Continuum spectra and potentials of Li–noble gas molecules

Abstract

The normalized emission spectrum of the Li(2p−2s) resonance transition has been measured in the presence of 10–1000 Torr of noble gas. Fluorescence at 100–3000 Å from the atomic line, due to the A–X and B–X bands of Li–noble gas molecules, has been measured as a continuum with 1.5 nm resolution. The lithium is optically excited in a 670 °K cell. The lithium is optically thin (∼10⁻⁶ Torr) so that the continuum emission per excited lithium atom is obtained from the normalized emission. The attractive A‐state potentials for Li–Ar, Kr, and Xe have been constructed by analysis of the A–X band spectra in the limit of high and low noble‐gas densities. At high densities each spectrum is due to an equilibrated vibrational distribution of A‐state molecules, whereas at low densities only free collision states contribute. The ratio of the two spectra thus depends on the excited state potential and has been used to determine this potential where it is attractive. Absorption and stimulated emission coefficients for Li–noble gas vapors are also deduced from the data.