhofer effect atomic absorption spectrometry.

    PubMed

    Rust, Jennifer A; Nóbrega, Joaquim A; Calloway, Clifton P; Jones, Bradley T

    2005-02-15

    The dark lines in the solar spectrum were discovered by Wollaston and cataloged by Fraunhofer in the early days of the 19th century. Some years later, Kirchhoff explained the appearance of the dark lines: the sun was acting as a continuum light source and metals in the ground state in its atmosphere were absorbing characteristic narrow regions of the spectrum. This discovery eventually spawned atomic absorption spectrometry, which became a routine technique for chemical analysis in the mid-20th century. Laboratory-based atomic absorption spectrometers differ from the original observation of the Fraunhofer lines because they have always employed a separate light source and atomizer. This article describes a novel atomic absorption device that employs a single source, the tungsten coil, as both the generator of continuum radiation and the atomizer of the analytes. A 25-microL aliquot of sample is placed on the tungsten filament removed from a commercially available 150-W light bulb. The solution is dried and ashed by applying low currents to the coil in a three-step procedure. Full power is then applied to the coil for a brief period. During this time, the coil produces white light, which may be absorbed by any metals present in the atomization cloud produced by the sample. A high-resolution spectrometer with a charge-coupled device detector monitors the emission spectrum of the coil, which includes the dark lines from the metals. Detection limits are reported for seven elements: 5 pg of Ca (422.7 nm); 2 ng of Co (352.7 nm); 200 pg of Cr (425.4 nm); 7 pg of Sr (460.7 nm); 100 pg of Yb (398.8 nm); 500 pg of Mn (403.1 nm); and 500 pg of K (404.4 nm). Simultaneous multielement analyses are possible within a 4-nm spectral window. The relative standard deviations for the seven metals are below 8% for all metals except for Ca (10.7%), which was present in the blank at measurable levels. Analysis of a standard reference material (drinking water) resulted in a mean percent

  13. Sub-10 ns single-shot dynamic recording in holographic polymeric medium by nonlinear absorption using excited state absorption process

    NASA Astrophysics Data System (ADS)

    Kamada, Kenji; Satoh, Kazuyuki; Tanaka, Yoshito

    2016-09-01

    Optical recording by a single shot of an 8 ns laser pulse in a dye-doped holographic polymeric medium was demonstrated with a peak power as low as 71 W at a wavelength of 402 nm. Nonlinear absorption triggered by two-photon absorption and enhanced by the succeeding process allows high-speed recording corresponding to 125 Mbps (3.4 times the recording speed of a Blu-ray Disc). The preformed holographic grating in the medium enhanced the readout signal through diffraction, resulting in a signal-to-noise ratio of about 15 dB. The recording capacity was estimated at ca. 80 GB/side for 100 µm/side by recording 20 layers, but that of over TB/side class would be possible for optical optimization. Theoretically, it can be improved to 10 TB/side for 800 µm/side by recording 400 layers.

  14. Transitional behavior between self-Kerr and cross-Kerr effects by two photons

    SciTech Connect

    Koshino, Kazuki

    2007-06-15

    The transitional behavior of the two-photon Kerr effect between the self-Kerr and cross-Kerr cases is investigated. To this end, we have developed a semiclassical method for evaluating the two-photon Kerr effect that is applicable to any two-photon input state. It is revealed that the maximum Kerr effect is obtained when the second photon is input with a delay time that corresponds to the absorption time of the first photon by the optical material.

  15. Anomalous nonlinear absorption in epsilon-near-zero materials: optical limiting and all-optical control.

    PubMed

    Vincenti, M A; de Ceglia, D; Scalora, Michael

    2016-08-01

    We investigate nonlinear absorption in films of epsilon-near-zero materials. The combination of large local electric fields at the fundamental frequency and material losses at the harmonic frequencies induce unusual intensity-dependent phenomena. We predict that the second-order nonlinearity of a low-damping, epsilon-near-zero slab produces an optical limiting effect that mimics a two-photon absorption process. Anomalous absorption profiles that depend on low permittivity values at the pump frequency are also predicted for third-order nonlinearities. These findings suggest new opportunities for all-optical light control and novel ways to design reconfigurable and tunable nonlinear devices.

  16. Absorption spectra of wide-gap semiconductors in their transparency region

    NASA Astrophysics Data System (ADS)

    Imangholi, Babak; Hasselbeck, Michael P.; Sheik-Bahae, Mansoor

    2003-11-01

    The linear absorption spectra of GaP, TiO 2, ZnSe, and ZnS are measured in their transparency range using a two-color, excite-probe Z-scan. ZnS has the lowest absorption coefficient (˜10 -5 cm -1) in the wavelength range 840-900 nm, making it an excellent material for use as a luminescence extracting lens in semiconductor laser cooling experiments. Direct observation of two-photon absorption in ZnSe using only low power, continuous laser beams is also reported.

  17. Exceptionally large two- and three-photon absorption cross-sections by OPV organometalation.

    PubMed

    Gao, Beibei; Mazur, Leszek M; Morshedi, Mahbod; Barlow, Adam; Wang, Huan; Quintana, Cristóbal; Zhang, Chi; Samoc, Marek; Cifuentes, Marie P; Humphrey, Mark G

    2016-07-01

    Oligo(p-phenylenevinylene)s (OPVs) containing up to 8 PV units and end-functionalized by ruthenium alkynyl groups have been prepared and their nonlinear absorption properties assessed using the Z-scan technique and employing low repetition rate femtosecond pulses. Exceptionally large two-photon absorption (ca. 12 500 GM at 725 nm) and three-photon absorption cross sections (ca. 1.6 × 10(-76) cm(6) s(2) at 1100 nm) are found for the 8PV-containing example, highlighting the potential of an "organometalation" approach to NLO-efficient organic materials. PMID:27297290

  18. HI Absorption in Merger Remnants

    NASA Technical Reports Server (NTRS)

    Teng, Stacy H.; Veileux, Sylvain; Baker, Andrew J.

    2012-01-01

    It has been proposed that ultraluminous infrared galaxies (ULIRGs) pass through a luminous starburst phase, followed by a dust-enshrouded AGN phase, and finally evolve into optically bright "naked" quasars once they shed their gas/dust reservoirs through powerful wind events. We present the results of our recent 21- cm HI survey of 21 merger remnants with the Green Bank Telescope. These remnants were selected from the QUEST (Quasar/ULIRG Evolution Study) sample of ULIRGs and PG quasars; our targets are all bolometrically dominated by AGN and sample all phases of the proposed ULIRG -> IR-excess quasar -> optical quasar sequence. We explore whether there is an evolutionary connection between ULIRGs and quasars by looking for the occurrence of HI absorption tracing neutral gas outflows; our results will allow us to identify where along the sequence the majority of a merger's gas reservoir is expelled.

  19. Computer programs for absorption spectrophotometry.

    PubMed

    Jones, R N

    1969-03-01

    Brief descriptions are given of twenty-two modular computer programs for performing the basic numerical computations of absorption spectrophotometry. The programs, written in Fortran IV for card input and output, are available from the National Research Council of Canada. The input and output formats are standardized to permit easy interfacing to yield more complex data processing systems. Though these programs were developed for ir spectrophotometry, they are readily modified for use with digitized visual and uv spectrophotometers. The operations covered include ordinate and abscissal unit and scale interconversions, ordinate addition and subtraction, location of band maxima and minima, smoothing and differentiation, slit function convolution and deconvolution, band profile analysis and asymmetry quantification, Fourier transformation to time correlation curves, multiple overlapping band separation in terms of Cauchy (Lorentz), Gauss, Cauchy-Gauss product, and Cauchy-Gauss sum functions and cell path length determination from fringe spacing analysis. PMID:20072266

  20. Quantum-enhanced absorption refrigerators

    NASA Astrophysics Data System (ADS)

    Correa, Luis A.; Palao, José P.; Alonso, Daniel; Adesso, Gerardo

    2014-02-01

    Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step towards the technological exploitation of autonomous quantum refrigerators.

  1. Multistage quantum absorption heat pumps.

    PubMed

    Correa, Luis A

    2014-04-01

    It is well known that heat pumps, while being all limited by the same basic thermodynamic laws, may find realization on systems as "small" and "quantum" as a three-level maser. In order to quantitatively assess how the performance of these devices scales with their size, we design generalized N-dimensional ideal heat pumps by merging N-2 elementary three-level stages. We set them to operate in the absorption chiller mode between given hot and cold baths and study their maximum achievable cooling power and the corresponding efficiency as a function of N. While the efficiency at maximum power is roughly size-independent, the power itself slightly increases with the dimension, quickly saturating to a constant. Thus, interestingly, scaling up autonomous quantum heat pumps does not render a significant enhancement beyond the optimal double-stage configuration.

  2. Acoustic Absorption in Porous Materials

    NASA Technical Reports Server (NTRS)

    Kuczmarski, Maria A.; Johnston, James C.

    2011-01-01

    An understanding of both the areas of materials science and acoustics is necessary to successfully develop materials for acoustic absorption applications. This paper presents the basic knowledge and approaches for determining the acoustic performance of porous materials in a manner that will help materials researchers new to this area gain the understanding and skills necessary to make meaningful contributions to this field of study. Beginning with the basics and making as few assumptions as possible, this paper reviews relevant topics in the acoustic performance of porous materials, which are often used to make acoustic bulk absorbers, moving from the physics of sound wave interactions with porous materials to measurement techniques for flow resistivity, characteristic impedance, and wavenumber.

  3. Backscatter absorption gas imaging system

    DOEpatents

    McRae, T.G. Jr.

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  4. Backscatter absorption gas imaging system

    DOEpatents

    McRae, Jr., Thomas G.

    1985-01-01

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  5. Transient simulation of absorption machines

    NASA Astrophysics Data System (ADS)

    Anand, D. K.; Allen, R. W.; Kumar, B.

    A model for a water-cooled Lithium-Bromide/water absorption chiller is presented. Its transient response both during the start-up phase and during the shut-off period is predicted. The simulation model incorporates such influencing factors as the thermodynamic properties of the working fluid, the absorbent, the heat-transfer configuration of different components of the chiller and related physical data. The time constants of different components are controlled by a set of key parameters that have been identified. The results show a variable but at times significant amount of time delay before the chiller capacity gets close to its steady-state value. The model is intended to provide an insight into the mechanism of build-up to steady-state performance. By recognizing the significant factors contributing to transient degradation, steps can be taken to reduce such degradation.

  6. Quantum-enhanced absorption refrigerators.

    PubMed

    Correa, Luis A; Palao, José P; Alonso, Daniel; Adesso, Gerardo

    2014-01-01

    Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step towards the technological exploitation of autonomous quantum refrigerators. PMID:24492860

  7. Olefin recovery via chemical absorption

    SciTech Connect

    Barchas, R.

    1998-06-01

    The recovery of fight olefins in petrochemical plants has generally been accomplished through cryogenic distillation, a process which is very capital and energy intensive. In an effort to simplify the recovery process and reduce its cost, BP Chemicals has developed a chemical absorption technology based on an aqueous silver nitrate solution. Stone & Webster is now marketing, licensing, and engineering the technology. The process is commercially ready for recovering olefins from olefin derivative plant vent gases, such as vents from polyethylene, polypropylene, ethylene oxide, and synthetic ethanol units. The process can also be used to debottleneck C{sub 2} or C{sub 3} splinters, or to improve olefin product purity. This paper presents the olefin recovery imp technology, discusses its applications, and presents economics for the recovery of ethylene and propylene.

  8. Neutron scattering and absorption properties

    SciTech Connect

    Holden, N.E.

    1993-12-01

    The Table in this report presents an evaluated set of values for the experimental quantities, which characterize the properties for scattering and absorption of neutrons. The neutron cross section is given for room temperature neutrons, 20.43{degree}C, corresponds to a thermal neutron energy of 0.0253 electron volts (eV) or a neutron velocity of 2200 meters/second. The neutron resonance integral is defined over the energy range from 0.5 eV to 0.1 {times} 10{sup 6} eV, or 0.1 MeV. A list of the major references used is given below. The literature cutoff data is October 1993. Uncertainties are given in parentheses. Parentheses with two or more numbers indicate values to the excited states(s) and to the ground state of the product nucleus.

  9. Graphene intracavity spaser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lozovik, Yu. E.; Nechepurenko, I. A.; Dorofeenko, A. V.

    2016-09-01

    We propose an intracavity plasmon absorption spectroscopy method based on graphene active plasmonics. It is shown that the plasmonic cavity contribution to the sensitivity is proportional to the quality factor Q of the graphene plasmonic cavity and reaches two orders of magnitude. The addition of gain medium into the cavity increases the sensitivity of method. Maximum sensitivity is reached in the vicinity of the plasmon generation threshold. The gain contribution to the sensitivity is proportional to Q1/2. The giant amplification of sensitivity in the graphene plasmon generator is associated with a huge path length, limited only by the decoherence processes. An analytical estimation of the sensitivity to loss caused by analyzed particles (molecules, nanoparticles, etc.) normalized by the single pass plasmon scheme is derived. Usage of graphene nanoflakes as plasmonic cavity allows a high spatial resolution to be reached, in addition to high sensitivity.

  10. Energy absorption by polymer crazing

    NASA Technical Reports Server (NTRS)

    Pang, S. S.; Zhang, Z. D.; Chern, S. S.; Hsiao, C. C.

    1983-01-01

    During the past thirty years, a tremendous amount of research was done on the development of crazing in polymers. The phenomenon of crazing was recognized as an unusual deformation behavior associated with a process of molecular orientation in a solid to resist failure. The craze absorbs a fairly large amount of energy during the crazing process. When a craze does occur the surrounding bulk material is usually stretched to several hundred percent of its original dimension and creates a new phase. The total energy absorbed by a craze during the crazing process in creep was calculated analytically with the help of some experimental measurements. A comparison of the energy absorption by the new phase and that by the original bulk uncrazed medium is made.

  11. Absorption Changes in Bacterial Chromatophores

    PubMed Central

    Kuntz, Irwin D.; Loach, Paul A.; Calvin, Melvin

    1964-01-01

    The magnitude and kinetics of photo-induced absorption changes in bacterial chromatophores (R. rubrum, R. spheroides and Chromatium) have been studied as a function of potential, established by added redox couples. No photochanges can be observed above +0.55 v or below -0.15 v. The loss of signal at the higher potential is centered at +0.439 v and follows a one-electron change. The loss of signal at the lower potential is centered at -0.044 v and is also consistent with a one-electron change. Both losses are reversible. A quantitative relationship exists between light-minus-dark and oxidized-minus-reduced spectra in the near infrared from +0.30 to +0.55 v. Selective treatment of the chromatophores with strong oxidants irreversibly bleaches the bulk pigments but appears to leave intact those pigments responsible for the photo- and chemically-induced absorption changes. Kinetic studies of the photochanges in deaerated samples of R. rubrum chromatophores revealed the same rise time for bands at 433, 792, and 865 mμ (t½ = 50 msec.). However, these bands had different decay rates (t½ = 1.5, 0.5, 0.15 sec., respectively), indicating that they belong to different pigments. Analysis of the data indicates, as the simplest interpretation, a first-order (or pseudo first-order) forward reaction and two parallel first-order (or pseudo first-order) decay reactions at each wavelength. These results imply that all pigments whose kinetics are given are photooxidized and the decay processes are dark reductions. These experiments are viewed as supporting and extending the concept of a bacterial photosynthetic unit, with energy migration within it to specific sites of electron transfer. PMID:14185583

  12. Inhibitory effect of nuts on iron absorption.

    PubMed

    Macfarlane, B J; Bezwoda, W R; Bothwell, T H; Baynes, R D; Bothwell, J E; MacPhail, A P; Lamparelli, R D; Mayet, F

    1988-02-01

    The effects on iron absorption of nuts, an important source of dietary protein in many developing countries, were measured in 137 Indian women. When the absorption from bread and nut meals (walnuts, almonds, peanuts, and hazelnuts) was compared with that from bread meals, the overall geometric mean absorption from the nut meals (1.8%) was significantly less than from the bread meals alone (6.6%, t = 9.8, p less than 0.0005). In contrast, coconut did not reduce absorption significantly. All the nuts tested contained significant amounts of two known inhibitors of Fe absorption (phytates and polyphenols) but the amounts in coconut were significantly less than in the other nuts. Fifty milligrams ascorbic acid overcame the inhibitory effects of two nuts that were tested (Brazil nuts and peanuts). This is different from that found previously for soy protein, another potent inhibitor of Fe absorption.

  13. Absorption bands in the spectrum of Io

    NASA Technical Reports Server (NTRS)

    Cruikshank, D. P.; Jones, T. J.; Pilcher, C. B.

    1978-01-01

    Near-infrared spectra of Io in the region from 2.8 to 4.2 microns are reported which show distinct absorption features, the most notable at 4.1 microns. Frozen volatiles or atmospheric gases cannot account for these absorptions, nor do they resemble those seen in common silicate rocks. Several candidate substances, most notably nitrate and carbonate salts, show absorption features in this spectral region; the deepest band in the spectrum may be a nitrate absorption. The satellite surface is shown to be anhydrous, as indicated by the absence of the 3-micron bound water band.

  14. Neural regulation of intestinal nutrient absorption.

    PubMed

    Mourad, Fadi H; Saadé, Nayef E

    2011-10-01

    The nervous system and the gastrointestinal (GI) tract share several common features including reciprocal interconnections and several neurotransmitters and peptides known as gut peptides, neuropeptides or hormones. The processes of digestion, secretion of digestive enzymes and then absorption are regulated by the neuro-endocrine system. Luminal glucose enhances its own absorption through a neuronal reflex that involves capsaicin sensitive primary afferent (CSPA) fibres. Absorbed glucose stimulates insulin release that activates hepatoenteric neural pathways leading to an increase in the expression of glucose transporters. Adrenergic innervation increases glucose absorption through α1 and β receptors and decreases absorption through activation of α2 receptors. The vagus nerve plays an important role in the regulation of diurnal variation in transporter expression and in anticipation to food intake. Vagal CSPAs exert tonic inhibitory effects on amino acid absorption. It also plays an important role in the mediation of the inhibitory effect of intestinal amino acids on their own absorption at the level of proximal or distal segment. However, chronic extrinsic denervation leads to a decrease in intestinal amino acid absorption. Conversely, adrenergic agonists as well as activation of CSPA fibres enhance peptides uptake through the peptide transporter PEPT1. Finally, intestinal innervation plays a minimal role in the absorption of fat digestion products. Intestinal absorption of nutrients is a basic vital mechanism that depends essentially on the function of intestinal mucosa. However, intrinsic and extrinsic neural mechanisms that rely on several redundant loops are involved in immediate and long-term control of the outcome of intestinal function.

  15. Observation of Two-Photon Absorption and Nonlinear Refraction in AlN

    NASA Astrophysics Data System (ADS)

    Zhao, Meng; Xu, Chun-Hua; Hu, Wei-Jie; Wang, Wen-Jun; Guo, Li-Wei; Chen, Xiao-Long

    2016-10-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 51372267, 51210105026 and 51172270, and the National Basic Research Program of China under Grant No 2013CB932901.

  16. Two-photon absorption and nonlinear refraction of birefringent mesoporous silicon films

    SciTech Connect

    Gayvoronsky, Vladimir Ya; Golovan, Leonid A; Kopylovsky, M A; Gromov, Yu V; Zabotnov, S V; Piskunov, N A; Kashkarov, Pavel K; Timoshenko, Viktor Yu

    2011-03-31

    The self-action of light in birefringent mesoporous silicon films is studied using picosecond laser pulses. Two mechanisms of self-action of light in mesoporous silicon are found. One of them manifests itself at laser intensities below 3 MW cm{sup -2} and tends to saturation. The other dominates at intensities above 10 MW cm{sup -2}. The former is related to the resonant excitation of electronic states on the surface of silicon nanocrystals, whereas the latter is due to the local fields in the nanocomposite. For the aforementioned ranges of the laser intensity, the cubic nonlinear susceptibility of the films exceeds that of single-crystal silicon by six and four orders of magnitude, respectively, and the figure of merit for the films exceeds that for single-crystal silicon by an order of magnitude. (nonlinear-optics phenomena)

  17. Solvent effect on the nonlinear absorption of 5,10-A(2)B(2) meso substituted porphyrins.

    PubMed

    Zawadzka, Monika; Wang, Jun; Blau, Werner J; Senge, Mathias O

    2013-10-01

    The effect of the solvent on the nonlinear absorptive properties of two series of 5,10-A2B2 porphyrins was investigated with an open Z-scan technique in the ns time regime. The recorded responses, which varied between compounds and solvents, were fitted to a four-level model where the one-photon excited state absorption is followed by a two-photon process arising from the higher excited states. For most of the compounds the positive nonlinear absorption in toluene was stronger than that in DMF and chloroform. This was attributed to enhanced two-photon absorption in toluene. For DMF and chloroform the solvent effects were most likely to be compound specific. It was demonstrated that the high saturation intensity of two-photon absorption shifts the RSA/SA turnover into a higher fluence range, which is desirable for optical limiting applications. This saturation intensity of two-photon absorption varied between compounds and solvents. Additionally, nonlinear scattering contributed strongly to the open Z-scan responses for many compounds in chlorobenzene and chloroform-chlorobenzene solutions. This was associated with the photodegradation of chlorobenzene.

  18. Influence of nanorod absorption spectrum width on superluminality effect for laser pulse propagation

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Lysak, Tatiana M.

    2016-03-01

    We investigate the influence of the finite absorption spectrum width on the soliton formation and superluminality phenomenon at a femtosecond pulse propagation in a medium with noble nanoparticles. These effects take place if a positive phase-amplitude grating is induced by laser radiation. We take into account the two-photon absorption (TPA) of laser radiation by nanorods, and time-dependent nanorod aspect ratio changing due to their melting or reshaping because of laser energy absorption, and the nanorod absorption spectrum width. On the basis of computer simulation we demonstrate these effects in a medium with positive phase-amplitude grating, induced by laser radiation, if a weak laser energy absorption takes place on the laser pulse dispersion length.

