Stereodynamics of rotational energy transfer in NO(A²Σ⁺) + Kr collisions

Abstract

Crossed molecular beam scattering and quantum scattering calculations reveal the dynamical mechanisms underlying rotationally inelastic scattering for NO(A) + Kr.

Differential Cross Sections for Pair-Correlated Rotational Energy Transfer in NO(A2Σ+) + N2, CO, and O2: Signatures of Quenching Dynamics

“…This conical intersection will not be accessible at our experimental collision energy (790 cm –1 ), and we therefore expect the scattering of NO­(A) + N 2 here to only include A-state RET. Although there is no full van der Waals (vdW) potential available for this system, it has been well-established that the minimum is in a linear ON-N 2 geometry, with a most recently reported well depth of −335 cm –1 . , It is therefore perhaps unsurprising that we see such strong forward scattering, as our extensive previous experiment and quantum scattering calculations on NO­(A) + Rg RET has demonstrated that even relatively modest-depth attractive wells (e.g., −93 cm –1 for NO­(A)-Ar) that are localized at the N-end of NO are efficient at inducing moderate Δ N ′ with strong forward scattering. ,, Indeed, the similarity of the forward scattering peaks in NO­(A) + N 2 to those observed in NO­(A) + Ar is perhaps an indication that the NO­(A)-N 2 minimum is, like that in NO­(A)-Ar, relatively tightly localized; the ON-Ar minimum ranges from approximately 0 to 40°.…”

“…The experimental apparatus has been described in detail before, and we only give an overview here. − , In brief, two pulsed molecular beams were crossed at right angles in the center of a stack of velocity-map ion-optics. A pulse of UV radiation at ≈226 nm, linearly polarized perpendicular to the molecular beam plane and resonant with the Q 1 (0.5) line of the NO­(A 2 Σ + – X 2 Π) (0,0) band, was used to excite NO molecules in one molecular beam to the NO­(A, v = 0, N = 0, j = 0.5) state.…”

“…We used this peeling methodology to fit the experimental data from collisions with O 2 and CO, which is presented here for the first time, and to fit the previously reported N 2 data over the entire angular range for direct comparison. As noted above, triangular basis functions spaced by 5° were used to represent the DCS, as these localized basis functions have been demonstrated to be well suited for the fitting of images with strong forward scattering . For each collider, 6 final internal energies were included, reported in Table .…”

“…Basis functions were generated with the assumption of 5 different collider final internal energies, based on those used in the analysis of data acquired from scattering with N 2 (vide infra), namely, 0, 84, 144, 220, and 312 cm –1 . The angular distributions have been described by evenly spaced triangular functions, as introduced in our recent study of NO­(A) + Kr stereodynamics . These functions are well suited to the fitting of strongly forward scattered data and have been used in fitting the data from collisions with N 2 , O 2 , and CO presented in this paper.…”

“…We have shown that NO­(A 2 Σ + , v = 0, j ) initial levels can be prepared in the scattering region of a crossed molecular beam apparatus, followed by state-specific detection of the rotationally inelastically scattered NO­(A, v = 0, N ′) products using velocity-map imaging, all within the ca. 200 ns fluorescence lifetime of NO­(A). − Using this methodology, we have extensively studied the dynamics of NO­(A) + Rg collisions, determining both state-to-state DCSs and product polarization-dependent DCSs for collisions with He, Ne, Ar, and Kr. − We have shown how the comparison of these detailed experimental measurements to close-coupled quantum scattering calculations may then be used as a sensitive test of the accuracy of the ab initio potentials …”