Charge and state population in dilute plasmas from beam-foil spectroscopy

Abstract

Beam-foil spectroscopy has a long history for determining charge state evolution, radiative decay lifetimes, spectral widths, and satellite structure. Many theoretical results predict a range of populations and state dependencies, but high resolution or a very large bandpass is normally required to test or investigate these. The current investigation has tested some key assumptions and models as applied to this relativistic regime, particularly for few-electron iron resonances and satellites. We conclude that there are two specific production mechanisms, one inside the target to low-n levels and one dominated by capture mechanisms at the exit of the foil, with particularly significant Rydberg cascades. Several systematics in high-precision measurements of these systems are discussed and quantified for the first time. The 2s–1s and 4f–2p satellites are explicitly investigated, and a dominant systematic is uncovered that is due to the variable location of spectral emission, downstream of the beam-foil target. PACS Nos.: 32.70.Jz, 34.10.+x, 52.20.Hv, 34.60.+z