  19. Functional polymers by two-photon 3D lithography

    NASA Astrophysics Data System (ADS)

    Infuehr, Robert; Pucher, Niklas; Heller, Christian; Lichtenegger, Helga; Liska, Robert; Schmidt, Volker; Kuna, Ladislav; Haase, Anja; Stampfl, Jürgen

    2007-12-01

    In the presented work, two-photon 3D lithography and selective single-photon photopolymerization in a prefabricated polydimethylsiloxane matrix is presented as an approach with potential applicability of waveguide writing in 3D by two-photon polymerization. Photopolymers based on acrylate chemistry were used in order to evaluate the optical capabilities of the available two-photon system. Several photoinitiators, tailored for two-photon absorption, were tested in a mixture of trimethylolpropane triacrylate and ethoxylated trimethylolpropane triacrylate. Best results were obtained with a recently synthesized diynone-based photoinitiator. Feature resolutions in the range of 300 nm were achieved. Due to the cross-conjugated nature of that donor-π-acceptor-π-donor system a high two-photon absorption activity was achieved. Therefore, a resin mixture containing only 0.025 wt% of photoinitiator was practical for structuring by two-photon polymerization. The required initiator content was therefore a factor of 100 lower than in traditional one-photon lithography. The aim of the second part of this work was to fabricate optical waveguides by selectively irradiating a polymer network, which was swollen by a monomer. The monomer was polymerized by conventional single-photon polymerization and the uncured monomer was removed by evaporation at elevated temperatures. This treatment leads to a local change in refractive index. Refractive index changes in the range of Δ n = 0.01 (Δ n/ n = 0.7%) were achieved, which is sufficient for structuring waveguides for optoelectronic applications.

  20. On the Ammonia Absorption on Saturn

    NASA Astrophysics Data System (ADS)

    Tejfel, Victor G.; Karimov, A. M.; Lyssenko, P. G.; Kharitonova, G. A.

    2015-11-01

    The ammonia absorption bands centered at wavelengths of 645 and 787 nm in the visible spectrum of Saturn are very weak and overlapped with more strong absorption bands of methane. Therefore, the allocation of these bands is extremely difficult. In fact, the NH3 band 787 nm is completely masked by methane. The NH3 645 nm absorption band is superimposed on a relatively weak shortwave wing of CH4 band, in which the absorption maximum lies at the wavelength of 667 nm. In 2009, during the equinox on Saturn we have obtained the series of zonal spectrograms by scanning of the planet disk from the southern to the northern polar limb. Besides studies of latitudinal variation of the methane absorption bands we have done an attempt to trace the behavior of the absorption of ammonia in the band 645 nm. Simple selection of the pure NH3 profile of the band was not very reliable. Therefore, after normalizing to the ring spectrum and to the level of the continuous spectrum for entire band ranging from 630 to 680 nm in the equivalent widths were calculated for shortwave part of this band (630-652 nm), where the ammonia absorption is present, and a portion of the band CH4 652-680 nm. In any method of eliminating the weak part of the methane uptake in the short wing show an increased ammonia absorption in the northern hemisphere compared to the south. This same feature is observed also in the behavior of weak absorption bands of methane in contrast to the more powerful, such as CH4 725 and 787 nm. This is due to the conditions of absorption bands formation in the clouds at multiple scattering. Weak absorption bands of methane and ammonia are formed on the large effective optical depths and their behavior reflects the differences in the degree of uniformity of the aerosol component of the atmosphere of Saturn.

  1. Fluid absorption solar energy receiver

    NASA Technical Reports Server (NTRS)

    Bair, Edward J.

    1993-01-01

    A conventional solar dynamic system transmits solar energy to the flowing fluid of a thermodynamic cycle through structures which contain the gas and thermal energy storage material. Such a heat transfer mechanism dictates that the structure operate at a higher temperature than the fluid. This investigation reports on a fluid absorption receiver where only a part of the solar energy is transmitted to the structure. The other part is absorbed directly by the fluid. By proportioning these two heat transfer paths the energy to the structure can preheat the fluid, while the energy absorbed directly by the fluid raises the fluid to its final working temperature. The surface temperatures need not exceed the output temperature of the fluid. This makes the output temperature of the gas the maximum temperature in the system. The gas can have local maximum temperatures higher than the output working temperature. However local high temperatures are quickly equilibrated, and since the gas does not emit radiation, local high temperatures do not result in a radiative heat loss. Thermal radiation, thermal conductivity, and heat exchange with the gas all help equilibrate the surface temperature.

  2. Transient simulation of absorption machines

    NASA Astrophysics Data System (ADS)

    Anand, D. K.; Allen, R. W.; Kumar, B.

    1982-08-01

    This paper presents a model for a water-cooled Lithium-Bromide/water absorption chiller and predicts its transient response both during the start-up phase and during the shutoff period. The simulation model incorporates such influencing factors as the thermodynamic properties of the working fluid, the absorbent, the heat-transfer configuration of different components of the chiller and related physical data. The time constants of different components are controlled by a set of key parameters that have been identified in this study. The results show a variable but at times significant amount of time delay before the chiller capacity gets close to its steady-state value. The model is intended to provide an insight into the mechanism of build-up to steady-state performance. By recognizing the significant factors contributing to transient degradation, steps can be taken to reduce such degradation. The evaluation of the residual capacity in the shut-off period will yield more realistic estimates of chiller COP for a chiller satisfying dynamic space cooling load.

  3. The absorption of polymeric composites

    NASA Astrophysics Data System (ADS)

    Řídký, R.; Popovič, M.; Rolc, S.; Drdlová, M.; Krátký, J.

    2016-06-01

    An absorption capacity of soft, viscoelastic materials at high strain rates is important for wide range of practical applications. Nowadays there are many variants of numerical models suitable for this kind of analysis. The main difficulty is in selection of the most realistic numerical model and a correct setup of many unknown material constants. Cooperation between theoretical simulations and real testing is next crucial point in the investigation process. Standard open source material database offer material properties valid for strain rates less than 250 s-1. There are experiments suitable for analysis of material properties with strain rates close to 2000 s-1. The high strain-rate characteristics of a specific porous blast energy absorbing material measured by modified Split Hopkinson Pressure Bar apparatus is presented in this study. Testing these low impedance materials using a metallic split Hopkinson pressure bar setup results in poor signal to noise ratios due to impedance mismatching. These difficulties are overcome by using polymeric Hopkinson bars. Conventional Hopkinson bar analysis cannot be used on the polymeric bars due to the viscoelastic nature of the bar material. One of the possible solution leads to complex and frequency depended Young modulus of testing bars material. This testing technique was applied to materials composed of porous glass/ceramic filler and polymeric binder, with density of 125 - 300 kg/m3 and particle size in range of 50 µm - 2 mm. The achieved material model was verified in practical application of sandwich structure includes polymeric composites under a blast test.

  4. Low absorptance porcelain-on-aluminum coating

    NASA Technical Reports Server (NTRS)

    Leggett, H.

    1979-01-01

    Porcelain thermal-control coating for aluminum sheet and foil has solar absorptance of 0.22. Specially formulated coating absorptance is highly stable, changing only 0.03 after 1,000 hours of exposure to simulated sunlight and can be applied by standard commercial methods.

  5. A Low-Cost Quantitative Absorption Spectrophotometer

    ERIC Educational Resources Information Center

    Albert, Daniel R.; Todt, Michael A.; Davis, H. Floyd

    2012-01-01

    In an effort to make absorption spectrophotometry available to high school chemistry and physics classes, we have designed an inexpensive visible light absorption spectrophotometer. The spectrophotometer was constructed using LEGO blocks, a light emitting diode, optical elements (including a lens), a slide-mounted diffraction grating, and a…

  6. High-Absorptance Radiative Heat Sink

    NASA Technical Reports Server (NTRS)

    Cafferty, T.

    1983-01-01

    Absorptance of black-painted open-cell aluminum honeycomb improved by cutting honeycomb at angle or bias rather than straight across. This ensures honeycomb cavities escapes. At each reflection radiation attenuated by absorption. Applications include space-background simulators, space radiators, solar absorbers, and passive coolers for terrestrial use.

  7. Absorption of ozone by porous particles

    SciTech Connect

    Afanas'ev, V.P.; Dorofeev, S.B.; Sinitsyn, V.I.; Smirnov, B.M.

    1981-11-01

    The absorption of ozone by porous zeolite, silica gel, and activated carbon particles has been studied experimentally. It was shown that in addition to absorption, dissociation of ozone on the surface plays an important and sometimes decisive role. The results obtained were used to analyze the nature of ball lightning.

  8. Do Atoms Really "Emit" Absorption Lines?

    ERIC Educational Resources Information Center

    Brecher, Kenneth

    1991-01-01

    Presents three absorption line sources that enhance student understanding of the phenomena associated with the interaction of light with matter and help dispel the misconception that atoms "emit" absorption lines. Sources include neodymium, food coloring and other common household liquids, and fluorescent materials. (MDH)

  9. Terahertz absorption spectrum of triacetone triperoxide (TATP)

    NASA Astrophysics Data System (ADS)

    Wilkinson, John; Konek, Christopher T.; Moran, Jesse S.; Witko, Ewelina M.; Korter, Timothy M.

    2009-08-01

    We report here, for the first time, the terahertz absorption spectrum of triacetone triperoxide (TATP). The experimental spectra are coupled with solid-state density functional theory, and preliminary assignments are provided to gain physical insight into the experimental spectrum. The calculated absorption coefficients are in excellent agreement with experiment.

  10. On the absorption of alendronate in rats.

    PubMed

    Lin, J H; Chen, I W; deLuna, F A

    1994-12-01

    Alendronate is an antiosteolytic agent under investigation for the treatment of a number of bone disorders. Since the compound is a zwitterion with five pKa values and is completely ionized in the intestine at the physiological pH, absorption is poor; less than 1% of an oral dose is available systemically in rats. In the present studies, absorption was found to be predominantly in the upper part of the small intestine. Administration of buffered solutions of alendronate (pH 2-11) did not improve absorption. Whereas food markedly impaired the absorption of alendronate, EDTA enhanced absorption in a dose-dependent manner. Pretreatment of rats with ulcerogenic agents, mepirizole, acetylsalicylic acid, or indomethacin, resulted in a 3-7-fold increase in the oral absorption of alendronate. The absorption of phenol red, added as an indicator of intestinal tissue damage, was also increased in rats with experimental peptic ulcers. The enhanced absorption of alendronate observed in rats with experimental peptic ulcers was attributed to the alteration of the integrity of the intestinal membrane. PMID:7891304

  11. Iron absorption from intrinsically-labeled lentils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Low iron (Fe) absorption from important staple foods may contribute to Fe deficiency in developing countries. To date, there are few studies examining the Fe bioavailability of pulse crops as commonly prepared and consumed by humans. The objectives of this study were to characterize the Fe absorpt...

  12. VAPID: Voigt Absorption-Profile [Interstellar] Dabbler

    NASA Astrophysics Data System (ADS)

    Howarth, Ian D.

    2015-06-01

    VAPID (Voigt Absorption Profile [Interstellar] Dabbler) models interstellar absorption lines. It predicts profiles and optimizes model parameters by least-squares fitting to observed spectra. VAPID allows cloud parameters to be optimized with respect to several different data set simultaneously; those data sets may include observations of different transitions of a given species, and may have different S/N ratios and resolutions.

  13. Absorption imaging of a single atom.

    PubMed

    Streed, Erik W; Jechow, Andreas; Norton, Benjamin G; Kielpinski, David

    2012-07-03

    Absorption imaging has played a key role in the advancement of science from van Leeuwenhoek's discovery of red blood cells to modern observations of dust clouds in stellar nebulas and Bose-Einstein condensates. Here we show the first absorption imaging of a single atom isolated in a vacuum. The optical properties of atoms are thoroughly understood, so a single atom is an ideal system for testing the limits of absorption imaging. A single atomic ion was confined in an RF Paul trap and the absorption imaged at near wavelength resolution with a phase Fresnel lens. The observed image contrast of 3.1 (3)% is the maximum theoretically allowed for the imaging resolution of our set-up. The absorption of photons by single atoms is of immediate interest for quantum information processing. Our results also point out new opportunities in imaging of light-sensitive samples both in the optical and X-ray regimes.

  14. Single-molecule imaging by optical absorption

    NASA Astrophysics Data System (ADS)

    Celebrano, Michele; Kukura, Philipp; Renn, Alois; Sandoghdar, Vahid

    2011-02-01

    To date, optical studies of single molecules at room temperature have relied on the use of materials with high fluorescence quantum yield combined with efficient spectral rejection of background light. To extend single-molecule studies to a much larger pallet of substances that absorb but do not fluoresce, scientists have explored the photothermal effect, interferometry, direct attenuation and stimulated emission. Indeed, very recently, three groups have succeeded in achieving single-molecule sensitivity in absorption. Here, we apply modulation-free transmission measurements known from absorption spectrometers to image single molecules under ambient conditions both in the emissive and strongly quenched states. We arrive at quantitative values for the absorption cross-section of single molecules at different wavelengths and thereby set the ground for single-molecule absorption spectroscopy. Our work has important implications for research ranging from absorption and infrared spectroscopy to sensing of unlabelled proteins at the single-molecule level.

  15. Novel absorption detection techniques for capillary electrophoresis

    SciTech Connect

    Xue, Y.

    1994-07-27

    Capillary electrophoresis (CE) has emerged as one of the most versatile separation methods. However, efficient separation is not sufficient unless coupled to adequate detection. The narrow inner diameter (I.D.) of the capillary column raises a big challenge to detection methods. For UV-vis absorption detection, the concentration sensitivity is only at the {mu}M level. Most commercial CE instruments are equipped with incoherent UV-vis lamps. Low-brightness, instability and inefficient coupling of the light source with the capillary limit the further improvement of UV-vis absorption detection in CE. The goals of this research have been to show the utility of laser-based absorption detection. The approaches involve: on-column double-beam laser absorption detection and its application to the detection of small ions and proteins, and absorption detection with the bubble-shaped flow cell.

  16. Creating semiconductor metafilms with designer absorption spectra.

    PubMed

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  17. Creating semiconductor metafilms with designer absorption spectra

    PubMed Central

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  18. A theoretical consideration of percutaneous drug absorption.

    PubMed

    Kubota, K; Ishizaki, T

    1985-02-01

    The percutaneous drug absorption process and its clinical significance are not fully known. In this article we propose a theoretical method to obtain two parameters (kd and kc) of percutaneous drug absorption from in vivo data. These parameters are related to diffusion of a drug through the skin and removal process at the skin-capillary boundary, respectively, characterizing several pharmacokinetic aspects of the drug applied to the skin. Moreover, by employing these two kinetic constants, a simulation of percutaneous drug absorption can be theoretically generated. On the basis of our theoretical considerations on the percutaneous drug absorption process described herein, we conclude that the percutaneous drug absorption process is better understood by employing two kinetic constants in a mathematical model and that its clinical application would be highly possible. PMID:4020622

  19. Broadband microwave absorption spectrometer for liquid media

    SciTech Connect

    Mukherjee, P.; Gosnell, T.R.; Bigio, I.J.

    1988-12-01

    A broadband, continuous-sweep microwave spectrometer has been constructed for measurements of the absorption coefficient of aqueous solutions and other liquid media. The spectrometer makes use of the phase fluctuation optical heterodyne technique, which provides a direct measure of the microwave power deposited in the sample. Consequently, in contrast to the standard dielectrometric techniques that indirectly determine the absorption coefficient via separate measurements of the real and imaginary parts of the dielectric constant, this spectrometer directly measures the microwave absorption coefficient. Broadband spectra are obtained using a transmission line to couple microwave power into the liquid sample. The absorption spectrum for deionized water in the range 3--20 GHz is presented as an example and shows excellent agreement with calculated values of the absorption coefficient based on previously published dielectric data.

  20. Creating semiconductor metafilms with designer absorption spectra

    NASA Astrophysics Data System (ADS)

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-07-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells.

  1. Two-photon directed evolution of green fluorescent proteins

    PubMed Central

    Stoltzfus, Caleb R.; Barnett, Lauren M.; Drobizhev, Mikhail; Wicks, Geoffrey; Mikhaylov, Alexander; Hughes, Thomas E.; Rebane, Aleksander

    2015-01-01

    Directed evolution has been used extensively to improve the properties of a variety of fluorescent proteins (FPs). Evolutionary strategies, however, have not yet been used to improve the two-photon absorption (2PA) properties of a fluorescent protein, properties that are important for two-photon imaging in living tissues, including the brain. Here we demonstrate a technique for quantitatively screening the two-photon excited fluorescence (2PEF) efficiency and 2PA cross section of tens of thousands of mutant FPs expressed in E. coli colonies. We use this procedure to move EGFP through three rounds of two-photon directed evolution leading to new variants showing up to a 50% enhancement in peak 2PA cross section and brightness within the near-IR tissue transparency wavelength range. PMID:26145791

  2. Two-photon directed evolution of green fluorescent proteins

    NASA Astrophysics Data System (ADS)

    Stoltzfus, Caleb R.; Barnett, Lauren M.; Drobizhev, Mikhail; Wicks, Geoffrey; Mikhaylov, Alexander; Hughes, Thomas E.; Rebane, Aleksander

    2015-07-01

    Directed evolution has been used extensively to improve the properties of a variety of fluorescent proteins (FPs). Evolutionary strategies, however, have not yet been used to improve the two-photon absorption (2PA) properties of a fluorescent protein, properties that are important for two-photon imaging in living tissues, including the brain. Here we demonstrate a technique for quantitatively screening the two-photon excited fluorescence (2PEF) efficiency and 2PA cross section of tens of thousands of mutant FPs expressed in E. coli colonies. We use this procedure to move EGFP through three rounds of two-photon directed evolution leading to new variants showing up to a 50% enhancement in peak 2PA cross section and brightness within the near-IR tissue transparency wavelength range.

  3. Time-dependent oral absorption models

    NASA Technical Reports Server (NTRS)

    Higaki, K.; Yamashita, S.; Amidon, G. L.

    2001-01-01

    The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.

  4. Two-Photon Activation of p-Hydroxyphenacyl Phototriggers: Toward Spatially Controlled Release of Diethyl Phosphate and ATP.

    PubMed

    Houk, Amanda L; Givens, Richard S; Elles, Christopher G

    2016-03-31

    Two-photon activation of the p-hydroxyphenacyl (pHP) photoactivated protecting group is demonstrated for the first time using visible light at 550 nm from a pulsed laser. Broadband two-photon absorption measurements reveal a strong two-photon transition (>10 GM) near 4.5 eV that closely resembles the lowest-energy band at the same total excitation energy in the one-photon absorption spectrum of the pHP chromophore. The polarization dependence of the two-photon absorption band is consistent with excitation to the same S3 ((1)ππ*) excited state for both one- and two-photon activation. Monitoring the progress of the uncaging reaction under nonresonant excitation at 550 nm confirms a quadratic intensity dependence and that two-photon activation of the uncaging reaction is possible using visible light in the range 500-620 nm. Deprotonation of the pHP chromophore under mildly basic conditions shifts the absorption band to lower energy (3.8 eV) in both the one- and two-photon absorption spectra, suggesting that two-photon activation of the pHP chromophore may be possible using light in the range 550-720 nm. The results of these measurements open the possibility of spatially and temporally selective release of biologically active compounds from the pHP protecting group using visible light from a pulsed laser.

  5. Two-Photon Activation of p-Hydroxyphenacyl Phototriggers: Toward Spatially Controlled Release of Diethyl Phosphate and ATP.

    PubMed

    Houk, Amanda L; Givens, Richard S; Elles, Christopher G

    2016-03-31

    Two-photon activation of the p-hydroxyphenacyl (pHP) photoactivated protecting group is demonstrated for the first time using visible light at 550 nm from a pulsed laser. Broadband two-photon absorption measurements reveal a strong two-photon transition (>10 GM) near 4.5 eV that closely resembles the lowest-energy band at the same total excitation energy in the one-photon absorption spectrum of the pHP chromophore. The polarization dependence of the two-photon absorption band is consistent with excitation to the same S3 ((1)ππ*) excited state for both one- and two-photon activation. Monitoring the progress of the uncaging reaction under nonresonant excitation at 550 nm confirms a quadratic intensity dependence and that two-photon activation of the uncaging reaction is possible using visible light in the range 500-620 nm. Deprotonation of the pHP chromophore under mildly basic conditions shifts the absorption band to lower energy (3.8 eV) in both the one- and two-photon absorption spectra, suggesting that two-photon activation of the pHP chromophore may be possible using light in the range 550-720 nm. The results of these measurements open the possibility of spatially and temporally selective release of biologically active compounds from the pHP protecting group using visible light from a pulsed laser. PMID:26962676

  6. Two-photon vibrational excitation of air by long-wave infrared laser pulses

    NASA Astrophysics Data System (ADS)

    Palastro, J. P.; Peñano, J.; Johnson, L. A.; Hafizi, B.; Wahlstrand, J. K.; Milchberg, H. M.

    2016-08-01

    Ultrashort long-wave infrared (LWIR) laser pulses can resonantly excite vibrations in N2 and O2 through a two-photon transition. The absorptive vibrational component of the ultrafast optical nonlinearity grows in time, starting smaller than but quickly surpassing the electronic, rotational, and vibrational refractive components. The growth of the vibrational component results in a novel mechanism of third-harmonic generation, providing an additional two-photon excitation channel, fundamental + third harmonic. The original and emergent two-photon excitations drive the resonance exactly out of phase, causing spatial decay of the absorptive vibrational nonlinearity. This nearly eliminates two-photon vibrational absorption. Here we present simulations and analytical calculations demonstrating how these processes modify the ultrafast optical nonlinearity in air. The results reveal nonlinear optical phenomena unique to the LWIR regime of ultrashort pulse propagation in the atmosphere.

