C.G. Lindén

An on-line multichannel electron spectrometer with high transmission

Abstract A high-transmission electron spectrometer has been designed to study conversion electrons in the decay following (particle, xn) reactions. A solenoidal magnetic field is used to transport the electrons away from the target and focus them on a cooled Si(Li) detector. The latter is situated about half a meter from the target, thus reducing the background due to electrons from γ-rays as well as the background which is due to scattered particles significantly. The energy resolution of the spectrometer is about 2.0 keV at electron energies of 500 keV. Spectra obtained from bombarding various targets with 48–51 MeV alpha particles are presented.

Rotational bands in 195, 197Tl

Abstract High-spin states in 195, 197 Tl have been populated with ( α , x n) reactions and studied by means of in-beam γ-ray and e − spectroscopic methods. Complementary studies of the decay of 195, 197 Pb to 195, 197 Tl have been carried out. Several new features have been observed in these nuclei. The 9 2 − bands of 195, 197 T1. extended to 27 2 (−) and 29 2 (−) , respectively, show a quenching of energy spacings between the 23 2 − , 25 2 − , 27 2 (− and 29 2 (− states. This has been interpreted as resulting from the coupling of a h 9 2 proton to the ( π h −2 11 2 ) 8+, 10+ configurations in the core nuclei 194, 196 Hg. Furthermore, positive-parity bands based on 15 2 + states were established up to the 35 2 (+) and 29 2 (+) states in 195, 197 Tl respectively. Probably these bands originate from the coupling of a h 9 2 proton to a broken neutron pair. This pair consists of a rotation-aligned i 13 2 neutron and a low- j neutron in the P 1 2 , P 3 2 or f 5 2 shell. It is known to constitute the 5 − bands in 194, 196 Hg.

Gamma-gamma energy correlations and moment of inertia in 130Ce

Abstract High-spin properties of 130Ce have been studied by using the reaction (12C, 6n). The γ-rays following this reaction were detected by six NaI(Tl) detectors in a two-dimensional coincidence arrangement. An experimental γ-ray energy-energy correlation spectrum was extracted from the original coincidence matrix. The matrix of the correlated spectrum shows a valley along the 45° diagonal extending up to Eγ ≈ 1.2 MeV, thus indicating a collective behaviour beyond the region of known discrete lines. From the width of the valley a collective moment of inertia is deduced.

High-spin properties of 173Re

Abstract The high-spin structure of 173 Re has been investigated by in-beam γ-ray spectroscopy. Strongly coupled bands based on the 5 2 + [402] and 9 2 − [514] Nilsson proton states and decoupled bands based on the h 11 2 and i 13 2 intruder proton orbitals have been established. The alignment of an i 13 2 neutron pair has been identified at h ω c = 0.25–0.29 MeV . The detailed behaviour of the neutron crossing shows a marked dependence on the proton configuration. Ratios of the reduced transition rates B (M1)/ B (E2) have been extracted for the ΔI = 1 bands and have been used to confirm the neutron origin of the alignment. The results are interpreted within the total routhian surface (TRS) approach.

High-spin phenomena in 174Os☆☆☆

High-spin states of 174Os have been investigated by means of the (Nd(S, 4n)Os)-Nd-146-S-32-Os-174 reaction using the ESSA30 multidetector system. The decay is dominated by the ground-state positive ...

On the moment of inertia in deformed Ba-Xe nuclei as deduced from gamma-gamma energy correlation experiments

Abstract The γ-rays following reactions induced by bombarding targets of 114, 116, 118, 120, 122 Sn with 118 MeV 12 C ions were investigated using six NaI(Tl) detectors in a two-dimensional coincidence arrangement. Experimental energy-correlation spectra were extracted from the original coincidence matrices. The energy-correlation spectra exhibit the features expected for rotational nuclei and were used to deduce information on the moment of inertia I (2) = ΔI/Δω . The gross properties of the behaviour of I (2) in the Ba-Xe region are discussed together with their interpretation within the cranked shell model (CSM).

Study of high spins in 173Os

High-spin states in 173Os have been studied by γγ-coincidence measurements following the 146Nd(32S, 5n)173Os reaction. Additional information has also been extracted from the reaction 144Sm(32S, 2pn)173Os. Four main sequencies have been identified as the two signature branches of the bands built on the [642]52+ and [523]52− Nilsson states. The band features have been analysed within the framework of the cranked shell model. The positive-parity band provides evidence for a v(i132)2 crossing at low frequency and a π(h112)2 and/or π(h92)2 cross In the negative-parity band the upbend starts at relatively low frequency indicating, presumably, an early v(i132)2 alignment. There is evidence for another two band crossings possibly due to v(i132)2 alignment of a different configuration and a high frequency proton alignment as in the positive-parity band. B(M1)/B(E2) ratios have also been extracted in both bands to deduce further information on the detailed structure of the bands.

The effective moment of inertia in 124Xe, 126–128Ba, 129,131Ce and 162Er isotopes

Abstract The γ-rays produced in the reactions of 118 MeV 12 C on 120 Sn, 122 Sn, 124 Te and 39.5 MeV 4 He on 161 Dy are investigated by using a sum spectrometer, a single NaI(Tl) detector and Ge(Li):s. Different nuclei were selected by setting gates on known transitions in the Ge(Li) spectra. The second effective moment of inertia I (2) eff is extracted and compared with values from known discrete γ-rays as well as with the results from cranked shell model and cranked Nilsson-Strutinsky calculations. The systematics of the i 13 2 neutron orbital is investigated.

The Effective Moment of Inertia in 130Ce and 129La

The moments of inertia Jeff(2) are measured for 130Ce and 129La, which were produced in the reaction (118 MeV) 12C on 124Te and identified by means of Ge(Li)-gates. Comparison with other measurements of discrete gamma transitions and of Jband(2) are made.

Isomeric states and rotational structure in the doubly-odd nucleus176Ta

The doubly-odd nucleus176Ta is investigated by means of in-beamγ-ray spectroscopy techniques using the reactions (α, 3n), (d, 2n) and (p, n). Life-time measurements in thens-region yield low-lying isomeric states withT1/2=13±1 ns and 30.5±1 ns, while measurements in the ms-region show the existence of a 1.1±0.1 ms isomeric state. A rotational sequence, withK=5 or 6 for the band-head, is also observed.