Low-spin states of153Gd observed in the decay of153Tb

Level structure of the 89-neutron nucleus¹⁵³Gd has been investigated by studying theEC-decay of isotope-separated¹⁵³Tb sources with several semiconductor detectors. In addition to singles gamma and electron spectra,γ-γ ande ^?-γ coincidences were investigated by using Ge(Li) and Si(Li) spectrometers and a high-capacity two-parameter recording system. In all, 191γ-rays are assigned to the decay of the 2.4d¹⁵³Tb. The proposed level scheme of¹⁵³Gd containing most of the observed transitions shows a very high density of low-spin states (45 states below 1.5MeV). Spin and/or parity assignments based mainly on coincidence data and measured transition multipolarities are proposed for a majority of these states. Nilsson model classifications of some levels are discussed. On the basis of logf t values the spin and parity of the ground state of¹⁵³Tb are suggested to be 3/2⁺ or 5/2⁺.     

Studies of γ-ray transitions in171Yb

The decay of¹⁷¹ Lu(t_1/2=8.2 day) to the levels of¹⁷¹Yb has been studied using large volume high resolution Ge(Li), x-ray Ge(Li) and NaI(Tl) detectors.γ-γ coincidence and directional correlation experiments have been performed. Spin-parity of 5/2^?, 7/2⁺, 5/2^?, 9/2⁺, 7/2^?, 7/2^?, 11/2⁺, 9/2^?, 9/2^? and 5/2^? have been assigned to the 75.87, 95.26, 122.37, 167.62, 208.00, 230.61, 259.02, 835.21, 948.37 and 1024.87 keV levels respectively. Several new coincidence relations have been observed in the present work. Two newγ-transitions at 141.45 and 821.30 keV observed and two levels at 766 and 944 keV been proposed. Multipolarity assignments have been made for most of theγ-transitions from theK-shell internal conversion coefficients obtained using the presentγ-ray intensities and the published conversion electron intensities. A revised level scheme for¹⁷¹Yb has been proposed and compared with published data. Radioactivity¹⁷¹Lu; measuredT _1/2,E _γ ,I _γ ,γγ coin,γγ (θ), I.C.C.,¹⁷¹Yb deduced levels,J, γ-mixing,π. Enriched targets, Ge(Li) detectors.     

Studies on the level structure of154Gd via the β-decay of154Eu nucleus

The excited states of¹⁵⁴Gd populated by theβ-decay of¹⁵⁴Eu (T _1/2=8.5y) have been studied. With a HPGe-NaI (T1) Compton suppression spectrometer and a HPGe-NaI(T1) coincidence circuitυ-ray singles spectra, coincidence spectra and theγ-γ directional correlational functions have been obtained. The deduced mixing ratios of multipolarities are presented. The energy levels and the relativeB(E2) values of the variousγ-transitions in¹⁵⁴Gd nucleus have been calculated both in the IBA model and it's extended version with boson surface delta interaction (BSDI).     

Decay of149Gd and directional correlations of gamma cascades in149Eu

The decay of¹⁴⁹Gd(9.4d) to the levels of¹⁴⁹Eu has been studied using large volume high resolution Ge(Li) and NaI(Tl) detectors,γ-γ coincidence and directional correlation experiments have been performed. Newγ-rays at energies 131.9, 278.6, 384.7, 415.7, 599.2, 726.5, 734.7, 956.4 and 1,231.1 keV in¹⁴⁹Eu have been observed. Three new levels in¹⁴⁹Eu have been placed at 956.4, 1,082.0 and 1,231.1 keV. Spin-parity assignments have been made to some of the levels in¹⁴⁹Eu. Multipolarity assignments have been made for most of the electromagnetic transitions from the conversion coefficients obtained through the knowledge of ourγ-transition intensities and the published conversion-electron intensities. Based on the newγ-transitions observed in the singles and coincidence spectra, a revised level scheme has been proposed for¹⁴⁹Eu and compared with previously published level schemes. Radioactivity¹⁴⁹Gd; measuredT _1/2,T _γ,γγ coin, γγ(θ), I.C.C.,¹⁴⁹Eu deduced levels,J,γ-mixing,π. Enriched targets, Ge(Li) detectors.     

