Gyroscopic Effect in Low-Energy Classical Capture of a Rotating Quadrupolar Diatom by an Ion

Abstract

The low-energy capture of homonuclear diatoms by ions is due mainly to the long-range part of the interpartner potential with leading terms that correspond to charge-quadrupole interaction and charge-induced dipole interaction. The capture dynamics is described by the perturbed-rotor adiabatic potentials and the Coriolis interaction between manifold of states that belong to a given value of the intrinsic angular momentum. When the latter is large enough, it can noticeably affect the capture cross section calculated in the adiabatic channel approximation due to the gyroscopic property of a rotating diatom. This paper presents the low-energy (low-temperature) state-selected partial and mean capture cross sections (rate coefficients) for the charge-quadrupole interaction that include the gyroscopic effect (decoupling of intrinsic angular momentum from the collision axis), quantum correction for the diatom rotation, and the correction for the charge-induced dipole interaction. These results complement recent studies on the gyroscopic effect in the quantum regime of diatom-ion capture (Dashevskaya, E. I.; Litvin, I.; Nikitin, E. E.; Troe, J. J. Chem. Phys. 2004, 120, 9989-9997).

Locking of the intrinsic angular momentum in the capture of quadrupole diatoms by ions

“…Indeed, as was found earlier[25], the plots AC s ð& i , Þj ¼0 and FW s ð& i , Þj ¼0 versus & i cross at a certain point, suggesting that all s (& i , , )j ¼0 pass through (or very close to) this point. This conclusion was exemplified by Figures 3 and 4 in [25] for ¼ 0.1 and ¼ 0.25.…”

“…In this way we generalise our earlier work on capture in translational-rotational canonical ensembles [23] and in j-specific translational canonical ensembles [24] of unpolarised collision partners. This also provides more detailed insight into the capture dynamics of polarised diatoms compared to earlier work [25]. The plan of the article is as follows.…”

“…The approximation uses the fact that since j is close to J, the orientation of j is approximately conserved in the space (this approximation combines the sudden limit with respect to the orientation of j and the adiabatic limit with respect to the change of the absolute value of j; it was called in [25] the fly-wheel, FW, approximation) and, therefore, the angle between R and j is approximately equal to the angle between R and J. Identifying with in U PR , we get the FW Hamiltonian in the form:…”

Relocking of intrinsic angular momenta in collisions of diatoms with ions: Capture of H2(j = 0,1) by H2+

“…(2.2) by averaging H over the angle of proper rotation of the diatom in a state with fixed j. 1,2 Then, H PRCl depends on the conjugate dynamical variables (R, P R ) and (ϕ, p ϕ ) where ϕ denotes the precession angle of the vector j about the collision axis and p ϕ is the projection of j onto the collision axis. In addition, H PRCl depends parametrically on the total and intrinsic angular momenta J and j.…”

Mutual Capture of Dipolar Molecules at Low and Very Low Energies. II. Numerical Study

“…For simplicity, we neglect the small correction proportional to d 4 in the square brackets in eq 2. 4 and we rewrite the preceding equations as…”