Effect of kinetic and electronic energy on the reactions of iron(1+) with hydrogen, deuterium hydride, and deuterium: state-specific cross sections for Fe+(6D) and Fe+(4F)

Abstract

Reactions of atomic iron ions with H/sub 2/, HD, and D/sub 2/ have been examined by using guided ion beam mass spectrometry. Individual reaction cross sections for the ground and first excited electronic states of Fe/sup +/ are determined by utilizing three different ion sources. The ground state, Fe/sup +/(/sup 6/D), is found to be relatively unreactive and, in reaction with HD, greatly favors production of FeD/sup +/. In contrast, the first excited state, Fe/sup +/(/sup 4/F), reacts efficiently and forms approx. =4 times as much FeH/sup +/ as FeD/sup +/ in reaction with HD. This disparate behavior is compared with that of their atomic transition-metal ions and is explained by using simple molecular orbital concepts. The results are analyzed to yield a bond dissociation energy at 0 K for FeH/sup +/ of 2.12 +/- 0.06 eV (48.9 +/- 1.4 kcal/mol).