Ground state properties and β-decay half-lives near 132Sn in a self-consistent theory

The level scheme of⁹⁵Tc has been investigated with Ge(Li)-detectors by observing the γ-rays after the decay of 1.65 h⁹⁵Ru. The energies and intensities of theγtransitions were extracted fromγ-singles andγγ-coincidence spectra. In the decay of⁹⁵Ru 88γ-transitions were observed; a scheme of⁹⁵Tc with 25 levels is proposed into which 86 transitions could be accomodated. Spin and parity assignments were made from log (ft) values andγ-ray branching ratios. The level structure of⁹⁵Tc is compared with that of the other odd Tc isotopes.     

Rotational bands in79Kr

The level scheme of⁷⁹Kr has been studied through the⁷⁹Br(p,n)⁷⁹Kr reaction at proton energies from 1·7 to 5·0 MeV.γ-ray and internal conversion electron measurements were made using Ge(Li) detectors and a six gap “Orange” electron spectrometer. The level scheme was established by determining the thresholds of variousγ-rays and byγ-γ and n-γ coincidence measurements. New levels at 402, 450, 660, 676, 695, 720, 810, 836, 907 and 1038 keV not observed in earlier radioactivity studies have been established. DefiniteJ ^π assignments have been made to most of the levels below 800 keV. Many of the low-lying levels are identified as rotational levels based on the (301 ↓) 1/2^?, (301 ↑) 3/2^? and (431 ↓) 1/2⁺ Nilsson states.     

Spectroscopy of highly excited states in29Si

Particleγ-ray coincidences have been measured in the²⁸Si (d,pγ) reaction at 6.5 and 7 MeV bombarding energy, in the²⁶Mg (α,nγ) reaction at 12, 14 and 15 MeV, and in the²⁷A1 (τ,pγ) reaction at 9 MeV. Theγ-decay has been observed for all bound states of²⁹Si and for 56 unbound states up to 12,960 KeV excitation energy. Particleγ-ray angular correlations were measured in the²⁸Si (d,pγ) reaction at 6.5 MeV and in the²⁶Mg (α,nγ) reaction at 12 MeV. Spin (-parity) assignments or restrictions were obtained for nearly all bound states and some high-spin states above the binding energy. The assignment of mirror levels in²⁹Si and²⁹P has been extended to 8.2 MeV excitation energy. The excitation energies of 41 positive-parity states are reproduced by shell model calculations. The possible existence of aK ^π=5/2⁺ band with prolate deformation is discussed.     

High-spin states in108Sn

High spin states in¹⁰⁸Sn have been investigated using the⁹²Mo(¹⁹F,p2nγ)¹⁰⁸Sn reaction. In-beam measurements ofγ-γ-coincidences,γ-ray excitation functions andγ-ray angular distributions were performed with Ge(Li)-detectors, one of which had a Nal Compton suppression shield. A level scheme for¹⁰⁸Sn has been constructed up to anI ^π=(14^?) state.     

On the decay of73Ga to levels in73Ge

Theγ-radiation following the β^? decay of⁷³Ga has been studied. Singlesγ andγγ coincidence spectra were recorded with Ge(Li)-detectors. 17γ-rays were assigned to transitions in⁷³Ge, where 11 excited levels are proposed. From logft values based onγ-transition intensities, spin and parity assignments for the levels were deduced. The half-life of⁷³Ga was measured to (4.86±0.03) h. From allowedβ-transitions the ground state of⁷³Ga was assigned 3/2^?.     

Yrast and side bands in the odd-odd160, 162Tm nuclei

High-spin states in²⁰⁵Bi, populated in the²⁰⁵Tl(α, 4n) reaction with bombarding energies around 50 MeV have been studied usingγ-ray spectroscopic techniques. Spins and parities have been assigned on the basis of angular distribution andγ-ray linear polarization measurements. States with spins up to 39/2⁺ and excitation energies around 6 MeV have been identified. Calculations using the empirical shell model have been performed in order to assign configurations.     

