High spin states in73Se observed by the reaction70Ge(α,nγ)

⁷³Se has been investigated by the reaction⁷⁰Ge(α, nγ). Gamma excitation functions (E _α=10–16 MeV), gamma angular distributions (E _α=18 MeV) and gamma-gamma coincidences (E _α=15 MeV)) have been taken. A level scheme has been established, spins and partities have been assigned. States of a rotational band on the 151.2 keV (5/2^?) state and an anomalous band have been identified. Nuclear Reaction⁷⁰Ge(α,nγ)E _α=15 and 18 MeV; measuredE _γ,I _γ,γ-γ-coin.,γ-angular distribution,γ-excitation function.⁷³Se deduced levels,J, π. Enriched target, Ge(Li).     

High spin states in77Se populated by the74Ge(α,n γ) reaction

⁷⁷Se has been investigated by the reaction⁷⁴Ge(α,nγ) at 14 MeV. Gamma singles spectra, gamma angular distributions and gamma-gamma coincidences have been taken. A level scheme has been established, spins and parities have been assigned. States of a rotational band on the 1/2^? ground state, a rotational band on the 5/2^? 249.7 keV state and an anormal band have been identified. Nuclear Reaction ⁷⁴Ge(α,n γ)E _α=14 MeV; measuredE _γ ,I _γ ,γ-γ-Coin.,γ-ang. distr.⁷⁷Se deduced levels,J, π. Enriched target, Ge (Li).     

High spin states in75Se populated by the72Ge(α,n) and73Ge(α, 2n) reaction

The⁷²Ge(α, n)⁷⁵Se and⁷³Ge(α, 2n)⁷⁵Se reactions have been studied at bombarding energies of 15 MeV and 22.5 MeV respectively using Ge(Li)-detectors.γ-singles spectra,γ-γ-coincidences,γ-angular distributions and excitation functions have been taken. A level scheme has been constructed, which contains a stretched spin and a normal rotational band. Nuclear reactions⁷²Ge(α, n)⁷⁵Se,⁷³Ge(α, 2n)⁷⁵Se; measuredE _γ ,I _γ ,γ-γ-coincidences,γ-angular distribution,γ-excitation function.⁷⁵Se deduced levels,J, π, γ-multipolarity. Enriched target, Ge(Li).     

79Se investigated by the reaction76Ge(α, nγ)

⁷⁹Se has been investigated by the reaction⁷⁶Ge(α, nγ). Gamma excitation functions (E _{α=10?15 MeV)}, gamma angular distributions and gamma-gamma coincidences (both at (E _{α=12 MeV)}, have been taken. A level scheme has been established, spins and partities have been assigned. The results are compared with rotational bands in neighbouring odd Se isotopes. Nuclear reaction⁷⁶Ge(α, nγ)E _α =12 MeV; measuredE _γ,I _γ,γ-γ coincidences,γ-angular distribution,γ-excitation function.⁷⁹Se deduced levels,J, π. Enriched target, Ge(Li).     

High-spin states in112Cd from the110Pd(α, 2n γ)-reaction

The decay scheme of¹¹²Cd has been studied by γ-ray spectroscopy with the¹¹⁰Pd(α, 2nγ) reaction. Spin and parity assignments were made on the basis of coincidence measurements, angular distributions and excitation functions. Twelve new energy levels were established. A vibrational-like positive-parity band up to spin 8⁺ and a negativeparity side band 5^?, (7^?), (9^?) were found. For the negative-parity states a (v_j, vh_11/2) configuration is suggested. Nuclear Reactions:¹¹⁰Pd(α,2nγ),E _α =15–22.5 MeV; measuredE _γ ,E _γ , (E,E _γ ),E _γ (θ),γ-γ- coincidence;¹¹²Cd deduced levels,J; enriched target.     

70Ge(α, γ)74Se cross section measurements at energies of astrophysical interest

The cross section of the reaction⁷⁰Ge(α, γ)⁷⁴Se has been measured over the bombarding energy range of 5.05 MeV <E _α < 7.80 MeV using single and coincidence gamma spectroscopy techniques. The experimental S-factor values are in agreement with theoretical statistical-model calculations. Reaction rates for the⁷⁰Ge(α, γ)⁷⁴Se and the inverse (γ, α) reactions have been determined for appropriate temperatures.     