  7. Synthesis and blue-violet two-photon excited fluorescence of a new organoboron compound

    NASA Astrophysics Data System (ADS)

    Cao, Duxia; Liu, Zhiqiang; Li, Guozhong; Liu, Guoqun; Zhang, Guohui

    2008-02-01

    A new A-π-D-π-A type organoboron compound, 3,6-bis(dimesitylboryl)- N-butyl-carbazole (abbreviated as BBC), with trivalent boron as electron acceptor and carbazole as electron donor and π-conjugated core, has been synthesized and its single and two-photon related photophysical properties experimentally investigated. Pumped by 720 nm laser pulses in femtosecond regime, it showed strong two-photon excited blue-violet fluorescence at 393 nm in toluene and 403 nm in THF. The measured two-photon absorption cross-section by two-photon fluorescence method in toluene and THF is 34 GM and 38 GM, respectively.

  8. Microwave and optical saturable absorption in graphene.

    PubMed

    Zheng, Zhiwei; Zhao, Chujun; Lu, Shunbin; Chen, Yu; Li, Ying; Zhang, Han; Wen, Shuangchun

    2012-10-01

    We report on the first experiments on saturable absorption in graphene at microwave frequency band. Almost independent of the incident frequency, microwave absorbance of graphene always decreases with increasing the power and reaches at a constant level for power larger than 80 µW, evidencing the microwave saturable absorption property of graphene. Optical saturable absorption of the same graphene sample was also experimentally confirmed by an open-aperture Z-scan technique by one laser at telecommunication band and another pico-second laser at 1053 nm, respectively. Herein, we are able to conclude that graphene is indeed a broadband saturable absorber that can operate at both microwave and optical band.

  9. The gastrointestinal absorption of the actinide elements.

    PubMed

    Harrison, J D

    1991-03-01

    The greatest uncertainty in dose estimates for the ingestion of long-lived, alpha-emitting isotopes of the actinide elements is in the values used for their fractional absorption from the gastrointestinal tract (f1 values). Recent years have seen a large increase in the available data on actinide absorption. Human data are reviewed here, together with animal data, to illustrate the effect on absorption of chemical form, incorporation into food materials, fasting and other dietary factors, and age at ingestion. The f1 values recommended by the International Commission on Radiological Protection, by an Expert Group of the Nuclear Energy Agency and by the National Radiological Protection Board are discussed.

  10. Extraordinary Absorption of Decorated Undoped Graphene

    NASA Astrophysics Data System (ADS)

    Stauber, T.; Gómez-Santos, G.; de Abajo, F. Javier García

    2014-02-01

    We theoretically study absorption by an undoped graphene layer decorated with arrays of small particles. We discuss periodic and random arrays within a common formalism, which predicts a maximum absorption of 50% for suspended graphene in both cases. The limits of weak and strong scatterers are investigated, and an unusual dependence on particle-graphene separation is found and explained in terms of the effective number of contributing evanescent diffraction orders of the array. Our results can be important to boost absorption by single-layer graphene due to its simple setup with potential applications to light harvesting and photodetection based on energy (Förster) rather than charge transfer.

  11. Selective coherent perfect absorption in metamaterials

    SciTech Connect

    Nie, Guangyu; Shi, Quanchao; Zhu, Zheng; Shi, Jinhui

    2014-11-17

    We show multi-band coherent perfect absorption (CPA) in simple bilayered asymmetrically split ring metamaterials. The selectivity of absorption can be accomplished by separately excited electric and magnetic modes in a standing wave formed by two coherent counterpropagating beams. In particular, each CPA can be completely switched on/off by the phase of a second coherent wave. We propose a practical scheme for realizing multi-band coherent perfect absorption of 100% that is allowed to work from microwave to optical frequency.

  12. Electric modulation of optical absorption in nanowires

    NASA Astrophysics Data System (ADS)

    Sakr, M. R.

    2016-11-01

    We have calculated the effect of an external electric field on the intersubband optical absorption of a nanowire subjected to a perpendicular magnetic field and Rashba effect. The absorption peaks due to optical transitions that are forbidden in the absence of the intersubband coupling experience strong amplitude modulation. This effect is quadratic in electric fields applied along the direction of quantum confinement or perpendicularly to tune the Rashba parameter. The electric field also induces frequency modulation in the associated spectrum. On the other hand, transitions that are normally allowed show, to a large extent, a parallel band effect, and accordingly they are responsible for strong optical absorption.

  13. Total absorption by degenerate critical coupling

    SciTech Connect

    Piper, Jessica R. Liu, Victor; Fan, Shanhui

    2014-06-23

    We consider a mirror-symmetric resonator with two ports. We show that, when excited from a single port, complete absorption can be achieved through critical coupling to degenerate resonances with opposite symmetry. Moreover, any time two resonances with opposite symmetry are degenerate in frequency and absorption is always significantly enhanced. In contrast, when two resonances with the same symmetry are nearly degenerate, there is no absorption enhancement. We numerically demonstrate these effects using a graphene monolayer on top of a photonic crystal slab, illuminated from a single side in the near-infrared.

  14. Optical absorption coefficients of pure water

    NASA Astrophysics Data System (ADS)

    Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.

    2002-10-01

    The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.

  15. Absorption mapping for characterization of glass surfaces.

    PubMed

    Commandré, M; Roche, P; Borgogno, J P; Albrand, G

    1995-05-01

    The surface quality of bare substrates and preparation procedures take on an important role in optical coating performances. The most commonly used techniques of characterization generally give information about roughness and local defects. A photothermal deflection technique is used for mapping surface absorption of fused-silica and glass substrates. We show that absorption mapping gives specific information on surface contamination of bare substrates. We present experimental results concerning substrates prepared by different cleaning and polishing techniques. We show that highly polished surfaces lead to the lowest values of residual surface absorption. Moreover the cleaning behavior of surfaces of multicomponent glasses and their optical performance in terms of absorption are proved to be different from those of fused silica.

  16. Absorption cross section of canonical acoustic holes

    SciTech Connect

    Crispino, Luis C. B.; Oliveira, Ednilton S.; Matsas, George E. A.

    2007-11-15

    We compute numerically the absorption cross section of a canonical acoustic hole for sound waves with arbitrary frequencies. Our outputs are in full agreement with the expected low- and high-frequency limits.

  17. Absorption chillers: Part of the solution

    SciTech Connect

    Occhionero, A.J. ); Hughes, P.J. ); Reid, E.A. )

    1991-01-01

    Acid rain, ozone depletion, global warming, and implementation economics are considered as they relate to the advisability of expanding the application of absorption chillers. Introductory and background information are provided to put the discussion in the proper context. Then all four issues are discussed separately as they relate to absorption chillers. Acid rain and ozone depletion concerns, and implementation economics, are found to support the expanded use of absorption chillers. The global warming concern is found to be more of a gray area, but the areas of benefit correspond well with the conditions of greatest economic advantage. All things considered, absorption chillers are believed to be part of the environmental and economic solution. It is further believed that integrated resource planning (IRP) processes that consider electric and gas technologies on an equal footing would come to the same conclusion for many regions of the United States. 9 refs., 3 tabs.

  18. Extraordinary Optical Absorption through Plasmonic Subwavelength Slits

    NASA Astrophysics Data System (ADS)

    White, Justin; Veronis, Georgios; Yu, Zongfu; Barnard, Edward; Chandran, Anu; Fan, Shanhui; Brongersma, Mark

    2009-03-01

    We report on the ability of resonant plasmonic slits to efficiently concentrate electromagnetic energy into a nanoscale volume of absorbing material placed inside or right behind the slit. This gives rise to extraordinary optical absorption (EOA) characterized by an absorption enhancement factor that well-exceeds the enhancements seen for extraordinary optical transmission (EOT) through slits. A semi-analytic Fabry-Perot model for the resonant absorption is developed and shown to quantitatively agree with full-field simulations. We show that absorption enhancements of nearly 1000% can be realized at 633nm for slits in aluminum films filled with silicon. This effect can be utilized in a wide range of applications, including high speed photodetectors, optical lithography and recording, and biosensors.

  19. Electromagnetically induced absorption via incoherent collisions

    SciTech Connect

    Yang Xihua; Sheng Jiteng; Xiao Min

    2011-10-15

    We conduct theoretical studies on electromagnetically induced absorption via incoherent collisions in an inhomogeneously broadened ladder-type three-level system with the density-matrix approach. The effects of the collision-induced coherence decay rates as well as the probe laser field intensity on the probe field absorption are examined. It is shown that with the increase of the collisional decay rates in a moderate range, a narrow dip due to electromagnetically induced transparency superimposed on the Doppler-broadened absorption background can be turned into a narrow peak under the conditions that the probe field intensity is not very weak as compared to the pump field, which results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. The physical origin of the collision-assisted electromagnetically induced absorption is analyzed with a power-series solution of the density-matrix equations.

  20. Induced Transparency and Absorption in Coupled Microresonators

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Chang, Hongrok

    2004-01-01

    We review the conditions for the occurrence of coherence phenomena in passive coupled optical microresonators. We derive the effective steady-state response and determine conditions for induced transparency and absorption in these systems.

  1. Substrate effects on absorption of coated surfaces.

    PubMed

    Roche, P; Commandré, M; Escoubas, L; Borgogno, J P; Albrand, G; Lazaridνs, B

    1996-09-01

    Photothermal deflection is used for mapping the absorption of bare and coated surfaces. The same area is mapped before and after coating and also after annealing. The great importance of the substrate with respect to the total losses of the coated component is emphasized. First the influence of surface contamination of the bare substrate on the total absorption of the coated substrate is studied for BK7 and fused-silica substrates. Then the mean value of the coated-substrate absorptance is shown to be strongly dependenton the type of substrate. Experimental results show that this effect is associated with a localization of the absorption at the near surface of the substrate and at the interfaces of the film.

  2. [Microwave absorption by magnetic nanoparticles in organisms].

    PubMed

    Bingi, V N

    2011-01-01

    An estimate of the rate of absorption of the electromagnetic microwaves by magnetic nanoparticles in organisms is presented. The absorption takes place due to the energy dissipation at the ferromagnetic resonance. Based on the known solution of the Landau-Lifshitz equation, the imaginary part of the complex magnetic susceptibility is evaluated that gives the absorption rate. It is shown that even in the conditions of thermal isolation of the particles, their temperature growth would be insignificant at absorption of the emission with the energy flux density of the order of 1 mW/cm2, and the given mechanism is unrelated to the observable effects of low-intensity microwaves. PMID:22279759

  3. Iron absorption from typical Latin American diets.

    PubMed

    Acosta, A; Amar, M; Cornbluth-Szarfarc, S C; Dillman, E; Fosil, M; Biachi, R G; Grebe, G; Hertrampf, E; Kremenchuzky, S; Layrisse, M

    1984-06-01

    The availability and daily absorption of iron was determined by the extrinsic label method in typical lower middle to lower class diets consumed in regions of Argentina, Brazil, Chile, Mexico, Peru, and Venezuela. Differences in iron absorption from meals up to 7-fold, could be attributed to the varying contents of absorption enhancers, eg, in meat, and of inhibitors in tea, vegetables, and wheat or maize bread. The total iron available in the diets from four countries did not meet the physiological requirements for normal subjects but deficient subjects fulfilled their requirements absorbing from 1.0 to 2.1 mg/day. In five diets heme iron (6 to 24% of the total) provided 34 to 73% of the iron absorbed. These data suggest that such absorption and utilization studies may be used to correlate the prevalence of iron deficiency in a population with certain diets and to guide fortification programs.

  4. Two-photon excitation in laser scanning fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Strickler, James H.; Webb, Watt W.

    1991-04-01

    Simultaneous absorption of two red photons from a strongly focused subpicosecond colliding pulse mode4ocked dye laser stimulates visible fluorescence emission from fluorophores having their normal absorption in the ultraviolet1. The quadratic increase of the two-photon excitation rate with excitation intensity restricts fluorescence emission to the focal volume thus providing the same depth resolution as does confocal microscopy. Image degradation due to out of focus backround is thus avoided. Photobleaching and most cellular photodamage are similarly confined to the focus thereby minimizing sample degredation during acquisition of the multiple sections required for 3-d image reconstruction. Fluorescence images of living cells and other thick photolabile fluorescence labled assemblies illustrate the depth discrimination of both two-photon fluorescence excitation and photobleaching. The quadratic intensity dependence of two-photon excitation allows 3-d spatially resolved photochemistry in particular the photolytic release of caged compounds such as neurotransmitters nucleotides fluorescent dyes and second messengers such as 1P3 and Ca. The two-photon release of cased ATP has been measured and release of a caged fluorescent dye has been shown. Point photobleaching and a 3-d " write once read many" optical memory have been demonstrated. Two-photon excitation of photo-initiated polymerization with a sharply focused single beam allows microfabrication of complex structures of arbitrary form. By scanning the focused beam through a liquid polymer with a UV excited initiator it is possible to harden the polymer only at the focus thereby creating

  5. Seasonal Solar Thermal Absorption Energy Storage Development.

    PubMed

    Daguenet-Frick, Xavier; Gantenbein, Paul; Rommel, Mathias; Fumey, Benjamin; Weber, Robert; Gooneseker, Kanishka; Williamson, Tommy

    2015-01-01

    This article describes a thermochemical seasonal storage with emphasis on the development of a reaction zone for an absorption/desorption unit. The heat and mass exchanges are modelled and the design of a suitable reaction zone is explained. A tube bundle concept is retained for the heat and mass exchangers and the units are manufactured and commissioned. Furthermore, experimental results of both absorption and desorption processes are presented and the exchanged power is compared to the results of the simulations. PMID:26842331

  6. Water absorption in mortar determined by NMR.

    PubMed

    Pel, L; Hazrati, K; Kopinga, K; Marchand, J

    1998-01-01

    Nuclear magnetic resonance (NMR) offers the possibility to determine moisture profiles in porous building materials. Moreover, the relaxation of the nuclear magnetic resonance signal can provide additional information on the water distribution in the microstructure. For mortar, it is shown that the transverse relaxation yields information on the distribution of water in the gel pores and capillary pores. Moisture profiles and relaxation were measured during water absorption. The effect of the drying treatment on the microstructure and the water absorption was investigated.

  7. Ultraviolet absorption cross sections of hydrogen peroxide

    NASA Technical Reports Server (NTRS)

    Lin, C. L.; Rohatgi, N. K.; Demore, W. B.

    1978-01-01

    Absorption cross-sections of hydrogen peroxide vapor and of neutral aqueous solutions of hydrogen peroxide were measured in the wavelength range from 195 to 350 nm at 296 K. The spectrophotometric procedure is described, and the reported cross-sections are compared with values obtained by other researchers. Photodissociation coefficients of atmospheric H2O2 were calculated for direct absorption of unscattered solar radiation, and the vertical distributions of these coefficients are shown for various solar zenith angles.

  8. Fluctuation sound absorption in quark matter

    NASA Astrophysics Data System (ADS)

    Kerbikov, B. O.; Lukashov, M. S.

    2016-09-01

    We investigate the sound absorption in quark matter due to the interaction of the sound wave with the precritical fluctuations of the diquark-pair field above Tc. The soft collective mode of the pair field is derived using the time-dependent Ginzburg-Landau functional with random Langevin forces. The strong absorption near the phase transition line may be viewed as a manifestation of Mandelshtam-Leontovich slow relaxation time theory.

  9. High temperature measurement of water vapor absorption

    NASA Technical Reports Server (NTRS)

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  10. Two-photon photodetector in a multiquantum well GaAs laser structure at 1.55 microm.

    PubMed

    Duchesne, D; Razzari, L; Halloran, L; Morandotti, R; SpringThorpe, A J; Christodoulides, D N; Moss, D J

    2009-03-30

    We report two-photon photocurrent in a GaAs/AlGaAs multiple quantum well laser at 1.55 microm. Using 1ps pulses, a purely quadratic photocurrent is observed. We measure the device efficiency, sensitivity, as well as the two-photon absorption coefficient. The results show that the device has potential for signal processing, autocorrelation and possibly two-photon source applications at sub-Watt power levels.

  11. Two- and three-photon absorption and frequency upconverted emission of silicon quantum dots.

    PubMed

    He, Guang S; Zheng, Qingdong; Yong, Ken-Tye; Erogbogbo, Folarin; Swihart, Mark T; Prasad, Paras N

    2008-09-01

    In this communication, we present the experimental results of two- and three-photon excitation studies on silicon quantum dots (QDs) in chloroform (as well as in water) by using femtosecond laser pulses with wavelengths of 778 and 1,335 nm and a pulse duration approximately 160 fs. The photoluminescence spectral distributions are nearly the same upon one-, two-, and three-photon excitation. With one- and two-photon excitation, the temporal relaxation measurements of photoluminescence emission manifest the same multiexponential decay behavior in the time range from 0.05 ns to 15 micros, characterized by three successive decay constants: 0.75 ns, 300 ns, and 5 micros, respectively. Finally, the two-photon absorption spectrum in the spectral range of 650-900 nm and the three-photon absorption spectrum in the spectral range of 1,150-1,400 nm have been measured.

  12. Two-photon excitation laser scanning microscopy: applications in neuroscience

    NASA Astrophysics Data System (ADS)

    Denk, Winfried

    1996-05-01

    High resolution fluorescence imaging in intact tissues faces special challenges posed by scattering of excitation and fluorescence light and the need to avoid photodynamic damage. Significant improvements over conventional widefield and confocal imaging are provided when two-photon excitation is used. Applications to the functional imaging of the calcium dynamics in synaptic spines, small invertebrate neurites, and auditory hair cells are shown. Two-photon absorption induced photolysis can also be used for scanning photochemical microscopy and for high resolution measurements of diffusional coupling between cellular compartments.

  13. Further advancement of differential optical absorption spectroscopy: theory of orthogonal optical absorption spectroscopy.

    PubMed

    Liudchik, Alexander M

    2014-08-10

    A modified version of the differential optical absorption spectroscopy (DOAS) method is presented. The technique is called orthogonal optical absorption spectroscopy (OOAS). A widespread variant of DOAS with smoothing of the registered spectrum and absorption cross sections being made employing a polynomial regression is a particular case of OOAS. The concept of OOAS provides a variety of new possibilities for constructing computational schemes and analyzing the influence of different error sources on calculated concentrations. PMID:25320931

  14. Water-related absorption in fibrous diamonds

    NASA Astrophysics Data System (ADS)

    Zedgenizov, D. A.; Shiryaev, A. A.; Kagi, H.; Navon, O.

    2003-04-01

    Cubic and coated diamonds from several localities (Brasil, Canada, Yakutia) were investigated using spectroscopic techniques. Special emphasis was put on investigation of water-related features of transmission Infra-red and Raman spectra. Presence of molecular water is inferred from broad absorption bands in IR at 3420 and 1640 cm-1. These bands were observed in many of the investigated samples. It is likely that molecular water is present in microinclusions in liquid state, since no clear indications of solid H_2O (ice VI-VII, Kagi et al., 2000) were found. Comparison of absorption by HOH and OH vibrations shows that diamonds can be separated into two principal groups: those containing liquid water (direct proportionality of OH and HOH absorption) and those with stronger absorption by OH group. Fraction of diamonds in every group depends on their provenance. There might be positive correlation between internal pressure in microinclusions (determined using quartz barometer, Navon et al., 1988) and affiliation with diamonds containing liquid water. In many cases absorption by HOH vibration is considerably lower than absorption by hydroxyl (OH) group. This may be explained if OH groups are partially present in mineral and/or melt inclusions. This hypothesis is supported by following fact: in diamonds with strong absorption by silicates and other minerals shape and position of the OH band differs from that in diamonds with low absorption by minerals. Moreover, in Raman spectra of individual inclusions sometimes the broad band at 3100 cm-1 is observed. This band is OH-related. In some samples water distribution is not homogeneous. Central part of the diamond usually contains more water than outer parts, but this is not a general rule for all the samples. Water absorption usually correlated with absorption of other components (carbonates, silicates and others). At that fibrous diamonds with relatively high content of silicates are characterized by molecular water. OH

  15. Absorption of ultraviolet radiation by antarctic phytoplankton

    SciTech Connect

    Vernet, M.; Mitchell, B.G. )

    1990-01-09

    Antarctic phytoplankton contain UV-absorbing compounds that may block damaging radiation. Compounds that absorb from 320-340 nm were observed in spectral absorption of both particulates and in methanol extracts of the particulates. The decrease in the total concentration of these UV compounds with respect to chlorophyll a, as measured by the ratio of in vitro absorption at 335 nm to absorption at 665 nm is variable and decreases with depth. We observed up to 5-fold decrease in this ratio for samples within the physically mixes surface layer. The absorption of UV radiation in methanol extracts, which peaks from 320 to 340 nm, may be composed of several compounds. Shifts in peak absorption with depth (for example, from 331 nm at surface to 321 nm at 75 m), may be interpreted as a change in composition. Ratios of protective yellow xanthophylls (diadinoxanthin + diatoxanthin) to photosynthetic fucoxanthin-like pigments have highest values in surface waters. As these pigments also absorb in the near UV, their function might extend to protection as well as utilization of UV radiation for photosynthesis. We document strong absorption in the UV from 320-330 nm for Antarctic marine particulates. Below this region of the solar energy spectrum, absolute energy levels of incident radiation drop off dramatically. Only wavelengths shorter than about 320 nm will be significantly enhanced due to ozone depletion. If the absorption we observed serves a protective role for phytoplankton photosynthesis, it appears the peak band is in the region where solar energy increases rapidly, and not in the region where depletion would cause significant variations in absolute flux.

  16. The ALFALFA HI Absorption Pilot Project

    NASA Astrophysics Data System (ADS)

    Macdonald, Erin; Darling, J.; ALFALFA Team

    2009-01-01

    We present the results of a pilot project to search for HI 21 cm absorption in the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) Survey. This project is the first to conduct a "blind" wide-area search for HI absorption in the local universe. The search covered 517.0 deg2 spanning 10.9h < α < 14.95h and +7.7o < δ < +16.3o. The ALFALFA survey covers -650 km s-1 < cz < 17,500 km s-1, for a Δz = 0.054 along each line of sight (11% of the cz span is lost to radio frequency interference and Galactic HI emission). There are 243 sources toward which all damped Lyα systems (N(HI) > 2x1020 cm-2) could be detected, and 3282 sources toward which N(HI) > 2x1021 cm-2 columns could be detected (assuming 100 K spin temperature, 30 km s-1 line width, and unity filling factor). We performed Green Bank Telescope follow-up observations of 13 possible absorption lines and the 250 strong sources (> 220 mJy) in our survey region. One previously known intrinsic HI absorption line in UGC 6081 was re-detected, but no additional lines were identified in the survey region. Nevertheless, this pilot project demonstrates the value and feasibility of large-area absorption line searches commensal with emission line surveys. An absorption line search of the entire 7000 deg2 ALFALFA Survey is a worthwhile undertaking, not only to identify HI absorption systems in the local universe, but to measure the fraction of HI gas not accounted for by emission line surveys. ALFALFA is a legacy survey at the Arecibo Observatory supported by NAIC and NSF.

