Beta decay of 94Pd and of the 71 s isomer of 94Rh

The β decay of ⁹⁴Pd and of the 71s isomer of ⁹⁴Rh was investigated by using total γ-ray absorption techniques. Several levels in ⁹⁴Rh are established, including a new low-lying isomer characterized by a half-life of 0.48(3)μs and a de-exciting transition of 55keV. E2 multipolarity is determined for this transition by measuring the intensities of its γ-rays and the characteristic X-rays from its electron conversion. On the basis of the measured reduced β-decay transition rates to known ⁹⁴Ru levels and shell model considerations, the spin-parity of the 71s and the 0.48μs isomers of ⁹⁴Rh is assigned to be (4⁺) and (2⁺), respectively. The β-decay strength distributions measured for ⁹⁴Pd and the 71s isomer of ⁹⁴Rh yield Q _EC values of 6700(320) and 9750(320)keV for these decays and give evidence for the population of those states below and above the magic N = 50 gap that belong to both components of the 0g spin-orbit doublet.     

Spin-flipβ − decay of even-even deformed nuclei110Ru and112Ru

Neutron-rich nuclides¹¹⁰Ru and¹¹²Ru produced in symmetric fission of²³⁸U by 20 MeV protons have been studied at the IGISOL facility by means ofβ-ray,γ-ray and conversion electron spectroscopy. A total of 12 and 6γ-transitions were observed in the decays of¹¹⁰Ru and¹¹²Ru, respectively. Multipolarities were determined for a few transitions. The beta decay half-life was determined to be 11.6±0.6 s for¹¹⁰Ru and 1.75±0.07 s for¹¹²Ru. As a side product, a new value of 2.1±0.3 s for theβ half-life of the¹¹²Rh 1⁺ state was obtained. The decay energy measured with the plastic scintillator was 2.81 ±0.05 MeV for¹¹⁰Ru and 4.52 ±0.08 MeV for¹¹²Ru. The beta decay schemes of¹¹⁰Ru and¹¹²Ru isotopes indicate that the main fraction of their beta strength resides in two 0⁺→1⁺ spin-flip transitions with their logf t values between 4.4 and 4.7. The decay energies and the energies of the 1⁺ GT states are compared with the macroscopic-microscopic model calculations. The observed GT-strengths are discussed in the framework of the deformed single-particle model.     

High spin states in94Ru and95Rh

The results of shell model calculations are presented and these support the experimental angular momentum assignments made for the high spin states in⁹⁴Ru and⁹⁵Rh. Only one disagreement between theory and experiment is encountered and this concerns the depopulation of the yrast 9^? state in⁹⁴Ru. A highly inhibitedE1 transition to the 8⁺ state is expected but not seen. The reason that seniority isomers are not observed in these nuclei is discussed.     

The beta decay of90g Tc and90m Tc

The level structure of⁹⁰Mo is investigated via the beta decay of^90g Tc and^90m Tc whose half-lives are measured to be 8.7±0.2 and 49.2±0.4 s, respectively. The decay properties are studied by means of beta and gamma spectroscopy techniques. The level structure of⁹⁰Mo populated in the decays of both isomers is proposed with deducedJ ^π values. Theβ-decay energies for^90g Tc and^90m Tc are 8.8±0.3 and 9.3±0.3 MeV, respectively. The structure is discussed in terms of the shell model.     

Decay studies of101m Rh and101g Rh

The level structure of¹⁰¹Ru has been investigated from the decays of^101m Rh and^101g Rh. For the gamma-ray measurements Ge(Li) detectors with effective volumes of 24 and 43 cm³ were used for singles and coincidence work, and several new transitions were observed. Conversion electron spectra from the^101m Rh decay were investigated with a 50 cm double-focussing beta spectrometer.K-conversion coefficients were determined by combining internal conversion and gamma-ray intensities. For the stronger transitions probable multipolarity assignments have been obtained from these coefficients and also fromK/L andL-subshell ratios. All transitions observed were fitted into a decay scheme, in which tentative spin-parity assignments of all states are given.     

The beta decay of88gNb and88mNb

The level structure of⁸⁸Zr is investigated via the beta decay of^88g Nb and^88m Nb whose half-lives are measured to be 14.4±0.2 m and 7.7±0.1 m, respectively. The decay properties are studied by means of beta and gamma spectroscopy techniques. The level structure of⁸⁸Zr populated in the decays of both isomers is proposed with deducedJ ^π values. Theβ-decay energies for^88g Nb and^88m Nb are measured to be 7.55±0.10 and 7.59±0.10 MeV, respectively. The structure is discussed in terms of the shell model.     