Collective excitations in145Ba

High-spin levels in¹²⁵Ba have been produced in the¹¹⁶Sn(¹² C, 3n) reaction and studied by in-beam spectroscopic methods. Two strongly populated band structures are observed. The odd-parity one is based on a 7/2^? state and can be explained as the result of the coupling between anh _11/2 neutron-hole and a prolate type triaxial core. The even-parity band, built on a 7/2⁺ state, corresponds to collective excitations associated with a neutron-hole in theg _7/2 shell. Comparisons with heavier odd-A Ba isotopes and discussions are made in the frame work of the triaxial core model. Nuclear Reactions¹¹⁶Sn(¹²C, 3nγ), E=45–55 MeV; measuredσ(E;E _γ,θ),γγ-coinc,γ-γ delay. Enriched target, Ge(Li) detectors.¹²⁵Ba deduced levels,J,π,γ-mixing.     

70Ge(α, γ)74Se cross section measurements at energies of astrophysical interest

The cross section of the reaction ⁷⁰Ge(α, γ)⁷⁴Se has been measured over the bombarding energy range of 5.05 MeVα<7.80 MeV using single and coincidence gamma spectroscopy techniques. The experimental S-factor values are in agreement with theoretical statistical-model calculations. Reaction rates for the ⁷⁰Ge(α, γ)⁷⁴Se and the inverse (γ, α) reactions have been determined for appropriate temperatures.     

The level structure of69Ge

Theγ-ray decay of the states in⁶⁹Ge has been studied using the reaction⁶⁶Zn(α, nγ)⁶⁹Ge atE _α =13 and 19 MeV. The level scheme and spin assignments were established by means of coincidence measurements, angular distributions and excitation functions. 27 new levels could be found or confirmed. It is suggested that⁶⁹Ge is a further example for the weak coupling phenomenon in the medium mass nuclei. Nuclear Reactions: ⁶⁶Zn(α, nγ)⁶⁹Ge,E _α =13–22 MeV, measuredE _γ ,I _γ ,I _γ (θ),E _γ =f(E _α ),γ-γ coincidences,⁶⁹Ge deduced levels,J, enriched target.     

High-spin states in106Cd

Levels of¹⁰⁶Cd, populated by¹⁰⁴Pd(α, 2nγ)¹⁰⁶Cd have been studied measuring direct and delayedγ-ray spectra,γ-γ coincidences andγ-ray angular distributions. A decay level scheme is proposed including states up to 4659.8 keV. IntenseE2 transition cascades have been observed. The half-life of an isomeric level located at 4659.8 keV has been measured:T _1/2= 62±6ns. Nuclear Reactions ¹⁰⁴Pd(α, 2nγ),E _α=31MeV; measuredE _γ,I _γ,γ-γ coinc, σ(θ)T _1/2.¹⁰⁶Cd deduced levels,J, π, Enriched targets. Ge(Li) detectors.     

High-spin states in26Mg

Theγ-decays of levels in²⁶Mg have been investigated up to 12.5 MeV excitation energy by proton-γ-ray coincidence measurements in the²³Na(α, pγ) reaction at 14.2 and 16 MeV bombarding energy. Lifetime-measurements, made with the Doppler-shift attenuation method, and proton-γ-ray angular-correlation measurements were performed at E_α=14.2 MeV. Many high-spin states were observed, among them levels at 6,978 (5⁺), 7,283(4^?), 7,395(5⁺), 7,953(5^?), 8,202(6⁺), 8,472(6⁺), 9,065(5), 9,112(6⁺), 9,169(6^?), 9,383 (6⁺), 9,542(5), 9,829(7⁺), 9,989(6⁺) and 12,479(8⁺, 7^?) keV excitation energy. The spectrum of positive-parity states and their electromagnetic properties are reproduced with good accuracy by shell-model calculations which employ a unifieds-d shell Hamiltonian and the unrestricted configuration space of the 0d _5/2 1s _1/2 0d _3/2 shell. Members of five inferred rotational bands, withK ^π=0⁺, 2⁺, 3⁺, 0⁺ and 3^? have been observed up to at leastI=6. TheK ^π=2⁺ band shows strong anomalies of excitation energies andE2 transition rates near theI=6 state. The static intrinsic quadrupole moments calculated from the shell model wave functions indicate transitions from prolate to oblate deformation within theK ^π=2⁺ band and also the ground state band. The lowest lyingI ^π=4⁺ state appears to be “spherical” and cannot be associated with a rotational band.     

Collective and two-particle excitations in78Se

Excited states in⁷⁸Se have been studied up to spin (12)? at about 5.8 MeV in the⁷⁶Ge(α, 2n) reaction using in-beamγ-ray spectroscopy. Mean lifetimes could be determined for 27 of the 33 levels observed by applying Doppler shift and pulsed-beam timing methods. According to theB(E2) values most of the levels have been grouped into collective bands. Irregularities in the level spacings of the yrast band above spin 6? are interpreted to be due to the interaction of the ground state band withg _9/2 two-proton and two-neutron excitations. The mutual mixing of these configurations is reflected by strongM 1 transitions between the mixed states. The interaction strengths between the configurations involved have been estimated from three-band mixing calculations.     

Recoil distance lifetime measurements in82Kr

The lifetimes τ=124±12, 6 _?2 ⁺⁴ and 380±100 ps of theE _x (I ^π )=3.46(8⁺), 2.92(6⁺) and 3.04(6^?) MeV states, respectively, populated by the reaction⁷⁶Ge(¹²C,α2n) were measured with the recoil distance method. In addition upper lifetime limits were obtained for nine states. The measured lifetimes and energies indicate a band crossing at aboutI ^π =8⁺, probably arising from the alignment of twog _9/2 neutrons. For the 3.04 MeV 6^? state as a second member of a band built on the 2.65 MeV 4^? state the measured lifetime points to a two-quasiparticle configuration. The positive-parity states have been discussed in the frame of the interacting boson approximation, nuclear field theory and the cranked shell model.     

A study of 28Si(α, γ)32S resonances below Eα = 3.83 MeV

The γ-decays of eleven resonances in the ²⁸Si(α,γ)³²S reaction below E_α = 3.83 MeV have been studied using a large Ge(Li) detector. Results for branching ratios differ considerably from previous NaI work. The previous discrepancy in radiative strengths for the 2.61 MeV resonance is explained by this data. The strengths of the first five resonances at E_α = 1.77, 1.99, 2.19, 2.37 and 2.42 MeV appear to be (39 ± 13)% lower than previously reported. Spin-parities of l^?, 2⁺ and 2⁺ have been assigned to the levels at 8.50, 8.69 and 8.86 MeV respectively. The radiative width of the E_p = 1.467 MeV, J^π = 3^? resonance in the ³¹P(p,γ)³²S reaction has also been measured.     

In-beam study of excited states in80Br

Excited states of the doubly-odd nucleus⁸⁰Br have been studied via the reactions⁸⁰Se(p, n),⁸⁰Se(d,2n) and⁷⁸Se(α, pn) using in-beamγ-ray spectroscopy. A positiveparity level sequence built on aI ^π=5⁺ state at 331.04 keV has been found up to spin (10). For this 5⁺ level de-exciting to the known 5^? isomeric state and for the 6⁺ level at 357.22 keV half-lives of 0.7 and 0.4 ns, respectively, have been determined. Negativeparity states have been observed up to spin (6). For the positive-parity level sequence the configuration (πg _9/2,vg _9/2) and collective excitations are proposed. Some of the negative-parity states are tentatively interpreted as arising from the configurations (πp _3/2,vg _9/2) and (πp _3/2, (vg _9/2) ₇ ^2/3 ).     

Negative-parity bands in the 88-neutron nuclei153Tb and155Ho

Bands of negative-parity levels have been observed in in-beam studies of¹⁵³Tb and¹⁵⁵Ho. The data are qualitatively accounted for in the rotation-alignment model as decoupled bands based on the h_11/2 proton orbital. Nuclear Reactions:¹⁵³Eu(α, 4nγ)¹⁵³Tb,E=45–55 MeV;¹⁵⁰Sm(¹⁰B, 5nγ)¹⁵⁵Ho,E=60–70 MeV; measuredE _γ,I _γ (0), γ ? γ coinc.,E _e, I _e ^K ,¹⁵³Tb and¹⁵⁵Ho deduced levels,J, π. Ge(Li) and Si(Li) detectors. Enriched targets.     

