Luminescence of the B2Σ+–X2Σ+ band system of AlO during plasma electrolytic oxidation of aluminum

Abstract

Two broad luminescence peaks with clearly pronounced structure, extending from roughly 18,200 to 18,800cm−1 and from 19,000 to 19,700cm−1 with the maxima at approximately 18,500 and 19,500cm−1, respectively, are obtained during plasma electrolytic oxidation of aluminum. They are assigned to the v′–v″=−1 and −2 band sequences of the B2Σ+–X2Σ+ emission transition of AlO. The measured intensity distributions are employed to estimate the population of vibrational levels of the upper electronic state, and consequently the mean plasma temperature. The composition of plasma containing aluminum and oxygen under assumption of thermodynamic equilibrium is calculated in the temperature up to 11,000K in order to explain the appearance of the observed spectral features.