Differential cross sections for H+D-2 -> HD(v(')=1, J(')=1,5,8)+D at 1.7 eV

A 1:4 mixture of HBr and D-2 is expanded into a vacuum chamber, fast H atom s are generated by photolysis of HBr ca. 210 nm, and the resulting HD (v(') , J(')) products are detected by (2+1) resonance-enhanced multiphoton ioniz ation (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+D-2-->HD(v(') =1, J(')=1,5,8)+D reactions at collision energies ca. 1.7 eV. The data reve al 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 c alculation based on the line of centers model with nearly elastic specular scattering accounts qualitatively for the observations. (C) 1999 American I nstitute of Physics. [S0021-9606(99)01527-5].