High-spin two-quasiparticle bands in76Br

Excited states of the doubly-odd nucleus V6Br have been studied with in-beam γ-ray spectroscopy techniques. In addition to the positive parity band that has been extended up to I=(13) a I^π=4^? isomer (T_1/2=0.5±0.2 ns) and two bands of negative parity have been identified. The bands are discussed in terms of two-quasiparticle configurations. For the band built on the 4_? isomer the configuration πg9/2?νf5/2 or p3/2 is proposed.     

Excited states of154Nd studied through the decay of154Pr

Excited states in the neutron-rich doubly-odd nucleus⁷⁸As have been identified for the first time by proton-γ and γ-γ coincidence measurements via the⁷⁶Ge(α, pn) reaction at 32, 36, and 40 MeV beam energy. Four levels have been found to decay with lifetimes in the nanosecond region. The 5⁽⁺⁾ to (10⁺) states are ascribed to the (πg _9/2?νg _9/2) intruder two-quasiparticle configuration with some collective components in the 9⁽⁺⁾ and (10⁺) states.     

New isomers and states of (πg 9/2 ⊗vg 9/2) parentage in84Rb

Excited states in the doubly-odd nucleus⁸⁴Rb have mainly been studied via the (α,n) reaction by means of in- beam γ-ray spectroscopy. Two new isomers have been found, a 5^? level at 467.1 keV and a 5⁽⁺⁾ level at 544.2 keV with half-lives of 9(2) ns. and 11(1) ns, respectively. On top of the 5⁽⁺⁾ isomer a level sequence with increasing spins up to 10 ? and probably positive parity has been identified. These states are ascribed to the configuration (πg_9/2?vg_9/2).     

Rotational and vibrational states in 115Te

High-spin states of the ¹¹⁵Te were studied by in-beam spectroscopy with the ⁸⁹Y (²⁹Si, p2n) fusion-evaporation reaction at a beam energy of 108 MeV. γ?γ coincidence and γ?γ angular correlation analyses were employed for determining the level scheme of ¹¹⁵Te. We have identified two vibrational-like bands built on the νh_11/2 and νg_7/2 quasiparticle states and the noncollective oblate states from the full alignment of quasiparticle configurations. In addition, a regular ΔI = 2 sequence with positive-parity was found for the first time in odd-A Te nuclei. This sequence is interpreted as a deformed structure resulting from three-quasiparticle alignment having the [π(g_7/2, h _11/2) ? ν(h _11/2)] configuration. Calculations of total Routhian surfaces and cranked shell model were performed and were used for assigning quasiparticle configurations to the states in ¹¹⁵Te.     

Collective bands in even mass Sn isotopes

Positive parity bands in ^{112, 114, 116, 118}Sn have been excited up to levels with spin and parity J^π = 12⁺ using Cd(α, 2nγ)Sn reactions. The experiments consisted of γ-ray excitation function, γ-γ coincidence, lifetime, γ-ray angular distribution, γ-ray linear polarization and conversion electron measurements. The observed bands show strong resemblances with ground-state bands of transitional nuclei in this mass region. It is pointed out that the J^π = 0⁺ band-heads originate from 2p-2h excitations in the Z = 50 proton shell. The excitation energies of the band-heads are calculated by means of the macroscopic-microscopic renormalization method. Pair correlations between the 2h and 2p configurations are included separately in a phenomenological way by taking into account the pairing energies of the Cd and Te ground states with respect to the Sn ground state.     

Particle × phonon multiplets in 65 147 Tb82

High-spin states of¹¹⁵Sb were studied by inbeamγ-ray spectroscopy using the⁸⁹Y (²⁹Si, 2pn) fusionevaporation reaction at a beam energy of 108 MeV. The experiments includedγ-γ coincidence and directional correlation of oriented nuclei (DCO) ratio measurements using six BGO Compton suppressed Ge detectors. An intruderΔJ=2 rotational band has been identified for the first time and it is interpreted as the h_11/2 proton coupled to a two particle-two hole (2p ? 2h) deformed state of the¹¹⁴Sn core. A ΔJ=1 rotational band based on the 2p ? 1h, π{g ₇ ^2/2 ?g ₉ ^2/?1 }, configuration has been extended to the 29/2⁺ state at an excitation energy of 5241 keV.     

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 ).     

Level properties of the light even Sb nuclei 112, 114, 116Sb

The level properties of ^{112, 114, 116}Sb have been investigated with the reactions ^112,114,116Sn(p, nγ)^112,114,116Sb and ¹¹⁵In(³He, xnγ)^112,114Sb (x = 6, 4). Singles γ and electron spectra, neutron-γ coincidences, γ-γ coincidences, excitation functions and half-lives were measured. Hauser-Feshbach calculations were performed for spin assignments. A number of new levels were found, including two 8^? isomeric states. The results are compared with recently performed 2qp calculations.     

In-beam gamma-ray spectroscopy of 116Te

High-spin states of the even-even ¹¹⁶Te were studied by in-beam g-ray spectroscopy using the ¹⁰³Rh (¹⁶O, p2n) fusion-evaporation reaction at a beam energy of 80 MeV. γ-γ coincidence and γ-γ angular correlation analyses were employed for determining the level scheme of ¹¹⁶Te. Levels up to I^π = 27^? and several new states were established. We identified two rotational bands with negative parity, one of which was newly established in the present work. We suggest that such two bands be associated with two proton [(g_7/2) ? (h_11/2)] and two neutron [(d_5/2) ? (h_11/2)] configurations, respectively.     

Collective structures and smooth band termination in 109Sn

Six rotational bands up to energies E _x = 24.7 MeV and spins J^π=(79/2^?) have been identified in ¹⁰⁹Sn using the GAMMASPHERE γ-detector array. Four of the bands show smoothly decreasing dynamic moments of inertia at rotational frequencies ?ω > 0.6 MeV. The bands arise at medium spins from a coupling of a valence d_5/2, g_7/2 or h_11/2 neutron to the deformed 2p2h proton excitation of the Z=50 core ¹⁰⁸Sn. At very high ?ω these bands show the typical behaviour of smoothly terminating bands, i.e. a gradual alignment of the angular momenta of the valence particles and holes corresponding to a transition from high collectivity to noncollective states.     

Structure of the doubly odd nucleus 180Ta: Description of 23 bands

The structure of the doubly-odd nucleus ¹⁸⁰Ta has been studied by γ–γ coincidence measurements with a DC beam at 52 and 57 MeV and time-correlated γ–γ coincidence measurements with a pulsed beam at 55 MeV via the ¹⁷⁶Yb(¹¹B, α3n)¹⁸⁰Ta reaction. In all measurements, γ-rays were detected in coincidence with charged particles. In the time-correlated γ–γ coincidence measurements with a pulsed ¹¹B beam, three rotational bands and one octupole vibrational band have been identified above the I^π=15⁻ T_1/2=30 μs isomer. The configuration of three bands built on 8⁺ states has been discussed by means of three-band mixing calculations. BCS calculations with blocking have been used in support of configuration assignment of four- and six-quasiparticle structures. Totally, 19 rotational bands, one β-, one γ- and two octupole-vibrational bands, plus one intrinsic state have been identified with two-, four- and six-quasiparticle configurations. The K values of these bands range from 0 to 19. The K-forbidden transition rates are discussed on the basis of mixing between states with widely different K-values. The BBCS calculations predict a K^π=22⁻ isomer not identified experimentally in this nor in previous works.A search for specific intermediate states which could explain the transformation from K^π=9⁻ to 1⁺ during the astrophysical s- and r- processes was negative.     

On theβ − decay of the 2s isomer in98Y and the existence of an intruder band in98Zr

The γ radiation from the ß^? decay of the high-spin isomer in⁹⁸Y has been studied at the separator JOSEF. A main goal was to get insight into the spins of levels in⁹⁸Zr which have been interpreted as members of an intruder band based on the 0₂ ⁺ state at 854 keV. The measuredγ-γ angular-correlations lead to the assignment of spins of 4 and 3 ? to the 2491 and 1844 keV levels, respectively, and contradict their interpretation as the 6⁺ and 4⁺ states of the proposed band. For the 2.0s isomer of⁹⁸Y, the ß{?}-decay properties suggest I=5 with a major configuration [πg_9/2,νs_1/2(g² _7/2)₀].     

The deformation of the ground and excited states in the Ag and Sn nuclei

The microscopic calculation of the potential energies in the ground and excited states of Ag and Sn nuclei has been performed. The single particle Nilsson potential and the shell correction Strutinski method have been used. The weak sensitivness to nonaxial deformation has been found for even neighbours of these nuclei. The small tendency towards prolate deformation of the ground and excited one-quasiparticle states originating from theg _9/2 proton subshell in^101–105Ag odd isotopes has been noticed. The behaviour with quadrupole e and hexadecapole ε₄ deformation of the ground and two-quasiparticle excited 0⁺ states originating from thed _5/2,g _9/2 andg _7/2 proton subshells andh _11/2 neutron subshell in^112–118Sn has been investigated. The small quadrupole deformation of the excited 0⁺ states has been found what is in agreement with the experimental data concerning the rotational bands build on the first excited 0⁺ states in Sn isotopes.     

Gamma-ray spectroscopy of87Y

The level structure of⁸⁷Y has been studied using in-beam γ-ray spectroscopic methods. Many previously unknown states have been observed. Members of theπ(g _9/2 )ν(g _9/2)^?2 multiplet are identified. The results are discussed in terms of the weak-coupling model.     

Microscopic study of positive-parity yrast bands of 224−234Th isotopes

The positive-parity bands in ^224???234Th are studied using the projected shell model (PSM) approach. The energy levels, deformation systematics, B(E2) transition probabilities and nuclear g-factors are calculated and compared with the experimental data. The calculation reproduces the observed positive-parity yrast bands and B(E2) transition probabilities. Measurement of B(E2) transition probabilities for higher spins and g-factors would be a stringent test for our predictions. The results of theoretical calculations indicate that the deformation systematics in ^224???234Th isotopes depend on the occupation of low k components of high j orbits in the valence space and the deformation producing tendency of the neutron–proton interaction operating between spin orbit partner (SOP) orbits, the [(2g_9/2) _π –(2g_7/2) _ν ] and [(1i_13/2) _π –(1i_11/2) _ν ] SOP orbits in the present context. In addition, the deformation systematics also depend on the polarization of (1h_11/2) _π orbit. The low-lying states of yrast spectra are found to arise from 0-quasiparticle (qp) intrinsic states whereas the high-spin states turn out to possess composite structure.     

The decay of theI π=8+ isomer in100Cd-neutron particle and proton hole states

The γ-decay and half life of the t_1/2=60(3) ns I^π=8⁺ isomer in¹⁰⁰Cd have been studied with a recoil catcher setup inside the multidetector π-array OSIRIS. Evaporation neutrons and charged particles from the reaction⁵⁸Ni+⁴⁶Ti were measured in coincidence with delayed γ-rays. Six new γ-ray transitions with intensities of 1–10% of the main γ-ray cascade were found, two new states established and firm spin-parity assignments were made to all states below the isomer. The new states were identified as the 4⁺ and 6⁺ members of the proton πg_9/2 ^?2 multiplet.     

