An effective Golden Rule decay rate expression for quasidissipative IVR processes

An effective Golden Rule rate expression is derived for the intramolecular vibrational decay dynamics of an initially prepared nonstationary state in an isolated polyatomic molecule. It is shown that the decay rate of the initial state depends on the properties of those states which are directly coupled to the initial state. In many cases, there may be a suppression of the exponential decay rate. An explanation for the insensitivity of some experimental C–H overtone linewidths with increasing excitation energy is also proposed.