Ab initio calculations on potential energy curves and radiative lifetimes for the band systems A2Π–X2Σ+ of magnesium monohalides MgX (X = F, Cl, Br, I)

•The first excited state of MgX (F, Cl, Br, and I) has been studied by high-level MRCI wavefunctions.•The calculations include Davidson modification and scalar relativistic correction.•The transition properties are evaluated and in good agreement with measurement.

Ab initio calculations on potential energy curves (PECs), spectroscopic constants, transition dipole moments, radiative transition probabilities and lifetimes for the ground state (X2Σ+) and the first excited state (A2Π) of MgX (X = F, Cl, Br, I) molecules are determined by high-level internally contracted multi-reference configuration interaction (ic-MRCI) method. In order to improve the calculation, the Davidson modification (+Q) and scalar relativistic correction are included. The present results show that most of spectroscopic constants are in accordance with the measurements, the equilibrium internuclear distance Re increases while the other spectroscopic constants reduce along with the increasing of the atomic number of the halogen from F to I. Diagonal vibrational transitions are found to be dominant for the A2Π→X2Σ+ system of MgX molecules. The corresponding radiative lifetimes of ν′ = 0 are computed to be 7.24, 9.98, 18.94 and 22.72 ns for MgF, MgCl, MgBr, and MgI, respectively. The calculated result of MgF molecule is in good agreement with the recent theoretical result of 7.16 ns, with a small relative error percent of 1.11%.

Graphical abstractThe PECs of the X2Σ+ and A2Π states of MgX (X = F, Cl, Br, I) molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide