Measurements of branching fractions using Fourier transform and grating spectroscopy

Abstract

The measurement of lifetimes using laser-induced fluorescence at the University of Wisconsin-Madison has been one of the most productive experiments in the measurement of atomic spectroscopic data. The NIST bibliographic database on Atomic Transition Probabilities lists over 60 papers with Jim Lawler as an author or coauthor on lifetimes of neutral and singly-ionized elements ranging from carbon to mercury. The applications of these measurements range from astrophysics to lighting research. However, it is necessary to combine these lifetimes with branching fractions in order to obtain the atomic transition probabilities, and these branching fractions are now frequently the limiting factor in the accuracy of the measurements. I shall describe how the combination of measurements of branching fractions using Fourier transform spectroscopy at NIST with those of weak lines using the UW echelle spectrograph can improve the reliability of these measurements and provide the atomic data for weak lines that are challenging to measure using Fourier transform spectroscopy alone.