The second 2+ state in144Sm and the decay of144Eu

The positron decay of¹⁴⁴Eu is reinvestigated using beta- and gamma-ray spectroscopy techniques. A decay scheme comprising three excited states and four transitions in¹⁴⁴Sm is constructed. Three new transitions are observed and have led to the establishment of a second 2⁺ state populated in this decay. The half-life of¹⁴⁴Eu has been accurately measured to be 10.2±0.1 s. Spin-parity assignments are made to all the levels involved in the decay. The structure of¹⁴⁴Sm is discussed in the light of different models.     

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.     

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 of140Gd to states inN=77140Eu

The structure of¹⁴⁰Eu has been investigated through the decay of¹⁴⁰Gd, which has a measured half-life of 16.2±0.8 s. A decay scheme is constructed, which comprises 22 transitions depopulating 16 excited states.     

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.     

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.     

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.     

The internal conversion of theN=81 Isotones139m Ce and141m Nd

A rapid gas-jet system was used for preparation ofβ ^?-samples of^139m Ce and^141m Nd. Conversion electrons and photons were detected simultaneously with absolutely calibrated detectors. Conversion coefficientsα _K = 0.0732±0.0023 andα _K=0.0824±0.0029, conversion ratiosK/L+...= 4.68±0.20 andK/L+...=4.58±0.23 were measured for^139m Ce, and^141m Nd, respectively. The calculated M4 values of Hager and Seltzer, and Dragoun et al. were confirmed within the experimental accuracy.     

139Sm,a new nuclide of relevance for the systematics of theN=77 isomers

The ground state and an isomeric state of¹³⁹Sm have been identified witht _1/2 ^m =9.5 ± 1.0 s andt _1/2 ^g =2.6 ± 0.3 min. The isomeric decay scheme is presented. It extends the chain of isomers withN=77. The distance between thed _3/2 andh _11/2-levels reaches a maximum forZ=60. This maximum is much more pronounced than expected from previous theoretical considerations and from systematic trends in theN=81 and 79 chains.     

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.     

Decay of126m Sb and the energy levels of126Te

The decay characteristics of 19 min^126m Sb have been studied using Ge(Li) and scintillation spectrometers. The sources of^126m Sb were obtained by the (n, p) reaction on enriched¹²⁶Te. The gamma rays of energies 414.4±0.3, 666.7±0.5 and 696.1±0.5 keV were found decaying with a half-life of 19 min. The study of beta spectra employing an anthracene crystal yielded two beta groups with end-point energies of 1.9±0.15 and 2.5±0.15 MeV. The results of singles and coincidence measurements have been incorporated into a decay scheme with excited states of¹²⁶Te at 666.7, 1,362.8 and 1,777.2 keV.     

Messung von HalbwertszeitenK-verbotener Übergänge ingg-Kernen der Seltenen Erden

The half-life of the 1,490 keV level in¹⁶²Dy has been measured in the decay of¹⁶²Ho^m (68 min) by delayed coincidences ofKX rays and (900-1,300) keV gamma radiation to be (1.94 ± 0.19) nsec. A half-life in¹⁷⁶Hf has been remeasured in the decay of¹⁷⁶Ta (8.1h) by delayed coincidences of KX rays and (1,100–1,200) keV gamma radiation to be (4.75 ± 0.25) nsec. In order to fix the level with this half-life in the level scheme of¹⁷⁶Hf, the gamma spectrum delayed to KX rays was measured. It is suggested that probably the 1,227.4 keV-level of¹⁷⁶Hf is delayed and has the spin 2^? or 3⁺.     

Structure of even-even138Nd from the decay of138Pm

The structure of¹³⁸Nd is investigated through theβ ⁺-decay of¹³⁸Pm, whose decay half-life is measured to be 3.24±0.05 min. A level structure comprising 27 excited states and 52 transitions is constructed. With the help of deducedft values and internal conversion coefficients, spin-parity assignments are made to many states in¹³⁸Nd and to the ground states of¹³⁸Pm. From the positron end-point energy measurement, the total decay energy is determined to be 5.4±0.2 MeV, which is compared with the predictions of several mass formulae and with the decay energy systematics of theN=77 isotones. The structure of¹³⁸Nd is discussed in the light of nuclear systematics of theN=78 isotones.     

