Eur. Phys. J. D 44, 35-45 (2007)
https://doi.org/10.1140/epjd/e2007-00173-x

Observation and interpretation of the Tm ³⁺ free ion spectrum

¹ Laboratoire Aimé Cotton, CNRS (UPR3321), bâtiment 505, Université Paris-Sud, 91405 Orsay Cedex, France
² LERMA, UMR8112 du CNRS, Observatoire de Paris-Meudon, 92195 Meudon, France
³ Université Pierre et Marie Curie-Paris6, 75005 Paris, France

Corresponding author: ^a ali.meftah@lac.u-psud.fr

Received: 22 December 2006
Revised: 16 March 2007
Published online: 1 June 2007

Abstract

The emission spectrum of thulium produced by a vacuum spark source was observed in the wavelength range from 700 to 2320 Å  on the 10.7 m normal-incidence vacuum ultraviolet spectrograph at the Paris-Meudon observatory. In the unknown spectrum of Tm IV, more than 760 lines have been identified for the first time as transitions between 157 levels of 4f¹¹5d, 33 levels of 4f¹¹6p, 9 levels of 4f¹¹6s and 10 levels of the 4f¹² ground configuration. A parametric interpretation of the levels has been carried out using the Cowan codes. Configuration interaction effects are discussed, in particular with the core-excited configurations 5p⁵4f¹³ and 5p⁵4f¹²5d. Radial Slater parameters derived from 4f¹² levels are larger than those pertaining to trivalent Tm ions in compounds. A selection of 105 prominent lines is given.