Properties of Fr-like Th3+from spectroscopy of high-LRydberg levels of Th

Abstract

Binding energies of high-L Rydberg states (L 7) of Th 2+ with n = 27-29 were studied using the resonant excitation Stark ionization spectroscopy (RESIS) method. The core of the Th 2+ Rydberg ion is the Fr-like ion Th 3+ whose ground state is a 5 2 F 5/2 level. The large-core angular momentum results in a complex Rydberg fine-structure pattern consisting of six levels for each value of L that is only partially resolved in the RESIS excitation spectrum. The pattern is further complicated, especially for the relatively-low-L levels, by strong nonadiabatic effects due to the low-lying 6d levels. Analysis of the observed RESIS spectra leads to determination of five properties of the Th 3+ ion: its electric quadrupole moment Q = 0.54(4); its adiabatic scalar and tensor dipole polarizabilities α d ,0 = 15.42(17) and α d ,2 = -3.6(1.3); and the dipole matrix elements connecting the ground 5 2 F 5/2 level to the low-lying 6 2 D 3/2 and 6 2 D 5/2 levels, | 5 2 F 5/2 ||D||6 2 D 3/2 | = 1.435(10) and | 5 2 F 5/2 ||D||6 2 D 5/2 | = 0.414(24). All are in atomic units. These are compared with theoretical calculations.

Correlation and relativistic effects in actinide ions

“…The radon-like Th 4+ ion is the most common charge state of thorium in chemical compounds [1]. This work is motivated in part by recent experiments [2][3][4][5] that investigated the spectroscopy of high-L Rydberg levels of actinide ions and the dipole and quadrupole polarizabilities. These measurements present an excellent opportunity for benchmark tests of a priori theoretical descriptions of such highly relativistic ions.…”

“…The dipole polarizability of Th 4+ was determined to be α d = 7.720 (7) a.u., and the quadrupole polarizability was found to be α Q = 21.5 (3.9) a.u. In 2011, properties of Fr-like Th 3+ were determined from spectroscopy of high-L Rydberg levels of Th 2+ ions [5].…”

Polarizabilities ofSi2+: A benchmark test of theory and experiment

“…In such cases, the polarization interaction provides the dominant contribution to the energy shift. This effect is utilized in resonant excitation Stark ionization spectroscopy (RESIS) [19][20][21][22][23][24][25][26][27][28] [26], and Rnlike Th 3+ [27]. Quadrupole polarizabilities and transition matrix elements have also been determined for some of these systems.…”

Radiative transitions between Rydberg states of polar diatomic molecule. Part I: Linearly polarized light

“…High-l non-penetrating RSs are of particular interest because the interpretation of their spectra allows to extract properties of the core (atomic or molecular) with high precision [11,12]. Recent identification of many new high-l series [13][14][15][16][17] in atomic spectra allows to expect appearing precise spectroscopic data on non-penetrating RSs in molecules.…”