Product internal-state distribution for the reaction H+HI→H2+I

Abstract

We have measured the nascent H2(v, j) product-state distribution from the H+HI→H2+I abstraction reaction. Laser photolysis of HI at 266 nm generated translationally hot H atoms with center-of-mass collision energies of 1.61 and 0.68 eV in the ratio 64:36. Quantum-state-specific detection of the molecular reaction product was accomplished via (2+1) resonance-enhanced multiphoton ionization and time-of-flight mass spectrometry. The H2 is formed with a high degree of internal excitation, including a vibrational population inversion between v=0 and v=1. Our product-state distribution agrees closely with that of Aker, Germann, and Valentini where comparison is possible. Rotational population distributions derived from the quasiclassical trajectory calculations of González and Sayós are generally too cold, whereas those of Aker and Valentini nearly reproduce the experimental distributions. Both calculations fail to predict, however, the observed vibrational inversion.