A neutron decoupled from a rotating odd core in 114Sb and 116Sb

The ^{113, 115}In(α, 3nγ)^{114, 116}Sb reactions have been studied using γ-ray spectroscopic techniques. The experiments included γ-ray excitation function, γ-γ coincidence, lifetime, γ-ray angular distribution and conversion electron measurements. A ΔJ = 1 rotational band has been observed in either of the ^{114, 116}Sb final nuclei. Energy spacings and electromagnetic properties of the band show strong resemblances with those of rotational bands in the adjacent odd-mass Sb nuclei. In addition two-quasiparticle and two-quasiparticle core coupled states have been observed in these nuclei. One isomer was identified in ¹¹⁶Sb, i.e. a J^π = 11⁺ state at 1889 keV ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext><mtext>\; =\; 4.0\pm 0.1\; </mtext><mtext>ns</mtext>}}$). A simple model is proposed which explains the ΔJ = 1 band in terms of rotational alignment of the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ neutron with the deformed rotating odd-A core.     

Circular polarization and γ-γ angular correlation measurements in the 39K(n, γ)40K reaction

Circular polarization measurements of the γ-radiation from polarized neutron capture combined with γ-γ angular correlation measurements in the ³⁹K(n,γ)⁴⁰K reaction lead to J^π = 2^? assignments to the E_x = 0.80, 2.05 and 2.42 MeV states of ⁴⁰K, and to spin restrictions for the states at E_x = 2.10, 3.44 and 4.25 MeV. Multipole mixing ratios for the γ-rays which de-excite these levels have been determined.     

Level structure in 117Sb investigated in the decay of the isomeric three-quasiparticle state

The level structure of ¹¹⁷Sb was investigated in the reactions ¹¹⁵In(α, 2nγ)^117mSb, ¹¹⁷Sn(d, 2nγ)^117mSb and ¹¹⁷Sn(p, nγ)^117mSb. In order to confirm level sequences and to assign spins and parities to levels populated in the decay of the isomeric three-particle state $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ = 340 μs), prompt and delayed γ-ray spectra, lifetimes, γ-γ coincidences, γ-ray angular distributions, conversion electrons and excitation functions were measured. The spin $\text{25}\text{2}$⁺ of the isomeric state can be explained by the three-particle configuration [$\text{π(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{); v(}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}^2\text{10}{}^{\mathrm{+}}\text{]}\text{25}\text{2}{}^{\mathrm{+}}$. This is supported by the experimentally determined g-factor of g = O.115 ± 0.006. Other levels in ¹¹⁷Sb can be interpreted as particle states coupled to anharmonic vibrations of the core. The existence of an excited $\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$ quasirotational band is experimentally proved and is supported by calculations of the equilibrium deformation.     

Decay properties of ground-state and isomer of 103In

The β-decay properties of ground-state and isomer of ¹⁰³In were investigated by means of γ-ray spectroscopy. The half-lives of ^103g In and ^103m In were determined to be 60 ± 1 s and 34 ± 2 s, respectively. Out of 149 γ transitions ascribed to the decay of ^103g In, 104 have been placed in a decay scheme including 55 excited states of ^103g Cd. The main part of the resulting distribution of the Gamow-Teller strength B(GT) is associated with the feeding of ¹⁰³Cd levels at excitation energies around 3 MeV. This observation can be interpreted as a sign of dominant feeding of three-quasiparticle states in ¹⁰³Cd, which correspond to the 1⁺(πg _9/2 ^?1 , vg_7/2)?πg_9/2 shell-model configuration spread over many levels. The sum of the B(GT) values deduced from the present γ-ray data amounts to 0. 34, which provides a lower limit to the total Gamow-Teller strength. The B(GT) distribution for ¹⁰³In decay is compared to the corresponding experimental results for ^105,107,109In and to theoretical predictions for ^99,101In. The latter were calculated by using an advanced spherical shell model. The β-branching ratio for the ^103m In decay is estimated and compared with the relevant values for the neighbouring indium isotopes including ¹⁰¹In whose half-life was determined to be 14. 9 ± 1.2 s.