Isotope shift studies of the visible and ultra-violet bands of A1O

Abstract

The blue-green and ultra-violet bands of A1O are obtained in emission from a d.c. arc between aluminium electrodes in an atmosphere of oxygen at low pressures. For isotopic studies, oxygen enriched in ¹⁸O to 50% is used. Isotope shifts observed for some of the intense bands of the c²Σ⁺-x²Σ⁺ system confirm the vibrational assignments proposed earlier. Three red-degraded double-headed bands at 25001 Angstrom, 25459 Angstrom and 25929 Angstrom form a ν−or+ progression of a new system. Isotope shift studies show that they arise from a ν´ = 0 level of an excited electronic state to ν−or+ = 0, 1 and 2 levels of a lower electronic state. During these studies the blue-green bands of Al¹⁸O are also photographed and their shifts measured with respect to the corresponding bands of Al¹⁶O.