Schwartz-Slawsky-Herzfeld

It is this result which is the basis of the Schwartz-Slawsky-Herzfeld (SSH) calculation of vibrational relaxation times in gases [29]. In subsequent work, Schwartz and Herzfeld [30] extended Zener s approach to a collision in three dimensions, and developed a scheme for evaluating the potential parameter / in terms of the popular 6 12 Lennard-Jones potential function... 

The Landau-Teller formula was generalized in SSH theory (Schwartz, Slawsky, Herzfeld, 1952) and, in particular, by Bilhng (1986). A semi-empirical numerical relation... 

Quantitative calculations of the rate constants ky y for vibrational transitions are relatively easy if the diatomic molecules are simulated by a harmonic oscillator interacting isotropically with the impinging atom (the so-called breathing sphere or the SSH (Schwartz-Slawsky-Herzfeld) model [3, 192, 339, 395] based on the one-dimensional Landau-Teller model [261]). Then the mean transition probability Py y per one gas-kinetic collision calculated to the first order of the semiclassical perturbation treatment is... 

Fig. 19. Temperature dependence of the rate constant of process COf (vg) + Ng -> COg + Nf [471]. Curve 1 refers to experimental results, curve 2 was calculated theoretically according to the Schwartz-Slawsky-Herzfeld theory and curve MN corresponds to the Sharma-Brau theory [434]...

To date, the theoretical results most useful for the discussion of collision induced intramolecular energy exchange have come from grossly oversimplified models of the collision. The most widely used of these models was proposed by Schwartz, Slawsky, and Herzfeld (SSH) and later modified by Tanczos and Stretton. ... 

In most of the numerous theoretical treatments of V-T energy transfer in non-chemical collisions, a simplified intermolecular potential is assumed for example, angular anisotropy is usually ignored. Furthermore, the coupling between the relative translational motion of A and BC and the vibration of BC is assumed to be weak. In the theory of Schwartz, Slawsky, and Herzfeld, -" for example, only collinear collisions are treated explicitly and A is assumed to interact only with B, so that the potential is... 

A simple well-known extension of a collinear Landau-Teller model is provided by the breathing sphere (BSP) model of Schwartz, Slawsky and Herzfeld [13] which fully retains the Landau-Teller exponential factor. More consistent treatment, which approximately takes into account the anisotropic character of the atom-molecule interaction, is based on the so-called infinite order sudden approximation (lOSA) [14] with respect to rotational transitions that accompany the vibrational transition. Within this approximation the rotation of the relaxing molecule plays the role of a spectator, which insignificantly modifies the exponent in Eq. (8) through quite unimportant redefinition of a. If, in addition, the quasiclassical correction to the semiclassical Landau-Teller exponent is small and the effect of the attractive part of the potential is weak, one can write the following simple expression for the deactivation rate constant within BSP or lOSA approximation ... 

Schwartz R N, Slawsky Z I and Herzfeld K F 1952 Calculation of vibrational relaxation times in gases J. Chem. Phys. 20 1591-9... 

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