Yu. P. Gangrsky

N and Z dependence of nuclear charge radii

This paper is devoted to the analysis of the general trends in the nucleon number dependence of the experimental root-mean-square (rms) charge radii. It is based on the data obtained by different methods of combined treatment of (i) radii changes determined from optical and—to a lesser extent—Kαx-ray isotope shifts, and (ii) absolute radii measured from muonic and electronic scattering experiments. These methods have recently been developed and now updated including experimental data up to the beginning of 2008. Thus, new sets of rms nuclear radii have been obtained covering 865 isotopes for 76 elements from 1 Ht o96Cm. New information on the isotopic and isotonic behaviour of the nuclear charge radius is obtained with a high accuracy compared to that of the directly measured radii values for the same element. Of special interest is that concerning the light elements and the appearance of non-traditional magic neutron and proton numbers, as N = 6, 14 and Z = 14; the doublemagic properties of 96 Zr are discussed in more detail. A quantitative criterion is introduced, which points to the peculiarities in the radii trend and offers an opportunity to investigate it more closely. The results provide important information which may serve as a guide to incorporate essential new features into the theoretical approaches. (Some figures in this article are in colour only in the electronic version)

Nuclear charge radii of neutron deficient titanium isotopes 44Ti and 45Ti

Optical isotope shifts of the unstable 44,45Ti isotopes, as well as those of stable 46−50Ti, have been investigated by collinear laser spectroscopy on fast ion beams using an ion guide isotope separator with a cooler-buncher. Changes in mean square charge radii across the neutron 1f7/2 shell are deduced. The evolution of the even-N Ti nuclear radii shows a generally increasing tendency with decreasing neutron number. This behaviour is significantly different to that of the neighbouring Ca isotopes which exhibit a symmetric parabolic behaviour across the shell. The trend of the Ti nuclear radii is consistent with the predictions of the relativistic mean-field theory. The charge radius of 44Ti is also compared to predictions of a 40Ca + α cluster model.

Nuclear charge radii changes of uranium and hafnium isotopes determined by laser spectroscopy

The present work reports measurements of isotope shifts and hyperfine structure in the optical spectra of two high-Z elements: Hf and U. The experiments are based on the observation of the resonance fluorescence in a well collimated atomic beam, excited by a tunable dye laser. The chains of the stable Hf isotopes and of233–236, 238U have been investigated and changes in ms nuclear charge radii have been deduced. The results have been discussed from the point of view of nuclear structure in the investigated regions.

Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers

Collinear laser spectroscopy experiments with the Sc+ transition 3d4s 3D2 → 3d4p 3F3 at λ = 363.1 nm were performed on the 42–46Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac–Fock calculations were performed in order to evaluate the specific mass-shift, MSMS, and field-shift, F, parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti radii, which increase towards the neutron shell closure N = 20, than the symmetric parabolic curve for Ca. The changes in mean-square charge radii of the isomeric states relative to the ground states for 44Sc and 45Sc were also extracted. The charge radii difference between the ground and isomeric states of 45Sc is in agreement with the deformation effect estimated from the B(E2) measurements but is smaller than the deformation extracted from the spectroscopic quadrupole moments.

Excitation of the high-spin 180Hf isomerand de-excitation of the 180Ta isomer in(γ,γ') reactions

The reaction mechanism of excitation and de-excitation of the high-spin isomers 180Hf (J=8-) and 180Ta (J=9-) in inelastic gamma-quanta scattering was investigated. An anomalously large integral cross section and isomeric ratio for 180Ta in comparison to 180Hf were obtained. Level properties influencing these relations are discussed.

Isomeric yield ratio of134I in photofission of232Th and238U

The isomeric yield ratios for134I, for the photofission of232Th and238U with 25-MeV bremsstrahlung have been determined using radiochemical techniques and γ-spectrometry. Angular moment a of the corresponding fission fragments, Jrms, were calculated by the statistical procedure of Huizenga and Vandenbosch. We have discovered a significant proton odd-even effect on Jrms values, and demonstrated its dependence on the nuclear structure of fragments.

Precise measurement of the hyperfine splitting and isotope shift of8S7/2→10P9/2 transition in241Am and243Am atoms

The hyperfine structure and isotope shift of8S7/2→10P9/2 atomic transition in241Am and243Am was measured with high-resolution by laser fluorescent spectroscopy method. The results concern nuclear moments and charge radii. We notice that the hyperfine structure for the actinide atoms are rather high compared with other elements. This offers ample scope for obtaining information about higher nuclear moments than Q and μ.

Production of spontaneously fissioning isomers 242Am and 344Am by slow neutron capture

Abstract The spontaneously fissioning isomers 242 Am and 244 Am were produced by slow neutron capture. The cross sections of isomer production were measured at different neutron energies. The correlation between isomer formation and prompt fission was observed. This correlation is discussed on the basis of the two-humped fission barrier hypothesis.

Light-induced drift of 22,23,24Na in a wide cold tube

Abstract This paper presents results of a test experiment for using the light-induced drift (LID) effect for measurements of the optical transition frequencies of short-lived isotopes and isomers. The LID of 23 Na atoms was observed in a wide (8 mm) cold glass tube. Isotope enrichments were measured for radioactive sodium isotopes. The 22 Na enrichment reaches a value of about 10. The LID velocities of 22 Na and 24 Na atoms reache values of ≈22 cm/s.

Isomeric ratios in reactions induced by gamma rays and fast neutrons in the isotopes of Re, Ir, and Au

Isomeric ratios were measured in the (γ, n) and (n, 2n) reactions leading to the formation of 184Re, 190Ir, and 196Au odd-odd nuclides. The measurements were performed by the activation method implemented for Re, Ir, and Au samples of natural isotopic composition that were irradiated with 14.7-MeV neutrons and bremsstrahlung photons of endpoint energy 22 MeV. Isomeric-and ground-state nuclei formed in these reactions were identified by their x-or γ-ray spectra and by their half-lives. The isomeric ratios were calculated on the basis of the statistical model, and the results were compared with experimental data, where by it was possible to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum. The effect of the nuclear structure on these parameters is discussed.