The decay of 174Tm and mixing of the Kπ = 5− two-quasiparticle states in 174Yb

The decay of 5.4 min ¹⁷⁴Tm has been investigated using Ge(Li) spectrometers in singles and coincidence measurements. A total of 43 γ-ray transitions, 26 of them not reported before, have been observed following the decay of ¹⁷⁴Tm. All transitions could be placed in a level scheme comprising 19 excited states of ¹⁷⁴Yb. The Nilsson model has been used to interpret the level structure. The mixing of two-quasineutron and two-quasiproton states is studied and the experimental mixing matrix element is compared with the results of theoretical calculations.     

The nuclear structure of 225Ra

The level structure of ²²⁵Ra has been studied using the (d, t) reaction with both unpolarised and polarised deuterons and the β^? decay of ²²⁵Fr. Cross sections and excitation energies have been measured for 41 levels below 1800 keV in the (d, t) reaction, and levels up to 724 keV have been established from the β^? decay measurements. The level structure is interpreted in terms of the Nilsson model.     

The β− decay of 102Mo

The ¹⁰²Mo activity was obtained by photofission of natural U and thermal-neutron induced fission of ²³⁵U, with subsequent chemical separation of the molybdenum fraction. In addition, nuclei with mass 102 were separated from fission products of ²³⁵U(n_th, f) using the mass separator LOHENGRIN. A decay scheme and absolute γ-intensities are deduced from measured γ-ray, X-ray and γ-coincidence spectra. Logftvalues are calculated. Shell-model calculations for a $\text{(πlg}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^3$$\text{(νlg}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^3$ multiplet have been carried out using effective nucleon-nucleon interactions. The γ-decay between low-lying, low-spin members of this multiplet was studied in detail and compared with the experimental data.     

The decay of 44Sc

The 3.9 h decay of the ⁴⁴Sc ground state has been investigated with a ⁴⁴Ti source. In a singles experiment with a Ge(Li) detector and a γ-γ coincidence experiment with a NaI(Tl)-Ge(Li) detector arrangement a (0.010 ± 0.002)% EC branch to the 3.30 MeV level of ⁴⁴Ca has been found. The γ-decay branching ratio of the 3.30 MeV level has been determined.     

The decay of 74Kr

The decay of ⁷⁴Kr has been studied. Its half-life was determined to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 11.50 ± 0.11}\text{min}$. A decay scheme is proposed, based on γ-γ and β⁺-γ coincidence measurements, which takes account of 99 % of the strength of 57 observed γ-rays. The total decay energy was measured to be Q_EC = 3327 ± 125 keV. The decay feeds the (0, 1)^?, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 25.3}\text{min}$ isomer of ⁷⁴Br.     

The decay of 101Ag

The decay of ¹⁰¹Ag have been studied using β- and γ-spectrometers in singles and coincidence modes. A half-life of 11.4 ± 0.3 min was obtained and a decay scheme was proposed. The first excited state was established at 80.3 keV and a half-life of 4.8 ± 0.5 ns was suggested. The resultant level structure of ¹⁰¹Pd is compared to a theoretical calculation with strong band mixing.     

The decay of 235U

Twenty-eight γ-rays, ten of which are reported for the first time, have been observed in the decay of ²³⁵U, and all have been placed in a revised level scheme for ²³¹Th. Three new levels at 390.27, 317.42 and 240.82 keV respectively have been proposed and the data are in accord with he results of coincidence studies. Reduced transition probabilities of inter-band γ-ray transitions are calculated from the data and compared with theory and an estimate of the intrinsic quadrupole moment, Q_O has been computed.     

The decay of 192Ir

The decay of ¹⁹²Ir has been studied with Ge(Li) spectrometers. Gamma-ray energies and relative intensities are reported. Four previously unreported transitions at 329, 420, 593 and 703 keV have been identified by half-life and a level in ¹⁹²Os at 909 keV has been established on the basis of energy considerations. Upper limits are given for the γ-ray intensities of previously reported transitions at 110, 212, 280, 739, 765 and 1055 keV.     