The141Eu nuclide and its decay properties

The nuclide¹⁴¹Eu is identified to have two beta decaying isomers,^141g Eu and^141m Eu, whose decay half-lives are measured to be 40.0±0.7 s and 3.3±0.3s, respectively. Their decay properties are studied by means of beta and gamma spectroscopy techniques. The states withJ ^π assignments in¹⁴¹Sm thus deduced are compared with those of the other odd-A, N=79 isotones. The total decay energy of^141g Eu is measured to be 6.03±0.10 MeV, which is compared with the predictions of several mass formulae and with the decay energy systematics of theN=78 isotones. The^141g Eu and^141m Eu are deduced to haveJ ^π =5/2⁺ and 11/2^?, respectively. A 96.4 keV isomeric transition between them is found to be anE3 transition with aB(E3)=1.6±0.4e ²fm⁶. The structure of¹⁴¹Eu is compared with that of the otherN = 78 isotones.     

Decay properties of139mSm and139Eu

The structure of¹³⁹Sm is investigated through the decay properties of^139mSm and¹³⁹Eu. The decay of^139mSm is measured to have a half-life of (10.7±0.6) s. Gamma-ray and internal conversion electron measurements lead to the construction of a decay pattern comprising seven transitions among five states. The decay of¹³⁹Eu with a measured half-life of (17.9± 0.6) s is studied with beta decay spectroscopy techniques. A decay scheme consisting fourteen states in¹³⁹Sm is proposed. Using deducedft values and transition multipolarities,J ^ρ assignments are made. Nuclear systematics of the odd-A, N=77 and 76 are discussed.     

Der Zerfall des94Sr

The nuclide⁹⁴Sr was isolated by chemical separation methods after thermal neutron induced fission of²³⁵U. Its decay properties were investigated employing semi-conductor spectrometers and coincidence techniques. A half-life of 74.1±0.3 sec was found. Besides the 1428.3 keV γ-ray we found 4 new γ-rays which could be placed in a decay scheme comprising three excited states of⁹⁴Y. The 1⁺ states in theuu-nuclides^90,92,94Y and^88,90,92Rb are compared.     

Structure of140Pm from beta decay of140Sm

The structure of¹⁴⁰Pm is investigated through the beta decay of¹⁴⁰Sm, whose half-life is measured to be (14.7 ± 0.2) m. A level structure comprising 41 transitions among 17 excited states is constructed. Using the deduced ft values and measured internal conversion coefficients, spin-parity assignments to several states in¹⁴⁰Pm were made. From beta end-point measurement, the total decay energy is deduced to beQ _EC =3.4±0.3 MeV, which is compared with the predictions of several mass formulae. The systematics of the odd-Z, N=79 isotones are discussed.     

States inN=79142Eu populated in the decay of142Gd

The structure of¹⁴²Eu is investigated through the beta decay of¹⁴²Gd, whose decay half-life is measured to be (69.1±1.0) s. A level scheme comprising 42 transitions depopulating 18 excited states is constructed. With the help of the deduced ft values and measured internal conversion coefficients, spin-parity assignments are proposed for several states in¹⁴²Eu. The level systematics of the doubly odd,N=79 isotones are discussed.     

Lifetime measurements on excited states in100Rh

Lifetime measurements of three excited states in¹⁰⁰Rh populated by the decay of¹⁰⁰Pd have been carried out. A two parameter delayedγ-γ-coincidence experiment using an intrinsic Ge and a plastic scintillation detector resulted in the following values:T _1/2(32.72 keV,¹⁰⁰Rh)=(27.6 ±0.6) nsT _1/2(74.8keV,¹⁰⁰Rh)=(213.6±2) nsT _1/2(158.8 keV,¹⁰⁰Rh)<0.5 ns. For the levels at 32.72 keV and 158.8 keV no former values are known.     

Structure of129Ba from the decay of129La

The structure of¹²⁹Ba is investigated through the beta decay of¹²⁹La, whose half-life is measured to be 11.6±0.2 m. The decay properties are studied by means of beta, gamma and conversion electron spectroscopy techniques. Many transitions are observed and a level scheme of¹²⁹Ba with deduced¹²⁹Ba values is proposed. The total decay energy of¹²⁹Ba is measured to be 3.72±0.05 MeV, which is compared with predictions of mass formulae. Low-lying structure of¹²⁹Ba is discussed in terms of collective models.     

States inN=80140Nd populated in the decay of140Pm

The level structure of theN=80,¹⁴⁰Nd has been investigated through the beta decay of^140m Pm and^140g Pm, whose decay half-lives were measured to be 5.95±0.05 min and 9.1±0.5 sec, respectively. Decay schemes for the two isomers have been constructed fromγ-ray measurements. With the help of the beta decayft values and internal conversion electron measurements, spins and parities were deduced for levels in¹⁴⁰Nd. Among the levels a 7^? state at 2222.0 keV and a 5^? state at 2273.3 keV are identified as two-neutron quasiparticle states. The (ie233-01) for^140m Pm and^140g Pm have been deduced as 7^? and 1⁺, respectively. From beta end-point measurements, the decay energies of the two isomers have been determined asQ _EC=6.48±0.07 MeV^140m (Pm) andQ _EC=6.08±0.10 MeV (^140gPm). The results are discussed in the light of nuclear systematics of theN=79 and 80 isotones.     

