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S. L. Dexheimer - One of the best experts on this subject based on the ideXlab platform.
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Observation of structural relaxation during exciton self-trapping via excited-State resonant impulsive stimulated Raman spectroscopy.
The Journal of chemical physics, 2015Co-Authors: Jason G. Mance, J. J. Felver, S. L. DexheimerAbstract:We detect the change in vibrational frequency associated with the transition from a deLocalized to a Localized Electronic State using femtosecond vibrational wavepacket techniques. The experiments are carried out in the mixed-valence linear chain material [Pt(en)2][Pt(en)2Cl2]⋅(ClO4)4 (en = ethylenediamine, C2H8N2), a quasi-one-dimensional system with strong electron-phonon coupling. Vibrational spectroscopy of the equilibrated self-trapped exciton is carried out using a multiple pulse excitation technique: an initial pump pulse creates a population of deLocalized excitons that self-trap and equilibrate, and a time-delayed second pump pulse tuned to the red-shifted absorption band of the self-trapped exciton impulsively excites vibrational wavepacket oscillations at the characteristic vibrational frequencies of the equilibrated self-trapped exciton State by the resonant impulsive stimulated Raman mechanism, acting on the excited State. The measurements yield oscillations at a frequency of 160 cm−1 corresponding to a Raman-active mode of the equilibrated self-trapped exciton with Pt-Cl stretching character. The 160 cm−1 frequency is shifted from the previously observed wavepacket frequency of 185 cm−1 associated with the initially generated exciton and from the 312 cm−1 Raman-active symmetric stretching mode of the ground Electronic State. We relate the frequency shifts to the changes in charge distribution and local structure that create the potential that stabilizes the self-trapped State.
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Exciton localization probed via excited-State resonant impulsive stimulated Raman spectroscopy
CLEO: 2013, 2013Co-Authors: Jason G. Mance, J. J. Felver, S. L. DexheimerAbstract:We probe the transition from a deLocalized to a Localized Electronic State in a quasi-one-dimensional system by the change in vibrational frequency detected by resonant impulsive Raman excitation of the excited State in a pump-pump-probe measurement.
Jason G. Mance - One of the best experts on this subject based on the ideXlab platform.
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Observation of structural relaxation during exciton self-trapping via excited-State resonant impulsive stimulated Raman spectroscopy.
The Journal of chemical physics, 2015Co-Authors: Jason G. Mance, J. J. Felver, S. L. DexheimerAbstract:We detect the change in vibrational frequency associated with the transition from a deLocalized to a Localized Electronic State using femtosecond vibrational wavepacket techniques. The experiments are carried out in the mixed-valence linear chain material [Pt(en)2][Pt(en)2Cl2]⋅(ClO4)4 (en = ethylenediamine, C2H8N2), a quasi-one-dimensional system with strong electron-phonon coupling. Vibrational spectroscopy of the equilibrated self-trapped exciton is carried out using a multiple pulse excitation technique: an initial pump pulse creates a population of deLocalized excitons that self-trap and equilibrate, and a time-delayed second pump pulse tuned to the red-shifted absorption band of the self-trapped exciton impulsively excites vibrational wavepacket oscillations at the characteristic vibrational frequencies of the equilibrated self-trapped exciton State by the resonant impulsive stimulated Raman mechanism, acting on the excited State. The measurements yield oscillations at a frequency of 160 cm−1 corresponding to a Raman-active mode of the equilibrated self-trapped exciton with Pt-Cl stretching character. The 160 cm−1 frequency is shifted from the previously observed wavepacket frequency of 185 cm−1 associated with the initially generated exciton and from the 312 cm−1 Raman-active symmetric stretching mode of the ground Electronic State. We relate the frequency shifts to the changes in charge distribution and local structure that create the potential that stabilizes the self-trapped State.
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Exciton localization probed via excited-State resonant impulsive stimulated Raman spectroscopy
CLEO: 2013, 2013Co-Authors: Jason G. Mance, J. J. Felver, S. L. DexheimerAbstract:We probe the transition from a deLocalized to a Localized Electronic State in a quasi-one-dimensional system by the change in vibrational frequency detected by resonant impulsive Raman excitation of the excited State in a pump-pump-probe measurement.