Tentative level diagram of146Pm below 1.1 MeV

The level scheme of the doubly odd nucleus¹⁴⁶Pm was investigated by means of in-beam spectroscopy. The¹⁴⁶Nd(p, n) reaction in the 3.5–8 MeV proton energy interval on enriched targets has been used to populate the exited states of¹⁴⁶Pm. High resolutionγ-ray spectra using Ge(Li) and hyperpure Ge detectors and conversion electrons with a mini-orange spectrometer were measured. Withγ-exitation functions andnγ-coincidences usingnγ-discriminated NE231 neutron detectors transitions in¹⁴⁶Pm were identified,γγ-coincidences gave information aboutγ-cascades. With these data a level scheme of 38 levels below 1.1 MeV exitation energy has been deduced including 73 transitions. For 12 transitions experimental conversion coefficients have been evaluated, which agree with the expected values forM1/E2-transitions.     

High-spin levels in138Ce and140Nd Observed in the (α, 4n γ) reactions

Levels of¹³⁸Ce and¹⁴⁰Nd have been studied using the¹³⁸Ba(α,4nγ)¹³⁸Ce and¹⁴⁰Ce(α, 4nγ)¹⁴⁰Nd reactions. Singleγ-ray spectra,γ-γ coincidence spectra, angular and time distributions with respect to the beam bursts have been measured. A number of higher excited states with excitation energies up to about 5 MeV and with spin value up to 12 are populated in both nuclei. The lower states with spins and parities 7^?, 5^?, 6^? and 10⁺ can be explained by two-quasiparticle neutron configurations of the types (h _11/2 ^?1 ,d _3/2 ^?1 ) 7^? , (h _11/2 ^?1 ,S _1/2 ^?1 ) 5^?, 6^? and (h _11/2 ^?2 ) 10⁺. Several high-spin states observed in¹³⁸Ce and¹⁴⁰Nd can be explained qualitatively as four-quasiparticle states with two-proton-two-neutron configurations. The 3^? state at an energy of 2,137.4 keV is observed in¹³⁸Ce. The evidence for the existence of the low-lying 3^? states in¹⁴⁰Nd at 2,124.0 keV is discussed. Beside the known 9.6 ms (7^?) isomeric state in¹³⁸Ce another state at 3,538.5keV (10⁺) with a half life of about 200 ns has been observed. The observed levels in the¹³⁸Ce and¹⁴⁰Nd nuclei are compared with theoretical predictions using delta force interaction.     

Spectroscopy of198,199Po

Excited states in^198,199Po have been studied by in-beamγ-ray spectroscopy. These nuclei were produced in the 4n and 5n reaction channels for 115 MeV²⁰Ne on¹⁸³W-targets. Multipolarities and mixing ratios ofγ-transitions were determined from DCO-ratios, leading to spin/parity assignments. In¹⁹⁸Po,γ-cascades have been observed above several excited levels that are similar to the vibration-like structure built on the ground state. In¹⁹⁹Po, the coupling of the oddi13/2 neutron seems to favor the spherical shape of the even core; no levels resembling the intruder states of the even nuclei are found. A semi-quantitative evaluation of the cross-sections for nuclei produced in fission and multi-particle transfer is presented.     

Structure of the mirror nuclei21Ne and21Na

Theγ-decay of levels in²¹Ne up to 10 MeV excitation energy has been investigated byn — γ coincidence measurements initiated with the¹⁸O(α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining then — γ angular correlation measurements performed atE _α=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleus²¹Na. The resulting values of E_x[keV]?J ^π are as follows: 4525-5⁺, 4686-3⁺, 5431-7⁺, 5549-3⁺, 5819-7^?, 6175-7⁺, 6268-9⁺, 6550-9, 6639-9, 7006-7⁺, 7041-9, 7356-7 or 9, 7422-11^(?), 7648-7⁺, 7981-11 or (7⁺), 8154-9, 8240-11, 8664-9^? or 11 or 13^?, 9401-13^?, 9867-13^? or 15⁺, 9941-13^? or 15 or 17⁺. The assignment of mirror levels in²¹Ne —²¹Na has been extended to the 6175 keV level of²¹Ne. Excitation energies, electromagnetic properties, Gamow?Teller matrix elements and spectroscopic factors of positive parity states are compared with the results of 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. Collective properties contained in shell model wave functions are explored up to the termination of bands atJ=17/2 or 19/2. The spectrum of intruder states in²¹Ne is observed to begin with a 5628 keV,J ^π=7/2⁺ state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands.     

