atoms Article EUV Beam-Foil Spectra of Titanium, Iron, Nickel, and Copper Elmar Träbert 1,2 1 Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, AIRUB, 44780 Bochum, Germany;
[email protected]; Tel.: +49-2343223451; Fax: +49-2343214169 2 Lawrence Livermore National Laboratory, Physics Division, Livermore, CA 94550-9234, USA Abstract: Beam–foil spectroscopy offers the efficient excitation of the spectra of a single element as well as time-resolved observation. Extreme-ultraviolet (EUV) beam–foil survey and detail spectra of Ti, Fe, Ni, and Cu are presented, as well as survey spectra of Fe and Ni obtained at an electron beam ion trap. Various details are discussed in the context of line intensity ratios, yrast transitions, prompt and delayed spectra, and intercombination transitions. Keywords: atomic physics; EUV spectra; beam–foil spectroscopy 1. Introduction Bengt Edlén demonstrated by laboratory experiments in the 1940s [1] that the long- time mysterious solar corona lines (in the visible spectrum) originated from electric-dipole forbidden transitions in the ground configurations of highly charged ions of Ca, Fe, and Ni, a hypothesis Grotrian [2] had formulated on the basis of some of Edlén’s earlier measurements of X-ray transitions. When in the 1960s and 1970s sounding rockets and satellites heaved spectrometers beyond Earth’s atmosphere and thus opened the new Citation: Träbert, E. EUV Beam-Foil field of direct X-ray and EUV observations of highly charged ions in the solar corona, Spectra of Titanium, Iron, Nickel, and researchers marveled at the rich EUV and X-ray spectra, especially of Fe. Brian Fawcett, Copper.