Luminescence of the B1Σ+–X1Σ+ band system of MgO during plasma electrolytic oxidation of magnesium alloy

A broad luminescence peak with clearly pronounced structure, extending from roughly 19,950 cm− 1 to 20,400 cm− 1 is obtained during plasma electrolytic oxidation of magnesium alloy (96% Mg, 3% Al, 1% Zn). It is assigned to the v′ − v″ = 0 band sequence of the B1Σ+–X1Σ+ emission transition of MgO. The measured intensity distribution is combined with quantum-chemical calculations in order to estimate the population of vibrational levels of the upper electronic state, and consequently to determine the plasma temperature. The composition of a plasma containing magnesium, oxygen, and hydrogen under assumption of local thermodynamic equilibrium is calculated in the temperature range up to 12,000 K and for pressure of 105, 106, 107, and 108 Pa, in order to explain the appearance of the observed spectral features.