  17. Uniform silica nanoparticles encapsulating two-photon absorbing fluorescent dye

    SciTech Connect

    Wu Weibing; Liu Chang; Wang Mingliang; Huang Wei; Zhou Shengrui; Jiang Wei; Sun Yueming; Cui Yiping; Xu Chunxinag

    2009-04-15

    We have prepared uniform silica nanoparticles (NPs) doped with a two-photon absorbing zwitterionic hemicyanine dye by reverse microemulsion method. Obvious solvatochromism on the absorption spectra of dye-doped NPs indicates that solvents can partly penetrate into the silica matrix and then affect the ground and excited state of dye molecules. For dye-doped NP suspensions, both one-photon and two-photon excited fluorescence are much stronger and recorded at shorter wavelength compared to those of free dye solutions with comparative overall dye concentration. This behavior is possibly attributed to the restricted twisted intramolecular charge transfer (TICT), which reduces fluorescence quenching when dye molecules are trapped in the silica matrix. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells with low cytotoxicity. - Graphical abstract: Water-soluble silica NPs doped with a two-photon absorbing zwitterionic hemicyanine dye were prepared. They were found of enhanced one-photon and two-photon excited fluorescence compared to free dye solutions. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells.

  18. UV laser long-path absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

    1994-01-01

    Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive

  19. Two-photon physics

    SciTech Connect

    Bardeen, W.A.

    1981-10-01

    A new experimental frontier has recently been opened to the study of two photon processes. The first results of many aspects of these reactions are being presented at this conference. In contrast, the theoretical development of research ito two photon processes has a much longer history. This talk reviews the many different theoretical ideas which provide a detailed framework for our understanding of two photon processes.

  20. X-ray absorption spectroscopy of metalloproteins.

    PubMed

    Ward, Jesse; Ollmann, Emily; Maxey, Evan; Finney, Lydia A

    2014-01-01

    Metalloproteins are enormously important in biology. While a variety of techniques exist for studying metals in biology, X-ray absorption spectroscopy is particularly useful in that it can determine the local electronic and physical structure around the metal center, and is one of the few avenues for studying "spectroscopically silent" metal ions like Zn(II) and Cu(I) that have completely filled valence bands. While X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) are useful for studying metalloprotein structure, they suffer the limitation that the detected signal is an average of all the various metal centers in the sample, which limits its usefulness for studying metal centers in situ or in cell lysates. It would be desirable to be able to separate the various proteins in a mixture prior to performing X-ray absorption studies, so that the derived signal is from one species only. Here we describe a method for performing X-ray absorption spectroscopy on protein bands following electrophoretic separation and western blotting.

  1. Absorption mode FTICR mass spectrometry imaging.

    PubMed

    Smith, Donald F; Kilgour, David P A; Konijnenburg, Marco; O'Connor, Peter B; Heeren, Ron M A

    2013-12-01

    Fourier transform ion cyclotron resonance mass spectrometry offers the highest mass resolving power for molecular imaging experiments. This high mass resolving power ensures that closely spaced peaks at the same nominal mass are resolved for proper image generation. Typically higher magnetic fields are used to increase mass resolving power. However, a gain in mass resolving power can also be realized by phase correction of the data for absorption mode display. In addition to mass resolving power, absorption mode offers higher mass accuracy and signal-to-noise ratio over the conventional magnitude mode. Here, we present the first use of absorption mode for Fourier transform ion cyclotron resonance mass spectrometry imaging. The Autophaser algorithm is used to phase correct each spectrum (pixel) in the image, and then, these parameters are used by the Chameleon work-flow based data processing software to generate absorption mode "Datacubes" for image and spectral viewing. Absorption mode reveals new mass and spatial features that are not resolved in magnitude mode and results in improved selected ion image contrast.

  2. Monitoring Emergent Absorption Troughs in Quasars

    NASA Astrophysics Data System (ADS)

    Hall, Patrick; Rodriguez Hidalgo, Paola; Brandt, W. Niel; Rogerson, Jesse; Filiz Ak, Nur; Chajet, Laura

    2014-02-01

    Outflows from luminous AGN are important ingredients in galaxy formation. These outflows manifest as broad absorption line (BAL) troughs in quasar spectra. Trough variability can be used to constrain the physical parameters of these absorbing structures through comparison to models and simulations of accretion disk winds. Monitoring appearing/disappearing BAL troughs can constrain the distribution of BAL trough lifetimes along our line of sight. By comparing spectra from the SDSS Data Release (DR) 7 and DR 9, we identified 68 quasars in whose spectra new absorption troughs have appeared over 300-1200 restframe days, including one trough outflowing at v=60,000 km/s. We propose to complete our third-epoch GMOS spectroscopy of the brightest of those quasars (48 in 2013AB and 9 proposed here) to measure the absorption strength in newly appeared troughs <=365 restframe days after their previous measurement. Preliminary 2013AB results indicate that troughs are not on average still strengthening between SDSS and Gemini epochs; we therefore propose observations of 40 targets to probe shorter rest-frame time separations. We also target 8 objects showing simultaneous absorption variations in multiple ionization states, to help develop methods to distinguish absorption variations from cloud motion vs. those from ionization changes within clouds.

  3. [Intestinal absorption kinetics of flurbiprofen in rats].

    PubMed

    Peng, Jun-Jie; Lin, Cong-Cong; Li, Jiang; Zhu, Zhi-Hong; Yang, Xing-Gang; Pan, Wei-San

    2013-03-01

    To study the in situ intestinal absorption kinetics of flrubiprofen in rats, the absorption of flurbiprofen in small intestine (duodenum, jejunum and ileum) and colon of rats was investigated using in situ single-pass perfusion method and the drug content was measured by HPLC. The effects of drug concentration on the intestinal absorption were investigated. The K(a) and P(app) values of flurbiprofen in the small intestine and colon had no significant difference (P > 0.05). Drug concentration (4.0, 10.0 and 16.0 mg x L(-1)) had no significant influence on the K(a) values (P > 0.05). However, when concentration was 4.0 mg x L(-1) and 10.0 mg x L(-1), significant effect on the P(app) values (P < 0.05) was found, but significant effect on the P(app) values was not shown between 10.0 mg x L(-1) and 16.0 mg x L(-1) (P > 0.05). The K(a) and P(app) values of flurbiprofen on the perfusion flow rate had significant difference (P < 0.05). Flurbiprofen could be absorbed at all segments of the intestine in rats and had no special absorption window. The absorption of flurbiprofen complies with the facilitated diffusion in the general intestinal segments, and accompany with the cytopsistransport mechanism probably. The perfusion flow rate had significant effect on the K(a) and P(app).

  4. Water-soluble two-photon absorbing nitrosyl complex for light-activated therapy through nitric oxide release.

    PubMed

    Zheng, Qingdong; Bonoiu, Adela; Ohulchanskyy, Tymish Y; He, Guang S; Prasad, Paras N

    2008-01-01

    A water-soluble nitrosyl complex with large two-photon absorption was synthesized by incorporating a two-photon absorbing chromophore with tetra(ethylene glycol) units, into the Roussin's red salt. The nitrosyl complex exhibits quenched emission due to energy transfer from the two-photon chromophore to the Roussin's red salt. The nitric oxide (NO) release induced by one- or two-photon irradiation was detected by EPR spectroscopy with a chemical probe, the Fe(II)- N-(dithiocarbamoyl)- N-methyl- d-glucamine (Fe-MGD) complex. Increased one- or two-photon excited fluorescence, with a concomitant photochemical release of NO, was observed upon one- or two-photon light irradiation. With the observed light-dependent cytotoxicity against cancer cells of the water-soluble nitrosyl complex, it was demonstrated that two-photon-functionalized nitrosyl complexes can be effective NO donors for light-activated treatment.

  5. Nonlinear optical absorption tuning in Bi3.15Nd0.85Ti3O12 ferroelectric thin films by thickness

    NASA Astrophysics Data System (ADS)

    Li, S.; Zhong, X. L.; Cheng, G. H.; Liu, X.; Zhang, Y.; Wang, J. B.; Song, H. J.; Tan, C. B.; Li, B.

    2015-04-01

    The tunability of nonlinear optical (NLO) absorption in Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin films was investigated through the open aperture Z-scan method with femtosecond laser pulses at the wavelength of 800 nm. NLO absorption responses of the BNT films were observed to be highly sensitive to the film thickness. As the film thickness increases from 106.8 to 139.7 nm, the NLO absorption changes from saturable absorption (SA) to reverse saturable absorption (RSA). When the film thickness further increases to 312.9 nm, the RSA effect is enhanced. A band-gap-related competition between the ground-state excitation and the two-photon absorption is responsible for the absorption switching behavior. Such a tunable NLO absorption can widen the photonic application of the BNT thin films.

  6. Super-Resonant Intracavity Coherent Absorption

    PubMed Central

    Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; De Natale, P.; Gagliardi, G.

    2016-01-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes. PMID:27364475

  7. High efficiency advanced absorption heat pump

    NASA Astrophysics Data System (ADS)

    Reid, E. A., Jr.

    1982-03-01

    A high efficiency absorption heat pump for the residential market is investigated. The performance targets established for this high efficiency absorption heat pump are a heating coefficient of performance of 1.5 and a cooling coefficient of performance of 0.8 at rating conditions, including parasitic electric power consumption. The resulting heat pump would have a space heating capacity of 68,000 BTU/hour, and a space cooling capacity of 36,000 BTU/hour at rating conditions. A very simplified schematic block diagram of the high efficiency absorption heat pump cycle is shown. High temperature, high pressure, refrigerant vapor is produced in the refrigerant generator and heat exchange system, is condensed to a liquid in the condenser, expanded to a low pressure vapor in the evaporator, and mixed with and reabsorbed into the weakened solution returned from the refrigerant generator and heat exchange system in the absorber.

  8. Cavity induced perfect absorption in metamaterials

    NASA Astrophysics Data System (ADS)

    Luu Dang, Hong; Nguyen, Hoang Tung; Dung Nguyen, Van; Bui, Son Tung; Tuyen Le, Dac; Ngo, Quang Minh; Vu, Dinh Lam

    2016-03-01

    We present novel resonant modes at the THz regime in a structure combining conventional metamaterial absorber (MA) with a cavity (MAC). The well-known structure consisting of three individual layers of periodic metallic dishes on the top, a dielectric layer in the middle, and a metallic film in the bottom is used, and the cavity is formed on the top layer by changing the geometry of the metallic dishes. MACs with various cavity parameters are designed and their absorption characteristics, such as magnetic field distribution, surface current, and power loss density at resonant frequencies of the designed structure, are numerically investigated. Resonant effects in this work may find applications in THz tunable and broadband MA, and our investigation on the dependence of the absorption frequency and absorption intensity on the geometric cavity of the designed structure will provide a general guideline for MAC design.

  9. Subwavelength total acoustic absorption with degenerate resonators

    NASA Astrophysics Data System (ADS)

    Yang, Min; Meng, Chong; Fu, Caixing; Li, Yong; Yang, Zhiyu; Sheng, Ping

    2015-09-01

    We report the experimental realization of perfect sound absorption by sub-wavelength monopole and dipole resonators that exhibit degenerate resonant frequencies. This is achieved through the destructive interference of two resonators' transmission responses, while the matching of their averaged impedances to that of air implies no backscattering, thereby leading to total absorption. Two examples, both using decorated membrane resonators (DMRs) as the basic units, are presented. The first is a flat panel comprising a DMR and a pair of coupled DMRs, while the second one is a ventilated short tube containing a DMR in conjunction with a sidewall DMR backed by a cavity. In both examples, near perfect absorption, up to 99.7%, has been observed with the airborne wavelength up to 1.2 m, which is at least an order of magnitude larger than the composite absorber. Excellent agreement between theory and experiment is obtained.

  10. Super-Resonant Intracavity Coherent Absorption.

    PubMed

    Malara, P; Campanella, C E; Giorgini, A; Avino, S; De Natale, P; Gagliardi, G

    2016-01-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator's quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes. PMID:27364475

  11. Super-Resonant Intracavity Coherent Absorption

    NASA Astrophysics Data System (ADS)

    Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; de Natale, P.; Gagliardi, G.

    2016-07-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes.

  12. Absorption technique for OH measurements and calibration

    NASA Technical Reports Server (NTRS)

    Bakalyar, D. M.; James, J. V.; Wang, C. C.

    1982-01-01

    An absorption technique is described which utilizes a stabilized frequency-doubled tunable dye laser and a long-path White cell with high mirror reflectivities both in the red and UV. In laboratory conditions it has been possible to routinely obtain a detection sensitivity of 3 parts in 1,000,000 over absorption paths less than 1 m in length and a detection sensitivity of approximately 6 parts in 100,000 over an absorption path of the order of 1 km. The latter number corresponds to 3,000,000 OH molecules/cu cm, and therefore the technique should be particularly useful for calibration the fluorescence instrument for OH measurements. However, the presence of atmospheric fluctuations coupled with intensity variation accompanying frequency scanning appears to degrade the detection sensitivity in outdoor ambient conditions, thus making it unlikely that this technique can be employed for direct OH monitoring.

  13. Nanofibrous membrane-based absorption refrigeration system

    SciTech Connect

    Isfahani, RN; Sampath, K; Moghaddam, S

    2013-12-01

    This paper presents a study on the efficacy of highly porous nanofibrous membranes for application in membrane-based absorbers and desorbers. Permeability studies showed that membranes with a pore size greater than about one micron have a sufficient permeability for application in the absorber heat exchanger. Membranes with smaller pores were found to be adequate for the desorber heat exchanger. The membranes were implemented in experimental membrane-based absorber and desorber modules and successfully tested. Parametric studies were conducted on both absorber and desorber processes. Studies on the absorption process were focused on the effects of water vapor pressure, cooling water temperature, and the solution velocity on the absorption rate. Desorption studies were conducted on the effects of wall temperature, vapor and solution pressures, and the solution velocity on the desorption rate. Significantly higher absorption and desorption rates than in the falling film absorbers and desorbers were achieved. Published by Elsevier Ltd.

  14. Demonstration of differential backscatter absorption gas imaging.

    PubMed

    Powers, P E; Kulp, T J; Kennedy, R

    2000-03-20

    Backscatter absorption gas imaging (BAGI) is a technique that uses infrared active imaging to generate real-time video imagery of gas plumes. We describe a method that employs imaging at two wavelengths (absorbed and not absorbed by the gas to be detected) to allow wavelength-differential BAGI. From the frames collected at each wavelength, an absorbance image is created that displays the differential absorbance of the atmosphere between the imager and the backscatter surface. This is analogous to a two-dimensional topographic differential absorption lidar or differential optical absorption spectroscopy measurement. Gas plumes are displayed, but the topographic scene image is removed. This allows a more effective display of the plume image, thus ensuring detection under a wide variety of conditions. The instrument used to generate differential BAGI is described. Data generated by the instrument are presented and analyzed to estimate sensitivity. PMID:18338030

  15. Rotational averaging of multiphoton absorption cross sections

    SciTech Connect

    Friese, Daniel H. Beerepoot, Maarten T. P.; Ruud, Kenneth

    2014-11-28

    Rotational averaging of tensors is a crucial step in the calculation of molecular properties in isotropic media. We present a scheme for the rotational averaging of multiphoton absorption cross sections. We extend existing literature on rotational averaging to even-rank tensors of arbitrary order and derive equations that require only the number of photons as input. In particular, we derive the first explicit expressions for the rotational average of five-, six-, and seven-photon absorption cross sections. This work is one of the required steps in making the calculation of these higher-order absorption properties possible. The results can be applied to any even-rank tensor provided linearly polarized light is used.

  16. Absorption and fluorescence spectroscopy on a smartphone

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Arafat; Canning, John; Cook, Kevin; Ast, Sandra; Rutledge, Peter J.; Jamalipour, Abbas

    2015-07-01

    A self-powered smartphone-based field-portable "dual" spectrometer has been developed for both absorption and fluorescence measurements. The smartphone's existing flash LED has sufficient optical irradiance to undertake absorption measurements within a 3D-printed case containing a low cost nano-imprinted polymer diffraction grating. A UV (λex ~ 370 nm) and VIS (λex ~ 450 nm) LED are wired into the circuit of the flash LED to provide an excitation source for fluorescence measurements. Using a customized app on the smartphone, measurements of absorption and fluorescence spectra are demonstrated using pH-sensitive and Zn2+-responsive probes. Detection over a 300 nm span with 0.42 nm/pixel spectral resolution is demonstrated. Despite the low cost and small size of the portable spectrometer, the results compare well with bench top instruments.

  17. Laser absorption phenomena in flowing gas devices

    NASA Technical Reports Server (NTRS)

    Chapman, P. K.; Otis, J. H.

    1976-01-01

    A theoretical and experimental investigation is presented of inverse Bremsstrahlung absorption of CW CO2 laser radiation in flowing gases seeded with alkali metals. In order to motivate this development, some simple models are described of several space missions which could use laser powered rocket vehicles. Design considerations are given for a test call to be used with a welding laser, using a diamond window for admission of laser radiation at power levels in excess of 10 kW. A detailed analysis of absorption conditions in the test cell is included. The experimental apparatus and test setup are described and the results of experiments presented. Injection of alkali seedant and steady state absorption of the laser radiation were successfully demonstrated, but problems with the durability of the diamond windows at higher powers prevented operation of the test cell as an effective laser powered thruster.

  18. Broadband absorption engineering of hyperbolic metafilm patterns

    NASA Astrophysics Data System (ADS)

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-03-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting.

  19. Broadband absorption engineering of hyperbolic metafilm patterns.

    PubMed

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-01-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting. PMID:24675706

  20. Plasmon absorption modulator systems and methods

    DOEpatents

    Kekatpure, Rohan Deodatta; Davids, Paul

    2014-07-15

    Plasmon absorption modulator systems and methods are disclosed. A plasmon absorption modulator system includes a semiconductor substrate, a plurality of quantum well layers stacked on a top surface of the semiconductor substrate, and a metal layer formed on a top surface of the stack of quantum well layers. A method for modulating plasmonic current includes enabling propagation of the plasmonic current along a metal layer, and applying a voltage across the stack of quantum well layers to cause absorption of a portion of energy of the plasmonic current by the stack of quantum well layers. A metamaterial switching system includes a semiconductor substrate, a plurality of quantum well layers stacked on a top surface of the semiconductor substrate, and at least one metamaterial structure formed on a top surface of the stack of quantum well layers.

  1. Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.

    NASA Astrophysics Data System (ADS)

    Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.

    2007-12-01

    Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the

  2. Iron absorption and transport-an update.

    PubMed

    Conrad, M E; Umbreit, J N

    2000-08-01

    Iron is vital for all living organisms. However, excess iron is hazardous because it produces free radical formation. Therefore, iron absorption is carefully regulated to maintain an equilibrium between absorption and body loss of iron. In countries where heme is a significant part of the diet, most body iron is derived from dietary heme iron because heme binds few of the luminal intestinal iron chelators that inhibit absorption of non-heme iron. Uptake of luminal heme into enterocytes occurs as a metalloporphyrin. Intracellularly, iron is released from heme by heme oxygenase so that iron leaves the enterocyte to enter the plasma as non-heme iron. Ferric iron is absorbed via a beta(3) integrin and mobilferrin (IMP) pathway that is not shared with other nutritional metals. Ferrous iron uptake is facilitated by DMT-1 (Nramp-2, DCT-1) in a pathway shared with manganese. Other proteins were recently described which are believed to play a role in iron absorption. SFT (Stimulator of Iron Transport) is postulated to facilitate both ferric and ferrous iron uptake, and Hephaestin is thought to be important in transfer of iron from enterocytes into the plasma. The iron concentration within enterocytes reflects the total body iron and either upregulates or satiates iron-binding sites on regulatory proteins. Enterocytes of hemochromatotics are iron-depleted similarly to the absorptive cells of iron-deficient subjects. Iron depletion, hemolysis, and hypoxia each can stimulate iron absorption. In non-intestinal cells most iron uptake occurs via either the classical clathrin-coated pathway utilizing transferrin receptors or the poorly defined transferrin receptor independent pathway. Non-intestinal cells possess the IMP and DMT-1 pathways though their role in the absence of iron overload is unclear. This suggests that these pathways have intracellular functions in addition to facilitating iron uptake.

  3. Potassium emission absorption system. Topical report 12

    SciTech Connect

    Bauman, L.E.

    1995-04-01

    The Potassium Emission Absorption System is one of the advanced optical diagnostics developed at Mississippi State University to provide support for the demonstration of prototype-scale coal-fired combustion magnetohydrodynamic (MHD) electrical power generation. Intended for application in the upstream of an MHD flow, the system directly measures gas temperature and neutral potassium atom number density through spectroscopic emission absorption techniques. From these measurements the electron density can be inferred from a statistical equilibrium calculation and the electron conductivity in the MHD channel found by use of an electron mobility model. The instrument has been utilized for field test measurements on MHD facilities for almost a decade and has been proven to provide useful measurements as designed for MHD nozzle, channel, and diffuser test sections. The theory of the measurements, a system description, its capabilities, and field test measurement results are reported here. During the development and application of the instrument several technical issues arose which when addressed advanced the state of the art in emission absorption measurement. Studies of these issues are also reported here and include: two-wavelength measurements for particle-laden flows, potassium D-line far wing absorption coefficient, bias in emission absorption measurements arising from dirty windows and misalignments, non-coincident multiwavelength emission absorption sampling errors, and lineshape fitting for boundary layer flow profile information. Although developed for NLHD application, the instrument could be applied to any high temperature flow with a resonance line in the 300 to 800 nm range, for instance other types of flames, rocket plumes or low temperature plasmas.

