scholarly journals Picosecond-Duration Vibrational Relaxation Kinetics in the Excited S1 State of Perylene and Anthracene Molecules

1983 ◽  
Vol 3 (1-6) ◽  
pp. 249-261 ◽  
Author(s):  
A. Freiberg ◽  
T. Tamm ◽  
K. Timpmann
Keyword(s):  
Steady State ◽  
Luminescence Spectrum ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Streak Camera ◽  
Relaxation Times ◽  
Temporal Behavior ◽  
Vibrational Energy Relaxation ◽  
The Matrix ◽  
Measured Relaxation

We present and discuss the results of a direct observation of the picosecond range temporal behavior of vibronic lines in the luminescence spectrum of the matrix-isolated perylene and anthracene molecules. A novel subtractive dispersion mount of monochromators in conjunction with the synchroscan streak camera has been used. From spectrochronograms measured at different excitation wavelengths the vibrational energy relaxation times have been obtained. These are in the range of 20–30 ps and are most probably determined by the existence of the phonon bath of the matrix. A comparison of the measured relaxation constants with those estimated from the steady-state hot luminescence spectrum has been made.

A nanosized rigid spherical inclusion with interfacial diffusion and sliding

2017 ◽  
Vol 23 (7) ◽  
pp. 1049-1060
Author(s):  
Xu Wang
Keyword(s):  
Steady State ◽  
Stress Field ◽  
Normal Stress ◽  
Spherical Inclusion ◽  
Surface Elasticity ◽  
Relaxation Times ◽  
Imperfect Interface ◽  
Time Dependent ◽  
Interfacial Diffusion ◽  
The Matrix

We examine the time-dependent deformations around a nanosized rigid spherical inclusion in an infinite elastic matrix under uniaxial tension at infinity. The elastic matrix is first endowed with separate Gurtin–Murdoch surface elasticity. Furthermore, interfacial diffusion and sliding both occur on the inclusion–matrix interface. Closed-form expressions of the time-dependent displacements and stresses in the matrix are derived by using Papkovich–Neuber displacement potentials. A concise and elegant expression of the steady-state normal stress on the surface of the inclusion is also obtained. It is seen that the displacements and stresses in the matrix evolve with two relaxation times which are reliant on three size-dependent parameters, one from surface elasticity and the other two from interfacial diffusion and sliding. Numerical results are presented to demonstrate the influence of surface elasticity on the relaxation times and on the stress distribution near the inclusion. It is observed that the surface elasticity can alter the nature of the steady state normal stress on the surface of the inclusion from tension to compression. When the radius of the inclusion is not greater than the ratio of residual surface tension to remote tension, the steady state normal stress on the surface of the inclusion is always compressive. The related problem of a nanosized rigid spherical inclusion with a spring-type imperfect interface is also solved. We find that it is feasible to design a neutral spherical inclusion that does not disturb a prescribed uniform uniaxial stress field or even any uniform stress field outside the inclusion through a judicious choice of the four imperfect interface parameters.

On the interpretation of measured rotational and vibrational relaxation times. II. Sudden change experiments

1976 ◽  
Vol 54 (15) ◽  
pp. 2372-2379 ◽  
Author(s):  
Huw Owen Pritchard
Keyword(s):  
Shock Wave ◽  
Relaxation Time ◽  
Vibrational Relaxation ◽  
Normal Mode Analysis ◽  
Relaxation Times ◽  
Sudden Change ◽  
Heat Bath ◽  
Mode Analysis ◽  
Wave Excitation ◽  
Measured Relaxation

This paper examines, in terms of the normal-mode analysis developed earlier (Part I), the nature of relaxations in which a diatomic gas, highly diluted in a heat bath of inert gas atoms, is subjected to a sudden change as in shock-wave excitation or laser schlieren experiments.It is shown in detail how the observed relaxation time in a shock-wave excitation to a fixed final temperature depends on the initial temperature. At the same time, it is confirmed that the characterisation as 'mainly rotational' of the measured relaxation time in H2 when it is heated from room temperature to 1500 K in a shock wave is perfectly plausible.On the other hand, the calculations show that in laser schlieren experiments in which the v = 1, J = 1 level of H2 is overpopulated, the vibrational relaxation time of H2 at the temperature in question is recovered, although interesting effects should appear if other J levels were populated initially, or if the experiments were carried out at much higher ambient temperatures.The calculations also demonstrate that it is not generally possible to derive relaxation times by following the variation in population of any particular level of the molecule: multiple overshoots sometimes occur, and apparent relaxation times both longer or shorter than the true relaxation times could often result from attempts to follow level populations as a function of time.