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.     

The structure of25Mg

Gamma-decay modes and spin(-parity) assignments of levels in²⁵Mg have been systematically investigated up to 10 MeV excitation energy by particle-γ-ray angularcorrelation measurements with the²⁴Mg(d, pγ) reaction at 6.5 MeV bombarding energy and with the²²Ne(α,nγ) reaction at 11.8, 12.5, 14.4 and 15.5 MeV bombarding energy. A level scheme has been established which is comprehensive up to 8.3 MeV excitation energy forI≦9/2 and up to 10 MeV for 9/2O d _5/2 — 1s _1/2-O d _3/2 shell and the unifieds-d shell Hamiltonian. The agreement is good to excellent. The first intruder states are located near 6.8 MeV excitation energy. The collective properties of²⁵Mg beyond the well established rotational bands are investigated using both the new experimental information and theB(E2)'s obtained from the shell model. The spectrum of²⁵Mg is completely rotational for the first five to six MeV above the yrast line. Shell modelB (M 1)'s reflect the Nilsson model structure of²⁵Mg in great detail. The prospectiveI ^π=9/2^?, 13/2^?, and 15/2^? members of the established negative-parity,K=1/2 band are found in levels atE _x=7801, 9410, and 8896 keV.     

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.     

Search for an isomer in94Rb

Measurements of theβ-ray half-life,γ-ray and X-ray spectra andγ-ray half-lives have been done with a plastic scintillation detector, a high resolution Ge(HP) detector and a 142 cm³ Ge(Li) detector to search for an isomeric state in⁹⁴Rb. Mass-separated activities of⁹⁴Rb were obtained from the He-jet type on-line mass-separator at the Kyoto University reactor. No isomeric transition was found in theγ-ray and X-ray measurements with the upper limits of 3×10^?4 and 8×10^?5, respectively, as compared with the 836.9 keV transition. Half-lives obtained from theγ-ray decay measurements are discussed in the light of classification given byQ _β -value measurements.     

Transition probabilities and energy levels in heavy odd-mass isotopes of Sn (A=119–125)

The de-excitation of levels in^119–125Sn populated in the decay of In isotopes has been studied using on-line isotope separators. Level half-lives have been measured in^119–123Sn. a near cancellation of the matrix element for B(E2; g_7/2→ d_3/2) is observed to occur in¹²¹Sn and is probably due to pairing effects. Very low lying 9/2^? levels have been observed in^121–125Sn and are suggested in^{127, 129}Sn. These levels have been interpreted as three quasi-particle states based on the unique parity h_11/2 level. A possible mixing of theg _7/2 level with a close lying 7/2⁺ three quasi-particle state in¹²³Sn is discussed. Radioactivity.^119–125In from²³⁵U(n, f) and²³⁸U(α, f), isotope separated sources; measuredE _γ ,I _γ , E_ce, I_ce,γγ-coin,Βγ-delay, deduced multipolarities.^119–123Sn deduced levels,I, π, B(λ). Ge(Li), Si(Li), NaI(Tl) and plastic detectors, Ge(Li)-Ge(Li) coin, plastic detector — NaI(Tl) delay.     

Der Zerfall des Fe53g und des Fe53m

Theγ-ray spectra from the decays of 8.5 min-Fe^53g and a new (2.51±0.02) min-Fe^53m have been investigated by means of Ge(Li)-detectors. As far as the Fe^53g -decay is concerned no other but the known 380 keV-transition (43%) has been observed indicating that the proceedingΒ ⁺-decay leads to the groundstate and first excited state of Mn⁵³ only. This contradicts formerΒ ⁺-spectroscopic results but is consistent with recent spin assignments. In the Fe^53m -decay fourγ-transitions have been found: 701 keV (100%), 1011 keV (76%), 1328 keV (76%), and 2339 keV (24%). The proposed level scheme of Fe⁵³: 0 keV (7/2^?), 1328 keV (9/2^?), 2339 keV (11/2^?), and 3040 keV (19/2^?, 2.5 min) is in agreement with results published recently byEskola. The level schemes of Mn⁵³ and Fe⁵³ are discussed in terms of the individual particle shell model.