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

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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.