Vibrational energy relaxation dynamics of diatomic molecules inside superfluid helium nanodroplets. The case of the I2 molecule

2018 ◽  
Vol 20 (1) ◽  
pp. 118-130 ◽  
Author(s):  
Arnau Vilà ◽  
Miguel Paniagua ◽  
Miguel González
Keyword(s):  
Superfluid Helium ◽  
Vibrational Relaxation ◽  
Time Scale ◽  
Theoretical Study ◽  
Vibrational Energy ◽  
Diatomic Molecules ◽  
Relaxation Dynamics ◽  
Vibrational Energy Relaxation ◽  
Helium Nanodroplets ◽  
Quantum Approach

The vibrational relaxation (VER) of a X2 molecule in a 4He superfluid nanodroplet (HeND; 0.37 K) was studied adapting a quantum approach recently proposed by us. In the first theoretical study on the VER of molecules inside HeND the I2 molecule was examined [cascade mechanism (ν → ν − 1; ν − 1 → ν − 2; …) and time scale of ns].

The influence of non-equilibrium transient effects on measurements of vibrational relaxation times and of dissociation rate constants

1982 ◽  
Vol 60 (23) ◽  
pp. 2927-2942 ◽  
Author(s):  
Heshel Teitelbaum
Keyword(s):  
Rate Constants ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Relaxation Times ◽  
Dissociation Rate ◽  
Harmonic Oscillators ◽  
Dissociation Limit ◽  
Transient Effects ◽  
Rate Law ◽  
Non Equilibrium

A semi-empirical analysis based on a rate law for vibrational relaxation of dissociating simple harmonic oscillators allows for a detailed study of measurements of vibrational relaxation times τ and of steady dissociation rate coefficients k0. It is shown that non-equilibrium populations of vibrational energy levels prevent attainment of the thermodynamically expected equilibrium energy. Even under near-isothermal and mild conditions, [Formula: see text], serious experimental errors result when the Bethe–Teller relaxation rate law is used. Closed form expressions are given which permit evaluation of these errors. Measurements should be analyzed using the rate law[Formula: see text]where ε is the vibrational energy per molecule, τ the relaxation time, kd the non-equilibrium rate coefficient, ετ the thermodynamically expected vibrational energy at temperature T, and (ε* + hv) the energy just above the dissociation limit. It is also shown that if[Formula: see text]a local minimum and maximum are predicted for measured density gradients in shock tube dissociations of diatomic molecules, where tine is the incubation time, D′ the effective dissociation energy, and x0 the mole fraction of dissociating molecules in an inert diluent. Expressions are given for extracting incubation times and rate constants from such studies when [Formula: see text]. Analysis of experimental data actually showing such phenomena (J. Chem Phys. 55, 4017 (1971)) is carried out. There are indications that any analysis which does not explicitly account for transient effects could result in errors in measured k0's of factors of 2 or more.

scholarly journals Picosecond Processes in Chemical Systems: Vibrational Relaxation

1983 ◽  
Vol 3 (1-6) ◽  
pp. 109-132 ◽  
Author(s):  
E. J. Heilweil ◽  
R. Moore ◽  
G. Rothenberger ◽  
S. Velsko ◽  
R. M. Hochstrasser
Keyword(s):  
Aqueous Solution ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Energy Relaxation ◽  
Simple System ◽  
Spectral Evolution ◽  
Vibrational Energy Relaxation ◽  
Dynamical Processes ◽  
Molecular Rearrangements ◽  
Chemical Systems

A review is presented of our recent studies of vibrational energy relaxation of moderately sized molecules in a variety of media and of the effect of vibrational relaxation on processes such as molecular rearrangements.Data are presented on intramolecular dynamical processes involving p-difluorobenzene and an experiment is described which allows the study of spectral evolution on the picosecond timescale under collision-free conditions.The vibrational (T1) relaxation of the apparently simple system consisting of a diatomic CN− ion in aqueous solution was studied and found to be in the range of a few picoseconds and to be concentration dependent. These results, and the effects of counterions, are suggested to be the result of aggregation of the ions. A discussion of the Raman lineshapes is given in relation to the measured T1 times.

