Molecular beam measurements of the D–H2 potential and recalibration of the reactive cross section

Abstract

Absolute integral cross sections have been measured for D–H2 at primary particle velocities v=7730 m/s and 9580 m/s with a 77 °K target. The number density of target particles was determined with an absolute accuracy of 1% by the method of dynamic expansion. The over-all error in the absolute cross sections is estimated to be about 1.5%. All available measurements of integral cross sections as a function of velocity were used to test literature potentials in a χ2 procedure. A new Born–Mayer–Spline–Van der Waals (BMSV) potential is proposed that is in reasonable agreement with recent ab initio calculations. The potential is also consistent with the differential total cross section measurement of Geddes, Krause, and Fite. This justifies the use of the new potential together with the differential measurements to perform an absolute calibration of the cross section for the D+H2 → HD+H reaction. The calibrated reactive cross section is found to be in reasonable agreement with measured bulk rate constants.