Molecular-Beam Kinetics: Reactions of Na with CH3I, Br2, and ICl

Abstract

Crossed-beam studies have been made of the reactions of Na with CH3I, Br2, and ICl. An approximate kinematic transformation of the measured laboratory angular distributions to the center-of-mass coordinate system yields distributions of the recoil angle for elastic and reactive scattering and estimates of the product recoil energies and total reaction cross sections, Qr. The results are qualitatively similar to those found in previous beam studies of the reactions of K, Rb, and Cs and are consistent with the early Polanyi flame experiments. As compared with the analogous K systems, the Na reactions exhibit the following properties: (1) smaller values of Qr (approximately 5, 90, and 100 Å2 for CH3I, ICl, and Br2, respectively); (2) most of the reaction exothermicity still appears as product excitation for Br2 and ICl, whereas a considerably larger fraction appears as recoil energy for CH3I; (3) the wide-angle nonreactive scattering falls off less rapidly; and (4) the Br2 and ICl stripping reactions produce more backward scattered product. These features are consistent with the electron-jump model for alkali atom reactions.