Rovibrationally resolved direct photodissociation of MgO

Abstract

ABSTRACT The photodissociation process of magnesium oxide (MgO) may be a main source of the magnesium atom in planetary exospheres due to the impact events on planets. In this work, we calculated the state-resolved cross-sections of the photodissociation of MgO for the transitions from the full range of rovibrational levels of the X1Σ+ and a3Π states, where the photon wavelength ranged from 50 to 5000 nm. The applications of the state-resolved cross-sections to the local thermodynamic equilibrium (LTE) conditions were also investigated for the temperatures ranging from 500 to 10 000 K. Based on the calculated LTE cross-sections, the photodissociation rates in the interstellar, solar, and blackbody radiation fields were obtained as well. The rates in all studied radiation fields increase with the temperature increasing and are dominated by the e3Σ− ← a3Π and F1Π ← X1Σ+ transitions. The knowledge of the photodissociation cross-sections and rates of MgO plays a key role in the investigations of the chemical behaviour of the alkaline-earth element Mg in planetary exospheres, atmospheres of cool stars, and envelopes of evolved stars.