In beam gamma spectroscopy of62Zn

The decay scheme of⁶²Zn has been investigated by studying the yield functions, angular distributions and coincidence relation-ships of theγ-rays emitted in the⁶³Cu(p, 2nγ) and⁶⁰Ni(α, 2nγ) reactions. Spins up to7? were assigned to the observed states. Nuclear Reactions ⁶⁰Ni(α, 2nγ)⁶²Zn,E _α=28–35 MeV and⁶³Cu(p, 2nγ)⁶²Zn,E _p = 22–31 MeV; measuredE _γ,I _γ(θ),I _γ(E _p , andI _γ,E _α-γ coincidences,⁶²Zn deduced decay scheme. Enriched target, Ge(Li) detectors.     

The four quasi-particle 178Hf isomeric state,its excitation energy and multipolarities of deexciting transitions

The decay properties of the 31 y ¹⁷⁸Hf isomeric state have been investigated by means of a Ge(Li)-NaI(Tl) Compton suppression device and a Si(Li) detector, as well as with Ge(Li) and Ge(Li), intrinsic Ge and Si(Li) coincidence arrangements. From the E3 character of the unobserved isomeric transition (11.7 ≦ E_IT ≦ 16.7 keV), deduced from L-subshell and M/L ratios, I^π, K of the isomeric level was determined as 16⁺, 16. The {p[404] ↓ + p1514] ↑ + n[514] ↓ + n[624]↑}_16⁺ + four quasi-particle configuration was assigned to this level at 2447.5 ± 2.5 keV. As proposed earlier the isomeric E3 transition decays to the 13^? level of the band built upon the I^π = 8^? isomer. The |g_K?g_R| values derived from $\text{E}\text{2}\text{M}\text{1}$ ratios of interband transitions show that the 8^? isomer contains about 36 % of the p[404] ↓ + p[514] ↑ configuration and about 64 % of the n[624] ↑ + n[514] ↓ configuration.     

The decay of83gSe and83mSe

The decay of the isomeric pair^83gSe (T1/2=22.6 min,I ^α = 9/2⁺) and^83mSe (T1/2=70 s,I ^α = 1/2^?) has been reinvestigated using straight Ge(Li) (^83gSe and^83mSe) and Ge(Li)-Ge(Li) coincidence spectrometry (^83gSe). Both decays populate entirely different⁸³Br levels, 11 of them being previously unreported. Fromγ-ray unbalances and from the known isomeric cross-section ratio of⁸²Se, β^?-branchings have been obtained, including a 34% branching of^83mSe to the ground state of⁸³Br. Logft-values are deduced, spin and parity values proposed and discussed.     

Isomere Wirkungsquerschnittsverhältnisse beim thermischen Neutroneneinfang im Bereich der 2p 1/2 und 1g 9/2 Schalenmodellzustände

Thermal capture cross sections and isomeric cross section ratios in thermal neutron capture were determined for even-even nuclei in the region of the 2p _1/2-1g _9/2 neutron shell. Capture cross sections for formation of Zn 69 ^m , Zn 71 ^m , Zn 71, Ge 71, Ge 75 ^m , Ge 77 ^m , Se 77 ^m , Se 79 ^m , Se 83 ^m , Se 83, Sr 85 ^m and Sr 87 ^m were measured by the activation method. From these data and additional measurements of cross section ratios the isomeric ratios for thermal capture in Zn 68, Zn 70, Ge 70, Ge 74, Ge 76, Se 76, Se 78, Se 80, Se 82 and Sr 84 were determined. In addition epithermal capture isomer ratios were determined for Zn 68, Ge 74, Ge 76, Se 80 and Sr 84. The isomer ratios are compared with calculations based on the statistical model ofHuizenga andVandenbosch. With the exception of Se 80 the measured ratios can be explained theoretically with reasonable values of the spin-cutoff-factorσ and gamma-ray multiplicityN, however there seems to be unexplained difference in eitherσ orN between the two groups of nuclei leading to either 1/2–7/2 or 1/2–9/2 isomers.