A note on60Co decay

Theγ-rays from⁶⁰Co have been studied with a 30 cm³ Ge(Li) detector. Gamma rays of energies 826.4 and 2,158.9 keV which are expected on the basis of the⁶⁰Co decay scheme were sought but not observed. Their intensities are <0.02% and <0.002%, respectively, of the⁶⁰Co disintegrations. Any direct feeding from the (5⁺)⁶⁰Co ground state to the (2⁺) 2,159 keV level is <0.022%, yielding a logft>12.3 for the 664 keV second-forbidden uniqueβ-transition. Radioactivity⁶⁰Co; measuredE _γ,I _γ.⁶⁰Ni deduced levels, logft. Ge(Li) detector.     

Levels in182W populated in the decay of182Ta

Theγ-rays emitted in theβ-decay of¹⁸²Ta have been reinvestigated with improved statistics in attempting to clarify the reported new levels at 1460.41, 1592.98, 1620.36, 1712.29 and 1762.91 keV in¹⁸²W observed in theβ-decay of¹⁸²Ta. The present study demonstrated that the fifteen newγ-rays, which were used to support the existence of the five new levels, are not relevant to theγ-decay of¹⁸²Ta. Therefore the five new levels are not populated in this decay. Additionally, theγ-ray with an energy of 1035.6 keV (0 ₂ ⁺ →2 ₁ ⁺ ) deexciting theβ-band head in¹⁸²W is observed for the first time in the present decay study and the previous tentative placement of the 351.0 keVγ-ray in the level scheme is confirmed by the present coincidence measurements.     

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.     

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.     

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 nuclear structure of198Au from the reaction197Au(n, γ)198Au

Precise energies and intensities of about 450γ-rays of the¹⁹⁷Au(n, γ)¹⁹⁸Au reaction have been investigated in the energy range from 30 keV to 1 MeV with a bentcrystal spectrometer. Prompt and delayedγ-γ coincidences have been studied with Ge(Li) detectors. A half-life of 124±4 ns has been measured for the state at 312.036 keV, which is found to decay to the ground state through the cascade 97.195–214.841 keV. A new level scheme based on these results has been constructed which contains 160 transitions. Spin and parity assignments have been made for most of the levels.     

In-beam gamma-ray and electron spectroscopy following the75As(p,n)75Se reaction

The level scheme of⁷⁵Se has been studied through the⁷⁵As (p, n) reaction at proton energies from 1.5 to 5.0 MeV.γ-ray and internal conversion electron measurements were made using NaI (T1) and Ge(Li) detectors and a six-gap electron spectrometer. A proportional counter and a thin window NaI(T1) detector were used to detectγ-rays with energies less than 30 keV. The level scheme has been established by observing the thresholds of variousγ-rays and byγ-γ and e^?-γ coincidence measurements. New levels at 133.0, 293.2, 790.0, 953.0, 1020.8, 1184.3, 1198.5 and 1258.2 keV not observed in earlier (p, n) studies have been established. Conversion coefficients of most of the low-lying transitions have been determined. Angular distributions of some of theγ-rays were also measured and compared with the statistical model calculations. DefiniteJ ^π assignments have been made to most of the low-lying levels. Life-times of the 112.1, 133.0, 286.7 and 293.2 keV levels have been measured to be 0.69±0.12, 5.3±0.6, 1.35±0.15 and 31±2 nsec respectively. The reduced transition probabilities for various low-lying transitions have been determined and compared with recent calculations. The 1/2^? and 9/2⁺ levels hitherto unknown in this nucleus has been identified. The structure of the low-lying levels is discussed in terms of the existing models.     

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.     

Properties of isomeric states and the πd 3/2-vi 13/2 multiplet in194Au

The level structure of¹⁹⁴Au has been studied by observing prompt and delayedγ-rays following¹⁹⁴Pt(p,n) and¹⁹⁵Pt(p,2n) reactions. The conversion electron andγ-ray spectra from the decay of the 0.42s (10^?) and 0.60s (5⁺) isomers at 476 keV and 107.4 keV, respectively, have been measured using the He-jet method. The half-lives of the 6⁺ (278.2 keV, 1.1±0.4 ns), 7⁺ (224.6 keV, 2.6±0.2 ns) and 8⁺ (406.8 keV, 2.9±0.4 ns) members of theπd _3/2-vi _13/2 multiplet have been obtained from the time distributions between cyclotron beam pulses andγ-rays depopulating these levels. A calculation made assuming a pure two-particle configuration for the multiplet predicts very well theB(E2) values for the transitions between the levels of this multiplet but the calculatedB(M1) values are not in agreement with experimental results.     

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.     

Atomic masses of rare earth isotopes145Pm,145Sm and151Gd,derived from decay measurements of145Sm and151Gd

The comparison of experimental with calculated K-capture probabilities yielded the decay energies of¹⁴⁵Sm and¹⁵¹Gd,Q _EC=622(5) and 463(3) keV, respectively. Earlier discrepancies in the mass adjustment of these isotopes were removed and adjusted masses for¹⁴⁵Sm,¹⁴⁵Pm and¹⁵¹Gd derived. In the decay of¹⁵¹Gd five newγ-rays were found and the half-life remeasured to be 129(4) d.     

The levels of144Pr from the decay of144Ce

The level scheme of¹⁴⁴Pr has been studied from the decay of¹⁴⁴Ce. The intensities and energies of gamma rays have been determined with a X-ray Ge(Li) detector. TheK-shell internal conversion coefficients for γ-rays have been measured with theK X-ray/γ-ray ratio method using NaI(Tl)—X-ray Ge(Li) coincidence techniques.     

