Isotopic vibration--vibration energy exchange in hydrogen chloride molecules at low temperatures

The temperature dependence of the isotopic VV energy exchange process H35Cl(1)+H37Cl(0)→H35Cl(0)+H37Cl(1) has been studied in the temperature range of 10--1000 K. As temperature increases the VV probability increases between 10--30 K, but above 50 K it decreases rapidly. The appearance of two regions of different temperature dependence has been discussed in terms of the local translational motion which causes the vibrational modes of two colliding molecules to couple efficiently in the presence of strong attractive interaction