Quantum mechanical close-coupling calculations have been used to obtain fully quantum state-resolved differential cross sections and opacity functions for the rotationally inelastic collisions of with He at collision energies of 63 and using the most recent ab initio potential energy surfaces of Kłos et al. [J. Chem. Phys. 112, 2195 (2000)]. Double peaks observed in the -doublet resolved differential cross sections are shown to be related to the presence of analogous peaks in the corresponding opacity functions. These structures can be linked directly to a specific expansion term in the potential, and reflect the fact that NO is not quite homonuclear.
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We label the -doublet levels or according to whether the index is or , respectively (Ref. 14).
Equations (1) and (2) implicitly assume that the NO internuclear distance is frozen at its equilibrium value.
Because upward virtual transitions to level involve either fewer steps or steps coupled by lower (and generally larger) potential expansion terms than downward virtual transitions into , the term seems to induce upward virtual transitions more strongly than downward ones.