Vibrational Energy Transfer in CHF3 -Mixtures

1976 ◽  
Vol 31 (10) ◽  
pp. 1268-1270 ◽  
Author(s):  
K. Frank ◽  
P. Hess
Keyword(s):  
Energy Transfer ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Relaxation Times ◽  
Rare Gas ◽  
Vibrational Energy Transfer

Abstract The vibrational relaxation times for pure CHF, and CHF3 diluted in H2, D2, Ar, Kr and Xe are 0.55; 0.01, 0.025, 2.6, 4.8, and 5.6 /μsec atm at 298 K. These measurements complete previous results obtained for the systems CHF3-He, Ne, Ar. Correlation of the rare-gas results according to SSH-theory shows that relatively small rotational contributions may be expected for the heavy collision partners Kr and Xe.

Two-Dimensional Infrared Spectroscopy From the Gas to Liquid Phase: Density Dependent J-Scrambling, Vibrational Relaxation, and the Onset of Liquid Character

2019 ◽  
Author(s):  
Greg Ng Pack ◽  
Matthew Rotondaro ◽  
Parth Shah ◽  
Aritra Mandal ◽  
Shyamsunder Erramilli ◽  
...  
Keyword(s):  
Vibrational Energy ◽  
Rotational Relaxation ◽  
Vibrational Energy Relaxation ◽  
Pump Probe ◽  
Solution Dynamics ◽  
Supercritical Phase ◽  
Supercritical Solution ◽  
Asymmetric Stretch ◽  
Two Dimensional Infrared Spectroscopy ◽  
Vibrational Equilibrium

Ultrafast 2DIR spectra and pump-probe responses of the N2O n 3 asymmetric stretch in SF6 as a function of density from the gas to supercritical phase and liquid are reported. 2DIR spectra unequivocally reveal free rotor character at all densities studied in the gas and supercritical region. Analysis of the 2DIR spectra determines that J-scrambling or rotational relaxation in N2O is highly efficient, occurring in ~1.5 to ~2 collisions with SF6 at all non-liquid densities. In contrast, N2O n 3 vibrational energy relaxation requires ~15 collisions, and complete vibrational equilibrium occurs on the ~ns scale at all densities. An independent binary collision model is sufficient to describe these supercritical state point dynamics. The N2O n 3 in liquid SF6 2DIR spectrum shows no evidence of free rotor character or spectral diffusion. Using these 2DIR results, hindered rotor or liquid-like character is found in gas and all supercritical solutions for SF6 densities ³ r * = 0.3, and increases with SF6 density. 2DIR spectral analysis offers direct time domain evidence of critical slowing for SF6 solutions closest to the critical point density. Applications of 2DIR to other high density and supercritical solution dynamics and descriptions are discussed. <br>

Vibrational Relaxation Times in Oxygen

1959 ◽  
Vol 30 (6) ◽  
pp. 1614-1615 ◽  
Author(s):  
Morris Salkoff ◽  
Ernest Bauer
Keyword(s):  
Vibrational Relaxation ◽  
Relaxation Times

Fluorescence from the Highly Excited States and Vibrational Energy Relaxation in Directly Linked Porphyrin Arrays

2002 ◽  
Vol 75 (5) ◽  
pp. 1023-1029 ◽  
Author(s):  
Nam Woong Song ◽  
Hyun Sun Cho ◽  
Min-Chul Yoon ◽  
Sae Chae Jeoung ◽  
Naoya Yoshida ◽  
...  
Keyword(s):  
Excited States ◽  
Vibrational Energy ◽  
Energy Relaxation ◽  
Vibrational Energy Relaxation
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