0000000000082493
AUTHOR
C. Baktash
Superdeformation in the Doubly Magic NucleusC2040a20
A rotational band with seven gamma -ray transitions between states with spin 2 (h) over bar and 16 (h) over bar has been observed in the doubly magic, self-conjugate nucleus Ca-40(20)20. The measured transition quadrupole moment of 1.80(-0.29)(+0.39)eb indicates a superdeformed shape with a deformation beta (2) = 0.59(-0.07)(+0.11). The features of this band are explained by cranked relativistic mean field calculations to arise from an 8-particle 8-hole excitation.
Lifetime measurements and terminating structures in87Nb
Two experiments have been performed using the Ni-58(S-32,3p) reaction at 135 MeV with Gammasphere and the Microball to study the high-spin structure of the transitional nucleus Nb-87. The first experiment using a thin target provided a considerable extension and refinement of the level scheme, as well as firm spin assignments from directional correlation of oriented nuclei. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of beta(2)similar to0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transi…
Yrast superdeformed band in59Cu
High-spin states in Cu-59 were populated using the fusion-evaporation reactions Si-28+ Ca-40 at a beam energy of 125 MeV and Ar-36+Si-28 at a beam energy of 143 MeV. The Gammasphere array in conjunction with ancillary detector systems allowed for the identification of a superdeformed rotational band in Cu-59, which was firmly linked to low-spin yrast states. Using directional correlations of oriented states, a spin-parity assignment of I-pi=25/2(+) to the band head was possible. The average quadrupole moment of the band is measured to be Q(t)=(2.24+/-0.40) e b. The characteristics of the band are compared to neighboring nuclei and predictions of different mean-field theories.
Three-step resonant photoionization spectroscopy of Ni and Ge: ionization potential and odd-parity Rydberg levels
In preparation of a laser ion source, we have investigated multi-step laser ionization via Rydberg and autoionizing states for atomic Ni and Ge using a mass separator with an ion beam energy of 20 keV. For both elements resonant three-step excitation schemes suitable for modern Ti:sapphire laser systems were developed. Rydberg series in the range of principal quantum numbers 20 n 80 were localized, assigned and quantum numbers were allocated to the individual resonances. Ionization potentials (IP) were extracted from fits of the individual series and quantum defects of individual levels were analysed for confirmation of series assignment. For Ni the ionization potential could be extracted w…
Laser ion source tests at the HRIBF on stable Sn, Ge and Ni isotopes
Abstract As one step in the ion source development for the Rare Isotope Accelerator, a hot-cavity laser ion source using an all-solid-state titanium–sapphire laser system has been tested at the Holifield Radioactive Ion Beam Facility. Resonance ionization of stable isotopes of Sn, Ge and Ni has been studied in a Ta hot cavity. Efficient three step resonant ionization schemes applying frequency tripling for the first excitation step and using auto-ionizing or atomic Rydberg states in the ionizing step have been identified for all three elements, resulting in laser ion beams of typically around 100 nA. By saturating most of the optical excitation steps involved, ionization efficiencies of 22%…
Optical spectroscopy and performance tests with a solid state laser ion source at HRIBF
An ISOLDE-type hot-cavity laser ion source based on high-repetition-rate Ti:Sapphire lasers has been set up at the Holifield radioactive ion beam facility. To assess the feasibility of the all-solid-state laser system for applications at advanced radioactive ion beam facilities, spectroscopy and performance tests have been conducted with this source. The results of recent studies on excitation schemes, source efficiency, beam emittance and ion time structure are presented.
Time profiles of ions produced in a hot-cavity resonant ionization laser ion source
Abstract The time profiles of Cu, Sn, and Ni ions extracted from a hot-cavity resonant ionization laser ion source are investigated. The ions are produced in the ion source by three-photon resonant ionization with pulsed Ti:Sapphire lasers. Measurements show that the time spread of these ions generated within laser pulses of about 30 ns duration could be larger than 100 μs when the ions are extracted from the ion source. A one-dimensional ion-transport model using the Monte Carlo method is developed to simulate the time dependence of the ion pulses. The prediction of the model agrees reasonably well with the experimental data. To reproduce the observed ion time profiles, we find it necessar…
In-Beam Study of213Rn,215Ra and217Ra: Strongly Enhanced E3 Transitions in Odd-A N= 127 Isotones
With the aim of searching for high-spin configurations involving the high-j neutron orbitals, excited states in 213Rn, 215Ra and 217Ra were populated in the bombardment of 208Pb with 13C ions. Gamma-ray singles, excitation functions and angular distributions, pulsed-beam-γ timing and γ-γ(t) coincidences were measured. Six isomeric levels were observed in 213Rn, three in 215Ra while none in 217Ra. The lowest-lying 15/2- states in all odd-A N = 127 isotones are de-excited by E3 transitions with a strength of about 23 W.u, suggesting that they are all coupled to the octupole phonon. In 217Ra no evidence for collective behavior is found despite its closeness to the actinide region. The low-lyin…