Half-life measurements and gamma spectroscopy in the decay184Re m →184W

The half-lives of the intrinsic states at 1,285.8 and 1,502.2 keV in¹⁸⁴W have been measured in the decay of¹⁸⁴Re ^m to be 8.33±0.18Μs and 2.35±0.10 ns, respectively. These half-lives determine absolute gamma-ray transition probabilities of eight transitions and yield upper limits for three transitions. The decay scheme of¹⁸⁴Re ^m →¹⁸⁴W is improved through measurements of delayed gamma-ray spectra with a Ge(Li) detector. Spin and Nilsson model interpretations are discussed.     

Der Zerfall des125m Xe,des127m Xe und des127g Xe

The decay of^125m Xe produced by the reaction¹²²Te(α, n)^125m Xe using a target enriched in¹²²Te (95.4%) and the decay of^127m Xe produced by the reaction¹²⁷J(d, 2n)^127m Xe have been investigated: ^125m Xe decays with a half-life ofT _1/2=(56±3) sec by ayy- cascade withE _γ1=(140.4 ±0.5) keV andE _γ2=(110.5 ±0.5) keV. The experimental conversion coefficients yield multipolarities ofE3 for the 140.4 keV isomeric transition and predominantlyM1 for the 110.5 keV-transition. ^127m Xe decays with a half-life ofT _1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofE _γ1=(172.5±0.3) keV and a predominantlyM1 transition ofE _γ2=(124.6±0.3) keV. In the decay of^127g Xe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-captureP _K618/P_K375=0.40 ±0.07 yields a total transition energyQ _EC=(664 ±4)keV. A spin of 1/2⁺ was assigned to the ground state.     

Bestimmung der Halbwertszeit von108m Ag über (n, 2n)-Querschnitte des Silbers

The half-life of^108m Ag was determined as (310±132) years by measuring the absolute activity of a sample containing a known number of^108m Ag nuclei. This could be done by evaluating the cross section for the production of the isomerσ ¹⁰⁹Ag(n, 2n)^108mAg=(670±266) mb. From the measured half-life a logft-value of 8.9 for the electron capture decay of the isomer to the 1770 keV state of¹⁰⁸Pd and a transition probability of (1.0±0.4) · 10^?2 Weisskopf units for the M4 transition to the 2^?state of¹⁰⁸Ag were derived. The cross section for thermal neutrons¹⁰⁷Ag(n, γ)^108mAg could be calculated to be (7.5±3.2) b by using a related measurement from the literature.     

The decay of 0.57 s114Cs

Fusion reactions between⁵⁸Ni projectiles and⁵⁸Ni target nuclei were used to produce¹¹⁴Cs activity, which was studied by on-line mass separation and decay spectroscopy. The obtained half-life of 0.57±0.02 s and the probability ratio of 44±3 between betadelayed proton and beta-delayed alpha emission represent data with improved precision. The absolute branching ratios for both particle decay modes were determined to be (7 ±2)×10^?2 and (1.6±0.6)×10^?3, respectively. These branching ratios and the shapes of particle spectra are discussed with reference to the statistical model calculations. Groundstate alpha decay of¹¹⁴Cs was observed with an alpha energy of 3,226±30 keV and a branching ratio of (1.8±0.6)×10^?4. An upper limit of the branching ratio for a possible ground-state proton decay was set at 5×10^?4. Fromγ-ray singles andγ-γ coincidence measurements, excited states in¹¹⁴Xe are proposed.     

The decay of 26-s 94Rh and 71-s 94Rh isomers

The structure of⁹⁴Ru is investigated through the beta decay of two isomers of⁹⁴Rh, and whose half-lives are measured to be 25.8±0.2 s and 70.6±0.6 s respectively. The decay properties are studied by means of beta and gamma spectroscopy techniques. The level structure of⁹⁴Ru populated in the decays of both isomers is proposed with deducedJ ^π values. Theβ-decay energy for71-s ⁹⁴Rh is measured to be 10.0±0.4 MeV. The structure is discussed in terms of shell model.     

Structure of69Ge

The beta decay of⁶⁹As is reinvestigated. Its decay half-life is measured to be 15.1±0.3 m. Using beta, gamma and conversion electron spectroscopy techniques, a decay scheme comprising 68 transitions among 28 excited states in⁶⁹Ge is proposed. Spin-parity assignments are made to many states andB(M1) andB(E2) are deduced for some transitions. The structure thus obtained for⁶⁹Ge is compared with that from other works and discussed in the light of nuclear models.     

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.