scholarly journals Pump- And Probe-Wavelength Dependencies of Picosecond Anti-Stokes Raman Spectrum of Trans-Stilbene in the S1 State

1999 ◽  
Vol 19 (1-4) ◽  
pp. 75-78 ◽  
Author(s):  
Takakazu Nakabayashi ◽  
Hiromi Okamoto ◽  
Mitsuo Tasumi
Keyword(s):  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Wavelength Dependence ◽  
Relaxation Dynamics ◽  
Vibrationally Excited ◽  
Time Resolved ◽  
Probe Wavelength ◽  
Trans Stilbene ◽  
Pump And Probe ◽  
Anti Stokes

Vibrational relaxation dynamics of trans-stilbene in the S1 state immediately after photoexcitation is studied by picosecond time-resolved anti-Stokes Raman spectroscopy with several pump and probe wavelengths. Pump-wavelength dependence of the anti- Stokes spectrum indicates that, when pump photons with high excess energy (≈5200cm-1) are used, the anti-Stokes Raman bands at 0 ps delay time arise from vibrationally excited transients with excess vibrational energy not thermally distributed in the molecule. Probe-wavelength dependence suggests that the vibrationally excited transients at 0 ps are mostly on the lowest excited vibrational levels, as far as the olefinic C═C stretching and the C–Ph stretching modes are concerned. The vibrational relaxation process of S1trans-stilbene is discussed on the basis of the observed results.

scholarly journals Picosecond Anti-Stokes Raman Excitation Profiles as a Method for Investigating Vibrationally Excited Transients

1999 ◽  
Vol 19 (1-4) ◽  
pp. 335-341 ◽  
Author(s):  
Hiromi Okamoto ◽  
Takakazu Nakabayashi ◽  
Mitsuo Tasumi
Keyword(s):  
Vibrational Energy ◽  
Vibrational Modes ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Quantum Numbers ◽  
Trans Stilbene ◽  
Raman Process ◽  
Vibrationally Hot Molecules ◽  
Raman Excitation Profiles ◽  
Anti Stokes

A method for estimating vibrational quantum numbers of vibrationally excited transients in solution is proposed. In this method, we calculate anti-Stokes Raman excitation profiles (REPs) which are characteristic of the initial vibrational states involved in the Raman process, and compare them with observed anti-Stokes intensities. We have applied this method to vibrationally hot molecules of canthaxanthin in the So state and those of trans-stilbene in the S1 state. For canthaxanthin, it has been found that the vibrationally excited transients are for the most part on the ν=1 level of the C═C stretching mode, and that excess vibrational energy is statistically distributed among all intramolecular vibrational modes. As for S1 stilbene, vibrational transients are shown to be mostly on the ν=1 level for two vibrational modes examined, while the excess vibrational energy is probably localised on the olefinic C═C stretching mode.

UlTRAFAST LATTICE RELAXATION DYNAMICS OF EXCITON IN A QUAISI-1-D METAL-HALOGEN COMPLEX

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3965-3968
Author(s):  
ATSUSHI SUGITA ◽  
TAKASHI SAITO ◽  
TAKAYOSHI KOBAYASHI ◽  
MASAHIRO YAMASHITA
Keyword(s):  
Wave Packet ◽  
Free Exciton ◽  
Mixed Valence ◽  
Lattice Relaxation ◽  
Relaxation Dynamics ◽  
Time Resolved ◽  
Pump And Probe ◽  
Probe Spectroscopy ◽  
Electronic Ground ◽  
The Ideal

A quasi-one-dimensional halogen-bridged mixed-valence metal complex is studied by time-resolved pump and probe spectroscopy with sub-5 fs time resolution. Two kinds of oscillatory signals are observed, which are attributed to the wave packet motions both in an electronic ground state and in a self-trapped exciton (STE) state. The onset of the wave packet motion is found to be delayed by about 50 fs, comparing with the ideal wave packet in the electronic excited state. The delay reflects the thermalization process in a free exciton (FE) state and a lattice relaxation process from FE to STE states.

Vibrational Energy Relaxation

2006 ◽  
Author(s):  
Abraham Nitzan
Keyword(s):  
Condensed Phase ◽  
Vibrational Relaxation ◽  
System Analysis ◽  
Vibrational Energy ◽  
Infrared Emission ◽  
Solid Matrix ◽  
Main Task ◽  
Vibrationally Excited ◽  
Two Phases ◽  
Solvent Molecules

An impurity molecule located as a solute in a condensed solvent, a solid matrix or a liquid, when put in an excited vibrational state will loose its excess energy due to its interaction with the surrounding solvent molecules. Vibrational energy accumulation is a precursor to all thermal chemical reactions. Its release by vibrational relaxation following a reactive barrier crossing or optically induced reaction defines the formation of a product state. The direct observation of this process by, for example, infrared emission or more often laser induced fluorescence teaches us about its characteristic timescales and their energetic (i.e. couplings and frequencies) origin. These issues are discussed in this chapter. Before turning to our main task, which is constructing and analyzing a model for vibrational relaxation in condensed phases, we make some general observations about this process. In particular we will contrast condensed phase relaxation with its gas phase counterpart and will comment on the different relaxation pathways taken by diatomic and polyatomic molecules. First, vibrational relaxation takes place also in low density gases. Collisions involving the vibrationally excited molecule may result in transfer of the excess vibrational energy to rotational and translational degrees of freedom of the overall system. Analysis based on collision theory, with the intermolecular interaction potential as input, then leads to the cross-section for inelastic collisions in which vibrational and translational/rotational energies are exchanged. If C∗ is the concentration of vibrationally excited molecules and ρ is the overall gas density, the relaxation rate coefficient kgas is defined from the bimolecular rate law When comparing this relaxation to its condensed phase counterpart one should note a technical difference between the ways relaxation rates are defined in the two phases.

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