J. J. Felver - One of the best experts on this subject based on the ideXlab platform.
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Observation of structural relaxation during exciton self-trapping via excited-State resonant impulsive stimulated Raman spectroscopy.
The Journal of chemical physics, 2015Co-Authors: Jason G. Mance, J. J. Felver, S. L. DexheimerAbstract:We detect the change in vibrational frequency associated with the transition from a deLocalized to a Localized Electronic State using femtosecond vibrational wavepacket techniques. The experiments are carried out in the mixed-valence linear chain material [Pt(en)2][Pt(en)2Cl2]⋅(ClO4)4 (en = ethylenediamine, C2H8N2), a quasi-one-dimensional system with strong electron-phonon coupling. Vibrational spectroscopy of the equilibrated self-trapped exciton is carried out using a multiple pulse excitation technique: an initial pump pulse creates a population of deLocalized excitons that self-trap and equilibrate, and a time-delayed second pump pulse tuned to the red-shifted absorption band of the self-trapped exciton impulsively excites vibrational wavepacket oscillations at the characteristic vibrational frequencies of the equilibrated self-trapped exciton State by the resonant impulsive stimulated Raman mechanism, acting on the excited State. The measurements yield oscillations at a frequency of 160 cm−1 corresponding to a Raman-active mode of the equilibrated self-trapped exciton with Pt-Cl stretching character. The 160 cm−1 frequency is shifted from the previously observed wavepacket frequency of 185 cm−1 associated with the initially generated exciton and from the 312 cm−1 Raman-active symmetric stretching mode of the ground Electronic State. We relate the frequency shifts to the changes in charge distribution and local structure that create the potential that stabilizes the self-trapped State.
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Exciton localization probed via excited-State resonant impulsive stimulated Raman spectroscopy
CLEO: 2013, 2013Co-Authors: Jason G. Mance, J. J. Felver, S. L. DexheimerAbstract:We probe the transition from a deLocalized to a Localized Electronic State in a quasi-one-dimensional system by the change in vibrational frequency detected by resonant impulsive Raman excitation of the excited State in a pump-pump-probe measurement.
Bing Yang - One of the best experts on this subject based on the ideXlab platform.
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a hybridized local and charge transfer excited State for highly efficient fluorescent oleds molecular design spectral character and full exciton utilization
Advanced Optical Materials, 2014Co-Authors: Weijun Li, Shitong Zhang, Chu Wang, Fangzhong Shen, Ping Lu, Bing YangAbstract:For a donor–acceptor (D–A) molecule, there are three possible cases for its low-lying excited State (S1): a π–π* State (a Localized Electronic State), a charge-transfer (CT) State (a deLocalized Electronic State), and a mixed or hybridized State of π–π* and CT (named here as the hybridized local and charge transfer (HLCT) State). The HLCT State is an important excited State for the design of next-generation organic light-emitting diode (OLED) materials with both high photoluminescence (PL) efficiency and a large fraction of singlet exciton generation in electroluminescence (EL). According to the principle of State mixing in quantum chemistry, a series of twisting D–A molecules are designed and synthesized, and their HLCT State characters are verified by both fluorescent solvatochromic experiments and quantum chemical calculations. The CT components in the HLCT State, which greatly affect the molecular optical properties, are found to be enhanced with a decrease of the twist angle of the D–A segment or an increase of the D–A intensity in these twisting D–A molecules. In OLEDs, using these HLCT compounds as the emitting layer, the maximum exciton utilization efficiency is harvested up to 93%. Surprisingly, an exception of Kasha's rule is revealed in some HLCT compounds: restricted internal-conversion (IC) from the high-lying triplet State (T2) to the low-lying triplet T1, and a reopened path of reverse intersystem crossing (RISC) from T2 to S1 or S2, based on the analysis of the excited-State energy levels and the measurement of the low-temperature spectrum. RISC from T2 to S1 (S2) as a “hot exciton” channel is believed to contribute to the large proportion of the radiative singlet excitons.
