The decay of 33 70 Se37

The decay of⁷⁰Se was studied using a 75 cm³ Ge(Li) detector, placed in an anti-compton shield, and a low-energy detector. Of the 36γ-rays observed 31 are placed in a levelscheme of⁷⁰As, based on coincidence- and sumrelations. Conversion electrons of two low energy transitions were observed in order to determine their multipolarity. The halflife is measured (41.1 min). Spins and parities of the excited levels were deduced and compared with shell model predictions and logft values of theEC/β ⁺ branches were calculated.     

β-γ-Zerfall des 5+-Niveaus in In 116 und γ-Verzweigungsverhältnisse in Sn 116

The γ-spectrum, emitted in the β-γ-decay of the 5⁺ state of In 116, has been measured with a Ge(Li)-detector. 19 unknown transitions in Sn 116 have been found, most of which could be fitted uniquely into the established level scheme. A new β-transition (logft=5.6) to the 3,096 keV level has been found. Branching ratios are given and a possible band structure in Sn 116 is discussed.     

Study of low-lying states in151Eu via (n,n′γ) reaction

The levels of¹⁵¹Eu have been investigated in the (n,n′γ) reaction using nuclear reactor fast neutrons. The energies, intensities and angular distributions of theγ-rays have been measured with the Ge(Li) spectrometer. Four rotational bands with the following band heads and Nilsson configurations have been identified: ground state band, 5/2⁺ [402]; 21.5 keV, 7/2⁺[404]; 196.5 keV, 3/2⁺[411]; 260.5 keV, 5/2⁺[413]. The low spin states at 332.2 and 336.2 keV have been tentatively assigned to the l/2⁺[411] Nilsson orbital, but 522.8, 580.0 and 587.0 keV states to the 1/2⁺[420] Nilsson orbital. The negative parity levels at 353.7, 522.1 and probably 546.2 keV have been proposed basing on theh _11/2 proton state.     

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.     

Low energy nuclear states in124Te

The energy level scheme of¹²⁴Te has been established on the basis of singlesγ-spectra, andγ-γ coincidence measurements carried out using a dual parameter data collection system. Ge(Li) detectors were used to study the gamma spectra produced in theβ ^? decay of¹²⁴Sb. Eleven new transitions and two new energy levels are proposed. Relative intensities, branching ratios,α(K) and logft values were calculated and multipolarities, spins and parities deduced. Comparisons are made with predictions of the Interacting Boson Model: in a first order perturbation approximation to theSU (5) limit, using the complete IBA-1 Hamiltonian, and in theO(6) limit.     

On the observability of enhancement effects in isochromat spectroscopic investigations of Pd and Rh

We have investigated theγ-rays from the decay of 46-min⁵¹Mn produced by the⁵⁰Cr (d, n) reaction. Twelveγ-rays were observed. Theseγ-rays have been incorporated into a level scheme of⁵¹Cr with levels at 0, 749.1, 1164.4, 1353.3, 1557.4, 1899.4, 2001.4, 2312.5 and 2829.7 keV. Branching ratios, logft values, and j^π assignments are discussed for these levels. The lifetime of the 749.1 keV level was measured to be T_1/2=7.6 ± 0.3 ns by utilizing the⁵¹V(p, n γ ⁵¹Cr reaction produced by a 3.8 MeV pulsed proton beam. The 749 keV,E2 transition is hindered by a factor of 34 compared to the Weisskopf estimate.     

Über die selbständige Polarisierung des Spins der Elektronen durch Ausstrahlung bei der Bewegung auf einer Spiralbahn im Magnetfeld

The nuclear half-life of the 287 keV second excited state of⁷⁵Se, populated by the reaction⁷⁵As(p, n)⁷⁵Se^* has been measured by the delayed coincidence technique. NaJ(Tl)- and Ge(Li)-detectors were used for measuringγ-energies and time-spectra. By slope analysis of the time-spectra we obtained a half-life of T_1/2(⁷⁵Se, 287 keV)=(30.0±0.4) ns. Possible spin assignments for the 287 keV state in⁷⁵Se from logft-values derived fromβ ⁺-decay data of⁷⁵Br to this level byBaskova et al are 3/2^? and 1/2^?. Application of an external magnetic field of 24 kG to the target nuclei yielded no measurable perturbation of the time-spectra, thus a spin value of 1/2^? for this level seems to be more probable.     

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.     

