Vibrational distributions of KrF(B) and XeCl(B) produced from ionic-recombination reactions of Kr+(2P3/2)+SF−6 and Xe+(2P3/2)+Cl−+He

Abstract

Nascent vibrational distributions of KrF(B) and XeCl(B) resulting from Kr+(2P3/2)+SF−6 and Xe+(2P3/2)+Cl−+He reactions have been determined by a spectral simulation of the bound–free B–X transition. The vibrational distribution of KrF(B) has a maximum at v′=0 and decreases exponentially with increasing v′. It is in reasonable agreement with the statistical prior distribution in which all vibrational and rotational degrees of freedom in the products are taken into consideration. It is therefore concluded that the Kr+(2P3/2)+SF−6 reaction proceeds through a long-lived [Kr+(2P3/2)SF−6] intermediate. The vibrational distribution of XeCl(B) decreases linearly with increasing v′. It is more vibrationally excited than the prior distribution, indicating that a (Xe+Cl−He) intermediate decomposes before a complete energy randomization. The average fractions of total available energy deposited into vibrational energy of the excimer 〈fv〉 are estimated to be 5.8% for the Kr+(2P3/2)+SF−6 reaction and 16% for the Xe+(2P3/2)+Cl−+He reaction. On the basis of the conservation of total angular momentum during the reactions, one reason for the low 〈fv〉 values is attributable to a very large impact parameter in the entrance channels, which requires a significant transfer of potential energy into rotational energy of the excimer and kinetic energy of the products. The other reason is a significant transfer of potential energy into kinetic energy because of the acceleration of the positive and negative ions due to a strong Coulombic attractive force.