0000000000010354
AUTHOR
J. Hattula
In-beam study of the 128, 130Xe nuclei
Abstract The level structure of 128,130Xe has been studied in the (α, 2nγ) and (3He, 3nγ) reactions on enriched Te targets using in-beam γ-ray spectroscopic methods. For both nuclei the existing information about positive-parity level structure was enriched and many new negative-parity two-quasiparticle states were observed. Isomeric states with the half-lives of 63 ± 12 ns in 128 Xe and 4.8 ± 0.5 ns in 130 Xe were found. For collective positive-parity states the interacting boson model, and calculations based on Bohr hamiltonian were compared with the experimental data.
High-j bands in 173Ir
Abstract High-spin states in rotational bands associated with the 11 2 − [505] , 1 2 − [541] and 1 2 + [660] Nilsson orbits have been observed in the previously unknown 173Ir nucleus using the 144Sm(32S,p2n) reaction at 163 MeV. The B(M1; I → I − 1)/B(E2; I → I −2) ratios have been extracted for the 11 2 − [505] band and compared with predictions of the semiempirical model by Donau and Frauendorf. The quasineutron band crossing frequencies and alignment gains are discussed in terms of the CSM model. Calculations for equilibrium deformations suggest different deformations for the three bands observed.
The use of the integral-bias summing coincidence spectrometer in directional correlation measurements
Abstract The performance of the integral-bias summing coincidence spectrometer (the sum-peak spetrometer) in measurements of directional correlations of gamma rays has been tested. As compared with the conventional method, the sum-peak spectrometer is easier to use and seems to yield results which agree with those obtained with the ordinary method. Because of the complex shapes of response functions of gamma rays above about 3 MeV, the new method is best suited to the study of cascading transitions below this energy, where the two methods appear to complement each other. The analysis of the sum-peak spectra in the present work is based on a simple graphical method which seems to yield satis…
High-spin states in110Cd
Levels of110Cd have been investigated via the96Zr(18O,4n)110Cd reaction by employing the NORD-BALL array of 17 Compton- suppressed Ge detectors. The yrast band has been observed up to I=28 ħ and 14.2 MeV excitation energy with band crossing at ħωc=0.35 MeV. At least three side bands have been constructed. The negative parity bands experience band crossings at ħωc ≈ 0.45 MeV.
Transition from Prolate to Oblate to Triaxial Shapes in158Yb
The decay of the entry states in ISIYb populated in the reactions of 149 MeV ,oNe with ,44Nd and lUNd has been investigated with a 4" multidetector system gated by a Ge counter. The average excitation energy, the ,.-ray spectra and the angular distribu tions as a function of multiplicity show several changes in the ,.-ray decay. These changes suggest a transition from prolate to particle aligned oblate connguration at low spin. At 1- 38-48 collective transitions with dipole and quad rupole component possibly built on high K single particle states are observed. Furthennore, above 1- 48 the dipole component disappears suggesting a further change toward more triaxial shape.
Lifetimes of yrast states in 110Cd
Abstract Lifetimes or lifetime limits of 20 yrast levels in 110 Cd have been measured using the recoil-distance method and the NORDBALL array of Compton-suppressed Ge detectors. From the reduced transition probabilities competing rotational and vibrational behaviour of 110 Cd is revealed. Also non-collective states, associated with proton configurations, have been observed.
Level structure of120Sn from the decay of120In and120Sb isomers
Gamma rays in the decay of the 3.2 s (1+) and 44 s (4, 5+)120In isomers and the 15.9 min (1+) and 5.8 d (8−)120Sb isomers have been investigated using Ge(Li) spectrometers and prompt and delayed Ge(Li)-NaI(Tl) coincidence techniques. The constructed level scheme of120Sn contains 18 levels at the following energies (keV): 0 (0+), 1171.6 (2+), 1875.6 (0+), 2096.9 (1, 2, 3), 2160.7 (0+), 2195.0 (4+), 2284.8 (5−), 2355.6 (2+), 2421.2 (1, 2, 3), 2466.3 (4+), 2482.1 (7−), 2643.5 (4+), 3058.6 (4+), 3179.7 (4+), 3349.9 (3, 4+), 3440 (3, 4+), 3447.6 (5, 6+) and 3777 (4+). The levels are compared with the levels obtained from recent charged-particle reaction studies and the structure of120Sn is brief…
A selective microscale x-ray fluorescence analyzing method for determination of trace elements
Abstract A new selective X-ray fluorescence analyzing method for trace element determination has been developed. In this method each trace element is measured independently. The excitation source is an X-ray tube that has a changeable anode and a variable high voltage. The exciting radiation is shaped with critical absorbers. The sample is viewed at backward angles through an absorber to reduce backscattered radiation. The estimated accuracy of this method is of the order of 10 per cent in thesub-ppm range of trace element concentration in organic samples. Measurement times are of the order of a few minutes.