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A Hybridized Local and Charge‐Transfer Excited State for Highly Efficient Fluorescent OLEDs: Molecular Design, Spectral Character, and Full Exciton Utilization
Advanced Optical Materials, 2014Co-Authors: Yuyu Pan, Shitong Zhang, Chu Wang, Fangzhong Shen, Liang Yao, Haichao Liu, Bing YangAbstract:For a donor–acceptor (D–A) molecule, there are three possible cases for its low-lying excited State (S1): a π–π* State (a Localized Electronic State), a charge-transfer (CT) State (a deLocalized Electronic State), and a mixed or hybridized State of π–π* and CT (named here as the hybridized local and charge transfer (HLCT) State). The HLCT State is an important excited State for the design of next-generation organic light-emitting diode (OLED) materials with both high photoluminescence (PL) efficiency and a large fraction of singlet exciton generation in electroluminescence (EL). According to the principle of State mixing in quantum chemistry, a series of twisting D–A molecules are designed and synthesized, and their HLCT State characters are verified by both fluorescent solvatochromic experiments and quantum chemical calculations. The CT components in the HLCT State, which greatly affect the molecular optical properties, are found to be enhanced with a decrease of the twist angle of the D–A segment or an increase of the D–A intensity in these twisting D–A molecules. In OLEDs, using these HLCT compounds as the emitting layer, the maximum exciton utilization efficiency is harvested up to 93%. Surprisingly, an exception of Kasha's rule is revealed in some HLCT compounds: restricted internal-conversion (IC) from the high-lying triplet State (T2) to the low-lying triplet T1, and a reopened path of reverse intersystem crossing (RISC) from T2 to S1 or S2, based on the analysis of the excited-State energy levels and the measurement of the low-temperature spectrum. RISC from T2 to S1 (S2) as a “hot exciton” channel is believed to contribute to the large proportion of the radiative singlet excitons.
Zhang Ji-ping - One of the best experts on this subject based on the ideXlab platform.
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Microscopic theory of pressure effects on the energy spectra of the tunable laser crystal Gd3Sc2Ga3O12 : Cr3+
Physical Review B, 2003Co-Authors: Ma Dong-ping, Zhang Ji-pingAbstract:In this work, a theory for shifts of energy spectra due to electron-phonon interaction (EPI) has been developed. Both the temperature-independent contributions and the temperature-dependent ones of acoustic and optical branches have been derived. The former results from the interaction between the zero-point vibration of the lattice and the Localized Electronic State. By means of both the theory for pressure-induced shifts (PS's) of energy spectra and the theory for shifts of energy spectra due to EPI, the "pure Electronic" PS's and the PS's due to EPI of the R-1 line, the R-2 line, and the U band of GSGG:Cr3+ have been calculated, respectively. The total calculated results are in good agreement with all the experimental data. The calculated results of normal-pressure energy spectra, g(parallel to)(R-1) and g(perpendicular to)(R-1) for GSGG:Cr3+ are also in good agreement with experiments. Their physical origins have been explained. It is found that the mixing degree of \t(2)(2)(T-3(1))e(4)T(2)> and \t(2)(3) E-2> base wave functions in the wave functions of R-1 level of GSGG:Cr3+ is remarkable under normal pressure, and the mixing degree rapidly decreases with increasing pressure. The change of the mixing degree with pressure plays a key role for not only the pure Electronic PS's of the R-1 line and the R-2 line, but also the PS's of the R-1 line and the R-2 line due to EPI. The pressure-dependent behavior of the pure Electronic PS of the R-1 line (or the R-2 line) is quite different from that of the PS of the R-1 line (or the R-2 line) due to EPI. It is the combined effect of them that gives rise to the total PS of the R-1 line (or the R-2 line). At 300 K and in the range of about 15-45 kbar, the mergence and/or order reversal between t(2)(2)(T-3(1))e(4)T(2) levels and t(2)(3) T-2(1) levels takes place, which causes the fluctuation of the rate of PS for t(2)(2)(T-3(1))e(4)T(2) (or t(2)(3) T-2(1)) with pressure. At 300 K, both the temperature-independent contribution to the R-1 line (or the R-2 line or the U band) from EPI and the temperature-dependent one are important, however, the temperature-independent contribution is much larger than the temperature-dependent one at 70 K.
