A method to obtain meV-collision-energy resolution in scattering studies:: application to the H+D2→HD(ν′=0,j′)+D(θrel<80°) reaction at Erel=1.275±0.011 eV

Previous work has shown that a one-to-one correspondence between the speed and scattering angle of state-selected AB products of the gas-phase reaction sequence AX + h nu --> A + X, A + BC --> AB + C can be exploited to measure state-to-state differential cross-sections without resorting to molecular beams. Here we demonstrate a modification to this photoinitiated technique that enables for the observation of the forward- and backward-scattered products of a reaction with improved collision energy resolution. This modification is demonstrated by its application to the measurement of the j' dependence of the yield of forward-scattered HD product in the reaction H + D-2 --> HD(nu' = 0, j') + D at 1.275 +/- 0.011 eV, The data obtained are consistent with quantum scattering calculations that do not include the geometric phase. (C) 1999 Elsevier Science B.V. All rights reserved.