A vibrational state-selected study of the reaction H+2(v′0)+H2(v′′0=0)→H+3+H using the tandem photoionization mass spectrometry and radio frequency ion guide methods

Abstract

A new ion–molecule rection apparatus, which consists of a photoionization source, a tandem mass spectrometer, and a radio frequency octopole reaction cell is described. Using a quadrupole mass filter to reject H⁺₃ background ions formed at the photoionization source, absolute total cross sections for the reaction H⁺₂ (v^’₀) +H₂ (v^’₀ =0)→H⁺₃ +H, have been measured as a function of the vibrational state of reactant H⁺₂, where v^’₀ =0–4, over the center‐of‐mass collision energy (E_c.m.) range of 0.04–15 eV. The experimental results are compared with phenomenological cross sections obtained in previous single gas cell studies, the quasiclassical trajectory calculations of Stine and Muckerman, and the recent similar calculations of Eaker and Schatz. The absolute total cross sections measured for v₀ =0 and 3 at E_c.m. =0.5, 1, 3, and 5 eV are found to be in agreement with ‘‘trajectory surface hopping’’ calculations which include nonadiabatic surface hopping throughout the reaction.