Measurement of the cross section for H+D2→HD(v′=3,j′=0)+D as a function of angle and energy

Abstract

Scattering of the HD(v′=3,j′=0) product from the H+D2 reaction is measured as a function of angle and collision energy from 1.39 to 1.85 eV. The plot of the cross section vs angle and energy is believed to be the first fully experimental plot of its kind reported for this benchmark reaction. Changes in the differential cross section (DCS) are observed in this collision energy range, including a forward-scattering component that peaks at about 1.64 eV and is a strong function of collision energy. This feature has been assigned to result from a barrier resonance, but its full interpretation is presently unsettled. These changes in the DCS do not manifest themselves as variations in the integral cross section (ICS), which varies less than 25% over the energy range measured. Comparisons of the DCSs and the ICS with quantum mechanical calculations show quantitative agreement, although some aspects of the DCS near 1.54 eV are not fully satisfactory.

A quasiclassical trajectory study of the time-delayed forward scattering in the hydrogen exchange reaction

“…11 The temporal and spatial separation of the mechanisms was demonstrated by using the snapshots from Althorpe's quantum wavepacket simulation of the reaction. 5,12 These simulations were able to reproduce time-of-flight data from the experiments of Ayers et al 3 with good agreement; thus, it was concluded that the time delay in the calculations is real. 11 Much of the controversy is focused on the mechanism͑s͒ required for this time-delayed forward scattering.…”

Corroboration of Theory for H + D2 → D + HD (v′ = 3, j′ = 0) Reactive Scattering Dynamics

“…In particular, Ayers et al 10 were only able to observe two to three distinct angles in the forward-scattered hemisphere (θ < 90°), whereas the present experiment resolves as many as eight angles in that range. This fact allows us to observe the shapes of the forward-scattered peaks that Monks et al 13 attributed to glory scattering arising from the interference of nearside and farside partial waves.…”

“…[8][9][10] At lower collision energies, the distribution is mainly side scattered; as the collision energy increases, this peak shifts toward forward scattering, creating a so-called "E-θ ridge", while side-and back-scattered E-θ ridges grow in concurrently. Oscillations in these ridges in the forward 11 and backward 12 regions of the DCS have been attributed to quantized bottleneck states.…”

Simultaneous Measurement of Reactive and Inelastic Scattering: Differential Cross Section of the H + HD → HD(v′, j′) + H Reaction

“…In addition, highly internally excited HD(ν , j ) products, particularly the HD(ν = 4, j ) manifold, exhibit a more isotropic angular distribution [9][10][11][12]. The deuterium atom Rydberg tagging technique was employed in the study of an H + HD → H 2 (ν , j ) + D hydrogen exchange variant [13,14], where the forward peak has been attributed to the well-known time-delayed mechanism observed in the H + D 2 → HD(ν = 2, 3, j = 0) + D reaction [8,[15][16][17][18][19]. Finally, Kliner et al [20] have studied the H + para-H 2 → ortho-H 2 (ν , j ) + H reaction.…”