Bimodal distribution of BaI vibrational states from the reaction Ba+CF3I

Abstract

Unrelaxed vibrational state distributions of BaI product are reported for the reaction Ba+CF3I→BaI+CF3, using laser-induced fluorescence. Product state distributions were measured using a beam–gas arrangement and a primitive angular distribution was also determined using a crossed-beam configuration. The BaI vibrational distribution is bimodal with a low vibrational component peaking at v∼27 and a high vibrational component peaking at v∼47. At least 75% of the BaI is produced in the high vibrational levels. The angular distribution indicates that the BaI formed in the high vibrational states is scattered in a forward direction with respect to the Ba beam, but the low vibrational component is not sharply forward scattered. The Ba+CF3I reaction is thought to proceed by two mechanisms: (1) attack in the direction of I–CF3, leading to BaI product formation with low vibrational energy; and (2) attack in the direction of CF3–I, either by initial attack of the CF3 end followed by migration or by attack of the I end at large impact parameters, leading to BaI product formation with high vibrational energy.