Ground state properties and β-decay half-lives near 132Sn in a self-consistent theory

The level scheme of⁹⁵Tc has been investigated with Ge(Li)-detectors by observing the γ-rays after the decay of 1.65 h⁹⁵Ru. The energies and intensities of theγtransitions were extracted fromγ-singles andγγ-coincidence spectra. In the decay of⁹⁵Ru 88γ-transitions were observed; a scheme of⁹⁵Tc with 25 levels is proposed into which 86 transitions could be accomodated. Spin and parity assignments were made from log (ft) values andγ-ray branching ratios. The level structure of⁹⁵Tc is compared with that of the other odd Tc isotopes.     

Zur Gamma- und Röntgenstrahlung von Holmium-164

The photon spectrum in the decay of¹⁶⁴Ho was investigated using a high resolution solid state detector separating theK-X-rays of Dy, Ho and Er. The two γ-rays depopulating the 3⁺ and 2⁺ levels in¹⁶⁴Ho were found to have energies of 56.6 and 37.3 keV. The 91.4 keV radiation of Er from our sample seems to have a non resolved high energy component with about 2.5% intensity. It may be due to the cross-over transition 3⁺→1⁺ or a sum line. The half-life of the isomeric state of¹⁶⁴Ho was found to be 36.7 ± 1 min. The total transition rates between different levels were calculated from the measured photon intensities. The fraction 0.27 found in the branching of thee ^?-capture feeding the 2⁺-state of Dy has nearly the same value as the analog branching in the β^?-decay. Combining the measured complex ground state decay curve and the transition intensities of the isomeric and of the ground state the ground state half-live can be deduced and was found to be (28.1 ± 1.0) min. The corresponding ratio of the ground state and the isomeric state production rates is 2.8₄:1. A ratio of 0.04 was found for the cross section of¹⁶⁵Ho (γ, 3n),¹⁶²Ho and¹⁶⁵Ho (γ,n)¹⁶⁴Ho for a 90 MeV bremsspectrum.     

The spin of the 1029 keV level in200Hg

The spin of the 1,029 keV level in²⁰⁰Hg has been determined to be 0 through measurements of theγ-γ-angular correlation of the 661 keV and 368 keVγ-rays following slow neutron capture in¹⁹⁹Hg. The upper limit for theγ-intensity ratioIγ(1,029 keV)/Iγ(661 keV) obtained from the curved crystal spectrometer (n, γ)-data is much lower than the ratio found during the²⁰⁰Tl→²⁰⁰Hg decay studies. This implies that the 1,029 keVγ-line seen in the decay work does not lead from the 1,029 keV level to the ground state in²⁰⁰Hg, but that it depopulates a level which is only weakly fed through the (n, γ)-process.     

Gamma radiation from the ground state decay of95Tc

The 20 h^95gTc decay to levels of⁹⁵Mo has been investigated studyingγ-singles andγγ-coincidences. The first excited state of⁹⁵Mo at 204 keV, previously assumed to be populated in the^95m Tc decay only, is found to be fed by aγ-transition of 870 keV deexciting the level at 1074 keV which is populated in the^95g Tc decay. More over three newγ-transitions of 477, 786 and 1552 keV deexciting the level at 1552 keV have been found. For the levels at 1074 and 1552 keV the range of possibleJ ^π assignments could be reduced.     

TheEC-decay of170Tm

The spectrum ofK X-rays andγ-rays following the decay of¹⁷⁰Tm has been reinvestigated using a high resolution Si(Li) detector. The intensities of theEC-branches from the ground state of¹⁷⁰Tm to the ground state as well as to the first excited level in¹⁷⁰Er have been measured. The total intensity of theEC-decay is (0.25 ± 0.05)% of all¹⁷⁰Tm disintegrations with (0.18 ± 0.05)% leading to the ground state and (0.07±0.02)% leading to the first excited level of¹⁷⁰Er. The energy of the de-excitingγ-ray has been determined to (78.7±0.5) keV. Its intensity is (0.28 ± 0.06)% of that of the 84.3 keVγ-ray in¹⁷⁰Yb.     

Resonances in the excitation functions of the alpha-particle and proton exit channels of the16O +12C system near the coulomb barrier

The energies and relative intensities of the γ-rays from the decay of⁶³Co (27.5 ± 0.3 sec) have been measured. New γ-transitions of 155.6, 913.6, 981.7, 1069.1 and 2174.5 keV have been observed and assigned to this decay.     

Untersuchung von57Co mit der Reaktion57Fe(p,n)57Co

A neutron time-of-flight investigation of the⁵⁷Fe(p, n)⁵⁷Co reaction performed at bombarding energies of 4.9, 5.6 and 6.2 MeV results in new energy levels of⁵⁷Co. In addition, gamma spectra andn-γ-coincidence spectra were taken to complete the decay scheme of⁵⁷Co up to an excitation energy of 4 MeV.     

Rotational bands in79Kr

The level scheme of⁷⁹Kr has been studied through the⁷⁹Br(p,n)⁷⁹Kr reaction at proton energies from 1·7 to 5·0 MeV.γ-ray and internal conversion electron measurements were made using Ge(Li) detectors and a six gap “Orange” electron spectrometer. The level scheme was established by determining the thresholds of variousγ-rays and byγ-γ and n-γ coincidence measurements. New levels at 402, 450, 660, 676, 695, 720, 810, 836, 907 and 1038 keV not observed in earlier radioactivity studies have been established. DefiniteJ ^π assignments have been made to most of the levels below 800 keV. Many of the low-lying levels are identified as rotational levels based on the (301 ↓) 1/2^?, (301 ↑) 3/2^? and (431 ↓) 1/2⁺ Nilsson states.