scholarly journals Excited-state dynamics of overlapped optically-allowed 1B(u)+ and optically-forbidden 1B(u)- or 3A(g)- vibronic levels of carotenoids: possible roles in the light-harvesting function.

2012 ◽  
Vol 59 (1) ◽  
Author(s):  
Yasushi Koyama ◽  
Yoshinori Kakitani ◽  
Hiroyoshi Nagae
Keyword(s):  
Internal Conversion ◽  
Selection Rule ◽  
Polar Solvent ◽  
Selective Excitation ◽  
Stimulated Emission ◽  
Quantum Beat ◽  
Pump Probe ◽  
Cross Term ◽  
Hand Pump ◽  
Probe Spectroscopy

Pump-probe spectroscopy after selective excitation of all-trans Cars (n = 9-13) in nonpolar solvent identified a symmetry selection rule of diabatic electronic mixing and diabatic internal conversion, i.e., '1B(u)(+)-to-1B(u)(-) is allowed but 1B(u)(+)-to-3A(g)(-) is forbidden'. Kerr-gate fluorescence spectroscopy showed that this selection rule breaks down, due to the symmetry degradation when the Car molecules are being excited, and, as a result, the 1B(u)(+)-to-3A(g)(-) diabatic electronic mixing and internal conversion become allowed. On the other hand, pump-probe spectroscopy after coherent excitation of the same set of Cars in polar solvent identified three stimulated-emission components (generated by the quantum-beat mechanism), consisting of the long-lived coherent cross term from the 1B(u)(+) + 1B(u)(-) or 1B(u)(+) + 3A(g)(-) diabatic pair and incoherent short-lived 1B(u)(+) and 1B(u)(-) or 3A(g)(-) split incoherent terms. The same type of stimulated-emission components were identified in Cars bound to LH2 complexes, their lifetimes being substantially shortened by the Car-to-BChl singlet-energy transfer. Each diabatic pair and its split components appeared with high intensities in the first component. The low-energy shifts of the 1B(u)(+)(0), 1B(u)(-)(0) and 3A(g)(-)(0) levels and efficient triplet generation were also found.

Ultrafast Energy And Electron Transfer In Conjugated Oligomer-Fullerene Molecules

2001 ◽  
Vol 665 ◽  
Author(s):  
P.A. van Hal ◽  
R.A.J. Janssen ◽  
G. Lanzani ◽  
G. Cerullo ◽  
M. Zavelani-Rossi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Energy Transfer ◽  
Time Constant ◽  
Transfer Reaction ◽  
Polar Solvent ◽  
Phenylene Vinylene ◽  
Intramolecular Electron Transfer ◽  
Pump Probe ◽  
Energy And Electron Transfer ◽  
Probe Spectroscopy

ABSTRACTThe intramolecular photoinduced energy and electron transfer within a fullereneoligothiophene-fullerene triad with nine thiophene units (C60-9T-C60) and an oligo(p-phenylene vinylene)-fullerene dyad with four phenyl groups (OPV4-C60) is investigated with femtosecond pump-probe spectroscopy with sub-10 fs and 200 fs time resolution in solvents of different polarity. Photoexcitation of the π-conjugated oligomer moiety in the triad and dyad results in an ultrafast singlet-energy transfer reaction to create the fullerene singlet-excited state with a time constant of 150-190 fs, irrespective of the polarity of the medium. In a polar solvent, intramolecular electron transfer occurs from the oligomer moiety to the C60 moiety with a time constant of 10-13 ps as a secondary reaction, subsequent to the ultrafast singlet-energy transfer. The charge-separated state has a lifetime of 50-80 ps and recombines to the ground state.

Broadband pump-probe spectroscopy with sub-10-fs resolution for probing ultrafast internal conversion and coherent phonons in carotenoids

2008 ◽  
Vol 350 (1-3) ◽  
pp. 45-55 ◽  
Author(s):  
D. Polli ◽  
M.R. Antognazza ◽  
D. Brida ◽  
G. Lanzani ◽  
G. Cerullo ◽  
...  
Keyword(s):  
Internal Conversion ◽  
Pump Probe ◽  
Coherent Phonons ◽  
Probe Spectroscopy

scholarly journals Ultrafast internal conversion dynamics of highly excited pyrrole studied with VUV/UV pump probe spectroscopy

2017 ◽  
Vol 146 (6) ◽  
pp. 064306 ◽  
Author(s):  
Spencer L. Horton ◽  
Yusong Liu ◽  
Pratip Chakraborty ◽  
Spiridoula Matsika ◽  
Thomas Weinacht
Keyword(s):  
Internal Conversion ◽  
Pump Probe ◽  
Probe Spectroscopy

Femtosecond Pump and Probe Spectroscopy on Poly(Para-Phenylenes)

1997 ◽  
Vol 488 ◽  
Author(s):  
W. Graupner ◽  
G. Cerullo ◽  
G. Kranzelbinder ◽  
G. Lanzani ◽  
S. Stagira ◽  
...  
Keyword(s):  
Stimulated Emission ◽  
Excitation Density ◽  
Relaxation Dynamics ◽  
Additional Absorption ◽  
Pump Probe ◽  
Band Emission ◽  
Decay Component ◽  
Pump And Probe ◽  
Ladder Polymer ◽  
Probe Spectroscopy

AbstractWe studied the sub-picosecond dynamics of photoexcitations in methyl-substituted poly(para--phenylene)-type ladder polymer (m-LPPP) films in a wide excitation density range up to values typical for the regime of narrow band emission by pump-probe spectroscopy. The singlet excitons relaxation dynamics, monitored at the stimulated emission (SE) peak at 2.53 eV, showed an intensity dependent ultrafast decay component, which occurs on a sub-picosecond time scale, ascribed to the onset of amplified spontaneous emission (ASE). In addition we identified photoinduced absorption (PA) bands of singlet excitons at 1.48 eV and polarons at 1.9 eV respectively. At high excitation density an additional absorption band becomes evident at 2.63 eV.

