Collision-Induced Fine-Structure Transitions of Hg(6³P₁ → 6³P₀) with N₂ and CO. 1. Initial Orbital Alignment Effects

Abstract

Effects of initial orbital alignment have been investigated for the fine-structure transitions of Hg(63P1 → 63P0) induced by collisions with N2 and CO in a crossed molecular beam experiment using a laser pump−probe technique. The orbital alignment effects are observed by monitoring the population of the product Hg(63P0) as a function of polarization angle (θ) of the linearly polarized pump laser, which prepares the Hg(63P1), relative to the direction of the initial relative velocity vector. The alignment effects in this study are represented by an asymmetry parameter β in the angle-dependent cross section, σ(θ) = σ0[1 + βP 2(cos θ)]. The measurement for Hg−N2 exhibits a large alignment effect with β = −0.50(7), but for Hg−CO a small effect with β = −0.20(6). Both processes show preference for perpendicular excitation of the pump laser with θ = 90°. The nonadiabatic transitions responsible for this fine-structure process therefore occur mainly via the B̃(23A‘ + 23A‘ ‘) molecular electronic state and not via the Ã(13A‘) state for Hg−N2. In contrast, the small effect for Hg−CO indicates that the contribution from the nonadiabatic transition via the à state is comparable with that via the B̃ state for Hg−CO.

COHERENTNONLINEARSPECTROSCOPY: From Femtosecond Dynamics to Control

“…These studies are challenging because they involve a larger number of chemical species that can interfere with the signals, and the concentration of collision partners is very small. The studies presented on the photoassociation of mercury atoms to form the excimer molecule are an important step in this direction (96,124,126,154,155,256,257).…”

Collision-Induced Fine-Structure Transitions of Hg(63P1 → 63P0) with N2 and CO. 2. Translational Energy Dependence

“…A. Overview. The experimental arrangement used in this study is similar to that described in the preceding paper (referred to as paper 1 in this article) and only a brief description will be given here. Experiments were performed under crossed-beam and beam-gas conditions combined with a laser pump−probe method.…”

Energy dependence of the intramultiplet mixing cross section in Hg–N2 collisions: Conical intersection mechanism, indication at tunneling and interference

“…Because of this, we do not believe that at the present stage one should go beyond the first order treatment and introduce more parameters. It is clear that more ab initio information on the vibronic PES is needed before one can attempt to provide a sound interpretation of other, more complicated, experimental data such as collisions with polarized Hg* atoms 11 and rotationally hot nitrogen molecules. 12…”

“…The non-physical (but integrable) divergence of p ¯LZ near e ¼ 1 is believed to have a negligible effect on s s LZ . Expression (11) can be used for the calculation of the cross section for a non-spherically symmetrical case in the so-called rotationally-sudden (RS) approximation. This approximation replaces an anisotropic collision problem by a set of isotropic problems parameterized by different, assumed constant, angles y with subsequent averaging over all the angles.…”

“…Only recently, a new information has emerged from the far-wing excitation study 10 and beam-beam and beam-gas study of the fine-structure transitions of Hg*( 3 P 1 ! 3 P 0 ) in collisions with N 2 and CO. 11,12 In particular, the translational energy dependence of the cross section for the transition 3 P 1 ! 3 P 0 of mercury in collisions with rotationally cold N 2 molecule was measured.…”