Absorption of Ultrasound in Organic Crystals.

In this paper we present our expression for the transition rate for a molecule in an organic crystal to absorb three phonons of lattice energy into the lowest frequency molecular vibrational mode Ol transition. Our model is a three dimensional simple cubic lattice with nearest neighbor central and noncentral forces between molecules situated at the lattice sites. After making some approximations we compare our expression with the transition rate determined from ultrasonic experiments on benzene, p-dichlorobenzene1 carbon tetrachloride, and cyclohexane and discuss the results, We also point out the improvement Our expression offers over the transition rate derived by Liebermann and used by other investigators.