  4. Aerosol optical absorption measurements with photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Liu, Qiang; Wang, Guishi; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-04-01

    Many parameters related to radiative forcing in climate research are known only with large uncertainties. And one of the largest uncertainties in global radiative forcing is the contribution from aerosols. Aerosols can scatter or absorb the electromagnetic radiation, thus may have negative or positive effects on the radiative forcing of the atmosphere, respectively [1]. And the magnitude of the effect is directly related to the quantity of light absorbed by aerosols [2,3]. Thus, sensitivity and precision measurement of aerosol optical absorption is crucial for climate research. Photoacoustic spectroscopy (PAS) is commonly recognized as one of the best candidates to measure the light absorption of aerosols [4]. A PAS based sensor for aerosol optical absorption measurement was developed. A 532 nm semiconductor laser with an effective power of 160 mW was used as a light source of the PAS sensor. The PAS sensor was calibrated by using known concentration NO2. The minimum detectable optical absorption coefficient (OAC) of aerosol was determined to be 1 Mm-1. 24 hours continues measurement of OAC of aerosol in the ambient air was carried out. And a novel three wavelength PAS aerosol OAC sensor is in development for analysis of aerosol wavelength-dependent absorption Angstrom coefficient. Reference [1] U. Lohmann and J. Feichter, Global indirect aerosol effects: a review, Atmos. Chem. Phys. 5, 715-737 (2005) [2] M. Z. Jacobson, Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409, 695-697 (2001) [3] V. Ramanathan and G. Carmichae, Global and regional climate changes due to black carbon, nature geoscience 1, 221-227 (2008) [4] W.P Arnott, H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description. Atmos. Environ. 33, 2845-2852 (1999).

  5. Enhanced absorption cycle computer model. Final report

    SciTech Connect

    Grossman, G.; Wilk, M.

    1993-09-01

    Absorption heat pumps have received renewed and increasing attention in the past two decades. The rising cost of electricity has made the particular features of this heat-powered cycle attractive for both residential and industrial applications. Solar-powered absorption chillers, gas-fired domestic heat pumps, and waste-heat-powered industrial temperatures boosters are a few of the applications recently subjected to intensive research and development. The absorption heat pump research community has begun to search for both advanced cycles in various multistage configurations and new working fluid combinations with potential for enhanced performance and reliability. The development of working absorptions systems has created a need for reliable and effective system simulations. A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system`s components and property subroutines containing thermodynamic properties of the working fluids. The user conveys to the computer an image of his cycle by specifying the different subunits and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system, and the heat duty at each unit, from which the coefficient of performance (COP) may be determined. This report describes the code and its operation, including improvements introduced into the present version. Simulation results are described for LiBr-H{sub 2}O triple-effect cycles, LiCl-H{sub 2}O solar-powered open absorption cycles, and NH{sub 3}-H{sub 2}O single-effect and generator-absorber heat exchange cycles. An appendix contains the User`s Manual.

  6. THE ABSORPTION SPECTRUM OF VISUAL PURPLE

    PubMed Central

    Chase, Aurin M.; Haig, Charles

    1938-01-01

    The absorption spectra of visual purple solutions extracted by various means were measured with a sensitive photoelectric spectrophotometer and compared with the classical visual purple absorption spectrum. Hardening the retinas in alum before extraction yielded visual purple solutions of much higher light transmission in the blue and violet, probably because of the removal of light-dispersing substances. Re-extraction indicated that visual purple is more soluble in the extractive than are the other colored retinal components. However, the concentration of the extractive did not affect the color purity of the extraction but did influence the keeping power. This suggests a chemical combination between the extractive and visual purple. The pH of the extractive affected the color purity of the resulting solution. Over the pH range from 5.5 to 10.0, the visual purple color purity was greatest at the low pH. Temperature during extraction was also effective, the color purity being greater the higher the temperature, up to 40°C. Drying and subsequent re-dissolving of visual purple solutions extracted with digitalin freed the solution of some protein impurities and increased its keeping power. Dialysis against distilled water seemed to precipitate visual purple from solution irreversibly. None of the treatments described improved the symmetry of the unbleached visual purple absorption spectrum sufficiently for it to resemble the classical absorption spectrum. Therefore it is very likely that the classical absorption spectrum is that of the light-sensitive group only and that the absorption spectra of our purest unbleached visual purple solutions represent the molecule as a whole. PMID:19873058

  7. Subbarrier absorption in a stationary superlattice

    NASA Technical Reports Server (NTRS)

    Arutyunyan, G. M.; Nerkararyan, K. V.

    1984-01-01

    The calculation of the interband absorption coefficient was carried out in the classical case, when the frequency of light was assumed to bind two miniband subbarrier states of different bands. The influence of two dimensional Mott excitons on this absorption was studied and a comparison was made with the experiment. All of these considerations were done taking into account the photon wave vector (the phase spatial heterogeneity). The basic traits of the energy spectra of superlattice semiconductors, their kinetic and optical properties, and possible means of electromagnetic wave intensification were examined. By the density matrix method, a theory of electrical and electromagnetic properties of superlattices was suggested.

  8. XUV Absorption by Solid Density Aluminum

    SciTech Connect

    Iglesias, C A

    2009-09-21

    An inverse bremsstrahlung model for plasmas and simple metals that approximates the cold, solid Al experimental data below the L-edge is applied to matter conditions relevant to XUV laser applications. The model involves an all-order calculation using a semi-analytical effective electron-ion interaction. The predicted increases in XUV absorption with rising temperature occur via two effects: increased availability of final states from reduced electron degeneracy and a stronger electron-ion interaction from reduced screening. Discrepancies in the temperature dependence as well as other details between the present approach and a recently proposed absorption model are discussed.

  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.

    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.

  10. 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.

  11. 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.

  12. Absorption spectroscopy: technique provides extremely high sensitivity.

    PubMed

    Provencal, R A; Paul, J B; Michael, E; Saykally, R J

    1998-06-01

    Technology associated with cavity ringdown laser absorption spectroscopy is reviewed. The technique is used to study general trace analysis, free radicals in flames and chemical reactors, molecular ions in electrical discharges, biological molecules and water clusters in supersonic jets, and vibrational overtones of stable molecules. Its specific enough to detect about 1-ppm fractional absorption by a gaseous sample in about 10 microseconds. The use of mirrors in ringdown sepctroscopy is explained. Other topics include the generation of pulsed infrared rays and the adaptation of ringdown spectroscopy for use with narrow-bandwidth continuous-wave lasers. PMID:11541906

  13. Maximum profit performance of an absorption refrigerator

    SciTech Connect

    Chen, L.; Sun, F.; Wu, C.

    1996-12-01

    The operation of an absorption refrigerator is viewed as a production process with exergy as its output. The relations between the optimal profit and COP (coefficient of performance), and the COP bound at the maximum profit of the refrigerator are derived based on a general heat transfer law. The results provide a theoretical basis for developing and utilizing a variety of absorption refrigerators. The focus of this paper is to search the compromise optimization between economics (profit) and the utilization factor (COP) for finite-time endoreversible thermodynamic cycles.

  14. Triplet absorption spectroscopy and electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Ghafoor, F.; Nazmitdinov, R. G.

    2016-09-01

    Coherence phenomena in a four-level atomic system, cyclically driven by three coherent fields, are investigated thoroughly at zero and weak magnetic fields. Each strongly interacting atomic state is converted to a triplet due to a dynamical Stark effect. Two dark lines with a Fano-like profile arise in the triplet absorption spectrum with anomalous dispersions. We provide conditions to control the widths of the transparency windows by means of the relative phase of the driving fields and the intensity of the microwave field, which closes the optical system loop. The effect of Doppler broadening on the results of the triplet absorption spectroscopy is analysed in detail.

  15. Monitoring of MOCVD reactants by UV absorption

    SciTech Connect

    Baucom, K.C.; Killeen, K.P.; Moffat, H.K.

    1995-07-01

    In this paper, we describe how UV absorption measurements can be used to measure the flow rates of metal organic chemical vapor deposition (MOCVD) reactants. This method utilizes the calculation of UV extinction coefficients by measuring the total pressure and absorbance in the neat reactant system. The development of this quantitative reactant flow rate monitor allows for the direct measurement of the efficiency of a reactant bubbler. We demonstrate bubbler efficiency results for TMGa, and then explain some discrepancies found in the TMAl system due to the monomer to dimer equilibrium. Also, the UV absorption spectra of metal organic and hydride MOCVD reactants over the wavelength range 185 to 400 nm are reported.

  16. Light absorption in conical silicon particles.

    PubMed

    Bogdanowicz, J; Gilbert, M; Innocenti, N; Koelling, S; Vanderheyden, B; Vandervorst, W

    2013-02-11

    The problem of the absorption of light by a nanoscale dielectric cone is discussed. A simplified solution based on the analytical Mie theory of scattering and absorption by cylindrical objects is proposed and supported by the experimental observation of sharply localized holes in conical silicon tips after high-fluence irradiation. This study reveals that light couples with tapered objects dominantly at specific locations, where the local radius corresponds to one of the resonant radii of a cylindrical object, as predicted by Mie theory.

  17. Intestinal absorption and biomagnification of organochlorines

    SciTech Connect

    Gobas, F.A.P.C. ); McCorquodale, J.R.; Haffner, G.D. )

    1993-03-01

    Dietary uptake rates of several organochlorines from diets with different lipid contents were measured in goldfish (Carassius auratus) to investigate the mechanism of intestinal absorption and biomagnification of organic chemical. The results suggest that intestinal absorption is predominantly controlled by chemical diffusion rather than lipid cotransport. Data for chemical uptake in human infants are presented to illustrate that biomagnification is caused by the digestion of food in the gastrointestinal tract. The findings are discussed in the context of two conflicting theories for the mechanism of biomagnification, and a mechanistic model is presented for the dietary uptake and biomagnification of organic chemicals in fish and mammals.

  18. Nasal Absorption of Macromolecules from Powder Formulations and Effects of Sodium Carboxymethyl Cellulose on Their Absorption.

    PubMed

    Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira

    2016-01-01

    The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules. PMID:27598527

  19. Mathematical model of zinc absorption: effects of dietary calcium, protein and iron on zinc absorption.

    PubMed

    Miller, Leland V; Krebs, Nancy F; Hambidge, K Michael

    2013-02-28

    A previously described mathematical model of Zn absorption as a function of total daily dietary Zn and phytate was fitted to data from studies in which dietary Ca, Fe and protein were also measured. An analysis of regression residuals indicated statistically significant positive relationships between the residuals and Ca, Fe and protein, suggesting that the presence of any of these dietary components enhances Zn absorption. Based on the hypotheses that (1) Ca and Fe both promote Zn absorption by binding with phytate and thereby making it unavailable for binding Zn and (2) protein enhances the availability of Zn for transporter binding, the model was modified to incorporate these effects. The new model of Zn absorption as a function of dietary Zn, phytate, Ca, Fe and protein was then fitted to the data. The proportion of variation in absorbed Zn explained by the new model was 0·88, an increase from 0·82 with the original model. A reduced version of the model without Fe produced an equally good fit to the data and an improved value for the model selection criterion, demonstrating that when dietary Ca and protein are controlled for, there is no evidence that dietary Fe influences Zn absorption. Regression residuals and testing with additional data supported the validity of the new model. It was concluded that dietary Ca and protein modestly enhanced Zn absorption and Fe had no statistically discernable effect. Furthermore, the model provides a meaningful foundation for efforts to model nutrient interactions in mineral absorption.

  20. Nasal Absorption of Macromolecules from Powder Formulations and Effects of Sodium Carboxymethyl Cellulose on Their Absorption.

    PubMed

    Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira

    2016-01-01

    The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules.

  1. Nasal Absorption of Macromolecules from Powder Formulations and Effects of Sodium Carboxymethyl Cellulose on Their Absorption

    PubMed Central

    Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira

    2016-01-01

    The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules. PMID:27598527

  2. Examination of the Measurement of Absorption Using the Reverberant Room Method for Highly Absorptive Acoustic Foam

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.; Chris Nottoli; Eric Wolfram

    2015-01-01

    The absorption coefficient for material specimens are needed to quantify the expected acoustic performance of that material in its actual usage and environment. The ASTM C423-09a standard, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberant Room Method" is often used to measure the absorption coefficient of material test specimens. This method has its basics in the Sabine formula. Although widely used, the interpretation of these measurements are a topic of interest. For example, in certain cases the measured Sabine absorption coefficients are greater than 1.0 for highly absorptive materials. This is often attributed to the diffraction edge effect phenomenon. An investigative test program to measure the absorption properties of highly absorbent melamine foam has been performed at the Riverbank Acoustical Laboratories. This paper will present and discuss the test results relating to the effect of the test materials' surface area, thickness and edge sealing conditions. A follow-on paper is envisioned that will present and discuss the results relating to the spacing between multiple piece specimens, and the mounting condition of the test specimen.

  3. π-Extended diketopyrrolopyrrole-porphyrin arrays: one- and two-photon photophysical investigations and theoretical studies.

    PubMed

    Alam, Md M; Bolze, F; Daniel, C; Flamigni, L; Gourlaouen, C; Heitz, V; Jenni, S; Schmitt, J; Sour, A; Ventura, B

    2016-08-21

    A complete one- and two-photon spectroscopic and photophysical characterization of three diketopyrrolopyrrole (DPP)-porphyrin conjugates is reported. The increased conjugation introduced by the incremental addition of one, two and four DPP units on the meso porphyrin positions strongly affects the optical properties of the systems. Ground and triplet excited state absorption spectra show a gradual broadening and bathochromic shift and a trend to lower energies is also observed for both fluorescence and phosphorescence emission. Interestingly, the fluorescence quantum yield increases along the series, leading to remarkable NIR emission properties for the larger derivatives. Unlike the model porphyrin, all derivatives exhibit high two-photon absorption activity. An increase in two-photon absorption cross-section in the regions 800-840 nm and 910-930 nm is observed moving from one DPP to two DPP appended units, with a value of the order of 4000 GM at 910 nm for the latter system. The four compounds show high efficiency in generating singlet oxygen, with yields ranging from 0.7 to 0.5, envisaging favourable applications in both one- and two-photon photodynamic therapies. A detailed theoretical exploration of both linear (absorption and emission) and non-linear (two-photon absorption) properties proposes an analysis of the experimental spectra and a comprehensive interpretation of the two-photon activity within the series of compounds.

  4. π-Extended diketopyrrolopyrrole-porphyrin arrays: one- and two-photon photophysical investigations and theoretical studies.

    PubMed

    Alam, Md M; Bolze, F; Daniel, C; Flamigni, L; Gourlaouen, C; Heitz, V; Jenni, S; Schmitt, J; Sour, A; Ventura, B

    2016-08-21

    A complete one- and two-photon spectroscopic and photophysical characterization of three diketopyrrolopyrrole (DPP)-porphyrin conjugates is reported. The increased conjugation introduced by the incremental addition of one, two and four DPP units on the meso porphyrin positions strongly affects the optical properties of the systems. Ground and triplet excited state absorption spectra show a gradual broadening and bathochromic shift and a trend to lower energies is also observed for both fluorescence and phosphorescence emission. Interestingly, the fluorescence quantum yield increases along the series, leading to remarkable NIR emission properties for the larger derivatives. Unlike the model porphyrin, all derivatives exhibit high two-photon absorption activity. An increase in two-photon absorption cross-section in the regions 800-840 nm and 910-930 nm is observed moving from one DPP to two DPP appended units, with a value of the order of 4000 GM at 910 nm for the latter system. The four compounds show high efficiency in generating singlet oxygen, with yields ranging from 0.7 to 0.5, envisaging favourable applications in both one- and two-photon photodynamic therapies. A detailed theoretical exploration of both linear (absorption and emission) and non-linear (two-photon absorption) properties proposes an analysis of the experimental spectra and a comprehensive interpretation of the two-photon activity within the series of compounds. PMID:27439678

  5. Stability properties of wines by absorption spectra

    NASA Astrophysics Data System (ADS)

    Larena, A.; Vega, J.

    1986-03-01

    The temporal evolution of absorption spectra (370-700 nm) of different spanish wines has been studied by us under the influence of air presence, and the light exposition. In particular, we have exposed the wines to a magenta light. Nevertheless, the color coordinates of wine show a little relative variation (0.1-1 %)

  6. Direct fired absorption machine flue gas recuperator

    DOEpatents

    Reimann, Robert C.; Root, Richard A.

    1985-01-01

    A recuperator which recovers heat from a gas, generally the combustion gas of a direct-fired generator of an absorption machine. The recuperator includes a housing with liquid flowing therethrough, the liquid being in direct contact with the combustion gas for increasing the effectiveness of the heat transfer between the gas and the liquid.

  7. Acetaminophen (paracetamol) oral absorption and clinical influences.

    PubMed

    Raffa, Robert B; Pergolizzi, Joseph V; Taylor, Robert; Decker, John F; Patrick, Jeffrey T

    2014-09-01

    Acetaminophen (paracetamol) is a widely used nonopioid, non-NSAID analgesic that is effective against a variety of pain types, but the consequences of overdose can be severe. Because acetaminophen is so widely available as a single agent and is increasingly being formulated in fixed-ratio combination analgesic products for the potential additive or synergistic analgesic effect and/or reduced adverse effects, accidental cumulative overdose is an emergent concern. This has rekindled interest in the sites, processes, and pharmacokinetics of acetaminophen oral absorption and the clinical factors that can influence these. The absorption of oral acetaminophen occurs primarily along the small intestine by passive diffusion. Therefore, the rate-limiting step is the rate of gastric emptying into the intestines. Several clinical factors can affect absorption per se or the rate of gastric emptying, such as diet, concomitant medication, surgery, pregnancy, and others. Although acetaminophen does not have the abuse potential of opioids or the gastrointestinal bleeding or organ adverse effects of NSAIDs, excess amounts can produce serious hepatic injury. Thus, an understanding of the sites and features of acetaminophen absorption--and how they might be influenced by factors encountered in clinical practice--is important for pain management using this agent. It can also provide insight for design of formulations that would be less susceptible to clinical variables.

  8. The Absorption Refrigerator as a Thermal Transformer

    ERIC Educational Resources Information Center

    Herrmann, F.

    2009-01-01

    The absorption refrigerator can be considered a thermal transformer, that is, a device that is analogous to the electric transformer. The analogy is based on the correspondence between the extensive quantities, entropy and electric charge and the intensive variables, temperature and electric potential. (Contains 1 footnote and 6 figures.)

  9. Absorption machine with desorber-resorber

    DOEpatents

    Biermann, Wendell J.

    1985-01-01

    An absorption refrigeration system utilizing a low temperature desorber and intermediate temperature resorber. The system operates at three temperatures and three pressures to increase the efficiency of the system and is capable of utilizing a lower generator temperature than previously used.

  10. Coupled dual loop absorption heat pump

    DOEpatents

    Sarkisian, Paul H.; Reimann, Robert C.; Biermann, Wendell J.

    1985-01-01

    A coupled dual loop absorption system which utilizes two separate complete loops. Each individual loop operates at three temperatures and two pressures. This low temperature loop absorber and condenser are thermally coupled to the high temperature loop evaporator, and the high temperature loop condenser and absorber are thermally coupled to the low temperature generator.

  11. Laser Absorption by Over-Critical Plasmas

    NASA Astrophysics Data System (ADS)

    May, J.; Tonge, J.; Fiuza, F.; Fonseca, R. A.; Silva, L. O.; Mori, W. B.

    2015-11-01

    Absorption of high intensity laser light by matter has important applications to emerging sciences and technology, such as Fast Ignition ICF and ion acceleration. As such, understanding the underlying mechanisms of this absorption is key to developing these technologies. Critical features which distinguish the interaction of high intensity light - defined here as a laser field having a normalized vector potential greater than unity - are that the reaction of the material to the fields results in sharp high-density interfaces; and that the movement of the electrons is in general relativistic, both in a fluid and a thermal sense. The results of these features are that the absorption mechanisms are qualitatively distinct from those at lower intensities. We will review previous work, by our group and others, on the absorption mechanisms, and highlight current research. We will show that the standing wave structure of the reflected laser light is key to particle dynamics for normally incident lasers. The authors acknowledge the support of the Department of Energy under contract DE-NA 0001833 and the National Science Foundation under contract ACI 1339893.

  12. Enhanced absorption in silicon metamaterials waveguide structure

    NASA Astrophysics Data System (ADS)

    Hamouche, Houria; Shabat, Mohammed M.

    2016-07-01

    Metamaterial waveguide structures for silicon solar cells are a novel approach to antireflection coating structures that can be used for the achievement of high absorption in silicon solar cells. This paper investigates numerically the possibility of improving the performance of a planar waveguide silicon solar cell by incorporating a pair of silicon nitride/metamaterial layer between a semi-infinite glass cover layer and a semi-infinite silicon substrate layer. The optimized layer thicknesses of the pair are determined under the solar spectrum AM1.5 by the effective average reflectance method. The transmission and reflection coefficients are derived by the transfer matrix method for values of metamaterial's refractive index in visible and near-infrared radiation. In addition, the absorption coefficient is examined for several angles of incidence of the transverse electric polarized (TE), transverse magnetic polarized (TM) and the total (TE&TM) guided waves. Numerical results provide an extremely high absorption. The absorptivity of the structure achieves greater than 98 %.

  13. Absorptive coating for aluminum solar panels

    NASA Technical Reports Server (NTRS)

    Desmet, D.; Jason, A.; Parr, A.

    1979-01-01

    Method for coating forming coating of copper oxide from copper component of sheet aluminum/copper alloy provides strong durable solar heat collector panels. Copper oxide coating has solar absorption characteristics similar to black chrome and is much simpler and less costly to produce.

