Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of ²⁴MgH

¹ School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, PR China
e-mail: yjcphysics@163.com; song-bin.zhang@snnu.edu.cn
² School of Physics, Henan Normal University, Henan 453000, PR China
³ College of Physics, Jilin University, Jilin 130012, PR China
⁴ Institute of Applied Physics and Computational Mathematics, Beijing 100088, PR China
⁵ Center for Applied Physics and Technology, Peking University, Beijing 100084, PR China

Received: 2 November 2023
Accepted: 17 February 2024

Abstract

Aims. A series of high-precision calculations for the electronic structure of MgH have been reported in the past two decades; however, most of them d not include the core-valence correlation and still exhibit distinct differences. Furthermore, the latest high-precision results have not been applied to the studies of photodissociation dynamics. The primary motivations of this paper are to calculate a more precise electronic structure of MgH consering a core-valence correlation and to prove the photodissociation cross-sections.

Methods. The electronic structure of MgH is investigated by multi-reference configuration interaction calculations with Davson correction (MRCI+Q). We performed two different sets of calculations to investigate the core-valence correlation and, as a result, obtained accurate potential energy curves (PECs) and transition dipole moments (TDMs). An extrapolation procedure was also employed to eliminate the error of basis set. Then, the photodissociation cross-sections were calculated using high-precision PECs and TDMs.

Results. The PECs and TDMs of the five lowest doublet electronic states, X²Σ+, B′²Σ+, E²Σ+, A²Π, and C²Π, are obtained from calculations including core-valence correlation, termed as CV-MRCI, while PECs of the ten lowest doublet states and three quartet states are also obtained from NCV-MRCI calculations without core-valence correlation. The spectroscopic constants and band oscillator strengths are also proved with high precision levels. The equilibrium R_e and vertical excitation energy T_e are only 0.1% different from the measurements. Based on the CV-MRCI results, the rovibrationally resolved photodissociation cross-sections for transitions from X²Σ+ to the other four states, as well as the total local thermodynamic equilibrium cross-sections for temperatures up to 10000 K, are calculated.