Rovibronic Spectroscopy of Alo from First Principle

Abstract

The spectrum of AlO is widely used in various applications including the explorations of interstellar space, studies of laser ablation, combustions of Al-containing fuels and so on. In this work, we reported the spectroscopy of the AlO radical at temperatures of 300 ~ 15000 K for the wavenumber range of 1 ~ 55000 cm-1. Firstly, we extended our previous calculations of the potential energy curves (PECs) and transition dipole moments (TDMs) for AlO (Bai, Qin & Liu, MNRAS, 2022, 510:1649-1656) to higher B2Σ+, D2Σ+, 1'2Π and 1''2Π electronic states, with the consideration of Davidson correction, scalar relativistic correction and core-valence correlation. Partition functions, Einstein coefficients and radiative lifetimes of AlO were then obtained by solving the nuclear-motion Schrödinger equation. The partition functions reveal that the AlO molecules mainly exist in the X2Σ+ state at temperatures of 10 ~ 6270 K and in the A2Π state at temperatures of 6270 ~ 15000 K in the thermodynamic equilibrium. Finally, line intensities and spectra for different electronic transitions of AlO were calculated. The results show that the X2Σ+ → A2Π transition dominates in the infrared waveband, the X2Σ+ → B2Σ+ transition plays a dominant role in the visible waveband, and the X2Σ+ → C2Π and X2Σ+ → D2Σ+ transitions dominate in the ultraviolet waveband. Comparisons of the TDMs, radiative lifetimes, line intensities and spectra with previous theoretical and experimental values indicate that our calculated data are reliable and may be used for the planetary exploration and radiation field calculation.

Keywords: partition functions, radiative lifetimes, line intensities, spectrum, AlO