Extreme ultraviolet beam-foil spectroscopy of highly ionized neon and argon

Abstract

A study of the extreme ultaviolet radiation emitted by ion beams of highly ionized neon and argon after passage through thin foils was conducted at the variable energy cyclotron at Texas A&M University. A grazing incidence spectrometer was equipped with a position sensitive microchannel plate (MCP) detector which improved the detection efficiency by two orders of magnitude. The position information of the MCP was determined to be linear over 90% of the 50 mm wide detector. Spectra spanning regions of over 100 Å were accumulated at a resolution of less than 1 Å. A wavelength calibration based on a second order equation of spectrometer position was found to result in an accuracy of ± 0.1 Å. Over 40 transitions of Ne VIII, Ne IX, and Ne X were observed in the wavelength region from 350 to 30 A from n-2-3,4,5; n-3-4,5,6,7,8; n-4-6,7; and n=-5-9. An intensity calibration of the detection system allowed the determination of the relative populations of n=3 states of Ne VIII and Ne IX. An overpopulation of states with low orbital angular momenta support electron capture predictions by the first order Born approximation. The argon beam-foil data confirmed the wavelength predictions of 30 previously unobserved transitions in the wavelength region from 355 to 25 Å from n-2-2; n-3-4; n-4-5,6,7; n-5-6,7; and n-6-8. Lifetime determinations were made by the simultaneous measurement of 26 argon lines in the spectral region from 295-180 Å. Many of the n-2-2 transitions agreed well with theory.