On Atomic Lifetimes and Environmental Density

Abstract

Atomic lifetime measurements span a wide range, from attoseconds to years. The frontier of exploratory lifetime measurements, presently, is in the long part of the above time range, with an eye on astrophysical problems. In a combination of review paper, tutorial, and Editorial, the physical environments and experiments are discussed, in which the results of such lifetime measurements matter. Although accurate lifetime measurement results are important for our understanding of atomic structure and dynamics, and for the diagnostics of various plasma environments, the order of magnitude is often precise enough to see why time resolution may be of interest in an experiment, from laser-produced plasmas of high densities to planetary nebulae of very low densities.