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.     

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.     

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.     

β + ratio andβ-delayedγ-decay of146Eu

The positron decay of¹⁴⁶Eu was investigated, firstly to derive for the allowed transition to the 2046 keV state in¹⁴⁶Sm the electron capture to positron decay ratio. The experimental valueEC/β ⁺=43.7(42) is found to be in agreement within the respective error intervals with the ones calculated from the formalism of allowed decay using the recentQ-values of¹⁴⁶Eu. Further on, theγ-decay properties of¹⁴⁶Eu have been reinvestigated with emphasis on implied modifications of the hitherto accepted decay scheme: 42 new levels and 33 newγ-transitions were placed in the revised level scheme, 12 of the previously reported levels were deleted. The level distribution of¹⁴⁶Sm is discussed within a statistical model. The indication for a non-statisticalβ-strength function is observed.     

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.     

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.     

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.     

The decay of140Pr to levels in140Ce

The decay of¹⁴⁰Pr was investigated by means of a Ge(Li) spectrometer. Excited states of¹⁴⁰Ce at 1,596.2, 1,903.1, 2,348.9, 2,522.5, 3,016.8 and 3,119.6 keV are fed in the beta decay of¹⁴⁰Pr. Spin and parity assignments for all observed levels have been made from electron capture and positon disintegration considerations and gamma branches. The experimental level scheme of¹⁴⁰Ce is compared with the results of shell model calculations forN=82 nuclei.     

Gamma-gamma directional correlations and coincidence studies in154Gd

The intensities, placements andE2/M1 mixing ratios of transitions in the decay of¹⁵⁴Eu have been carefully studied to provide accurate data for microscopic calculations. Coincidence relationships in the decay of¹⁵⁴Eu have been studied extensively with a multiparameterγ-γ coincidence system with two large volume Ge(Li) detectors. Spectra in coincidence with twenty energy gates were analyzed. Twenty-nine new coincidence relationships were established and confirmed most, but not all, of several levels previously assigned by energy fits only. From an analysis of coincidence spectra and singles spectra with a 18% efficiency Ge(Li) detector new information on the gamma-ray intensities were obtained. Precise values of theE2/M1 mixing ratios of transitions from the gamma- and beta-vibrational bands to the g.s. band have been determined fromγ-γ directional correlation measurements with a NaI(Tl)-Ge(Li) detector coincidence system. Mixing ratios were obtained for a number of other transitions including those fromK ^π =0^? and 2⁺ bands from direct and skipped cascade correlations.     

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.     

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.     

Study of the excited states of175Yb from the Decay of175Tm

The decay of¹⁷⁵Tm was investigated by means of Ge(Li) spectrometers. Excited states of¹⁷⁵Yb at 104.5, 514.8, 555.8, 601.9, 638.9, 697.7, 811.5, 871.4, 919.8, 991.8, 1,009.4, (1,066.7), 1,308.9, 1,468.0, 1,497.0, (1,620), 1,682.4, 1,690.7, 1,793.3, 1,864.5, 1,891.5, (2,081.0), 2,093.0, 2,114.5 and 2,138.2 keV are observed in the beta decay of¹⁷⁵Tm. Spin and parity assignments for all observed levels have been made from beta disintegration considerations and gamma branches. The experimental level scheme is described in terms of the Nilsson model and possible three-quasiparticle excitations are discussed.     

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.     

Band mixing in156Gd and158Gd

A detailed investigation of the energies and intensities of the γ-rays that depopulate the low spin levels of the β- and γ-vibrational bands of¹⁵⁶Gd and the γ-vibrational band of¹⁵⁸Gd has been conducted. Both singles and γ-γ coincidence measurements were made on sources of 15-d¹⁵⁶Eu and 46-min¹⁵⁸Eu by use of large volume, high resolution Ge(Li) detectors. In addition to the γ-band at 1154.09 keV, twoK ^π=0⁺ bands were observed in¹⁵⁶Gd with band heads at 1049.45 and 1168.11 keV, respectively. The 2⁺ and 3⁺ members of the γ-vibrational band in¹⁵⁸Gd were observed at 1187.12 and 1265.43 keV, respectively, as well as a newK ^π=0⁺ band at 1195.98 keV. A first order perturbational treatment of the branching ratios was applied to both nuclei. In addition, the mixing between the ground state, the β-, and the γ-vibrational bands of¹⁵⁶Gd is considered from two approaches, but neither satisfactorily explains all the experimentalB(E2) ratios.     

