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.     

Reinvestigation of the decay scheme of the short-lived isomeric states in112In

The two short-lived isomeric states in¹¹²In have been reinvestigated by means of the¹¹²Cd(d, 2n) and¹⁰⁹Ag (α, n) reactions. Measurements of delayed X- andγ-ray, lifetime and TDPAD spectra have been performed. A 6.32(3) keVγ-ray has been identified in the isomeric decay and anM1 multipolarity has been assigned to it on the basis of the measured internal conversion coefficients:α _L =196(39) andα _tot=231(35). TheE1+M2(δ =+0.24(4)) andE2 multipolarities have been determined for the 263 and 188 keV transitions deexciting the 8^?(T _1/2=2.82(2) μs) and 7⁺ (T _1/2=0.93(2) μs) isomeric states, respectively. A revised isomeric decay scheme is presented.     

Low-lying states in112In

Low-lying states below 500 keV excitation in¹¹²In have been investigated via the¹¹²Cd(p, nγ) reaction. New levels have been established atE ^x=206.5keV and 456.1 keV from the measuredγ-ray excitation functions,γ?γ coincidences and the precision measurements of the (p, n) threshold energy of the ground state and of the 206.5 keV state of¹¹²In. Spins and parities of the 206.5 keV state (2⁺) and the 456.1 keV state (3⁺) and multipolarities and mixing ratios of the deexcitationγ-rays have been determined from the angular distributions and linear polarizations of the deexcitation γ-rays as well as the excitation functions of the residual levels. Possible configurations of the newly-found levels are discussed. Half-lives of two states have been remeasured:T _1/2=15.2±0.1 min for the ground state andT _1/2=20.9±0.1 min for the 156.4 keV (4⁺) state. The ground stateQ-value for the¹¹²Cd(p, n)¹¹² In reaction has been measured to be ?3.376±0.006 MeV.     

Low-lying excited states of106Ag studied with the103Rh (α,nγ)106Ag and104Pd (α,pnγ)106Ag Reactions

The level scheme of¹⁰⁶Ag has been studied using the¹⁰³Rh(α,nγ)¹⁰⁶Ag and¹⁰⁴Pd(α,pnγ)¹⁰⁶Ag Reactions. The experimental information is taken fromγ-ray coincidence data using Ge(Li)-Ge(Li) and HPGe-planar Ge(Li) configurations andγ-ray angular distributions. With these measurements 126 γ rays have been assigned to¹⁰⁶Ag with 116 deexciting 78 states below 2.26 MeV in excitation. The location of the 8.4-day 6⁺ isomer is established at 89.63±0.09 keV. Many of the low-lying states are interpreted in terms of a slightly deformed rotor model.     

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).     

Conversion coefficients and E0 transitions in102, 104, 106Pd

In in-beam (p, p′) experiments, electron and γ-spectra were measured in the electron energy range of 500-1840 keV for¹⁰²Pd and¹⁰⁴Pd, and 600–1580 keV for¹⁰⁶Pd. The conversion coefficients of all transitions in this range were obtained with accuracies of about 20%, in some favourable cases 10%. Special attention was given to 0⁺′-0⁺ transitions from the two-phonon triplets to the ground states with the following results for the branching ratios 0⁺′-0⁺ (ground state) to 0⁺′-2⁺ (one-phonon state):¹⁰²Pd:T _k (E0)/T _γ (E2)<(2.1±3.6)·10^{?7 104}Pd:T _k (E0)/T _γ (E2)=(6.0±1.4)·10^{?5 106}Pd:T _k (E0)/T _γ (E2)=(6.0±2.0)·10^?4     

New aspects of the rotational model in25Mg

Spin assignments have been made to the²⁵Mg levels in theE _x=5–6 MeV region fromγ-ray angular distributions measured in the²²Ne(α, n y) reaction atE _α=8.0 and 8.8 MeV and fromp-γ angular correlations measured in the²⁴Mg(d, p γ) reaction atE _d=6 MeV. Unique spin assignments ofJ=7/2, 5/2, 5/2, and 9/2 could be made to the levels atE _x=5005, 5511, 5851, and 5967 keV, respectively. Ambigious assignments have been made to the levels atE _x=5245, 5524, 5785, 6032 keV (J=11/2, 7/2), 5455 keVJ=13/2, 9/2), and 5738 keV (J=3/2, 5/2). The present data confirm previous assignments ofJ=1/2 to the levels atE _x=5108 and 5466 keV, respectively. Lifetime estimates have been obtained, using the Doppler-shift attenuation method, for the levels atE _x=5245 keV (τ=30–60 fs), 5785 keV (τ=50–100 fs), 5967 keV (τ=50–100 fs), and 5455 keV (τ>1ps). All other levels in theE _x=5–6 MeV region haveτ<60 fs. A breakdown of theK-selection rule has been observed in theγ-decay of some high spin states, indicating a deviation from the strong coupling model.     