A low-spin isomer in 74Br; Its half-life and decay scheme

The isotope ⁷⁴Br was produced as the daughter of ⁷⁴Kr. This production mode leads to a ⁷⁴Br isomer whose half-life was measured to be 25.3 ± 0.3 min. A decay scheme based on the 85 observed β-delayed γ-rays suggests the spin assignment (0, 1)^?. Previous detailed studies have reported a 41.5 ± 1.5 min, 4^? isomer of ⁷⁴Br which is produced directly in nuclear reactions. There is no indication which of the two isomers represents the ground state of ⁷⁴Br.     

The beta decay of 137Cs

Evidence is presented to support the view that the approximate shape factor $\text{C = q}{}^2\text{+}\text{b}\text{?}\text{p}{}^2$ does not adequately describe the second-forbidden beta decay of ¹³⁷Cs. An improved formula is given, with single-particle estimates of the nuclear matrix-element ratios. According to this model the coefficient of p² involves considerable cancellation between matrix elements; when due allowance is made for this, good fits to the experimental data are obtained, leading to better estimates of the decay scheme parameters.     

The beta decay of 18N and T = 2 states of mass 18

The ¹⁸N(β^?)¹⁸O decay was observed via the ⁹Be(¹⁸O, p2α)¹⁸N reaction, utilizing helium-transport techniques and Ge(Li) spectroscopy. In addition to the previously reported β-decay to the ¹⁸O 4456 keV level (J^π = 1^?) branches were observed to levels at excitation energies (in keV) of 1982 (J^π = 2⁺). 5530(2^?), 6198(1^?). 6350(2^? or 1⁺), 6880(0^?), and 7771(2^?). The percentage β-branches, in order of increasing excitation energy, are 3.9 ± 1.5, 54.6 ± 1.0, 3.1 ± 0.4, 1.4 ± 0.2, 2.2 ± 0.3, 14.8 ± 0.8 and 5.0 ± 0.5. respectively, with 15 % assumed on the basis of calculations to proceed to non-γ-emitting states. These measurements allow definite assignments J^π = 1^? for the ¹⁸N ground state and J^π = 0^? for the ¹⁸O 6880 keV state. Additional measurements determine the ¹⁸N half-life to be T_{1 2} = 624 ± 12 ms. A shell-model calculation for mass 18 was carried out in a full 1?ω basis. The predictions for the T = 2 energy level spectrum and for ¹⁸N β-decay are discussed.     

On the decay of 201Bi and 199Bi

Level schemes for ²⁰¹Pb and ¹⁹⁹Pb, studied from the radioactive decay of bismuth isobars, are proposed on the basis of γ-ray, electron spectra and γ-γ coincidence measurements. The experimental results are compared mainly with those of two theoretical approaches.     

The decay scheme of 127Ba and half-lives of some low-lying excited states in 123, 125, 127, 129Cs

Radioactive sources of ^{123, 125, 127, 129}Ba obtained in the spallation reaction have been studied with Ge(Li), Si(Li), NaI(Tl) and plastic detectors. On the basis of γ-ray energies, intensities, energy sums and coincidence information, the decay scheme has been proposed for ¹²⁷Ba. No high-spin isomer of ¹²⁷Ba has been observed. The lifetimes of $\text{5}\text{2}$⁺ → $\text{1}\text{2}$⁺ transitions in ^{123, 125, 127, 129}Cs have been measured. No evidence for the shape isomerism in ¹²⁷Cs has been found.     

The electron capture decay of 131Ba

The decay of ¹³¹Ba has been investigated by means of a 4π internal source scintillation spectrometer and a Ge(Li) detector. The L/K. and M/L electron capture ratios of the allowed transitions to the 373, 620 and 1048 keV levels in ¹³¹Cs have been measured. From these electron capture ratios, the ifQ_EC value and the exchange and overlap corrections X^L/K and X^M/L have been derived.     

The electron capture decay of 195Au

The decay of ¹⁹⁵Au has been investigated by means of a 4π internal source scintillation spectrometer and a Ge(Li) detector. Electron capture branching ratios and several L/K and M+…/L capture ratios have been measured. The atomic electron capture transition energy and the cross-over decay probability of the 130 keV state have been calculated.     

