Rotational temperature dependence of the branching ratio for the reaction of Kr⁺(²P_3/2) ions with HD

Branching ratios for the reaction of Kr⁺(²P _3/2) with HD, which produces KrH⁺ and KrD⁺, have been measured in a variable temperature-selected ion flow drift tube apparatus as a function of average center-of-mass kinetic energy 〈KE _cm〉 at two temperatures, 93 and 300 K. At the lowest energy employed, 〈KE_cm〉 = 0.012 eV, the KrD⁺ channel is favored, and its contribution decreases with increasing kinetic energy. The data are in agreement with previous measurements. The dependence of the branching ratio on the rotational temperature of HD is derived from the data. The rotational temperature dependence is small and appears to be in the opposite direction to the kinetic energy dependence, i.e., increasing rotational energy appears to decrease the fraction of KrH⁺ produced. The data are compared with models and with the rotational temperature dependence found for the reaction of O⁺ with HD. Rate constants for the reactions of Kr⁺(²P_3/2) with H₂ and HD were measured at 300 K and no drift field and found to be 2.8±0. 7×10^-10 cm³ s^-1 and 4.0±1. 0×10^-10 cm³ s^-1, respectively. The latter number supports the previous beam measurement and disagrees with a previous selected ion flow tube result.