An accurate many-body expansion potential energy surface for AlH 2 (2 2 A') and quantum dynamics in Al( 3 P) + H 2 ( v 0 = 0-3, j 0 = 0, 2, 4, 6) collisions.

An accurate potential energy surface is constructed for the excited state of AlH 2 by fitting extensive ab initio points calculated at the multi-reference configuration interaction level based on aug-cc-pV( Q +d)Z and aug-cc-pV(5+d)Z basis sets. All the calculated energies are corrected via the many-body expansion method and extrapolated to the complete basis set limit. The various topographic features of the new potential energy surface are investigated to demonstrate the correct behavior of Al( 3 P) + H 2 (X 1 Σ g + ) and AlH(a 3 Π) + H( 2 S) dissociation limits. By employing the time-dependent wave packet approach, the integral scattering cross-sections obtained from the Coriolis coupling calculation and the centrifugal sudden approximation, respectively, are compared in detail and show that the former has a higher effect on the reaction. Moreover, the thermal rate constants for Al( 3 P) + H 2 ( v 0 = 0-3, j 0 = 0, 2, 4, 6) in the temperature range of 0-5000 K are calculated, thereby providing insights into the influence of ro-vibrational quantum numbers on the thermal rate constants.