The level structure of 184W FROM THE β− decay of 184Ta

Levels of ¹⁸⁴W populated in the decay of 8.7 h ¹⁸⁴Ta have been studied by a variety of experimental techniques. As a result of β and γ-ray energy and intensity determinations and extensive β-γ and γ-γ coincidence measurements, a detailed ¹⁸⁴Ta decay scheme accommodating more than 99.5% of the decay intensity has been established. Intense β-ray groups of end-point energies 1165±26 and 1123±26 keV populate levels in ¹⁸⁴W at 1699 and 1746 keV, which de-excite predominantly to the 8.3 μs isomeric level at 1285 keV, recently identified as the $\text{1}\text{2}{}^{\mathrm{?}}\text{[510]ν?}\text{11}\text{2}{}^{\mathrm{+}}\text{[615]ν K}{}^{\mathrm{\pi }}\text{= 5}{}^{\mathrm{?}}$ band origin. The 1699 keV level also de-excites to members of a $\text{1}\text{2}{}^{\mathrm{?}}\text{[510]ν?}\text{7}\text{2}\text{[503]ν K}{}^{\mathrm{\pi }}\text{= 3}{}^{\mathrm{+}}$ band based at 1425 keV. New information about the properties of the γ-vibrational and K = 2 octupole bands in ¹⁸⁴W is presented and the possible configurations of the levels directly populated in the β^? decay are discussed. The configuration $\text{7}\text{2}{}^{\mathrm{+}}\text{[404]π ?}\text{3}\text{2}{}^{\mathrm{?}}\text{[512]ν K}{}^{\mathrm{\pi }}\text{= 5}{}^{\mathrm{?}}$ is indicated for the ¹⁸⁴Ta ground state.     

The decay of 4 min 158Tm

The decay of 4 min ¹⁵⁸Tm has been investigated with on-line mass-separated samples obtained from the Orsay ISOCELE separator. Measurements of γ-rays, conversion electron lines and γ-γ bi-dimensional coincidences were performed. About 180 transitions were ascribed to the decay and two thirds of them were placed in a decay scheme. The β-band and the γ-band were identified with bandheads situated at 806.40 and 820.13 keV respectively. In addition, a number of other vibrational bands (β-γ, β-β, K^π = 0^? and 1^?) are proposed. The decay properties of those bands are discussed in the framework of current nuclear models. The log ft values suggest a 2^? assignment for ¹⁵⁸Tm with the possible configuration (p404J↓-n521↑).     

The decay properties of 3.25 min 169Hf and 2.05 min 167Hf

The decays of 3.25 min ¹⁶⁹Hf and 2.05 min ¹⁶⁷Hf have been studied with high-resolution Ge(Li) and Si(Li) detectors. The total decay energy of ¹⁶⁹Hf determined from our experimental $\text{K}\text{β}{}^{\mathrm{+}}$ ratio is 3.29^+0.05_?0.13 MeV. The allowed unhindered character of the main β-branches in the decay of both isotopes allows unique Nilsson model assignments.     

The decay of 159Tm (9.0 min) to 159Er

The decay of ¹⁵⁹Tm ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 9.0±0.4min}$) has been investigated with Ge(Li) andSi(Li) detectors, B-spectrographs and a toroidal spectrometer using isotopically separated samples produced by the YASNAPP facility at Dubna. The singles γ-ray spectrum, the conversion electron spectrum, the positron spectrum, prompt and delayed γ-γ coincidences were measured. Using strong thulium activities, conversion electrons were also measured with high resolution b-spectrographs. In the ¹⁵⁹Tm decay 81 new γ-ray transitions were observed. A decay scheme of ¹⁵⁹Tm is proposed involving 12 excited states in ¹⁵⁹Er. The first members of the rotational bands $\text{3}\text{2}$^?[521], $\text{5}\text{2}$^?[523], $\text{3}\text{2}$⁺[402 + 651], $\text{11}\text{2}$^?505 and $\text{7}\text{2}$^?[514] and the $\text{5}\text{2}$, $\text{7}\text{2}$ and $\text{9}\text{2}$ states of a strongly perturbed positive parity band were identified. The Q-value of ¹⁵⁹Tm was determined to be 3.4±0.3 MeV.     

Beta decay of 28P

The β⁺ decay of ²⁸P has been studied with a Ge(Li)-NaI(Tl) escape-suppression spectrometer. The number of ²⁸Si γ-transitions observed following ²⁸P decay has been increased from 15 to 34. New β⁺ branches were observed to ²⁸Si levels at 7416, 9796 and 10209 keV and sharper limits were placed on unobserved gb⁺ transitions.