Differential cross sections for H+D2→HD(v′=1, J′=1,5,8)+D at 1.7 eV

Abstract

A 1:4 mixture of HBr and D2 is expanded into a vacuum chamber, fast H atoms are generated by photolysis of HBr ca. 210 nm, and the resulting HD (v′, J′) products are detected by (2+1) resonance-enhanced multiphoton ionization (REMPI) in a Wiley–McLaren time-of-flight spectrometer. The photoloc technique allows a direct inversion of HD (v′, J′) core-extracted time-of-flight profiles into differential cross sections for the H+D2→HD(v′=1, J′=1,5,8)+D reactions at collision energies ca. 1.7 eV. The data reveal a systematic trend from narrow, completely backward scattering for HD (v′=1, J′=1) toward broader, side scattering for HD (v′=1, J′=8). A calculation based on the line of centers model with nearly elastic specular scattering accounts qualitatively for the observations.