  14. Molecular absorption in transition region spectral lines

    NASA Astrophysics Data System (ADS)

    Schmit, D. J.; Innes, D.; Ayres, T.; Peter, H.; Curdt, W.; Jaeggli, S.

    2014-09-01

    Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra. Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence. Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary. The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales and introduces a new complexity into our understanding of solar thermal structure. It lends credence to previous numerical studies that found evidence for elevated pockets of cool gas in the chromosphere. Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org

  15. Corrosion inhibitor for aqueous ammonia absorption system

    DOEpatents

    Phillips, B.A.; Whitlow, E.P.

    1998-09-22

    A method is described for inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425 F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25 C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425 F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer. 5 figs.

  16. Corrosion inhibitor for aqueous ammonia absorption system

    DOEpatents

    Phillips, Benjamin A.; Whitlow, Eugene P.

    1998-09-22

    A method of inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425.degree. F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25.degree. C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425.degree. F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer.

  17. CHLORINE ABSORPTION IN S(IV) SOLUTIONS

    EPA Science Inventory

    The report gives results of measurements of the rate of Chlorine (Cl2) absorption into aqueous sulfite/bisulfite -- S(IV) -- solutions at ambient temperature using a highly characterized stirred-cell reactor. The reactor media were 0 to 10 mM S(IV) with pHs of 3.5-8.5. Experiment...

  18. Effects of backlight structure on absorption experiments

    SciTech Connect

    Iglesias, C A

    2004-11-08

    The impact of spectral details in the backlight of absorption spectroscopy experiments is considered. It is shown that experimentally unresolved structure in the backlight spectrum can introduce significant errors in the inferred transmission. Furthermore, it is shown that a valuable experimental procedure previously used to test the accuracy of the data fails to reveal these errors.

  19. Acetaminophen (paracetamol) oral absorption and clinical influences.

    PubMed

    Raffa, Robert B; Pergolizzi, Joseph V; Taylor, Robert; Decker, John F; Patrick, Jeffrey T

    2014-09-01

    Acetaminophen (paracetamol) is a widely used nonopioid, non-NSAID analgesic that is effective against a variety of pain types, but the consequences of overdose can be severe. Because acetaminophen is so widely available as a single agent and is increasingly being formulated in fixed-ratio combination analgesic products for the potential additive or synergistic analgesic effect and/or reduced adverse effects, accidental cumulative overdose is an emergent concern. This has rekindled interest in the sites, processes, and pharmacokinetics of acetaminophen oral absorption and the clinical factors that can influence these. The absorption of oral acetaminophen occurs primarily along the small intestine by passive diffusion. Therefore, the rate-limiting step is the rate of gastric emptying into the intestines. Several clinical factors can affect absorption per se or the rate of gastric emptying, such as diet, concomitant medication, surgery, pregnancy, and others. Although acetaminophen does not have the abuse potential of opioids or the gastrointestinal bleeding or organ adverse effects of NSAIDs, excess amounts can produce serious hepatic injury. Thus, an understanding of the sites and features of acetaminophen absorption--and how they might be influenced by factors encountered in clinical practice--is important for pain management using this agent. It can also provide insight for design of formulations that would be less susceptible to clinical variables. PMID:26013309

  20. Gamma ray astrophysics. [emphasizing processes and absorption

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1974-01-01

    Gamma ray production processes are reviewed, including Compton scattering, synchrotron radiation, bremsstrahlung interactions, meson decay, nucleon-antinucleon annihilations, and pion production. Gamma ray absorption mechanisms through interactions with radiation and with matter are discussed, along with redshifts and gamma ray fluxes.

  1. Infrared differential absorption for atmospheric pollutant detection

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1974-01-01

    Progress made in the generation of tunable infrared radiation and its application to remote pollutant detection by the differential absorption method are summarized. It is recognized that future remote pollutant measurements depended critically on the availability of high energy tunable transmitters. Futhermore, due to eye safety requirements, the transmitted frequency must lie in the 1.4 micron to 13 micron infrared spectral range.

  2. Normal and abnormal intestinal absorption by humans

    PubMed Central

    Heizer, William D.

    1979-01-01

    Adults eating a Western diet digest and absorb ingested food containing approximately 100 g fat, 350 g carbohydrate, and 75 g protein daily. Normal fat absorption requires adequate gastric, pancreatic, liver-biliary, mucosal, and lymphatic function. Carbohydrate and protein absorption is much less dependent on liver-biliary and lymphatic function. The intestine has a large reserve capacity for digestion and absorption of nutrients which is due to both excess function and to adaptive changes which increase function in one segment of the digestive-absorptive system when it is decreased or lost in another segment. The large reserve capacity explains why most of the prevalent intestinal diseases seldom cause clinically detectable changes in absorption. However, there are more than 30 less-common human diseases which cause malabsorption of one or more nutrients. Those that cause the malabsorption syndrome, i.e., steatorrhea and weight loss, can be conveniently categorized according to the major deficiency leading to the absorptive defect as follows: insufficient pancreatic enzyme activity, insufficient bile acid, disease of the small intestinal wall, multiple defects, mechanism unknown, and drug-induced malabsorption. A few diseases, most of which are congenital, cause malabsorption of only one or a few related nutrients such as lactose malabsorption in lactase deficiency. Most of the tests currently in use for detecting and diagnosing the cause of malabsorption are relatively insensitive and nonspecific. Chemical analysis of the fat in a three-day stool collection remains the single best test for diagnosing the malabsorption syndrome. However, a breath test using Triolein labeled with either the radioactive or stable isotope of carbon may be an important recent advance. Other breath tests are also currently being investigated for quantitating absorption or malabsorption of various substances including bile acids and various sugars. Studies of the function of the

  3. Suppression of the four-wave mixing amplification via Raman absorption

    NASA Astrophysics Data System (ADS)

    Romanov, Gleb; O'Brien, Chris; Novikova, Irina

    2016-11-01

    We propose a method to controllably suppress the effect of the four-wave mixing caused by the coupling of the strong control optical field to both optical transitions in the ? system under the conditions of electromagnetically induced transparency (EIT). At sufficiently high atomic density, this process leads to amplification of a weak optical signal field, that is detrimental for the fidelity of any EIT-based quantum information applications. Here we show that an additional absorption resonance centred around the Stokes field frequency, generated in such a four-wave mixing process, may efficiently suppress the unwanted probe amplification without affecting properties of the EIT interaction. We discuss the possibility of creating such tunable absorption using two-photon Raman absorption resonances in the other Rb isotope, and present some preliminary experimental results.

  4. Optical nonlinear absorption characteristics of Sb{sub 2}Se{sub 3} nanoparticles

    SciTech Connect

    Muralikrishna, Molli Kiran, Aditha Sai Ravikanth, B. Sowmendran, P. Muthukumar, V. Sai Venkataramaniah, Kamisetti

    2014-04-24

    In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb{sub 2}Se{sub 3}) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10 - 40 nm. Elemental analysis was performed using EDAX. By employing open aperture z-scan technique, we have evaluated the effective two-photon absorption coefficient of Sb{sub 2}Se{sub 3} nanoparticles to be 5e-10 m/W at 532 nm. These nanoparticles exhibit strong intensity dependent nonlinear optical absorption and hence could be considered to have optical power limiting applications in the visible range.

  5. Four new two-photon polymerization initiators with varying donor and conjugated bridge: Synthesis and two-photon activity

    NASA Astrophysics Data System (ADS)

    Hao, Fuying; Liu, Zhaodi; Zhang, Mingliang; Liu, Jie; Zhang, Shengyi; Wu, Jieying; Zhou, Hongping; Tian, YuPeng

    2014-01-01

    A specific series of dumbbell-shaped bis-carbazoles or bis-phenothiazines dyes (1, 2, 3 and 4) constructed with styrene or biphenylethyne as the π-bridge have been synthesized and characterized. Detailed spectral properties including linear absorption, one and two-photon fluorescence properties were investigated. The results show that extending conjugated chain and introducing donors have substantial effect on their photophysical properties. Among them, two-photon absorption cross sections (σ) of the four dyes in DMF determined by the Z-scan technique are successively increased from 1 to 4 with enhancing electron-donating ability and extending conjugated chain, but electron-donating ability has larger contribution to the σ values than extending conjugated chain based on the comparison of small molecules (D-π-D). Two-photon initiation polymerization (TPIP) microfabrication experiments have been carried out using compound 4 as an initiator under irradiation of 200 fs, 76 MHz femtosecond laser at 760 nm. The results confirm that the four dyes can be effectively used as organic two-photon photopolymerization initiators.

  6. Development of Updated ABsorption SIMulation Software (ABSIM)

    SciTech Connect

    Yang, Zhiyao; Tang, Xin; Qu, Ming; Abdelaziz, Omar; Gluesenkamp, Kyle R

    2014-01-01

    ABsorption SIMulation, ABSIM, was developed for the simulation of absorption systems by The Oak Ridge National Laboratory during 1980s and 1990s. ABSIM provides a platform for users to investigate various cycle configurations and working fluids, to calculate their operating parameters, to predict their performance, and to compare them with each other on a uniform basis. ABSIM is indeed a very useful and accurate tool for researchers to investigate various absorption systems. However, it has not been well maintained: it is incompatible with recent operating systems; the interface needs improved user-friendliness, and the system needs better parameter setting and debugging tools to help achieve convergence. Therefore, it is highly needed to update and improve ABSIM. The paper presents recent efforts to improve ABSIM s compatibility with current operating systems, user interface, and analysis capabilities. The paper details the features and functions of the newly updated ABSIM software. The new ABSIM still uses the previously validated calculation engine of the old ABSIM. The new graphic user interfaces (GUI) were developed in Qt, which is an open source license GUI software based on C++. XML was used as the database for data storage in the new ABSIM. The new ABSIM has been designed to be easily learned and used. It has enhanced editing and construction functions, plus enhanced analysis features including parametric tables, plotting, property plots, and master panels for debugging. A single effect water/LiBr absorption system is used as a case study in this paper to illustrate the features, capabilities, and functions of the new ABSIM. This case study was actually an example system available in the old ABSIM. The new version of ABSIM will be continuously developed to include additional subroutines for the components in liquid desiccant systems. The new ABSIM will be available to public for free. The ultimate goal of the new ABSIM is to allow it to become a simulation

  7. Epidermal melanin absorption in human skin

    NASA Astrophysics Data System (ADS)

    Norvang Nilsen, Lill T.; Fiskerstrand, Elisanne J.; Nelson, J. Stuart; Berns, Michael W.; Svaasand, Lars O.

    1996-01-01

    The principle of laser induced selective photothermolysis is to induced thermal damage to specific targets in such a manner that the temperature of the surrounding tissue is maintained below the threshold for thermal damage. The selectivity is obtained by selection of a proper wavelength and pulse duration. The technique is presently being used in the clinic for removal of port-wine stains. The presence of melanin in the epidermal layer can represent a limitation to the selectivity. Melanin absorption drops off significantly with increasing wavelength, but is significant in the entire wavelength region where the blood absorption is high. Treatment of port-wine stain in patients with high skin pigmentation may therefore give overheating of the epidermis, resulting in epidermal necrosis. Melanosomal heating is dependent on the energy and duration of the laser pulse. The heating mechanism for time scales less than typically 1 microsecond(s) corresponds to a transient local heating of the individual melanosomes. For larger time scales, heat diffusion out of the melanosomes become of increased importance, and the temperature distribution will reach a local steady state condition after typically 10 microsecond(s) . For even longer pulse duration, heat diffusing from neighboring melanosomes becomes important, and the temperature rise in a time scale from 100 - 500 microsecond(s) is dominated by this mechanism. The epidermal heating during the typical 450 microsecond(s) pulse used for therapy is thus dependent on the average epidermal melanin content rather than on the absorption coefficient of the individual melanosomes. This study will present in vivo measurements of the epidermal melanin absorption of human skin when exposed to short laser pulses (< 0.1 microsecond(s) ) from a Q-switched ruby laser and with long laser pulses (approximately 500 microsecond(s) ) from a free-running ruby laser or a long pulse length flashlamp pumped dye laser. The epidermal melanin

  8. Two-photon vibrational spectroscopy for biosciences based on surface-enhanced hyper-Raman scattering

    PubMed Central

    Kneipp, Janina; Kneipp, Harald; Kneipp, Katrin

    2006-01-01

    Two-photon excitation is gaining rapidly in interest and significance in spectroscopy and microscopy. Here we introduce a new approach that suggests versatile optical labels suitable for both one- and two-photon excitation and also two-photon-excited ultrasensitive, nondestructive chemical probing. The underlying spectroscopic effect is the incoherent inelastic scattering of two photons on the vibrational quantum states called hyper-Raman scattering (HRS). The rather weak effect can be strengthened greatly if HRS takes place in the local optical fields of gold and silver nanostructures. This so-called surface-enhanced HRS (SEHRS) is the two-photon analogue to surface-enhanced Raman scattering (SERS). SEHRS provides structurally sensitive vibrational information complementary to those obtained by SERS. SEHRS combines the advantages of two-photon spectroscopy with the structural information of vibrational spectroscopy and the high-sensitivity and nanometer-scale local confinement of plasmonics-based spectroscopy. We infer effective two-photon cross-sections for SEHRS on the order of 10−46 to 10−45 cm4·s, similar to or higher than the best “action” cross-sections (product of the two-photon absorption cross-section and fluorescence quantum yield) for two-photon fluorescence, and we demonstrate HRS on biological structures such as single cells after incubation with gold nanoparticles. PMID:17088534

  9. A Two-Photon Fluorescent Probe for Lysosomal Thiols in Live Cells and Tissues

    PubMed Central

    Fan, Jiangli; Han, Zhichao; Kang, Yao; Peng, Xiaojun

    2016-01-01

    Lysosome-specific fluorescent probes are exclusive to elucidate the functions of lysosomal thiols. Moreover, two-photon microscopy offers advantages of less phototoxicity, better three dimensional spatial localization, deeper penetration depth and lower self-absorption. However, such fluorescent probes for thiols are still rare. In this work, an efficient two-photon fluorophore 1,8-naphthalimide-based probe conjugating a 2,4-dinitrobenzenesulfonyl chloride and morpholine was designed and synthesized, which exhibited high selectivity and sensitivity towards lysosomal thiols by turn-on fluorescence method quantitatively and was successfully applied to the imaging of thiols in live cells and tissues by two-photon microscopy. PMID:26794434

  10. Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

    NASA Technical Reports Server (NTRS)

    Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.

    1988-01-01

    Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.

  11. Femtosecond all-optical parallel logic gates based on tunable saturable to reverse saturable absorption in graphene-oxide thin films

    SciTech Connect

    Roy, Sukhdev Yadav, Chandresh

    2013-12-09

    A detailed theoretical analysis of ultrafast transition from saturable absorption (SA) to reverse saturable absorption (RSA) has been presented in graphene-oxide thin films with femtosecond laser pulses at 800 nm. Increase in pulse intensity leads to switching from SA to RSA with increased contrast due to two-photon absorption induced excited-state absorption. Theoretical results are in good agreement with reported experimental results. Interestingly, it is also shown that increase in concentration results in RSA to SA transition. The switching has been optimized to design parallel all-optical femtosecond NOT, AND, OR, XOR, and the universal NAND and NOR logic gates.

  12. Terahertz absorption of dilute aqueous solutions

    NASA Astrophysics Data System (ADS)

    Heyden, Matthias; Tobias, Douglas J.; Matyushov, Dmitry V.

    2012-12-01

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  13. Terahertz absorption of dilute aqueous solutions.

    PubMed

    Heyden, Matthias; Tobias, Douglas J; Matyushov, Dmitry V

    2012-12-21

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  14. Absorption of solar radiation by clouds: observations versus models.

    PubMed

    Cess, R D; Zhang, M H; Minnis, P; Corsetti, L; Dutton, E G; Forgan, B W; Garber, D P; Gates, W L; Hack, J J; Harrison, E F; Jing, X; Kiehi, J T; Long, C N; Morcrette, J J; Potter, G L; Ramanathan, V; Subasilar, B; Whitlock, C H; Young, D F; Zhou, Y

    1995-01-27

    There has been a long history of unexplained anomalous absorption of solar radiation by clouds. Collocated satellite and surface measurements of solar radiation at five geographically diverse locations showed significant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere than predicted by theoretical models. It has often been suggested that tropospheric aerosols could increase cloud absorption. But these aerosols are temporally and spatially heterogeneous, whereas the observed cloud absorption is remarkably invariant with respect to season and location. Although its physical cause is unknown, enhanced cloud absorption substantially alters our understanding of the atmosphere's energy budget.

  15. Absorption of Solar Radiation by Clouds: Observations Versus Models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M. H.; Minnis, P.; Corsetti, L.; Dutton, E. G.; Forgan, B. W.; Garber, D. P.; Gates, W. L.; Hack, J. J.; Harrison, E. F.; Jing, X.; Kiehl, J. T.; Long, C. N.; Morcrette, J.-J.; Potter, G. L.; Ramanathan, V.; Subasilar, B.; Whitlock, C. H.; Young, D. F.; Zhou, Y.

    1995-01-01

    There has been a long history of unexplained anomalous absorption of solar radiation by clouds. Collocated satellite and surface measurements of solar radiation at five geographically diverse locations showed significant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere than predicted by theoretical models. It has often been suggested that tropospheric aerosols could increase cloud absorption. But these aerosols are temporally and spatially heterogeneous, whereas the observed cloud absorption is remarkably invariant with respect to season and location. Although its physical cause is unknown, enhanced cloud absorption substantially alters our understanding of the atmosphere's energy budget.

  16. Thermally detected optical absorption in sophisticated nitride structures

    NASA Astrophysics Data System (ADS)

    Vasson, A.; Shubina, T. V.; Leymarie, J.

    2005-02-01

    The thermally detected optical absorption (TDOA) is applied to elucidate peculiarities of absorption in nitride structures of unusual morphology like GaN nanocolumns or InN layers with various imperfections. A study of GaN structures permits us to establish position of an absorption edge in TDOA spectra. We demonstrate that the absorption edge is different in GaN regions of opposite polarities. In InN with metallic In inclusions, this technique enable separation of InN interband absorption and extinction related to the Mie resonances, if the latter are below the principal absorption edge.

  17. Synopsis of Mid-latitude Radio Wave Absorption in Europe

    NASA Technical Reports Server (NTRS)

    Torkar, K. M.; Friedrich, M.

    1984-01-01

    Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts.

  18. Dust in MG II Absorption Systems

    NASA Astrophysics Data System (ADS)

    Malhotra, S.

    The dust absorption feature at 2175 AA is detected in a composite spectrum of Mg II absorbers. The composite absorber spectrum is obtained by taking the geometric mean of 92 quasar spectra after aligning them in the rest-frame of 96 absorbers. By aligning the spectra according to absorber redshifts we reinforce the spectral features of the absorbers, and smooth over possible bumps and wiggles in the emission spectra. The width of the observed absorption feature is 200-300 AA (FWHM), or 0.4-0.6 microns^{-1} and the central wavelength is 2240 AA. The Galactic dust feature has a central wavelength of 2176 AA and FWHM = 0.8-1.25 microns^{-1}. Simulations show that this discrepancy between the properties of the 2175 AA feature in Mg II absorbers and Galactic ISM can be mostly explained by the different methods used to measure them (cf. Malhotra 1997).

  19. Absorption lineshapes of molecular aggregates revisited

    SciTech Connect

    Gelzinis, Andrius; Valkunas, Leonas; Abramavicius, Darius

    2015-04-21

    Linear absorption is the most basic optical spectroscopy technique that provides information about the electronic and vibrational degrees of freedom of molecular systems. In simulations of absorption lineshapes, often diagonal fluctuations are included using the cumulant expansion, and the off-diagonal fluctuations are accounted for either perturbatively, or phenomenologically. The accuracy of these methods is limited and their range of validity is still questionable. In this work, a systematic study of several such methods is presented by comparing the lineshapes with exact results. It is demonstrated that a non-Markovian theory for off-diagonal fluctuations, termed complex time dependent Redfield theory, gives good agreement with exact lineshapes over a wide parameter range. This theory is also computationally efficient. On the other hand, accounting for the off-diagonal fluctuations using the modified Redfield lifetimes was found to be inaccurate.

  20. Integrated vacuum absorption steam cycle gas separation

    DOEpatents

    Chen, Shiaguo; Lu, Yonggi; Rostam-Abadi, Massoud

    2011-11-22

    Methods and systems for separating a targeted gas from a gas stream emitted from a power plant. The gas stream is brought into contact with an absorption solution to preferentially absorb the targeted gas to be separated from the gas stream so that an absorbed gas is present within the absorption solution. This provides a gas-rich solution, which is introduced into a stripper. Low pressure exhaust steam from a low pressure steam turbine of the power plant is injected into the stripper with the gas-rich solution. The absorbed gas from the gas-rich solution is stripped in the stripper using the injected low pressure steam to provide a gas stream containing the targeted gas. The stripper is at or near vacuum. Water vapor in a gas stream from the stripper is condensed in a condenser operating at a pressure lower than the stripper to concentrate the targeted gas. Condensed water is separated from the concentrated targeted gas.

  1. Overview-absorption/Rankine solar cooling program

    NASA Astrophysics Data System (ADS)

    Wahlig, M.; Heitz, A.; Boyce, B.

    1980-03-01

    The tasks being performed in the absorption and Rankine program areas run the gamut from basic work on fluids to development of chillers and chiller components, to field and reliability testing of complete cooling systems. In the absorption program, there are six current and five essentially completed projects. In the Rankine program, there are five current projects directly supported by DOE, and three projects funded through and managed by NASA/MSFC (Manned Space Flight Center, Huntsville, Alabama). The basic features of these projects are discussed. The systems under development in five of these current projects were selected for field testing in the SOLERAS program, a joint US-Saudi Arabian enterprise. Some technical highlights of the program are presented.

  2. [Carbohydrate absorption and malabsorption (author's transl)].

