VIBRATIONAL ENERGY TRANSFER IN LIQUIDS

Abstract

Vibrational relaxation times in liquids can range over 12 orders of magnitude: Our own $work^{1}$ on liquid nitrogen yields a $V \rightarrow T$ relaxation time of $\sim$ 1 sec while for $CH_{3}CCl_{3}$ and other small organic molecules $V \rightarrow V$ relaxation is $\sim 10^{-1}{2}$ $sec.^{2}$ These and other data appear consistent with a sample $model^{3}$ which essentially treats the liquid as a high density gas where isolated binary collisions cause vibrational relaxation. Further tests of the binary collision model are most convincing from measurements of simple liquid systems. We have Just measured the vibrational relaxation time of liquid $N_2$ doped with $CH{4}$, CO and $O_{2}$ at $77^\circ K$ by pulsed laser and spectroscopic techniques. Rate constants for $V \rightarrow V$ energy transfer from $N_{2}$ to the dopants and $V \rightarrow T$ relaxation times have been obtained. These rates are all consistent with the binary collision model.