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Physical Review A

Spin-rotation interaction in cold and ultracold collisions of N2+(Σ+2) with He3 and He4

Grégoire Guillon, Thierry Stoecklin, A. Voronin

Published May 31, 2007• 15 citations
Publisher

Abstract

In a recent work we compared spin-free collisions of $\mathrm{N}_{2}{}^{+}$ with $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ using a newly developed potential energy surface. We found that such collisions exhibit a strong isotope effect in the ultracold regime. In the present study we consider the role of the spin-rotation interaction in cold $\mathrm{He}\text{\ensuremath{-}}\mathrm{N}_{2}{}^{+}$ collisions. We find that our spin-free vibrational quenching cross sections are not affected. Conversely, the cross sections for rotational quenching are strongly modified in the ultracold regime and exhibit resonance structures which are analyzed. These structures, which are not observed when the spin-rotation interaction is omitted, are shown to be due to the Feshbach resonances associated with the nonconservation of parity.

DOI
10.1103/physreva.75.052722

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A quantum-mechanical investigation of the vibrational deactivation of ${}^{14}{\mathrm{N}}_{2}(\ensuremath{\nu}=1,{j}_{\mathrm{rot}}=j)$ in the ultracold collisions with 3He{}^{3}\mathrm{He}3He atoms is presented. Ab initio potential-energy calculations are carried out at BCCD(T) level and a global three-dimensional potential-energy surface is obtained by fitting ab initio points within the reproducing kernel Hilbert space method. Close coupling scattering calculations are performed at collision energy ranging from ${10}^{\ensuremath{-}6}$ to 2000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. It is shown that the potential-energy surface supports a series of shape and Feshbach resonances. Their influence on the behavior of elastic and inelastic cross sections and quenching rate coefficients is discussed. It is demonstrated that, similar to the ${\mathrm{H}\mathrm{e}\ensuremath{-}\mathrm{O}}_{2}$ system, the rate coefficients exhibit three different regimes: Wigner regime at very low temperatures, van der Waals regime at intermediate temperatures due to series of resonances, and the usual rovibration--translation energy transfer regime at high temperatures.
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