Electromagnetic transition probabilities in 130Ce
Abstract Lifetimes of excited nuclear states have been measured in 130Ce using the coincidence-plunger technique. The employed nuclear reaction was 98Mo(36S, 4n)130Ce at a beam energy of 150 MeV. The measurement has been performed at the NSF Daresbury using the ESSA 30 set-up. It was possible to determine lifetimes for the 4+ to 16+ states in 130Ce. The experimental B(E2) values could be well reproduced by calculations using the triaxial rotor model with β = 0.26 and γ = 21° as well as the rotation vibration model (β = 0.25).
Simultaneous recording of true and random coincidences using a two-parameter analyzer system
Abstract A description is given of a simple fast coincidence method which allows the simultaneous recording of coincidence and random coincidence spectra. The method is based on the properties of a standard two-parameter pulse-height analyzer system, and no special electronics is required.
Non-yrast level structure of135Pr
Levels of135Pr populated in the (p,2n) reaction were studied using methods of in-beamγ-ray and conversion electron spectroscopy. Many low-lying positive-parity states give evidence of a deformation ofβ=0.15–0.20. The same conclusion is evident from band structures built on these positive-parity states and on theh11/2 negative-parity state. The triaxial rotor-plus-particle model reproduces quite well band structures withβ=0.20 andγ= 21°.
Levels of118Sn populated in the decay of118In and118Sb isomers
Gamma-rays in the disintegration of 5.0 s (1+), 8.5 s (7−, 8−), and 4.4 min (4+, 5+)118In isomers and of 3.5 min (1+) and 5.1 h (8−)118Sb isomers have been investigated using Ge(Li) detectors and Ge(Li)-NaI(Tl) coincidence spectrometers. The decay schemes of these isomers have been constructed incorporating 17 levels in the product nucleus,118Sn, at the following energies (in keV): 0 (0+), 1229.5 (2+), 1757.5 (0+), 2043.1 (2+), 2056.4 (0+), 2280.3 (4+), 2321.3 (5−), 2326.4 (1+, 2+), 2402.7 (4+), 2488.8 (4+), 2496.5 (0+), 2575.2 (7−), 2677.3, 2733.7 (2+), 2929.8, 2963.5 (4+), and 3137.1 (0+). The structure of118Sn is briefly discussed in view of results from recent quasiparticle-model calcul…
Directional correlations of some γ-ray cascades in200Hg
Directional correlation functions of 10 γ-ray cascades in200Hg have been measured using a200Tl source and a Ge(Li)-NaI(Tl) coincidence spectrometer arrangement. Values of the mixing parameter δ for several transitions are determined, and the spin assignments for the following levels in200Hg are established (level energies are given in keV): 1029.4 (0+), 1254.2 (2+), 1573.7 (2+), 1593.4 (2+), 1641.5 (2+), 1730.9 (2+) and 1775.6 (3+).
On the yrast two proton-two neutron hole states in208Po
High-spin levels in208Po, populated in the208Pb(α,4n)-reaction, were studied usingα-particles in the energy region 41–51 MeV. The energies of levels above the 6+ level have an uncertainty of about 10 keV due to the fact that the 8+→6+ transition has not been observed so far, but this transition has previously been established to be converted neither in theK-shell nor in theL-shells. It was found that the yrast cascade ofγ-rays from a 19+ level at 5896+e keV feeds levels of lower spin which all can be explained as originating from two proton-two neutron hole configurations. In the higher part of the cascade it is mainly the neutron holes which change their configuration, while the lower part…
Study of band crossings in 130Xe
Abstract Excited states in 130Xe were populated in the reaction 130 Te (α, 4 n ) , and the subsequent de-excitation was studied using in-beam γ-ray spectroscopic methods. High-spin states were observed to a possible spin of 19 kh at an excitation energy of 7 MeV. Band-crossings due to h 11 2 neutrons and protons were observed. The triaxial cranked shell model was applied in order to study the quasiparticle content of different bands. Excitation energies of two-quasiparticle states were calculated in the framework of the semiempirical shell model.