High spin isomer in151Sm

An investigation of the high spin isomer in¹⁵¹Sm was performed via the¹⁵⁰Nd(α, 3nγ) reaction at a projectile energy of 35 MeV. A newγ-transition, 693.6 keV was identified having an exponential delayed component. The transition feeds the 1912 keV state of the negative parity band built on theh _11/2 state. This transition was also observed in coincidence withγ-rays belonging to¹⁵¹Sm in theγ-γ coincidence experiment atE _α =37 MeV. A new isomeric state having energyE _x =2605.8 keV and half lifeT _1/2=23.1±3.5 ns is proposed.     

Analysis of average primary gamma-transition intensities and cross sections of the113Cd(n, γ) reaction

A combined analysis of the available data on the primaryγ-ray intensities from the¹¹³Cd(n, γ) reaction atE _n=1.9 and 24.3 keV neutron energies together with the data on¹¹³Cd neutron capture cross sections in theE _n=3–200 keV energy region was carried out. The neutron strength functions were determined asS _n0=(0.260±0.073) 10^?4 and S_n1=(5.06±0.67) 10^?4. No spin-orbit splitting of thep-wave neutron strength function was found. The energy dependence of theE 1 radiative strength function {ie147-01} was fitted by the Kadmenski-Furman model somewhat better than by a standard Lorentzian. TheM 1 giant resonance parameters were obtained as E _G ^{M 1} =8.8±1.6 MeV and Γ _G ^{M 1} = 4.7±2.6 MeV. The neutron capture cross section of¹¹³Cd from its isomeric state ({ie147-02}=11/2^?, E ₁ ^m =263.7 keV) was calculated.     

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).     

Levels in154Eu populated by thermal neutron capture

The level scheme of¹⁵⁴Eu has been investigated by means of thermal neutron captureγ-rays and conversion electrons. The high energyγ-ray spectrum from thermal neutron capture in enriched¹⁵³Eu has been studied in the energy range of 5700 to 6500 keV. Low energyγ radiation has been observed with Ge(Li) and Si(Li) detectors from 5 to 300 keV and conversion electrons have been measured from 15 to 300 keV. Low energy (n, γγ) coincidences and half lives of transitions have been measured. The data, combined with three very recent studies of the 8^? isomer decay in¹⁵⁴Eu has led to the construction of a level scheme with 12 excited levels. Nuclear Reaction¹⁵³Eu(n, γ),E _n =thermal, measuredE _γ ,I _γ ,E _ce ,I _ce ,γγ-coincidence, halflives,¹⁵⁴Eu deduced levels.     

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.     

New search for 0νEC/EC and 2νEC/EC decay of 106Cd

The studies aimed at decreasing the background of the TGV-2 spectrometer have led to constructive changes in the cryostat and increased the sensitivity of the 32-detector spectrometer. New search for 0νEC/EC, 2νEC/EC) decays of ¹⁰⁶Cd was started with ～13.6 g of ¹⁰⁶Cd with enrichment of 75%. The evaluation of the experimental data accumulated for 4800 h was performed. Limits (at 90% CL) on the half-lives of 0νEC/EC resonant decay of ¹⁰⁶Cd to the 2741 keV excited state of ¹⁰⁶Pd (T _1/2 ≥ 6.5 × 10¹⁹ y) and on t 2νEC/EC decay to the ground state of ¹⁰⁶Pd (0⁺ → 0⁺, g.s.) (T _1/2 ≥ 1.7 × 10²⁰ y) were obtained. The limits on the other branches of ¹⁰⁶Cd decay—2νEC/EC decay to the 2⁺, 512 keV and 0 ₁ ⁺ , 1334 keV excited states of ¹⁰⁶Pd and 2νβ⁺β⁺ and 2νβ⁺ EC decays of ¹⁰⁶Cd to the ground and excited states of ¹⁰⁶Pd were improved.     

Structure of28Si from the spectroscopy of high-spin states

A search for high-spin states in²⁸Si has been performed byn?y coincidence measurements in the²⁵Mg(α,nγy) reaction atE _α=14 and 15.5 MeV. Spin-parity assignments of the observed levels were obtained fromn?γ angular correlation and lifetime measurements atE _α=14.5 MeV. Theγ-decay of the 9,164 keV level was investigated separately with the²⁷Al(p, γ) reaction at theE _p=2,160 and 2,312 keV resonances. Rotational bands withK ^π=3^? (comprising levels atE _x=6,879, 8,413, 10,188 and 12,204 keV),K ^π =5^? (comprising levels atE _x=9,702, 11,577 and 13,741 keV) andK ^π=0⁺ (comprising levels atE _x=6,691, 7,381, 9,164 and 11,509 keV) were observed. The finding of the latter band supports the idea of coexisting oblate and prolate shapes in²⁸Si. A level at 14,643 keV excitation energy has the properties of theI ^π=8⁺ member of the ground state band. There are additional positive-parity high-spin states which do not fit into rotational bands. All types of positive-parity states are well accounted for by shell model calculations.     

