Full-dimensional potential energy surface for the H2 + N2 system and quantum scattering calculations of collision-induced rotational energy transfer.

Abstract

A full-dimensional global potential energy surface (PES) for the H2 + N2 system is constructed using the permutation invariant polynomial-neural network method, based on high-level ab initio energy points computed at the CCSD(T)-F12a/AVQZ level. To accurately describe the long-range interactions, a multipole expansion parameterized by ab initio data is incorporated into the PES. Quantum close-coupling scattering calculations are reported for rotationally inelastic transitions in H2 + N2 collisions using the full-dimensional PES. Cross sections for rotational excitation of N2 within a rigid rotor model are found to be in excellent agreement with those obtained using a four-dimensional (4D) PES reported by Gomez et al. [Chem. Phys. Lett. 445, 99 (2007)]. Cross sections for pure rotational quenching of H2, as well as quenching of H2 accompanied by rotational excitation of N2, exhibit dense resonance structures. For collision energies above 2.0 cm-1, the results are in close agreement with those obtained using the 4D PES of Gomez et al., including the positions of the sharp resonances. At lower collision energies, however, noticeable differences appear, indicating a strong sensitivity of the resonance features to the PES in this regime. An accurate simulation of energy transfer in collisions between rovibrationally excited H2 and D2 with N2 can now be addressed using the full-dimensional PES reported in this study.