    PubMed

    Caspary, W F

    1977-06-01

    Starch is digested intraluminally by alpha-amylase to maltose, maltotriose, and alpha-limit dextrins. These products, as well as the disaccharides sucrose and lactose, undergo enzymatic hydrolysis to monosaccharides at the brush border surface. The monosaccharides enter the absorbing cell by specific transport mechanisms ("carriers"). Primary carbohydrate (CH) intolerance is characterized by the congenital or acquired absence of individual brush border enzymes or of monosaccharide "carriers" without morphologic abnormalities of the intestinal villus: lactose, sucrose and trehalose intolerance and glucose-galactose malabsorption (brush border diseases). Secondary CH intolerance arises when surface digestion and absorption are reduced due to structural changes of the intestinal mucosa: e.g., decrease or absence of villi with sprue and reduction of the absorbing surface with intestinal resection. Watery diarrhea is the lead symptom. Many drugs delay or interfere with CH absorption. This action may be viewed either as an unwanted side effect or as a welcome therapeutic principle.

  3. O VI absorption in interstellar cloud surfaces

    NASA Technical Reports Server (NTRS)

    Cowie, L. L.; Jenkins, E. B.; Songaila, A.; York, D. G.

    1979-01-01

    The velocity profiles of O VI absorption lines of 24 stars, observed in early Copernicus surveys, have been compared with the line profiles of Si III (1206.51 A) and N II (1083.99 A). The velocity structures of the O VI lines appear to be correlated with those of the material in the lower ionization stages. It is argued that the O VI absorption arises in the coronal gas of the conductive interface between hot gas, responsible for extended, soft X-ray emission, and cooler interstellar clouds. The velocity broadening of both sets of lines is attributed to motions of the cloud surfaces induced by pressure fluctuations in the interstellar medium.

  4. Absorption of lead through the skin.

    PubMed

    Rastogi, S C; Clausen, J

    1976-01-01

    Absorption of lead through the skin was studied by comparing the effect produced by lead naphthenate or lead acetate solution, when coated on the skin of rats, with data obtained from subcutaneous injections of these solutions. Body weight and liver size and weight decreased in the case of rats receiving the subcutaneous dose. delta-Aminolevulinic acid dehydratase (ALA-D) in liver was decreased in all rats having been treated with lead compounds. The distribution of absorbed lead has been evaluated by assay of the lead content in brain, liver, kidney, spleen and muscle in the rats. The results of this study seem to verify that absorption of lead through the skin does occur and the findings confirm lead naphthenate to be more toxic than lead acetate.

  5. Ultraviolet Absorption by Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Madronich, S.; Lee-Taylor, J. M.; Hodzic, A.; Aumont, B.

    2014-12-01

    Secondary organic aerosols (SOA) are typically formed in the atmosphere by the condensation of a myriad of intermediates from the photo-oxidation of volatile organic compounds (VOCs). Many of these partly oxidized molecules have functional groups (chromophores) that absorb at the ultraviolet (UV) wavelengths available in the troposphere (λ ≳ 290 nm). We used the explicit chemical model GECKO-A (Generator of Explicit Chemistry and Kinetics for Organics in the Atmosphere) to estimate UV absorption cross sections for the gaseous and particulate components of SOA from different precursors (biogenic and anthropogenic) and formed in different environments (low and high NOx, day and night). Model predictions are evaluated with laboratory and field measurements of SOA UV optical properties (esp. mass absorption coefficients and single scattering albedo), and implications are presented for surface UV radiation trends, urban actinic flux modification, and SOA lifetimes.

  6. Moisture absorption in thin polymer films

    NASA Astrophysics Data System (ADS)

    Soles, Christopher; Lenhart, Joseph; Jones, Ronnie; Prabhu, Vivek; Lin, Eric; Wu, Wen-Li

    2003-03-01

    We explore the kinetics and dynamics of moisture transport in a series of poly(hydroxystyrene), poly(tert-butoxycarboxystyrene), and epoxy films as a function of film thickness. Specular X-ray reflectivity is used to monitor the equilibrium swelling in films exposed to water vapor while a quartz crystal microbalance is used to track the kinetics of the absorption process. For relatively thick films we find that the equilibrium swelling is nominally consistent with the bulk moisture absorption properties of the polymer. However, when the film thickness drops below 100 nm, enhanced swelling occurs and the extent of the enhancement increases with resin polarity. Below the same thickness threshold of 100 nm, we also observe a strong retardation in the uptake kinetics, i.e., a decrease in the effective diffusion coefficient of the water. The results are discussed in detail with respect to confinement of the polymer films.

  7. Exciton absorption in narrow armchair graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Monozon, B. S.; Schmelcher, P.

    2016-11-01

    We develop an analytical approach to the exciton optical absorption for narrow gap armchair graphene nanoribbons (AGNR). We focus on the regime of dominant size quantization in combination with the attractive electron-hole interaction. An adiabatic separation of slow and fast motions leads via the two-body Dirac equation to the isolated and coupled subband approximations. Discrete and continuous exciton states are in general coupled and form quasi-Rydberg series of purely discrete and resonance type character. The corresponding oscillator strengths and widths are derived. We show that the exciton peaks are blue-shifted, become broader and increase in magnitude upon narrowing the ribbon. At the edge of a subband the singularity related to the 1D density of states is transformed into finite absorption via the presence of the exciton. Our analytical results are in good agreement with those obtained by other methods including numerical approaches. Estimates of the expected experimental values are provided for realistic AGNR.

  8. Wavelength mismatch effect in electromagnetically induced absorption

    NASA Astrophysics Data System (ADS)

    Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

    2016-07-01

    We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch-near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers.

  9. Spectrophotometry of six broad absorption line QSOs

    NASA Technical Reports Server (NTRS)

    Junkkarinen, Vesa T.; Burbidge, E. Margaret; Smith, Harding E.

    1987-01-01

    Spectrophotometric observations of six broad absorption-line QSOs (BALQSOs) are presented. The continua and emission lines are compared with those in the spectra of QSOs without BALs. A statistically significant difference is found in the emission-line intensity ratio for (N V 1240-A)/(C IV 1549-A). The median value of (N V)/(C IV) for the BALQSOs is two to three times the median for QSOs without BALs. The absorption features of the BALQSOs are described, and the column densities and limits on the ionization structure of the BAL region are discussed. If the dominant ionization mechanism is photoionization, then it is likely that either the ionizing spectrum is steep or the abundances are considerably different from solar. Collisional ionization may be a significant factor, but it cannot totally dominate the ionization rate.

  10. Absorption of Thermal Neutrons in Uranium

    DOE R&D Accomplishments Database

    Creutz, E. C.; Wilson, R. R.; Wigner, E. P.

    1941-09-26

    A knowledge of the absorption processes for neutrons in uranium is important for planning a chain reaction experiment. The absorption of thermal neutrons in uranium and uranium oxide has been studied. Neutrons from the cyclotron were slowed down by passage through a graphite block. A uranium or uranium oxide sphere was placed at various positions in the block. The neutron intensity at different points in the sphere and in the graphite was measured by observing the activity induced in detectors or uranium oxide or manganese. It was found that both the fission activity in the uranium oxide and the activity induced in manganese was affected by non-thermal neutrons. An experimental correction for such effects was made by making measurements with the detectors surrounded by cadmium. After such corrections the results from three methods of procedure with the uranium oxide detectors and from the manganese detectors were consistent to within a few per cent.

  11. Collisionless absorption in sharp-edged plasmas

    SciTech Connect

    Gibbon, P. ); Bell, A.R. )

    1992-03-09

    The absorption of subpicosecond, obliquely incident laser light is studied using a 11/2D particle-in-cell code. Density scale lengths from {ital L}/{lambda}=0.01 to 2 and laser irradiances between {ital I}{lambda}{sup 2}=10{sup 14} and 10{sup 18} W cm{sup {minus}2} {mu}m{sup 2} are considered. Vacuum heating'' (F. Brunel, Phys. Rev. Lett. 59, 52 (1987)) dominates over resonance absorption for scale lengths {ital L}/{lambda}{lt}0.1, and is most efficient when {ital v}{sub osc}/{ital c}{congruent}3.1({ital L}/{lambda}){sup 2}. Absorbed energy is carried mainly by a superhot'' electron population with {ital U}{sub hot}{similar to}({ital I}{lambda}{sup 2}){sup 1/3--1/2}.

  12. Two-Photon or Higher-Order Absorbing Optical Materials for Generation of Reactive Species

    NASA Technical Reports Server (NTRS)

    Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R. (Inventor); Perry, Joseph W. (Inventor)

    2013-01-01

    Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

  13. Two-photon or higher-order absorbing optical materials for generation of reactive species

    NASA Technical Reports Server (NTRS)

    Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R. (Inventor); Perry, Joseph W. (Inventor)

    2003-01-01

    Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

  14. Two-photon or higher-order absorbing optical materials for generation of reactive species

    NASA Technical Reports Server (NTRS)

    Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R (Inventor); Perry, Joseph W (Inventor)

    2007-01-01

    Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

  15. Liquid for absorption of solar heat

    SciTech Connect

    Nakamura, T.; Iwamoto, Y.; Kadotani, K.; Marui, T.

    1984-11-13

    A liquid for the absorption of solar heat, useful as an heat-absorbing medium in water heaters and heat collectors comprises: a dispersing medium selected from the group consisting of propylene glycol, mixture of propylene glycol with water, mixture of propylene glycol with water and glycerin, and mixture of glycerin with water, a dispersant selected from the group consisting of polyvinylpyrrolidone, caramel, and mixture of polyvinylpyrrolidone with caramel, and a powdered activated carbon as a black coloring material.

  16. Impedance Matched Absorptive Thermal Blocking Filters

    NASA Technical Reports Server (NTRS)

    Wollack, E. J.; Chuss, D. T.; U-Yen, K.; Rostem, K.

    2014-01-01

    We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match 50 Omega and its response has been validated from 0-to-50GHz. The observed return loss in the 0-to-20GHz design band is greater than 20 dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.

  17. Impedance Matched Absorptive Thermal Blocking Filters

    NASA Technical Reports Server (NTRS)

    Wollack, E. J.; Chuss, D. T.; Rostem, K.; U-Yen, K.

    2014-01-01

    We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match 50O and its response has been validated from 0-to-50GHz. The observed return loss in the 0-to-20GHz design band is greater than 20 dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.

  18. Absorption spectroscopy with quantum cascade lasers

    NASA Technical Reports Server (NTRS)

    Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.

    2001-01-01

    Novel pulsed and cw quantum cascade distributed feedback (QC-DFB) lasers operating near lambda=8 micrometers were used for detection and quantification of trace gases in ambient air by means of sensitive absorption spectroscopy. N2O, 12CH4, 13CH4, and different isotopic species of H2O were detected. Also, a highly selective detection of ethanol vapor in air with a sensitivity of 125 parts per billion by volume (ppb) was demonstrated.

  19. Atomic absorption spectroscopy with high temperature flames.

    PubMed

    Willis, J B

    1968-07-01

    An account is given of the history of the development of high temperature flames for the atomic absorption measurement of metals forming refractory oxides. The principles governing the design of premix burners for such flames, and the relative merits of different types of nebulizer burner systems are described. After a brief account of the structure and emission characteristics of the premixed oxygen-acetylene and nitrous oxide-acetylene flames, the scope and limitations of the latter flame in chemical analysis are discussed.

  20. Scanning imaging absorption spectrometer for atmospheric chartography

    NASA Technical Reports Server (NTRS)

    Burrows, John P.; Chance, Kelly V.

    1991-01-01

    The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY is an instrument which measures backscattered, reflected, and transmitted light from the earth's atmosphere and surface. SCIAMACHY has eight spectral channels which observe simultaneously the spectral region between 240 and 1700 nm and selected windows between 1940 and 2400 nm. Each spectral channel contains a grating and linear diode array detector. SCIAMACHY observes the atmosphere in nadir, limb, and solar and lunar occultation viewing geometries.

  1. Nonequilibrium gas absorption in rotating permeable media

    NASA Astrophysics Data System (ADS)

    Baev, V. K.; Bazhaikin, A. N.

    2016-08-01

    The absorption of ammonia, sulfur dioxide, and carbon dioxide by water and aqueous solutions in rotating permeable media, a cellular porous disk, and a set of spaced-apart thin disks has been considered. The efficiency of cleaning air to remove these impurities is determined, and their anomalously high solubility (higher than equilibrium value) has been discovered. The results demonstrate the feasibility of designing cheap efficient rotor-type absorbers to clean gases of harmful impurities.

  2. Fasting Increases Tobramycin Oral Absorption in Mice▿

    PubMed Central

    De Leo, Luigina; Di Toro, Nicola; Decorti, Giuliana; Malusà, Noelia; Ventura, Alessandro; Not, Tarcisio

    2010-01-01

    The pharmacokinetics of the aminoglycoside tobramycin was evaluated after oral administration to fed or fasting (15 h) mice. As expected, under normal feeding conditions, oral absorption was negligible; however, fasting induced a dramatic increase in tobramycin bioavailability. The dual-sugar test with lactulose and l-rhamnose confirmed increased small bowel permeability via the paracellular route in fasting animals. When experiments aimed at increasing the oral bioavailability of hydrophilic compounds are performed, timing of fasting should be extremely accurate. PMID:20086144

  3. Detector absorptivity measuring method and apparatus

    NASA Technical Reports Server (NTRS)

    Sheets, R. E. (Inventor)

    1976-01-01

    A method and apparatus for measuring the absorptivity of a radiation detector by making the detector an integral part of a cavity radiometer are described. By substituting the detector for the surface of the cavity upon which the radiation first impinges a comparison is made between the quantity of radiation incident upon the detector and the quantity reflected from the detector. The difference between the two is a measurement of the amount of radiation absorbed by the detector.

  4. Oxalic acid decreases calcium absorption in rats

    SciTech Connect

    Weaver, C.M.; Martin, B.R.; Ebner, J.S.; Krueger, C.A.

    1987-11-01

    Calcium absorption from salts and foods intrinsically labeled with /sup 45/Ca was determined in the rat model. Calcium bioavailability was nearly 10 times greater for low oxalate kale, CaCO/sub 3/ and CaCl/sub 2/ than from CaC/sub 2/O/sub 4/ (calcium oxalate) and spinach (high in oxalates). Extrinsic and intrinsic labeling techniques gave a similar assessment of calcium bioavailability from kale but not from spinach.

  5. Search for absorption edges in superexpansion bursts

    NASA Astrophysics Data System (ADS)

    in't Zand, Jean

    2013-09-01

    Our goal is to measure with the LETGS a series of bright type-I X-ray bursts with strong photospheric radius expansion ('superexpansion') to search for absorption edges due to the ashes of nuclear burning. We request a quick TOO, to be triggered by ISS-MAXI and Swift-BAT, with a total exposure time of 100 ks to obtain the detection of about 10 bursts.

  6. Theoretical antideuteron-nucleus absorptive cross sections

    NASA Technical Reports Server (NTRS)

    Buck, W. W.; Norbury, J. W.; Townsend, L. W.; Wilson, J. W.

    1993-01-01

    Antideuteron-nucleus absorptive cross sections for intermediate to high energies are calculated using an ion-ion optical model. Good agreement with experiment (within 15 percent) is obtained in this same model for (bar p)-nucleus cross sections at laboratory energies up to 15 GeV. We describe a technique for estimating antinucleus-nucleus cross sections from NN data and suggest that further cosmic ray studies to search for antideuterons and other antinuclei be undertaken.

  7. Gas in scattering media absorption spectroscopy - GASMAS

    NASA Astrophysics Data System (ADS)

    Svanberg, Sune

    2008-09-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS).

  8. Breaking temporal symmetries for emission and absorption

    PubMed Central

    Hadad, Yakir; Soric, Jason C.; Alu, Andrea

    2016-01-01

    Time-reversal symmetries impose stringent constraints on emission and absorption. Antennas, from radiofrequencies to optics, are bound to transmit and receive signals equally well from the same direction, making a directive antenna prone to receive echoes and reflections. Similarly, in thermodynamics Kirchhoff’s law dictates that the absorptivity and emissivity are bound to be equal in reciprocal systems at equilibrium, e(ω,θ)=a(ω,θ), with important consequences for thermal management and energy applications. This bound requires that a good absorber emits a portion of the absorbed energy back to the source, limiting its overall efficiency. Recent works have shown that weak time modulation or mechanical motion in suitably designed structures may largely break reciprocity and time-reversal symmetry. Here we show theoretically and experimentally that a spatiotemporally modulated device can be designed to have drastically different emission and absorption properties. The proposed concept may provide significant advances for compact and efficient radiofrequency communication systems, as well as for energy harvesting and thermal management when translated to infrared frequencies. PMID:26984502

  9. Intestinal absorption of biotin in the rat

    SciTech Connect

    Bowman, B.B.; Selhub, J.; Rosenberg, I.H.

    1986-07-01

    We examined the absorption of biotin using the in vivo intestinal loop technique. Jejunal segments from male rats were filled with solutions containing (/sup 3/H)biotin and (/sup 14/C)inulin in Krebs-Ringer phosphate buffer, pH 6.5. Absorption was determined on the basis of luminal tritium disappearance after correction for inulin recovery. At biotin concentrations of 0.1 and 5.0 microM, luminal biotin disappearance was linear for at least 10 min. At biotin concentrations ranging from 2.3 nM to 75 microM, 10-28% of the administered dose was absorbed in 10 min. The concentration dependence of luminal biotin disappearance is consistent with the presence of both saturable and nonsaturable (linear) components of biotin uptake, with estimated Km = 9.6 microM and Jmax = 75.2 pmol/(2.5 cm loop X min). The rate constant for nonsaturable uptake is 3.1 pmol/(2.5 cm loop X min X microM). We conclude that at biotin concentrations less than 5 microM, biotin absorption proceeds largely by the saturable process, whereas at concentrations above 25 microM, nonsaturable uptake predominates. Additional studies demonstrated significantly less biotin uptake in the ileum than in the jejunum, a finding in agreement with previous in vitro studies.

  10. Breaking temporal symmetries for emission and absorption

    NASA Astrophysics Data System (ADS)

    Hadad, Yakir; Soric, Jason C.; Alu, Andrea

    2016-03-01

    Time-reversal symmetries impose stringent constraints on emission and absorption. Antennas, from radiofrequencies to optics, are bound to transmit and receive signals equally well from the same direction, making a directive antenna prone to receive echoes and reflections. Similarly, in thermodynamics Kirchhoff's law dictates that the absorptivity and emissivity are bound to be equal in reciprocal systems at equilibrium, e(ω,θ)=a(ω,θ), with important consequences for thermal management and energy applications. This bound requires that a good absorber emits a portion of the absorbed energy back to the source, limiting its overall efficiency. Recent works have shown that weak time modulation or mechanical motion in suitably designed structures may largely break reciprocity and time-reversal symmetry. Here we show theoretically and experimentally that a spatiotemporally modulated device can be designed to have drastically different emission and absorption properties. The proposed concept may provide significant advances for compact and efficient radiofrequency communication systems, as well as for energy harvesting and thermal management when translated to infrared frequencies.

  11. Absorption Features in Soil Spectra Assessment.

    PubMed

    Vašát, Radim; Kodešová, Radka; Borůvka, Luboš; Jakšík, Ondřej; Klement, Aleš; Drábek, Ondřej

    2015-12-01

    From a wide range of techniques appropriate to relate spectra measurements with soil properties, partial least squares (PLS) regression and support vector machines (SVM) are most commonly used. This is due to their predictive power and the availability of software tools. Both represent exclusively statistically based approaches and, as such, benefit from multiple responses of soil material in the spectrum. However, physical-based approaches that focus only on a single spectral feature, such as simple linear regression using selected continuum-removed spectra values as a predictor variable, often provide accurate estimates. Furthermore, if this approach extends to multiple cases by taking into account three basic absorption feature parameters (area, width, and depth) of all occurring features as predictors and subjecting them to best subset selection, one can achieve even higher prediction accuracy compared with PLS regression. Here, we attempt to further extend this approach by adding two additional absorption feature parameters (left and right side area), as they can be important diagnostic markers, too. As a result, we achieved higher prediction accuracy compared with PLS regression and SVM for exchangeable soil pH, slightly higher or comparable for dithionite-citrate and ammonium oxalate extractable Fe and Mn forms, but slightly worse for oxidizable carbon content. Therefore, we suggest incorporating the multiple linear regression approach based on absorption feature parameters into existing working practices. PMID:26555184

  12. Absorption of trapped particles by Jupiter's moons

    NASA Technical Reports Server (NTRS)

    Hess, W. N.; Birmingham, T. J.; Mead, G. D.

    1973-01-01

    Absorption effects of the four innermost moons in the radial transport equations for electrons and protons in Jupiter's magnetosphere are presented. The phase space density n at 2 R sub J for electrons with equatorial pitch angles less than 69 deg is reduced by a factor of 4.2 x 1000 when lunar absorption is included in the calculation. For protons with equatorial pitch angles less than 69 deg, the corresponding reduction factor is 3.2 x 100000. The effect of the satellites becomes progressively weaker for both electrons and protons as equatorial pitch angles of pi/2 are approached, because the likelihood of impacting a satellite becomes progressively smaller. The large density decreases which we find at the orbits of Io, Europa, and Ganymede result in corresponding particle flux decreases that should be observed by spacecraft making particle measurements in Jupiter's magnetosphere. The characteristic signature of satellite absorption should be a downward pointing cusp in the flux versus radius curve at the L-value corresponding to each satellite.

  13. Absorption Features in Soil Spectra Assessment.

    PubMed

    Vašát, Radim; Kodešová, Radka; Borůvka, Luboš; Jakšík, Ondřej; Klement, Aleš; Drábek, Ondřej

    2015-12-01

    From a wide range of techniques appropriate to relate spectra measurements with soil properties, partial least squares (PLS) regression and support vector machines (SVM) are most commonly used. This is due to their predictive power and the availability of software tools. Both represent exclusively statistically based approaches and, as such, benefit from multiple responses of soil material in the spectrum. However, physical-based approaches that focus only on a single spectral feature, such as simple linear regression using selected continuum-removed spectra values as a predictor variable, often provide accurate estimates. Furthermore, if this approach extends to multiple cases by taking into account three basic absorption feature parameters (area, width, and depth) of all occurring features as predictors and subjecting them to best subset selection, one can achieve even higher prediction accuracy compared with PLS regression. Here, we attempt to further extend this approach by adding two additional absorption feature parameters (left and right side area), as they can be important diagnostic markers, too. As a result, we achieved higher prediction accuracy compared with PLS regression and SVM for exchangeable soil pH, slightly higher or comparable for dithionite-citrate and ammonium oxalate extractable Fe and Mn forms, but slightly worse for oxidizable carbon content. Therefore, we suggest incorporating the multiple linear regression approach based on absorption feature parameters into existing working practices.

