M. E. Hanni

Properties of Fr-like Th3+from spectroscopy of high-LRydberg levels of Th2+

Binding energies of high-L Rydberg states (L^3 7) of Th2+ with n=27-29 were studied using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) method. The core of the Th2+ Rydberg ion is the Fr-like ion Th3+ whose ground state is a 5 2F5/2 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 non-adiabatic effects due to the low-lying 6d levels. Analysis of the observed RESIS spectra leads to determination of five properties of the Th3+ ion: its electric quadrupole moment, Q = 0.54(4), its adiabatic scalar and tensor dipole polarizabilities, ad,0 = 15.42(17) and ad,2 = -3.6(1.3), and the dipole matrix elements connecting the ground 52F5/2 level to the low lying 62D3/2 and 62D5/2 levels, |<52F5/2||D||62D3/2>| = 1.435(10) and |<52F5/2||D||62D5/2>| = 0.414(24). All are in atomic units. These are compared with theoretical calculations.

Properties of Fr-like Th{sup 3+} from spectroscopy of high-L Rydberg levels of Th{sup 2+}

Binding energies of high-L Rydberg states (L{>=} 7) of Th{sup 2+} with n = 27-29 were studied using the resonant excitation Stark ionization spectroscopy (RESIS) method. The core of the Th{sup 2+} Rydberg ion is the Fr-like ion Th{sup 3+} whose ground state is a 5 {sup 2}F{sub 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{sup 3+} ion: its electric quadrupole moment Q = 0.54(4); its adiabatic scalar and tensor dipole polarizabilities {alpha}{sub d,0} = 15.42(17) and {alpha}{sub d,2} = -3.6(1.3); and the dipole matrix elements connecting the ground 5 {sup 2}F{sub 5/2} level to the low-lying 6 {sup 2}D{sub 3/2} and 6 {sup 2}D{sub 5/2} levels, | |=1.435(10) and | |=0.414(24). All are in atomic units. These are compared with theoretical calculations.

Dipole transition strengths in Ba+from Rydberg fine-structure measurements in Ba and Ba+

The fine structure of high-L n = 19 and 20 Rydberg states of Ba{sup +} has been measured precisely using the resonant excitation Stark ionization spectroscopy technique, allowing for a determination of the Ba{sup 2+} polarizability: {alpha}{sub D}(Ba{sup 2+}) = 10.75(10) a.u. This result, in combination with an improved model of the K splittings in Ba Rydberg levels, allows for a more precise determination of the Ba{sup +} dipole transition strengths connecting the 6 {sup 2}S{sub 1/2} ground state to the 6 {sup 2}P{sub 1/2} and 6 {sup 2}P{sub 3/2} excited states. The results, in atomic units, are = 3.3251(21) and = 4.7017(27).

Polarizability of Rn-like Th{sup 4+} from spectroscopy of high-L Rydberg levels of Th{sup 3+}

Binding energies of high-L Rydberg levels of Th{sup 3+} were measured using the resonant excitation Stark ionization spectroscopy technique. Analysis of the data with the long-range polarization model leads to determination of dipole and quadrupole polarizabilities of the free Th{sup 4+} ion, {alpha}{sub d} = 7.61(6) a.u., {alpha}{sub Q} = 47(11) a.u.