Verzweigungsverhältnisse undβ +-Maximalenergie beim Zerfall von Ag108

The branching ratios of Ag¹⁰⁸ have been remeasured with scintillation spectrometers. There is evidence for a weak 177 keV-β ^?-branch going to the 1473 keV level of Cd¹⁰⁸, followed by aγ-γ-cascade of (841+632)keV. Spin and parity 2+ of this level are supported by logft=4.7 of theβ ^?-branch. Theβ ⁺-spectrum has been measured for the first time yielding an end point energy of (880±25)keV, in agreement with the value derived from theK/β ⁺ratio.     

Spin values of the low lying nuclear levels of201Hg

Gamma-gamma directional correlations have been investigated for the cascades of 135-30 keV and 135-32 keV in²⁰¹Hg from the decay of²⁰¹Tl. A combination of NaI (Tl) and Si (Li) detectors was used for the experiments. Spin values ofI=1/2, 3/2 and 1/2 have been assigned to 1.58, 32.19 and 167.49 keV energy levels. In addition, the relative intensities of theγ rays have been measured with a Ge (Li) detector system. The results are 2.2±0.2, 2.2±0.2, 26.5±1.3, 1.6±0.1 and 100 for theγ rays of 30.60, 32.19, 135.34, 165.88 and 167.43 keV energies, respectively.     

The decay of 20 min179Re

The decay of 20 min¹⁷⁹Re has been studied by means of Ge(Li) and Si(Li) detectors and a magneticβ-ray spectrometer. From the measured positon endpoint aQ-value of 2690±50 keV has been deduced. The decay scheme given is supported by coincidence relations. Fast beta transitions (logft≈5.1) to levels at 720keV and 1680 keV in¹⁷⁹W can be explained by a three quasi-particle character for these states. Nilsson assignments to these and other levels are discussed.     

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.     

In-beam study of174Lu isomers

Levels in¹⁷⁴Lu have been investigated using the¹⁷⁶Yb(p,3n) reaction. Prompt and delayedγ-ray spectra have been observed with a 0.56-cm³ Ge(Li) detector by a multispectrum analysis method. The half-life and decay mode of two isomeric levels, one at 240.8keV (395±15ns) and the other at 365.1keV (145±3ns) have been firmly established. Hindrance factors are discussed. New delayed transitions in¹⁷⁵Lu are also noted.     

Electron capture ratios in206Bi

The level scheme of⁹⁷Tc has been investigated by observing theγ-rays following the decay of 2.9-d⁹⁷Ru.γ-singles andγγ-coincidence measurements were carried out with Ge(Li)-detectors. The time difference of coincident γ-rays was measured as a third parameter. From the coincidence events, the intensities ofγγ-cascades were extracted. The⁹⁷Ru decay gives rise to 18γ-lines which could be fitted into a level scheme of⁹⁷Tc consisting of 9 levels. Spin and parity assignments of the levels were made from log(ft) values andγ-ray branching ratios. Discrepancies concerning the energy of the first 3/2^? state and the existence of a 946 keV level are discussed.     

The Decay of130La to levels in130Ba

Theγ-radiation associated with the β⁺ decay of¹³⁰La to levels in¹³⁰Ba is studied. The level scheme is established on the basis of theγ-γ coincidence measurements emploing two Ge(Li) detectors. The available experimental data are compared to collective model calculations withγ-soft P.E.S. andγ-dependent inertial functions. To reproduce levels energyB _ββ value twice as large as other mass parameters is needed.Radioactivity: ¹³⁰La [from¹³⁰Ba(p, n),E _p=10MeV]; measuredE _γ,I _γ,γγ-coin.¹³⁰Ba deduced levels,J, π, logft. Enriched target, Ge(Li) detectors.     

Studies in the decay of103Ru

The decay of¹⁰³Ru to¹⁰³Rh has been studied using a double-focussing spectrometer for the electron and negaton spectra and a Ge(Li) detector for gamma-ray measurements. TheL-conversion groups of the 40, 53, and 497 keV transitions were resolved at high resolution and unambigous multipolarity assignments were obtained for these transitions. The level scheme proposed resembles in principle that suggested by previous investigators. One essential difference is the doublet character of the state around 0.65 MeV. Tentative spin-parity values have been assigned to all levels from the deduced multipolarities and logft values.     

