Laserspectroscopic studies of collective properties of neutron deficient Ba Nuclei

Abstract

Isotope shifts and hyperfine structure of the BaI resonance-line (2 = 553.6 nm) have been measured by dye laser induced resonance fluorescence on an atomic beam for 135m, 129g~ 129m. 126Ba thus extending previous high resolution measurements of neutron deficient Ba nuclides (N < 82). The experimental results, now available for 16 Ba isotopes and isomers with A=14(~126, are used to deduce differences of rms charge radii, magnetic dipole and electric quadrupole moments. While the groundstates display a pronounced odd-even staggering the h 11/2 isomers 135'~Ba and 133tuBa show a decreased staggering. Conspicuously the isomer shift of the g 7/2 + isomer ~29mBa proves to be negative. The nuclear structure information is discussed in the context of gammaspectroscopic studies of transitional nuclei with 50<N, Z <82 and on the basis of a quasi-particle-plus-triaxial rotor model. The isotope shift discrepancy observed is fairly well described by the droplet model.

Hyperfine-structure and isotope-shift measurements in the 6s 5d?6p 5d transitions of Ba I in the far-red spectral region

“…In the 6p5d configuration a statistically significant J-dependence can hardly be proved. Making the assumption of no J-dependence in the electron density for the 6s6p3p state, a configuration average of the King-plot slopes for the 6s 2 +--~6s6p transitions is evaluated from the 7,911A intercombination transition (*So-3Px) and the 1S o -IP~ resonance transition at 5,535/~ measured by Beck et al [6]. The following ratio is then obtained z~ P6s2 ~ 6s6p __ 1.044 (14).…”

“…Furthermore polarization of the inner s-shells heavily affects the hyperfine structure but has no major effect on the electron density at the nucleus. By the use of our estimation of F~, instead of the semi-empirical one, by Fischer et al, the evaluated change in nuclear meansquare radii 6(ra) AA' from optical isotope shift [1,6,7,9,10] will be increased by about 40 %. Quite recently muonic x-ray measurements of the nuclear charge radii and 3(r a) values were presented by Shera et al [12].…”

“…It should be noticed that the value for the 4,934 Ba-ion transition deviate considerably from the commonly used [1,6,7,9,10] value Fr = -4.98GHz/fm 2 given by Fischer et al [7]. The electron density at the nucleus was in their work taken from experimental hyperfine structure by using the semi-empirical Goudsmit-Fermi-Segr6 formula corrected for relativistic and screening effects.…”

“…From optical isotope shift data the change in nuclear meansquare radii ~(r2) A'A' can be evaluated, if the electronic parts of both the field shift and specific mass shift have been estimated. The good agreement of the 6(r 2) values evaluated in the earlier optical analyses [1,6,9] compared with the analysis of the new muonic experiments [12] must be fortuitous, since the semi-empirical electronic factor F~ used deviates considerably from the muonic one. The explanation is that the semi-empirical estimation of the specific mass shift (SMS) used in the optical analyses deviates considerably from the SMS value derived from muonic data by Shera et al [12], compensating for the difference in F~.…”

Theoretical isotope shifts in neutral barium

“…Bekk et al [5] measured IS by laser-induced resonance fluorescence on an atomic beam of a sample of barium. In continuity of the work by Nowicki etal.…”