Investigations of very neutron-deficient isotopes below100Sn in40Ca-induced reactions

Very neutron-deficient isotopes of rhodium, palladium, silver, cadmium and indium in theN=50 region were studied at the GSI on-line mass separator following bombardment of^{58, 60, 62}Ni and^{63, 65}Cu targets with 4.0 MeV/u ions of⁴⁰Ca. The known properties of the β-delayed proton precursor^95m Pd were confirmed, but a search for direct proton decay of^95m Ag was not successful. Beta-delayed proton activities observed at mass-numbers 94, 96, 97 and 100 were assigned to the precursors⁹⁴Rh(66±14 s),⁹⁶Ag(5.1±0.4s),⁹⁷Cd(3 _?2 ⁺⁴ s) and¹⁰⁰In. In addition,⁹⁴Pd(9.0±0.5 s) was identified from β-γ-X studies. Individual decay schemes of^95m96Pd and^{96, 98}Ag are reported.     

A new beta decaying isomer of131Sn; partial level scheme of131Sb

Gamma spectrum and half life of¹³¹Sn decay have been measured using the unslowed fission fragment separator Lohengrin at the high flux reactor of the Institute Laue-Langevin, Grenoble. Two beta-decaying isomers are evidenced, with half-lives of 39±2 s and 50±2 s. Additional confirmation of this isomerism is given by fission fragment-γ delayed coincidence, leading to a partial level scheme of¹³¹Sb including an isomeric level of 50±8 μs life-time at 1676.6 keV.     

Investigation of very neutron deficient Ru and Rh nuclei with the help of (40Ca;yp+zαγ) reactions

⁴⁰Ca beams from the Munich tandem and from the Munich heavy ion postaccelerator have been used to produce very neutron deficient Ru and Rh nuclei with⁵⁸Ni (⁴⁰Ca,yp+zαγ) reactions. The nuclei⁹²Ru,⁹⁴Ru and⁹⁵Rh have been studied with in-beam γ ray spectroscopy consisting of the measurement of excitation functions, γ γ coincidences, γ ray angular distributions and life times with the recoil distance method. The following new level energies, spin parity values and half-lives have been deduced:⁹²Ru: 865.3 keV 2⁺; 1,855.8 (4⁺); 2,672.7 (6⁺); 2,834.6 (8⁺) 100±14 ns; 3,640.3 (10⁺), 4,206.1 (12⁺)⁹⁴Ru: 2,624.7 (5^?) 530 _?200 ⁺⁵⁰⁰ ps; 3,991.7 (10⁺); 4,197.9 (9^?); 4,489.3 (11^?) 780±120 ps; 4,717.1 (12⁺) 35±3ps; 5,568.4 (13^?); 5.826.8 (14^?); 6,360.3 (14^?); 6,614.7 (13⁺); 7,158.3 (14⁺); 7,774.1 (15); 8,412.1 (16); 9,042.2 (17)⁹⁵Rh: 1,350.7 (13/2⁺); 2,067.2 (17/2⁺); 2,236.2 (17/2^?) 15±5ns; 2,449.0 (21/2⁺) 2.1±0.3 ns; 3,241.2 (21/2^?); 3,724.1 (25/2⁺); 3.908.9 (25/2^?); 4,307.2 (27/2⁺); 4,457.9; 4,716.9; 5,063.2; 6,797.3; 7,627.4 The residual activities have been studied with multi spectra analysis'. The decay scheme of⁹⁴Rh(25±2 s) has been established.     

Decay of108, 109, 110Sb

The structure of¹¹⁰Sn is investigated through the decay of¹¹⁰Sb, whose half-life is measured to be 24.0±0.3 s. Gamma ray spectroscopy measurements lead to the construction of a decay scheme comprising 36 transitions among 18 levels in¹¹⁰Sn. Spin and parity of the states involved in the decay are deduced. New isotopes^109,108sb are identified and their decay properties are discussed. The decay half-life of¹⁰⁹Sb is measured to be 18.3±0.5 s and that of¹⁰⁸Sb to be 7.0±0.5 s.     

Structure of N=81144Eu from the decay of144Gd

The structure of¹⁴⁴Eu is investigated through the beta decay of¹⁴⁴Gd, whose decay half-life is measured to be (4.47±0.06) m. A level scheme comprising 67 transitions depopulating 24 excited states is constructed. With the help of the deducedf t values and measured internal conversion coefficients, spin-parity assignments are proposed for several states in¹⁴⁴Eu. This level structure is discussed using the systematics of the odd-A N=81 and N=82 isotones which are investigated by a spherical BCS calculation.