Subpicosecond vibrational relaxation of the S1 states of azulene and guaiazulene in solution

1995 ◽  
Vol 73 (2) ◽  
pp. 303-306 ◽  
Author(s):  
Dietrich Tittelbach-Helmrich ◽  
Brian D. Wagner ◽  
Ronald P. Steer
Keyword(s):  
Vibrational Relaxation ◽  
Internal Conversion ◽  
Vibrational Energy ◽  
Energy Content ◽  
Pump Probe ◽  
Decay Times ◽  
Probe Experiment ◽  
Pump Probe Experiment ◽  
Probe Spectroscopy ◽  
Electronic Ground

The S1 population decay times of azulene and 1,4-dimethyl-7-isopropylazulene (guaiazulene) in solution have been determined as a function of their initial vibrational energy content, [Formula: see text] using a pump–probe experiment with subpicosecond time resolution. The S1 lifetime of azulene does not depend on [Formula: see text] for energies up to 1760 cm−1, whereas the lifetime of the shorter-lived S1 state of guaiazulene is independent of [Formula: see text] only for energies up to ~1000 cm−1. At higher energies, the lifetime decreases with increasing [Formula: see text] and exhibits the same behavior in two structurally different solvents. It is suggested that internal conversion to the electronic ground state from a vibrationally unrelaxed S1 state is responsible for the effects observed in guaiazulene, and that intramolecular vibrational redistribution occurs with a time constant of several hundred femtoseconds. Keywords: pump–probe spectroscopy, azulene, femtosecond processes.

Nondegenerate Optical Pump-Probe Spectroscopy of Highly Excited Group III Nitrides

1999 ◽  
Vol 572 ◽  
Author(s):  
T. J. Schmidt ◽  
J. J. Song ◽  
S. Keller ◽  
U. K. Mishra ◽  
S. P. DenBaars ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Group Iii Nitrides ◽  
Stimulated Emission ◽  
Band Edge ◽  
Optical Pump ◽  
Pump Probe ◽  
Group Iii ◽  
Free Carriers ◽  
Emission Threshold ◽  
Probe Spectroscopy

ABSTRACTWe report the results of nondegenerate optical pump-probe absorption experiments performed on GaN and InGaN thin films and quantum wells under the conditions of strong optical band to band excitation. The evolution of the band edge in these materials was monitored as the number of photoexcited free carriers was increased beyond that required to achieve population inversion and observe stimulated emission. The band edge of InGaN is shown to exhibit markedly different high excitation behavior than that of GaN, explaining in part the reduction in stimulated emission threshold that typically accompanies the incorporation of indium into GaN to form InGaN. A comparison of the band edge absorption changes observed in pump-probe experiments to the gain spectra measured in variable-stripe gain experiments is also given.

Pump–probe spectroscopy on photoinitiators for stimulated-emission-depletion optical lithography

2011 ◽  
Vol 36 (16) ◽  
pp. 3188 ◽  
Author(s):  
Thomas J. A. Wolf ◽  
Joachim Fischer ◽  
Martin Wegener ◽  
Andreas-Neil Unterreiner
Keyword(s):  
Optical Lithography ◽  
Stimulated Emission ◽  
Pump Probe ◽  
Stimulated Emission Depletion ◽  
Probe Spectroscopy

scholarly journals Ultrafast Electron/Energy Transfer and Intersystem Crossing Mechanisms in BODIPY-Porphyrin Compounds

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 312
Author(s):  
Yusuf Tutel ◽  
Gökhan Sevinç ◽  
Betül Küçüköz ◽  
Elif Akhuseyin Yildiz ◽  
Ahmet Karatay ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Fluorescence Spectra ◽  
Visible Region ◽  
Energy Transfer Mechanism ◽  
Free Base ◽  
Pump Probe ◽  
Harvesting Efficiency ◽  
Probe Spectroscopy ◽  
Absorption Features ◽  
Transfer Mechanisms

Meso-substituted borondipyrromethene (BODIPY)-porphyrin compounds that include free base porphyrin with two different numbers of BODIPY groups (BDP-TTP and 3BDP-TTP) were designed and synthesized to analyze intramolecular energy transfer mechanisms of meso-substituted BODIPY-porphyrin dyads and the effect of the different numbers of BODIPY groups connected to free-base porphyrin on the energy transfer mechanism. Absorption spectra of BODIPY-porphyrin conjugates showed wide absorption features in the visible region, and that is highly valuable to increase light-harvesting efficiency. Fluorescence spectra of the studied compounds proved that BODIPY emission intensity decreased upon the photoexcitation of the BODIPY core, due to the energy transfer from BODIPY unit to porphyrin. In addition, ultrafast pump-probe spectroscopy measurements indicated that the energy transfer of the 3BDP-TTP compound (about 3 ps) is faster than the BDP-TTP compound (about 22 ps). Since the BODIPY core directly binds to the porphyrin unit, rapid energy transfer was seen for both compounds. Thus, the energy transfer rate increased with an increasing number of BODIPY moiety connected to free-base porphyrin.

Classical theory of ultrafast pump-probe spectroscopy: Applications to I2 photodissociation in Ar solution

1994 ◽  
Vol 61 (1-3) ◽  
pp. 153-165 ◽  
Author(s):  
Robert M. Whitnell ◽  
Kent R. Wilson ◽  
YiJing Yan ◽  
Ahmed H. Zewail
Keyword(s):  
Classical Theory ◽  
Pump Probe ◽  
Probe Spectroscopy
Sign in / Sign up

Export Citation Format

Share Document