The decays of 21.55 min 162gTm and 24.3 s 162Tm (a new isomer)

The decay of the 21.55 min ground state and of the 24.3 s isomeric state of ¹⁶²Tm was investigated with semiconductor detectors. The γ-ray spectrum was investigated with a Compton-suppression Ge(Li)-NaI(Tl) arrangement. A Si (Li) detector, mounted in an electron transport solenoid, was used to investigate the conversion electron spectrum. Three-dimensional coincidence measurements were performed with large-volume Ge(Li) detectors. The ¹⁶²Tm ground state has spin-parity 1^? and Nilsson assignment p[411]↓?n[521]↑. An allowed β-transition (log ft ≈ 6.4) was observed to a 2^?, 2 octupole vibrational level at 1572.84 keV. The Q-value determined from positon-gamma coincidence measurements is 4705 ± 70keV. The discrepancy of the experimental K /β⁺ ratio with theoretical predictions might possibly be explained by a large number of unobserved weak γ-rays besides the total of 315 stronger ones observed in this study. The average β-strength function was calculated to be 1.2 × 10^?5. Among the 50 levels observed in the decay, the 2⁺, 4⁺ and 6⁺ members of the ground-state band, the 2⁺, 3⁺ and 4⁺ members of the γ-band, several 0⁺ and 2⁺ members of the K = 0 β-bands and 1^?, 2^? and 3^? octupole vibrational levels were identified. Parameter values Z_γ(0) and Z_γ(2) determining the mixing between the γ-band and the ground-state band, allow no conclusive evidence about unequalness of the intrinsic quadrupole moments of the ground states and the γ-band. The Z(0) parameters, determining the mixing between the β-bands and the ground-state band, and X parameters determining the ratio of E0 to E2 transition probabilities, were deduced. A previously unreported 24.3 sec isomer in ¹⁶²Tm was observed to decay in 10% of the cases by an allowed unhindered (log ft = 4.7) β-ray transition to a level at 1712.20 keV in ¹⁶²Er. The Nilsson configurations assigned to the isomeric and 1712.20 keV levels are p[523]↑ + n[521]↑₅₊ and n[523]↓ + n[521]↑₄₊ respectively. The isomeric level decays in 90% of the cases by an E3 transition (E_IT < 125 keV) to a p[404]↓ ?n[521]↑_2? level at 66.90 keV in ¹⁶²Tm, which decays by an (M1+ < 40 % E2) to the 21.55 min ¹⁶²Tm 1^? ground state.     

Investigation of22Na excited states

Fourteen²¹Ne(p, γ)²²Na resonances have been observed in the rangeE _p =300–1,300 keV. Theγ-decay of all these resonances has been investigated by means of a 38 cm³ Ge(Li) detector. Energies and branching ratios of several bound states have been determined. TheQ-value was determined as 6,738.5±1.7 keV. Lifetimes of seven states were determined with the Doppler-shift attenuation method. The observed upper limit (τ _m ≦4 fs) of the lifetime for the 4,071 keV state, regarded as the analogue of the third excited state in²²Ne, and the transition observed from this state to the 1,528 keV state do not support the proposed rotational band structure of the²²Na low-lying states.     

Detailed Ge(Li)-Ge(Li) coincidence studies of levels in152Sm and152Gd

The decay of 12.4 y¹⁵²Eu to¹⁵²Sm and¹⁵²Gd was studied in a high resolution singles measurement and two 4096×2048 Ge(Li)-Ge(Li) coincidence studies. Forty-five gates were analyzed in order to confirm or establish the placement of the γ rays as well as to accurately determine the intensities of the 12 doublets, which included several not previously reported. A new γ-β interband transition, 4 _γ ⁺ →2 _β ⁺ (561.4 keV), a possible 3 _γ ⁺ →2 _β ⁺ (423.7 keV) transition, and a new 330.9 keV transition between the 4 _γ ⁺ level and theI ^π K=3^?0 octupole level were established from coincidence data. Levels at 1757.0 keV in¹⁵²Sm and 1282.5, 1318.7, and 1692.2 keV in¹⁵²Gd are now established on the basis of coincidence data. These data also establish for the first time the population in the¹⁵²Eu decay levels at 1680.0 and 1047.9 keV in¹⁵²Sm and¹⁵²Gd, respectively, as well as a new level at 1700.8 keV in¹⁵²Sm.     

Die Zerfälle des Rh97g und des Rh97m

The decays of Rh^97g and Rh^97m were investigated using Ge(Li)- and Si(Li)-detectors and a Ge(Li)—Ge(Li)-coincidence circuit. The isomeric transition with an energy of 259 keV was identified by its conversion electrons and decays with a half-life of (48.0±0.8) min. Therefore, the half-lives (30.3±0.9) min and (47.9±0.6) min obtained from theγ-studies were attributed to the decays of Rh^97g and Rh^97m respectively. The proposed decay schemes have 31 excited states of Ru⁹⁷ and account for 84 of the 110 observedγ-transitions, especially for the 37 strongest ones. Twelve of the proposed levels having spins and parities 1/2^? or 3/2^? and excitation energies between 2200 keV and 3600 keV are interpreted as being due to 2p _1/2-neutron-hole-states.