S. Liberman

Hyperfine structure and isotope shift of the D2 line of 118–145Cs and some of their isomers

Abstract High-resolution laser spectroscopy has been performed on 118–145 Cs and 119m, 121m, 122m, 130m, 134m, 135m, 136m, 138m, Cs.The Cs nuclei have been produced either by spallation of La or by fission of U by the 600 MeV proton beam, from the SC at CERN. The hyperfine structures, spins, and isotope shifts have been measured. The charge radii changes deduced from the isotope shifts exhibit shell effects at N = 82, isomeric staggering for N = 64,66,67 and a strong odd-even staggering for all isotopes with N

Hyperfine structures and isotope shifts of 207–213,220–228Fr; Possible evidence of octupolar deformation

Abstract Hyperfine structures and isotope shifts of 207–213,220–228 Fr have been measured by high-resolution laser spectroscopy. Nuclear moments and changes in the mean-square charge radii are deduced. They are compared with analogous data for radium and discussed in terms of the octupole deformation mode.

Isotope shifts, spins and hyperfine structures of 118,146Cs and of some francium isotopes

Abstract High-resolution laser spectroscopy using thermal atomic beams has been performed on-line with the ISOLDE facility at CERN. It allowed the measurement of the spins, isotope shifts and hyperfine structures of the D2 line of 118,146Cs, and that of the hyperfine factors of the first P 1 2 level of 133,135,137,139,141,143Cs and 210,212,213,221Fr. Previous data concerning 207–213,220–228Fr have also been reanalysed. All results are discussed in terms of deformations with special attention to the possible occurrence of octupole deformations.

Shape transition in neutron deficient Pt isotopes

Abstract Isotope shift (IS) and hyperfine structure (HFS) measurements have been performed for 185,187,189,191,195 Pt using the PILIS (Post ISOCELE Laser Isobar Separation) apparatus installed at the ISOCELE facility. Magnetic and quadrupole moments have been deduced from the HFS results. The change radius changes determined for these odd nuclei from the IS results, added to the δ r 2 > values of the even- A nuclei, are compared to the results of lattice Hartee-Fock+BCS calculations for asymmetric solutions. 185 Pt is confirmed to be prolate shaped whereas 187,189,191 Pt are likely triaxial in their ground states.

Rydberg atoms in parallel magnetic and electric fields. I. Experimental studies of the odd diamagnetic multiplet of lithium: n mixing and core effects

A quasihydrogenic complete diamagnetic manifold is investigated experimentally. The spectra are obtained in a uniform magnetic field by exciting in a one-step process, using polarised laser light, the lithium atoms of an atomic beam. The whole structure of the M=0 odd diamagnetic multiplet has been recorded for the first time. This experiment provides a confirmation for the existence of the two classes of states predicted for the diamagnetic Hamiltonian of atomic hydrogen in the weak-field limit. The fundamental features of diamagnetism still subsist for such high field strengths so that the diamagnetic interaction cannot be regarded as a perturbation with respect to the Coulomb problem. The intermanifold coupling and the influence of effects due to the ionic core in the lithium atom are evaluated quantitatively.

Accurate wavenumbers of the first resonance doublet of francium atoms and relativistic contribution to isotope shifts in the resonance doublets of francium and caesium atoms

The results of a new experiment using high-resolution Doppler-free laser spectroscopy are reported. Firstly, the wavenumbers of the D1 and D2 lines of Fr atoms have been accurately measured: sigma (D1)-12237.409 (2) cm-1 and sigma (D2)=13923.998 (2) cm-1. Secondly, the isotope shifts of the D1 and D2 lines have been compared for Fr and Cs atoms. The contribution of the p1/2 electron to the volume shift has been measured relative to that of the s1/2 electron as 4.75(25)*10-2 for Fr and 1.4(3)*10-2 for Cs. They are discussed in terms of semi-empirical calculations as well as relativistic Dirac-Fock ones.

Rydberg atoms in parallel magnetic and electric fields. III. Experimental investigations of the Stark structure of the diamagnetic manifold of lithium

For pt. II see ibid., vol.21, no.21, p.3499-521 (1988). A high-resolution laser spectroscopy experiment performed on an atomic beam of lithium has allowed the authors to analyse systematically the photoexcitation spectra from the ground state in the presence of parallel electric and magnetic fields. For the strengths studied, the Stark and diamagnetic energies are small compared with the energy separation between states with different principal quantum numbers n. Complete n manifolds have been experimentally investigated and the structure of the energy spectrum has been investigated as a function of the intensity of one of the fields, the other one being kept constant. This experiment provides a confirmation for the existence of the three classes of states predicted from an analysis of the properties of the Hamiltonian of atomic hydrogen.

Resonant ionization spectroscopy of laser‐desorbed gold isotopes

A system for laser spectroscopic studies on implanted radioactive samples has been developed and installed at the ISOCELE isotopes separator. Mass separated gold isotopes collected in a graphite substrate are desorbed by pulses from a Nd/YAG laser. Three synchronized dye laser pulses produce ions in a resonant ionization process; these are detected and identified in a time‐of‐flight mass spectrometer. Results of isotope shift and hyperfine structure measurements on gold isotopes with A=186, 187, 190, 192, 194, 195 and 196 are presented.

Hyperfine Spectroscopy of Radioactive Alkali Isotopes

Systematic experimental studies of long series of radioactive isotopes of the same element are now becoming a rapidly developing area. The results obtained in the case of Hg isotopes for instance [1], give a good idea of the attractiveness of such a type of investigation. Moreover, similar studies of radioactive Na isotopes of mass number 21 to 31 have already been performed using high resolution laser spectroscopy [2], and have shown for the first time for such a light element, an appreciable volume shift contribution to the total isotope shift. Obviously, hyperfine results, as well as nuclear spin determinations and precise isotope shift measurements give an ensemble of data that seem to be of crucial importance to a better understanding of nuclear properties and suggest new refinements in theoretical models. The further the isotopes are from magic numbers, the larger the nuclear deformations are expected to be. One has therefore to deal with essentially short-lived species, which requires one to work on-line behind the accelerators where they are produced. In the previously mentioned case of Na atoms for instance, the nuclei were obtained by fission reactions of uranium targets bombarded by 20 GeV protons delivered by the PS synchrotron of C.E.R.N..

Experimental Investigation and Analysis of Rydberg Atoms in the Presence of Parallel Magnetic and Electric Fields

A complete quasi-hydrogenic diamagnetic manifold is experimentally investigated as well as the evolution of the structure obtained by adding a small electric field parallel to the magnetic field. The experiment has been performed on lithium atoms excited in a one step process in M = 0 odd Rydberg states. The pure diamagnetic structure has revealed the existence of two classes of states which have been previously predicted by the analysis of an approximate constant of the motion \( \Lambda = 4{{A}^{2}} - 5A_{Z}^{2}(\vec{A} \) is the Runge-Lenz vector) and the semi-classicaly theory has proved to be a useful tool to interpret entirely the structure. In the presence of an electric field, the two classes of states evolve differently, three classes are now observed which are to be related to the existence and the properties of the approximate constant of the motion: