Spectrum of singly charged uranium (U II): Theoretical interpretation of energy levels, partition function and classified ultraviolet lines

Abstract

In an attempt to improve U II analysis, the lowest configurations of both parities have been interpreted by means of the Racah-Slater parametric method, using Cowan codes. In the odd parity, including the ground state, 253 levels of the interacting configurations 5f37s2 + 5f36d7s + 5 f36d2 + 5 f47p + 5 f5 are interpreted by 24 free parameters and 64 constrained ones, with a root mean square (rms) deviation of 60 cm-1. In the even parity, the four known configurations 5 f47s, 5 f46d, 5 f26d27s, 5 f26d7s2 and the unknown 5 f26d3 form a basis for interpreting 125 levels with a rms deviation of 84 cm-1. Due to perturbations, the theoretical description of the higher configurations 5 f37s7p + 5 f36d7p remains unsatisfactory. The known and predicted levels of U II are used for a determination of the partition function. The parametric study led us to a re-investigation of high resolution ultraviolet spectrum of uranium recorded at the Meudon Observatory in the late eighties, of which the analysis was unachieved. In the course of the present study, a number of 451 lines of U II has been classified in the region 2344-2955 Å. One new level has been established as 5 f36d7p (4 I)6K(J = 5.5) at 39113.98 ±0.1 cm-1.