Crossed molecular beams study of the reaction D + H2 → DH + H at collision energies of 0.53 and 1.01 eV

This paper reports the first product differential cross section (DCS) measurements for the D+H2→DH+H reaction as a function of laboratory (LAB) scattering angle with sufficient resolution to resolve product DH vibrational states. Using a D-atom beam produced by the photodissociation of DI at 248 nm, product velocity and angular distributions were measured at 12 LAB angles at a nominal collision energy of 0.53 eV and at 22 LAB angles at a nominal collision energy of 1.01 eV with a crossed molecular beams apparatus. After correction of the raw product time-of-flight (TOF) spectra for modulated background, a comparison with recent exact quantum mechanical scattering calculations was made using a Monte Carlo simulation of the experimental conditions. The simulation showed that although the theoretical predictions agree qualitatively with the measurements, some significant discrepancies exist. Using the Monte Carlo simulation, a best-fit set of DH(v,j) DCS’s which showed good agreement with the measurements was found. At the detailed level of the state-to-state DCS, significant differences were observed between theory and experiment for rotationally excited DH(v, j) products. The discrepancies observed suggest that some regions of the current ab initio H3 potential energy surfaces, particularly the bending potential at high energies, may need further examination.