Advanced experimental techniques for measuring oscillator strengths of vacuum ultraviolet lines

Abstract

Advanced experimental techniques for measuring oscillator strengths of atomic and ionic transitions in the vacuum ultraviolet (VUV) are described. A VUV time-resolved laser-induced-fluorescence experiment for radiative lifetime measurements on atoms and ions in a beam is operational. Recent work on VUV transitions of Si I and B I is described. These lifetimes provide the essential absolute normalization for converting relative oscillator strengths to absolute transition probabilities. Emission measurements of branching fractions at VUV and longer wavelengths are proposed. A large echelle spectrograph equipped with a CCD detector array will be used. This experiment will provide the sensitivity, resolving power, and data handling capability required for extensive high quality emission branching fraction measurements. We further propose to use absorption measurements on hollow cathode discharges to determine relative absorption oscillator strengths. A demonstration of a new technique for absorption spectroscopy on glow discharges is reported. The new technique provides the sensitivity, dynamic range, and data handling capability required for extensive high quality absorption measurements. Relative absorption and emission oscillator strengths will be least-square adjusted using the bowtie method and normalized with accurate radiative lifetimes.