Rovibrationally Resolved Photodissociation of AlH via Excited Electronic States

Abstract

Abstract Photodissociation processes are of great importance for modeling interstellar chemistry since it is a key destruction pathway for small molecules. Here, we present a detailed ab initio study of AlH photodissociation. Potential energy curves and transition dipole moments for AlH are obtained by using the internally contracted multireference configuration interaction method and the Davidson correction (icMRCI+Q), as well as the aug-cc-pV6Z basis set. Except for the X1Σ+, A1Π, and C1Σ+ states, five higher excited 31Σ+, 21Π, 31Π, 41Σ+, and 41Π states are considered in order to investigate the photodissociation pathways in the vacuum ultraviolet region. State-resolved cross sections of transitions from all the rovibrational levels of the X1Σ+ state to seven singlet excited states are computed for photon wavelengths ranging from 500 Å to the threshold. Photodissociation cross sections in local thermal equilibrium (LTE) are obtained at temperatures from 500 to 10,000 K. Applications of the LTE cross sections to compute photodissociation rates in the standard interstellar radiation field and blackbody radiation field are briefly discussed.