High-spin states in27Al

The²⁴Mg(α, p γ) reaction has been studied atα-particle energies of 13, 15, and 15.2 MeV. Using method II of Litherland and Ferguson spin assignments or restrictions thereof could be made to the²⁷Al levels atE _x =5500 keV (I=11/2, 7/2), 6950 keV (I=11/2, 7/2), 7226 keV (I=9/2), 7286 keV (I=9/2–13/2), 7399 keV (I=11/2, 7/2) and 7443 keV (I=13/2, 9/2). Using the Doppler-shift attenuation method a lifetimeτ=20–50 fs was obtained for theE _x =7399 keV level and a limitτ<20 fs for the levels atE _x =7443, 7286, 7226, 6950, 6718, and 6287 keV, respectively. Further spin assignments in²⁷Al were obtained by a study of the²⁶Mg(p, γ) reaction at the E_p=2174 keV resonance. Fromγ-ray angular distributions the resonance spin was determined as I=9/2 (previous assignmentI=7/2) and the spin of theE _x =5959 keV level was determined asI=7/2. Tentative spin assignments were made to the levels atE _x =6537 keV (I=7/2) and 6718 keV (I=9/2). From the combined evidence of the²⁴Mg(α, p) and²⁶Mg(p, γ) reactions the spin of the 6287 keV level was found to beI=7/2. The results are compared with shell model calculations and the Nilsson model.     

Evidence for the coexistence of spherical and deformed states in38Ar

The³⁸Ar levels at E_x=5350, 7289 and 9341 keV have been investigated using the³⁵Cl(α,pγ) reaction at E_α=l4 and 14.5 MeV. From particle-γ-ray angular correlations the spin assignments J(5350)=4, J(7289)=6,4 and J(9341)=8,6,4 have been obtained. Life-time measurements using the Doppler-shift attenuation method yielded τ(9341)=106±25 fs and τ(7289)=77±30 fs, while the lifetime τ(5350)=200±50 fs was known previously. All levels have positive parity and decay by enhanced E2 transitions. Hence we propose that they are the J^π=4⁺, 6⁺ and 8⁺ members, respectively, of a K^π=0⁺ rotational band which has the E_x=3377keV, J^π=0⁺ and the 3937 keV, J^π=2⁺ levels as further members. The enhancement of inband E2 transitions is 30 _?6 ⁺¹⁰ W.u. (4→2), 35 _?14 ⁺³⁰ W.u. (6→4) and 20–36 W.u. (8 → 6), respectively, yielding an average intrinsic quadrupole moment Q₀=850 _?125 ⁺²⁰⁰ mb. The moment of inertia is given by h²2θ=92 keV. The present data are in good agreement with the predictions of a deformed state in³⁸Ar that coexists with the spherical states.     

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).     

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.     

Transition probabilities and the structure of some negative-parity states in126,130Xe and132Ba

The lifetimes of several negative-parity states in^126,130Xe and¹³²Ba have been determined by means of the generalized centroid-shift method. The reactions^124,128Te(α,2n) and¹²²Sn(¹³C, 3n) have been used. Following results were obtained:T _1/2(2758 keV)=1.3±0.2 ns in¹²⁶Xe,T _1/2(2060 keV)=0.20±0.10 ns,T _1/2(2104 keV)=0.50±0.10 ns,T _1/2(2376 keV)=0.30±0.10 ns andT _1/2(2973 keV)=4.6±0.4 ns in¹³⁰Xe as well asT _1/2(2120 keV)=0.40 _?0.10 ^+0.20 ns in¹³²Ba. A systematics of the B(E2; 7 _? ¹ ?5 ₁ ^? ) values in theN=76 nuclei is presented. Electric dipole and quadrupole transition rates are discussed in terms of octupole and quadrupole collectivity. The structure of the 5 ₁ ^? and 7 ₁ ^? states is considered. Nuclear reactions:^124,128Te(α, 2 _n ),E=26 MeV,¹²²Sn (¹³C, 3n),E=53 MeV; measuredE _γ I _γ , γ-r.f. DeducedT _1/2, B(σL) in^126,130Xe and¹³²Ba. Ge detectors. Generalized centroid-shift analysis.     

Search for double beta decay of <Superscript>106</Superscript>Cd in the TGV-2 experiment

An investigation of double beta decay (β⁺β⁺, β⁺/EC, EC/EC) of ¹⁰⁶Cd was performed at the Modane underground laboratory (at a water equivalent depth of 4800 m) using a TGV-2 spectrometer with 32 detectors. Evaluation of the experimental data accumulated over 12 400 h of measuring ～13.6 g of ¹⁰⁶Cd with an enrichment of 75% was performed. New limits (at a confidence level of 90%) on the half-lives of the 0νEC/EC resonant decay of ¹⁰⁶Cd to the 2741 keV excited state of ¹⁰⁶Pd ? T _1/2 ≥ 1.5 × 10²⁰ y and on 2νEC/EC decay to the ground state of ¹⁰⁶Pd (0⁺ → 0⁺, g.s.) ? T _1/2 ≥ 3.9 × 10²⁰ y were obtained. The limits of the 2νEC/EC decay of ¹⁰⁶Cd to the 2⁺, 512 keV and 0 ₁ ⁺ , 1334 keV excited states of ¹⁰⁶Pd and 2νβ⁺β⁺- and the 2νβ⁺ EC decays of ¹⁰⁶Cd to the ground and excited states of ¹⁰⁶Pd were improved.