VARIATION OF MOLECULAR-PROPERTIES WITH VIBRATION-ROTATION

Molecular properties depend on the state of rotation and vibration. As a result of recent experimental developments such a dependence has been detected by several techniques for a variety of molecular properties of a large number of compounds. By expanding the property P as a power series in the reduced normal coordinates it is possible to derive an expression relating P to the state of rotation and vibration. In the present paper this is done for an asymmetric rotor molecule in a vibrational state (v1v2… vn) and a rotational state (Jt). Terms in the expansion of P up to those quartic in the reduced normal coordinates are taken into account. The expression is of the form. where Pe(0) is the value of the property at equilibrium, PJτ, AiJτ and Bij depend on the parameters describing the potential energy surface and the property surface, and a superscript Jτr denotes a dependence on rotational state through the quantities <Jτ|Πα|Jτ> where-Πα denotes the rotational angular momentum about a principal axis of rotation. © 1979 Taylor & Francis Ltd.