  14. Breaking temporal symmetries for emission and absorption.

    PubMed

    Hadad, Yakir; Soric, Jason C; Alu, Andrea

    2016-03-29

    Time-reversal symmetries impose stringent constraints on emission and absorption. Antennas, from radiofrequencies to optics, are bound to transmit and receive signals equally well from the same direction, making a directive antenna prone to receive echoes and reflections. Similarly, in thermodynamics Kirchhoff's law dictates that the absorptivity and emissivity are bound to be equal in reciprocal systems at equilibrium, e(ω, θ)=a(ω, θ), with important consequences for thermal management and energy applications. This bound requires that a good absorber emits a portion of the absorbed energy back to the source, limiting its overall efficiency. Recent works have shown that weak time modulation or mechanical motion in suitably designed structures may largely break reciprocity and time-reversal symmetry. Here we show theoretically and experimentally that a spatiotemporally modulated device can be designed to have drastically different emission and absorption properties. The proposed concept may provide significant advances for compact and efficient radiofrequency communication systems, as well as for energy harvesting and thermal management when translated to infrared frequencies. PMID:26984502

  15. Circadian regulators of intestinal lipid absorption.

    PubMed

    Hussain, M Mahmood; Pan, Xiaoyue

    2015-04-01

    Among all the metabolites present in the plasma, lipids, mainly triacylglycerol and diacylglycerol, show extensive circadian rhythms. These lipids are transported in the plasma as part of lipoproteins. Lipoproteins are synthesized primarily in the liver and intestine and their production exhibits circadian rhythmicity. Studies have shown that various proteins involved in lipid absorption and lipoprotein biosynthesis show circadian expression. Further, intestinal epithelial cells express circadian clock genes and these genes might control circadian expression of different proteins involved in intestinal lipid absorption. Intestinal circadian clock genes are synchronized by signals emanating from the suprachiasmatic nuclei that constitute a master clock and from signals coming from other environmental factors, such as food availability. Disruptions in central clock, as happens due to disruptions in the sleep/wake cycle, affect intestinal function. Similarly, irregularities in temporal food intake affect intestinal function. These changes predispose individuals to various metabolic disorders, such as metabolic syndrome, obesity, diabetes, and atherosclerosis. Here, we summarize how circadian rhythms regulate microsomal triglyceride transfer protein, apoAIV, and nocturnin to affect diurnal regulation of lipid absorption.

  16. The two-photon excitation cross section of 6MAP, a fluorescent adenine analogue.

    PubMed

    Stanley, Robert J; Hou, Zhanjia; Yang, Aiping; Hawkins, Mary E

    2005-03-01

    6MAP is a fluorescent analogue of adenine that undergoes Watson-Crick base pairing and base stacking in double-stranded DNA. The one-photon absorption spectrum of 6MAP is characterized by a maximum around 330 nm with moderate quantum yield fluorescence centered at about 420 nm. To take advantage of this probe for confocal and single-molecule microscopy, it would be advantageous to be able to excite the analogue via two photons. We report the first determination of the two-photon excitation cross section and spectrum for 6MAP from 614 to 700 nm. The power dependence of the fluorescence indicates that emission results from the absorption of two photons. The one-photon and two-photon emission line shapes are identical within experimental error. A study of the concentration dependence of the fluorescence yield for one-photon excitation shows no measurable quenching up to about 5 microM. The maximum in the two-photon excitation spectrum gives a two-photon cross section, delta(TPE), of 3.4 +/- 0.1 Goeppert-Mayer (G.M.) at 659 nm, which correlates well with the one-photon absorption maximum. This compares quite favorably with cross sections of various naturally fluorescent biological molecules such as flavins and nicotiamide. In addition, we have also obtained the two-photon-induced fluorescence emission spectrum of quinine sulfate. It is approximately the same as that for one-photon excitation, suggesting that two-photon excitation of quinine sulfate may be used for calibration purposes.

  17. The two-photon excitation cross section of 6MAP, a fluorescent adenine analogue.

    PubMed

    Stanley, Robert J; Hou, Zhanjia; Yang, Aiping; Hawkins, Mary E

    2005-03-01

    6MAP is a fluorescent analogue of adenine that undergoes Watson-Crick base pairing and base stacking in double-stranded DNA. The one-photon absorption spectrum of 6MAP is characterized by a maximum around 330 nm with moderate quantum yield fluorescence centered at about 420 nm. To take advantage of this probe for confocal and single-molecule microscopy, it would be advantageous to be able to excite the analogue via two photons. We report the first determination of the two-photon excitation cross section and spectrum for 6MAP from 614 to 700 nm. The power dependence of the fluorescence indicates that emission results from the absorption of two photons. The one-photon and two-photon emission line shapes are identical within experimental error. A study of the concentration dependence of the fluorescence yield for one-photon excitation shows no measurable quenching up to about 5 microM. The maximum in the two-photon excitation spectrum gives a two-photon cross section, delta(TPE), of 3.4 +/- 0.1 Goeppert-Mayer (G.M.) at 659 nm, which correlates well with the one-photon absorption maximum. This compares quite favorably with cross sections of various naturally fluorescent biological molecules such as flavins and nicotiamide. In addition, we have also obtained the two-photon-induced fluorescence emission spectrum of quinine sulfate. It is approximately the same as that for one-photon excitation, suggesting that two-photon excitation of quinine sulfate may be used for calibration purposes. PMID:16851408

  18. Encapsulation effects on carbonaceous aerosol light absorption

    SciTech Connect

    Sedlacek, A.J.; Onasch, T.; Davidovits, P.; Cross, E.; Mazzoleni, C.

    2010-03-15

    The contribution of aerosol absorption on direct radiative forcing is still an active area of research, in part, because aerosol extinction is dominated by light scattering and, in part, because the primary absorbing aerosol of interest, soot, exhibits complex aging behavior that alters its optical properties. The consequences of this can be evidenced by the work of Ramanathan and Carmichael (2008) who suggest that incorporating the atmospheric heating due to brown clouds (plumes containing soot byproducts from automobiles, biomass burning, wood-burning kitchen stoves, and coal-fired power plants) will increase black carbon (BC) radiative forcing from the Intergovernmental Panel on Climate Change best estimate of 0.34 Wm-2 (±0.25 Wm-2) (IPCC 2007) to 0.9 Wm-2. This noteworthy degree of uncertainty is due largely to the interdependence of BC optical properties on particle mixing state and aggregate morphology, each of which changes as the particle ages in the atmosphere and becomes encapsulated within a coating of inorganic and/or organic substances. In July 2008, a laboratory-based measurement campaign, led by Boston College and Aerodyne, was initiated to begin addressing this interdependence. To achieve insights into the interdependence of BC optical properties on particle mixing state and aggregate morphology, measurements of both the optical and physical properties of flame-generated soot under nascent, coated, and denuded conditions were conducted. This poster presents data on black carbon (BC) light absorption measured by Photothermal Interferometry (Sedlacek and Lee 2007). In addition to examining nascent BC—to provide a baseline measurement—encapsulation with varying thicknesses of either dioctyl sebacate (DOS) or sulfuric acid was conducted to glean insights into the interplay between particle mixing state and optical properties. Additionally, some experiments were carried out where BC was coated and then denuded. In the case of DOS-coated soot, a

  19. Molecular aspects of intestinal calcium absorption.

    PubMed

    Diaz de Barboza, Gabriela; Guizzardi, Solange; Tolosa de Talamoni, Nori

    2015-06-21

    Intestinal Ca(2+) absorption is a crucial physiological process for maintaining bone mineralization and Ca(2+) homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3 steps: the entrance of Ca(2+) across the brush border membranes (BBM) of enterocytes through epithelial Ca(2+) channels TRPV6, TRPV5, and Cav1.3; Ca(2+) movement from the BBM to the basolateral membranes by binding proteins with high Ca(2+) affinity (such as CB9k); and Ca(2+) extrusion into the blood. Plasma membrane Ca(2+) ATPase (PMCA1b) and sodium calcium exchanger (NCX1) are mainly involved in the exit of Ca(2+) from enterocytes. A novel molecule, the 4.1R protein, seems to be a partner of PMCA1b, since both molecules co-localize and interact. The paracellular pathway consists of Ca(2+) transport through transmembrane proteins of tight junction structures, such as claudins 2, 12, and 15. There is evidence of crosstalk between the transcellular and paracellular pathways in intestinal Ca(2+) transport. When intestinal oxidative stress is triggered, there is a decrease in the expression of several molecules of both pathways that inhibit intestinal Ca(2+) absorption. Normalization of redox status in the intestine with drugs such as quercetin, ursodeoxycholic acid, or melatonin return intestinal Ca(2+) transport to control values. Calcitriol [1,25(OH)₂D₃] is the major controlling hormone of intestinal Ca(2+) transport. It increases the gene and protein expression of most of the molecules involved in both pathways. PTH, thyroid hormones, estrogens, prolactin, growth hormone, and glucocorticoids apparently also regulate Ca(2+) transport by direct action, indirect mechanism mediated by the increase of renal 1,25(OH)₂D₃ production, or both. Different physiological conditions, such as growth, pregnancy, lactation, and aging, adjust intestinal Ca(2+) absorption according to Ca(2+) demands. Better knowledge of the molecular details of intestinal Ca(2

  20. Molecular aspects of intestinal calcium absorption

    PubMed Central

    Diaz de Barboza, Gabriela; Guizzardi, Solange; Tolosa de Talamoni, Nori

    2015-01-01

    Intestinal Ca2+ absorption is a crucial physiological process for maintaining bone mineralization and Ca2+ homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3 steps: the entrance of Ca2+ across the brush border membranes (BBM) of enterocytes through epithelial Ca2+ channels TRPV6, TRPV5, and Cav1.3; Ca2+ movement from the BBM to the basolateral membranes by binding proteins with high Ca2+ affinity (such as CB9k); and Ca2+ extrusion into the blood. Plasma membrane Ca2+ ATPase (PMCA1b) and sodium calcium exchanger (NCX1) are mainly involved in the exit of Ca2+ from enterocytes. A novel molecule, the 4.1R protein, seems to be a partner of PMCA1b, since both molecules co-localize and interact. The paracellular pathway consists of Ca2+ transport through transmembrane proteins of tight junction structures, such as claudins 2, 12, and 15. There is evidence of crosstalk between the transcellular and paracellular pathways in intestinal Ca2+ transport. When intestinal oxidative stress is triggered, there is a decrease in the expression of several molecules of both pathways that inhibit intestinal Ca2+ absorption. Normalization of redox status in the intestine with drugs such as quercetin, ursodeoxycholic acid, or melatonin return intestinal Ca2+ transport to control values. Calcitriol [1,25(OH)2D3] is the major controlling hormone of intestinal Ca2+ transport. It increases the gene and protein expression of most of the molecules involved in both pathways. PTH, thyroid hormones, estrogens, prolactin, growth hormone, and glucocorticoids apparently also regulate Ca2+ transport by direct action, indirect mechanism mediated by the increase of renal 1,25(OH)2D3 production, or both. Different physiological conditions, such as growth, pregnancy, lactation, and aging, adjust intestinal Ca2+ absorption according to Ca2+ demands. Better knowledge of the molecular details of intestinal Ca2+ absorption could lead to the development of

  1. Molecular aspects of intestinal calcium absorption.

    PubMed

    Diaz de Barboza, Gabriela; Guizzardi, Solange; Tolosa de Talamoni, Nori

    2015-06-21

    Intestinal Ca(2+) absorption is a crucial physiological process for maintaining bone mineralization and Ca(2+) homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3 steps: the entrance of Ca(2+) across the brush border membranes (BBM) of enterocytes through epithelial Ca(2+) channels TRPV6, TRPV5, and Cav1.3; Ca(2+) movement from the BBM to the basolateral membranes by binding proteins with high Ca(2+) affinity (such as CB9k); and Ca(2+) extrusion into the blood. Plasma membrane Ca(2+) ATPase (PMCA1b) and sodium calcium exchanger (NCX1) are mainly involved in the exit of Ca(2+) from enterocytes. A novel molecule, the 4.1R protein, seems to be a partner of PMCA1b, since both molecules co-localize and interact. The paracellular pathway consists of Ca(2+) transport through transmembrane proteins of tight junction structures, such as claudins 2, 12, and 15. There is evidence of crosstalk between the transcellular and paracellular pathways in intestinal Ca(2+) transport. When intestinal oxidative stress is triggered, there is a decrease in the expression of several molecules of both pathways that inhibit intestinal Ca(2+) absorption. Normalization of redox status in the intestine with drugs such as quercetin, ursodeoxycholic acid, or melatonin return intestinal Ca(2+) transport to control values. Calcitriol [1,25(OH)₂D₃] is the major controlling hormone of intestinal Ca(2+) transport. It increases the gene and protein expression of most of the molecules involved in both pathways. PTH, thyroid hormones, estrogens, prolactin, growth hormone, and glucocorticoids apparently also regulate Ca(2+) transport by direct action, indirect mechanism mediated by the increase of renal 1,25(OH)₂D₃ production, or both. Different physiological conditions, such as growth, pregnancy, lactation, and aging, adjust intestinal Ca(2+) absorption according to Ca(2+) demands. Better knowledge of the molecular details of intestinal Ca(2

  2. Effect of absorption promoters on subcutaneous absorption of human epidermal growth factor in rats.

    PubMed

    Murakami, T; Misaki, M; Kojima, Y; Yamada, M; Yuki, M; Higashi, Y; Amagase, H; Fuwa, T; Yata, N

    1993-03-01

    Subcutaneous administration of human epidermal growth factor (hEGF) to rats gave a significantly smaller value of area under the curve (AUC) of concentration in plasma of immunoreactive hEGF versus time than intravenous administration, probably because the slow entry rate into the blood circulation and consequently the enzymic degradation of hEGF at the injection site. In the present study, absorption promoters such as sodium caprate, N-acylamino acids, disodium ethylenediamine-tetraacetate (EDTA), and sodium glycocholate were used because they were expected to inhibit the enzymic degradation of hEGF at the injection site and to facilitate the entry of hEGF into the blood circulation. Coadministration of an absorption promoter with hEGF significantly increased the entry rate and AUC value of immunoreactive hEGF compared with the case without the absorption promoter. The enzymic degradation of hEGF in the supernatant of the rat subcutaneous tissue homogenates and in the buffer solution containing leucine aminopeptidase or protease was markedly inhibited by the presence of the absorption promoters except EDTA. On the other hand, only EDTA increased the initial entry rate of FITC-dextran (M(r), 4000), which is not metabolized at the injection site, although all absorption promoters including EDTA markedly increased the extravasation of Evans blue. Thus, the increased subcutaneous bioavailability of hEGF in the presence of absorption promoters (except EDTA) was mainly attributed to the inhibitory effect of absorption promoters against the enzymic degradation of hEGF at the subcutaneous tissues. PMID:7680713

  3. An analytic formula for heating due to ozone absorption

    NASA Technical Reports Server (NTRS)

    Lindzen, R. S.; Will, D. I.

    1972-01-01

    An attempt was made to devise a simple expression or formula to describe radiative heating in the atmosphere by ozone absorption. Such absorption occurs in the Hartley, Huggins, and Chappuis bands and is only slightly temperature and pressure dependent.

  4. Ultrafast near-infrared nonlinear absorption in a multiferroic single crystal of bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Matsubara, Eiichi; Mochizuki, Takeshi; Nagai, Masaya; Ito, Toshimitsu; Ashida, Masaaki

    2015-09-01

    We studied the ultrafast third-order optical nonlinearity in a single crystal of multiferroic bismuth ferrite (BiFeO3) in the near-infrared range of 0.5-1.0 eV, where the material is fundamentally transparent, at room temperature. With pump pulses at 1.55 eV, which is off-resonant to the strong inter-band charge transfer (CT) transition, we observed instantaneous transient absorption with a pencil-like temporal profile originating from the two-photon CT transition from the oxygen 2p to the iron 3d levels. In contrast, under pumping with 3.10 eV photons, the pencil-like absorption change was not observed but decay profiles showed longer time constants. Although the two-photon absorption coefficient estimated to be 1.5 cm/GW is 10 (100) times smaller than that of two (one)-dimensional cuprates, it is larger than those of common semiconductors such as ZnSe at the optical communication wavelength.

  5. Attosecond Electron Wave-Packet Interference Observed by Transient Absorption

    SciTech Connect

    Holler, M.; Schapper, F.; Gallmann, L.; Keller, U.

    2011-03-25

    We perform attosecond time-resolved transient absorption spectroscopy around the first ionization threshold of helium and observe rapid oscillations of the absorption of the individual harmonics as a function of time delay with respect to a superimposed, moderately strong infrared laser field. The phase relation between the absorption modulation of individual harmonics gives direct evidence for the interference of transiently bound electronic wave packets as the mechanism behind the absorption modulation.

  6. Attosecond electron wave-packet interference observed by transient absorption.

    PubMed

    Holler, M; Schapper, F; Gallmann, L; Keller, U

    2011-03-25

    We perform attosecond time-resolved transient absorption spectroscopy around the first ionization threshold of helium and observe rapid oscillations of the absorption of the individual harmonics as a function of time delay with respect to a superimposed, moderately strong infrared laser field. The phase relation between the absorption modulation of individual harmonics gives direct evidence for the interference of transiently bound electronic wave packets as the mechanism behind the absorption modulation.

  7. Observation of confinement effects through liner and nonlinear absorption spectroscopy in cuprous oxide

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

    2015-02-01

    Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.

  8. Excited State Absorption from Real-Time Time-Dependent Density Functional Theory.

    PubMed

    Fischer, Sean A; Cramer, Christopher J; Govind, Niranjan

    2015-09-01

    The optical response of excited states is a key property used to probe photophysical and photochemical dynamics. Additionally, materials with a large nonlinear absorption cross-section caused by two-photon (TPA) and excited state absorption (ESA) are desirable for optical limiting applications. The ability to predict the optical response of excited states would help in the interpretation of transient absorption experiments and aid in the search for and design of optical limiting materials. We have developed an approach to obtain excited state absorption spectra by combining real-time (RT) and linear-response (LR) time-dependent density functional theory (TDDFT). Being based on RT-TDDFT, our method is aimed at tackling larger molecular complexes and materials systems where excited state absorption is predominantly seen and many time-resolved experimental efforts are focused. To demonstrate our method, we have calculated the ground and excited state spectra of H₂⁺ and H₂ due to the simplicity in the interpretation of the spectra. We have validated our new approach by comparing our results for butadiene with previously published results based on quadratic response (QR). We also present results for oligofluorenes, where we compare our results with both QR-TDDFT and experimental measurements. Because our method directly measures the response of an excited state, stimulated emission features are also captured; although, these features are underestimated in energy which could be attributed to a change of the reference from the ground to the excited state.

  9. Split-flow regeneration in absorptive air separation

    DOEpatents

    Weimer, Robert F.

    1987-01-01

    A chemical absorptive separation of air in multiple stage of absorption and desorption is performed with partial recycle of absorbent between stages of desorption necessary to match equilibrium conditions in the various stages of absorption. This allows reduced absorbent flow, reduced energy demand and reduced capital costs.

  10. 14 CFR 25.723 - Shock absorption tests.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Shock absorption tests. 25.723 Section 25... absorption tests. (a) The analytical representation of the landing gear dynamic characteristics that is used in determining the landing loads must be validated by energy absorption tests. A range of tests...

  11. 14 CFR 29.723 - Shock absorption tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Shock absorption tests. 29.723 Section 29.723 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... absorption tests. The landing inertia load factor and the reserve energy absorption capacity of the...

  12. 14 CFR 25.723 - Shock absorption tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Shock absorption tests. 25.723 Section 25... absorption tests. (a) The analytical representation of the landing gear dynamic characteristics that is used in determining the landing loads must be validated by energy absorption tests. A range of tests...

  13. 14 CFR 29.723 - Shock absorption tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Shock absorption tests. 29.723 Section 29.723 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... absorption tests. The landing inertia load factor and the reserve energy absorption capacity of the...

  14. 14 CFR 27.723 - Shock absorption tests.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Shock absorption tests. 27.723 Section 27.723 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... absorption tests. The landing inertia load factor and the reserve energy absorption capacity of the...

  15. 14 CFR 27.723 - Shock absorption tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Shock absorption tests. 27.723 Section 27.723 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... absorption tests. The landing inertia load factor and the reserve energy absorption capacity of the...

  16. 14 CFR 27.723 - Shock absorption tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Shock absorption tests. 27.723 Section 27.723 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... absorption tests. The landing inertia load factor and the reserve energy absorption capacity of the...

  17. 14 CFR 23.723 - Shock absorption tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Shock absorption tests. 23.723 Section 23... Landing Gear § 23.723 Shock absorption tests. (a) It must be shown that the limit load factors selected... exceeded. This must be shown by energy absorption tests except that analysis based on tests conducted on...

  18. 14 CFR 25.723 - Shock absorption tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Shock absorption tests. 25.723 Section 25... absorption tests. (a) The analytical representation of the landing gear dynamic characteristics that is used in determining the landing loads must be validated by energy absorption tests. A range of tests...

  19. 14 CFR 29.723 - Shock absorption tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Shock absorption tests. 29.723 Section 29.723 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... absorption tests. The landing inertia load factor and the reserve energy absorption capacity of the...

  20. 14 CFR 23.723 - Shock absorption tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Shock absorption tests. 23.723 Section 23... Landing Gear § 23.723 Shock absorption tests. (a) It must be shown that the limit load factors selected... exceeded. This must be shown by energy absorption tests except that analysis based on tests conducted on...