H.K. Carter

Nuclear moments of the neutron-deficient thallium isotopes

The nuclear moments of the neutron-deficient187,188Tl isotopes were determined by measuring the hyperfine structure splittings of the λ=535 nm line in neutral thallium. An optical efficiency of 2×10−4 photons per radioactive ion was achieved using collinear fast beam laser spectroscopy with a large solid angle fiber optical array detector. Most of the moments can be interpreted fairly well in the single particle model.

Unisor on‐line nuclear orientation facility

The UNISOR on‐line nuclear orientation facility consists of a He3–He4 dilution refrigerator on line to the isotope separator. Nuclei are implanted directly onto a target foil soldered to the bottom accessed cold finger of the refrigerator. A 1.5 T superconducting magnet polarizes the ferromagnetic target foils and determines the axis of symmetry. Up to eight gamma detectors can be positioned around the refrigerator, each 9 cm from the target. A unique feature of this system is that the k=4 term in the directional distribution function can be deduced so that a single solution for the mixing ratio can be found.

Nuclear spectroscopy using lasers at Oak Ridge National Laboratory: experiments with stable (past) and radioactive (future) tandem beams

Abstract Fast beam collinear laser spectroscopy has yielded information on nuclear structure on the long chain of neutron deficient Tl isotopes (186 ≤ A ≤ 205) using heavy ion fusion evaporation reactions to produce Tl-ion beams which for the most neutron deficient isotope were only about 104/s. The new radioactive heavy ion beam facility projected to be completed in 1995 requires even higher sensitivities at the few 10 nuclei/s level. Two examples to realize such ultra-sensitive measurements employing laser techniques are described. They are: field-ionization spectroscopy in a fast beam and stored ion spectroscopy in a novel linear combined trap.

On-line nuclear orientation of70As

On-line nuclear orientation was performed on70As. Anisotropy data have been obtained at 8.7mK for 29 gamma transitions. Multipole mixing ratios have been extracted for 17 transitions. Our results are in good agreement with existing data for the ten previously measured transitions. Our first time data for the 1496 keV, 2+→2+ γ-ray suggest the 2536 keV level is a good candidate for a mixed symmetry level.

Isotope shift measurements on the neutron-deficient thallium isotopes

Isotope shifts of the neutron-deficient thallium isotopes were measured on-line at the UNISOR mass separator. Spectroscopy was carried out using collinear fast beam laser spectroscopy in neutral thallium. The changes of the mean square charge radii were derived from the measurements. The changes in charge radii of the I=7 isotopes, including the newly measured188Tl, are compared to the results in mercury and lead.

On-line nuclear orientation study of184Au

The184Au→184Pt decay, studied on-line with the UNISOR facility at HHIRF, is discussed. Gamma-ray and conversion-electron spectroscopy of184Pt as well as on-line nuclear orientation measurements of184Au were done. A new low-lying level scheme of184Pt is proposed. Two coexisting bands with different deformations and their respective γ-vibrational bands are established. Internal conversion coefficients for interband transitions between states with the same spin are extracted from the spectroscopy measurements. The relative E0 contents of the transitions are determined by combining internal conversion coefficients with E2/M1 mixing ratios deduced from gamma-ray anisotropies measured from oriented nuclei.

Determination of the magnetic dipole moment of114Sb Via on-line nuclear orientation

The magnetic dipole moment of114Sb has been measured using on-line nuclear orientation (OLNO) at the UNISOR Nuclear Orientation Facility (UNISOR/NOF). The value was determined to be 1.72 (8) nuclear magnetons. The observed anisotropy of the 1299 keV transition was fitted as a function of temperature making allowance for incomplete thermalization of the114Sb nuclei prior to decay. The relaxation constant, Ck, is discussed, as is the ground state structure of114Sb.

Nuclear structure studies of187Ir via on-line nuclear orientation

A more complete level scheme is presented here for the decay of187Pt, incorporating many new lines and levels up to 2.4 MeV. Emphasis has been placed on the extraction of multipole mixing ratios from nuclear orientation data. Analysis of that data, however, required a more complete understanding of the level structure (including, in particular, branching ratios, conversion coefficients, and level feedings), prompting the collection of new spectroscopy data. The low-lying, positive-parity levels are described in terms of (odd-proton) single-particle Nilsson states coupled to a triaxial core. Multipole mixing ratios are compared to those calculated in the Particle-Plus-Triaxial-Rotor Model.

Intruder States, Coexistence, and Approaches to Deformation: The Study of 120Xe and the = 66 Isotones

In this chapter, new results of γ-ray and conversion-electron spectroscopic studies of the structure of 120Xe will be reported. These results will be described along with the results of previous studies of intruder structures in the Te and Xe mass region. The observed structures will be contrasted with other intruder structures identified in the Sn, Cd, and Pd isotopes. The role of intruder structures in the development of nuclear deformation will be discussed.

Search for low-spin superdeformed states in nuclei☆

Abstract Since the first discovery in 1986 of a rotational band at high angular momentum with deformation parameters near β =0.6, a great deal of research has been devoted to the study of these superdeformed (SD) bands in nuclei leading to the identification of similar bands in numerous nuclei in the mass 130, 150, and 190 regions. While superdeformed shape isomers have been observed at low spin in the actinides via spontaneous fission and in a few cases via γ decay, below mass 200 the low-spin members of the SD bands have not been observed. Theoretical calculations are able to account for the relative stability of the superdeformed bands in the nuclei where they have been observed. These calculations suggest that in the Hgue5f8Pb region the SD shape should be stable at a rotational frequency of 0. Several experiments have been performed to search for the population and decay of the lower spin members of the SD bands in the mass 190 region and some are still in progress. To this date, none has provided conclusive observation of the 0 + bandhead of a superdeformed band. The experimental techniques utilized in several of these are described.