Rotational and vibrational relaxation

In [162] experiments on methane provided a linear pressure dependence of the contour width. This made it possible to find the dephasing cross-section and to discriminate between contributions of rotational and vibrational relaxation to the contour width. This was done under the above-mentioned simplifying assumption that they are additive. (Let us note that processing of experimental data on linear molecules was always performed under this assumption.) The points found by this method are shown in Fig. 3.15, curves (4) and (6). 

J.G. Parker. Rotational and Vibrational Relaxation in Diatomic Gases. Phys. Fluids, 2 449-462,1959. 

The first two of these processes, rotational and vibrational relaxation, do not usually cause a loss of fluorescence. The molecule is still in an electronically excited state and can radiate but at different wavelengths from the initial state. It is therefore possible to observe these relaxation processes by using some method to disperse or select the wavelength of the fluorescence. 

Some interesting examples of the effects of rotational and vibrational relaxation on the fluorescence decay profile of levels near and above a predissociation are provided by the studies by Clyne and McDermid [37—40], and Clyne and Heaven [41, 42] on the B—X systems of the hetero- and homo-nuclear diatomic inter halogens. 

Whittenburg SL, Wang CH. Light scattering studies of rotational and vibrational relaxations of acetonitrile in carbon tetrachloride. J Chem Phys 1977 66 4255-4262. 

Raman Spectroscopic Study of Rotational and Vibrational Relaxation of CF3H in the Supercritical State... 

Rotational and vibrational relaxation in Na-Na, free jet studied 145 using LIF... 

In molecular fluids, rotational and vibrational relaxation can effect the density fluctuation. It is then necessary to supplement the equations of fluid mechanics with equations describing the molecular relaxation. We shall consider this momentarily. The whole picture developed here must be modified in the neighborhood of the critical point or near a phase transition. The long range correlations discussed in Sections 10.1 and 10.7 then affect the whole structure of the theory. See, for example, the review of Stanley, et al. (1971) and particularly references to the work of Kawasaki cited therein. Some aspects of scattering in the critical region are considered in Sec. (10.7). 

It should be noted that even if the attractive part of the intermolecular potential plays a nonnegligible role in the vibrational relaxation, there is no apparent correlation between rotational and vibrational relaxation rates. As may be seen from the foregoing discussion, ratios may vary by... 

The temperature dependence on the IR absorption and Raman scattering bandwidths of some fundamental modes of Aj, B, and B2 symmetries of thiophene has been investigated in the region 400-1600 cm <81CPH251>. The spectroscopic study was carried out in the liquid phase which requires simultaneous investigation of the bands. Results show that the IR and anisotropic Raman bandwidths increase with increasing temperature and more so in the latter case. The rotational diffusion coefficients obtained from the bandwidths indicate that the rotational and vibrational relaxation phenomena occur simultaneously. The IR and isotropic and anisotropic Raman band profiles of the Aj symmetry mode have also been studied in the liquid phase <81CPH265>. 

Solvation, solute rotation and vibration relaxation, and electron-transfer reactions in room temperature ionic liquids 07ACR1130. 

Initial studies of rotational and vibrational relaxation of atom-molecule systems at cold and ultracold temperatures have mostly focused on van der Waals systems such as He-H2 [19-22], He-CO [23,24], and He-02 [25]. Owing to the importance of some of these systems in astrophysical environments, extensive calculations of low-temperature behavior of rate coefficients have been performed for collisions of H2 [19] and CO [23,24] with both He and He. For both systems reasonably accurate intermolecular potentials have been reported. The initial calculations on the He-H2 system employed the potential energy surface (PES) of Muchnick and Russek (MR) [26]. For He-H2, vibrational excitation of the H2 molecule has adramatic effect on the zero-temperature quenching rate coefficients. As illustrated in Figure 3.1, the vibrational quenching rate coefficients increase by about three orders of magnitude between u = 1 and u = 10 of the H2 molecule [19]. 

Shim, Y, Jeong, D., Manjari, S., Choi, M. Y, and Kim, H. J. 2007. Solvation, solute rotation and vibration relaxation, and electron-transfer reactions in room-temperature ionic liquids. Acc. Chem. Res. 40, 1130-1137. 

Parker, J. G. (1959). Rotational and vibrational relaxation in diatomic gases. Phys. Fluids, 2, 449-462. 

S Okazaki, N Terauchi, 1 Okada. Raman spectroscopic study of rotational and vibrational relaxation of CF3H in the supercritical state. J Mol Liquids 65/66 309, 1995. 

Fig. 12.13. Experimental arrangement and level scheme for measuring collision-induced rotational and vibrational relaxation processes in molecular ground states...

The model used in the previous two sections shows how charged groups maintain their hydration shell at aqueous interfaces and how that was used to understand rotational and vibrational relaxation. The same model can be used for solvation dynamics.We compute the solvation dynamics following the transition (// = 0) (/< = 12D) and the reverse transition n = 12D) - (/t = 0) of a diatomic solute held at different locations in the water liquid/vapor interface and in the water/CCl4 interface. The equilibrium and nonequilibrium correlation functions both approximate a biexponential relaxation. Table 2 summarizes the average relaxation times in picoseconds. 

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