G. Garcia Bermudez

High-spin states in 49Ti and the empirical (f72)n model

Abstract High-spin states in 49 Ti have been populated through the 48 Ca(α, 3n) reaction. Excitation function, γ-ray angular distributions, γ-γ coincidences and half-lives were determined. Levels with the following energies (in keV) spins and parities are proposed 1542.5, 11 2 − ; 2505.8, 15 2 − ; 3290.6, 17 2 − and 4382.6, 19 2 (−) . These levels and their decay scheme are found to be very well described by the empirical ( f 7 2 ) n model.

In-beam study of 70As

Abstract Nuclear states of 70 As were studied through the 69 Ga(α, 3n), 60 Ni(12C, np) and 63 Cu( 10 B, 2np) reactions at various bombarding energies between 30 and 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences, and γ-time distributions with respect to the beam bursts, were determined. Levels at 32.0, 167.0, 390.4, 485.4, 566.7, 869.1, 887.9, 898.7, 933.4, 1045.7, 1675.9, 1752.0, 1809.2, and tentatively at 2030 keV, were observed. All levels below 900 keV can be identified with levels seen with the (p, nγ) reaction. Tentative spin assignments extend up to J = 9. Two previously reported isomers are confirmed. The present measurements yield 3.3±0.7 and 4.4±0.1 ns for the 485.4 and 887.9 keV states, respectively. No collective features, as in the lighter isotone 68 Ga, were found. The levels below 1 MeV are likely to be described by simple shell-model configurations. The spacing of the proposed J = (4), (5), and (6) levels is analogous to that in 72 As and 74 As. The behavior of their excitation energy as a function of N suggests the configurations {π p 3 2 −1 , ν g 9 2 } or {π f 5 2 , ν g 9 2 } for these states.

In-beam study of 78Br

Abstract High-spin states in 78Br decaying into the 4+ isomer at 180.8 keV were excited via the 77Se(α, 2np) and 76Ge (7Li, 5n) reactions. A sequence of closely lying levels with I ⩽ 8 is found between 227.6 and 467.6 keV. The highest state in this group is populated by a relatively strong 904.1 keV ΔI = 2 transition. These features provide a basis for a comparison with the positive-parity ground-state Coriolis-distorted band of 79Kr, in the light of a rotor plus one- and two-quasiparticle descriptions. Other previously reported low-spin states are also seen weakly with this reaction. Two new isomeric states of 9±1 ns at 337.8 keV and 84±8 ns at 227.6 keV are found. The latter decays into the 4+ isomer through a 46.8 keV transition, which lies unresolved from the 46.3 keV line. The existence of this doublet explains an earlier discrepancy.

The high-spin structure of 100Rh☆

Abstract High-spin states of 100Rh have been populated with the reactions 99Ru(α, 2np) and 98Mo(6Li, 4n) and their γ-decay has been studied with Ge(Li) detectors in singles and coincidence. Angular and time distributions of the γ-rays were also measured. As a result 14 new levels spanning spins up to I = 16 built on the 5+, 4.5 min isomer at 107 keV have been established, and a half-life of T 1 2 = 120 ± 5 nsec has been determined for the 7+ state at 111.9 keV. The rotor-plus-two-quasiparticle model has been used to describe the observed level structure. The pn interaction is shown to be of negligible effect. On the other hand, the introduction of a soft core is essential. The application of the VMI model with the parameters extracted from the 98Ru core yields a remarkably good agreement. This is the first time that the anomalous VMI root ( I 0 has been applied to a doubly odd nucleus.

High-spin states in 94Tc

Abstract High-spin states in 94Tc have been populated through the 93Nb(α, 3n) reaction. Excitation functions, γ-ray angular distributions, γγ coincidences and half-lives were measured. New levels, with the following energies (in keV), spins and parities are proposed: 1373.5, 9+; 1447.3, (8+); 2064.0, (11+); 2066.2, (9−); 2234.9, (10−); 2346.7, (13+); 2420.7, (11−); 3454.1, (13−); and 4059.3, (15−). The existence of an isomer with 50 ns 1 2

Level structure of 82Rb, studied through the 81Br(α, 3n) reaction

Abstract Nuclear states of 82Rb were studied through the 81Br(α, 3n) reaction at various bombarding energies between 30 and 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences and γ-time distributions with respect to the beam bursts were determined. Levels at 123.2, 187.7, 233.6, 796.3, 1214.1 keV and tentatively at 1835.5 keV were observed. It was not possible to establish whether the lowest state of the proposed level scheme corresponds to the ground state or to the T 1 2 = 6.2 h isomeric state. The 45.9 and 64.5 keV γ-rays do not exhibit any measurable lifetime and a limit T 1 2 ≦ 5 ns has been determined. The situation is similar for the 123.2 keV γ-ray, although in this case the presence of a long-lived component cannot be ruled out.