The collisional depolarization of Σ2S+1 radicals by closed shell atoms: Theory and application to OH(A Σ2+)+Ar

Abstract

Classical and quantum mechanical expressions for the j-j(') vector correlation (also referred to as the rotational tilt) are presented for the situation in which the initial and final relative velocity directions are unresolved. The quantum mechanical expressions are compared with previous descriptions in the literature. It is shown that in the case of (2S+1)Sigma radicals in collision with closed shell species, a tensor opacity formalism can be employed in quasiclassical trajectory calculations to provide classical estimates of both open shell spin-rotation state and nuclear hyperfine state changing (or conserving) cross sections. Polarization parameters are also obtained from the same formalism. The method is applied to calculations on the OH(A (2)Sigma(+))-Ar system using a recently developed potential energy surface. The results of both the closed and open shell quasiclassical trajectory calculations are found to compare favorably with those from close-coupled closed and open shell quantum mechanical scattering calculations. The accompanying paper provides an experimental test of these calculations and of the potential energy surface they employ.

Elastic depolarization and polarization transfer in CN(A2Π,v= 4)+Ar collisions

“…The nuclear spin is expected to be a spectator in the collision, as observed in OH(A)+Ar collisions. 23,25,34 After collision, I…”

“…Γ , in terms of the microscopic rates for transfer from an initial state j jm to some final state ' ' j m j 34,36,70 (note that in what follows, Γ will be used to represent rates whilst, k will represent rate constants):…”

“…23,25,34 As noted earlier in the discussion, this OH(A)-Ar PES has a deep attractive well, which is highly anisotropic, and provides efficient elastic depolarization for a wide range of initial j.…”

“…17,[19][20][21][22][23]33 Comparison with full quantum scattering calculations on accurate ab-initio PESs has helped to unravel the influence of different parts of the PES on RET and elastic depolarization. Brouard and co-workers have used an independent technique, Zeeman quantum beat spectroscopy, to study elastic and inelastic depolarization in the OH(A)-Ar system, [23][24][25]34 and most recently NO(A 2 Σ + )-Ar/He. 35 For OH(A), excellent processes.…”

Model Analysis of Rotationally Inelastic Ar + H2O Scattering in an Electric Field

“…6,7,8 Molecules colliding within a planetary atmosphere or in the interstellar space are commonly subjected to magnetic and radiative fields, but the effects such fields may exert on their collision dynamics have so far received little attention. 9,10,11 However, since external fields offer the means to control collision dynamics -either coherently, 12 or via the steric effect, 13 or by tuning the energy levels, especially those of trapped molecules 14 -the study of collisions in fields has been gaining ground recently.…”