Precise atomic masses of147Eu,147Gd,and151Tb derived from their decay properties

Theβ-decay energies of¹⁴⁷Eu,¹⁴⁷Gd, and¹⁵¹Tb were determined by usingγ-spectroscopical methods. The comparison of experimental with calculatedK-capture probabilities yielded theQ _EC values 1.690( _?16 ⁺²¹ )MeV and 2.203( _?13 ⁺¹⁹ )MeV for¹⁴⁷Eu and¹⁴⁷Gd, respectively. By measuring the ratio of positron decay to electron capture for two branches in¹⁴⁷Eu decay, the decay energiesQ _EC=1.702(13) MeV andQ _EC=1.709(18)MeV were derived. Also fromEC/β ⁺ ratios the valuesQ _EC=2.225(75) MeV for¹⁴⁷Gd, andQ _EC=2.566(12)MeV for¹⁵¹Tb were obtained. Earlier discrepancies in the mass adjustment of these isotopes were removed. In course of the present studiesγ-decay properties of¹⁴⁷Eu and¹⁴⁷Gd were reinvestigated.     

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 des Elektroneneinfangs am Kern176m Lu

The electron capture of^176m Lu to the ground state and to the first excited state of¹⁷⁶Yb has been observed by measuring the YbK x-rays and the 82,2 keV gamma-rays from the gamma decay of the first excited state in¹⁷⁶Yb. With the data of the 88,36 keV gammarays following the beta decay of^176m Lu to the first excited state of¹⁷⁶Hf the electron capture/beta decay ratio of^176m Lu was found to be (0,95±0,16)·10^?4. The electron capture branching ratio to the ground state and to the first excited state of¹⁷⁶Yb was found to be 40/60±30%. By analyzing the 88,36keV gamma-rays and the HfKx-rays the halflife of^176m Lu was evaluated to be 3,66±0,04 h. The value for theK-conversion coefficient of the 88,36keV transition was determined from the x-ray/gamma-ray ratio to be 1,19±0,09.     

Radioactive decay of 1.7-h149Nd to levels of transitional149Pm

Sources of¹⁴⁹Nd were produced by thermal-neutron irradiation of enriched¹⁴⁸Nd. High resolution Ge(Li) spectrometers were used to collect gamma-ray singles and coincidence spectra in the study of the decay of 1.7-h¹⁴⁹Nd. A total of 214 gamma rays have been assigned to the decay of¹⁴⁹Nd, and 201 of these transitions have been placed in a level scheme of¹⁴⁹Pm involving 42 excited states. Absolute values for the beta-group intensities were determined for transitions to the¹⁴⁹Pm levels, and spin and parity assignments were made for many of the observed states. The experimentally determined level structure of¹⁴⁹Pm was compared with corresponding levels in other odd-mass Pm and Eu nuclides. Interpretations were made in terms of the core-coupling model. Radioactive decay¹⁴⁸Nd(n, γ)¹⁴⁹Nd; measuredE _γ,I _γ,γ-γ coinc.¹⁴⁹Pm deduced levels,J,π. Compton-suppression. Ge(Li) detector. Enriched targets.     

Implications on the chiral quark bag from the deuteron asymptoticD-state

Fission yields of^124–132In in the thermal neutron fission of²³⁵U were determined for the first time. Charge displacementsΔZ=Z _p?Z _UCD were calculated for the corresponding mass chains. Both fission yields and charge displacement values were compared with those obtained by systematics by Wahl et al. and Wolfsberg. It was found that the fission yields of the In isotopes obey the gaussian distribution. The displacement function of Wolfsberg seems to give the better representation of the experimental results. Half-lives of^124–131In were determined from beta decay curves.