Effect of vibrational excitation on the molecular beam reactions of Ca and Sr with HF and DF

Abstract

The reactions of Ca and Sr with HF and DF are studied using a beam–gas configuration as a function of reagent and product vibration to obtain state‐to‐state reaction rates. A beam of alkaline earth metal atoms enters a scattering chamber containing hydrogen fluoride. The HF and DF reagents are pumped from v=0 to v=1 by a pulsed HF or DF laser; the alkaline earth monofluoride products are detected by a pulsed tunable probe laser. The product internal state distribution is determined from the laser excitation spectrum. While no products could be detected for reactions with DF(v=1) or DF(v=0), the rate constant for the Ca and Sr reactions with HF(v=1) are both at least four orders of magnitude larger than the reactions with HF(v=0). The implications of these results on bond energies and the fate of the excess energy of reaction are discussed.