Identification of the nuclide 226U

Identification of the uranium isotope ²²⁶U is reported. This nuclide was produced in bombardments of ²³²Th with 140 MeV ⁴He ions. It is observed to decay by α-particle emission with a half-life of 0.5±0.2 sec and has an α-particle energy of E_α = 7.43±0.03 MeV, giving a Q-value of Q_α = 7.56±0.03 MeV. Detection was achieved by on-line counting and pulsed-cyclotron beam techniques. It is also observed that the maximum yields for (α, p(x ? 1 )n) reactions are about ten times greater than those for (α, xn) reactions at these energies.     

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 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 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 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.     

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 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 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 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 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.     

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 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.     

Possible evidence for shape isomeric γ-decay in μ− atoms of 238U

A search for the γ-decay of the shape isomer in muonic ²³⁸U excited by radiationless transitions has been performed. Seven delayed transitions in the energy region of 700 to 3200 keV have been observed with a large Ge(Li) detector. Two transitions with E_γ = 2215 and 3131 keV have been attributed to the decay of the shape isomeric state into levels in the first well. The isomeric shift of the second minimum E₁₁ ≈ 600 keV in the presence of the muon and the decrease of the lifetime of the shape isomer to τ = 12 ± 2 ns give arguments in favour of the connection of shape isomerism with large quadrupole deformations.     

Gamma transitions in 59Ni following the β+ decay of 59Cu

The γ-ray decay spectrum of 82 s ⁵⁹Cu produced by the ⁵⁸Ni(p, γ) ⁵⁹Cu reaction has been studied with a 40 cm³ Ge(Li) detector. The number of γ-rays now known for this decay has more than doubled. Additional direct β⁺ branches to the 1679.7($\text{5}\text{2}{}^{\mathrm{?}}$), 2414.8($\text{3}\text{2}{}^{\mathrm{?}}$) and 2681 keV states of ⁵⁹Ni have been identified with log ft values of 5.5, 5.5 and 6.0, respectively. A major change is the reassignment of the 1340.4 keV γ-ray to a 1679.7 → 339.3 keV transition. A limit of log $\text{ft ≧ 6.9}$ is given for the direct feeding of the 1337($\text{7}\text{2}{}^{\mathrm{?}}$) keV state, together with limits for direct population of other energetically available states. The new weak γ-ray branches found for the 878.0, 1301.5 and 1679.7 keV levels are in excellent agreement with the recent theoretical calculations of Glaudemans et al.     

Excited levels of 233Pa by alpha decay of 237Np

α-spectrometry using Si(Au) detectors has been performed with thin samples of ²³⁷Np; αγ bi-parametric coincidences have permitted an analysis and unfolding of the spectrum and give data about the level scheme. Direct and α-coincident γ-spectra have been measured using Ge(Li) and Si(Li) detectors, obtaining the characteristic electromagnetic transitions in ²³³Pa. Nine new γ-transitions are found, relative to the most recent compilation made by Ellis. In the level scheme, the existence of a level at 306.1 keV is confirmed. A level at 257.1 keV, previously suggested, is evidenced. The level at 300.5 keV is proposed as the $\text{7}\text{2}{}^{\mathrm{?}}$ component of the $\text{5}\text{2}\text{(523)}$ band, hence proposing the 306.1 keV level as the $\text{7}\text{2}{}^{\mathrm{+}}$ term of the $\text{5}\text{2}\text{(642)}$ band.     

Chemically induced shifts of 235U and 234U neutron resonances

Transmission spectra were measured with the time-of-flight technique at the Dubna pulsed reactor for samples of metallic U, UO₂, U₃O₈, and UO₃ enriched in ²³⁵U, and were compared in the regions of nine low-energy resonances to observe chemically induced shifts. After elimination of contributions caused by different Doppler broadenings, the shifts are interpreted as changes of the mean-square charge radius for nuclei capturing neutrons. The 〈r²〉 of the compound-nucleus states show on average a weak diminution as compared with the ground-state value.     

The decay scheme of 228Fr and K = 0 BANDS in 228Ra

The γ-rays following the β^?-decay of ²²⁸Fr have been studied by means of γ-ray singles including multi-spectrum analysis and γ-γ coincidence measurements using Ge(Li) spectrometers. Most of the observed γ-transitions could be placed in the level scheme of ²²⁸Ra. The accuracy the energy of the first-excited state in ²²⁸Ra has been improved and 35 new excited levels have been established, 11 of them grouped into the ground-state band, the low-lying K^π = 0^? band with the head at 474.14 keV and two excited K^π = 0⁺ bands with heads at 721.17 and 1041.9 keV. Candidates for two close-lying K^π = 2⁺ bands have also been found. It is concluded that the ground state octupole deformation, if any, is less pronounced in ²²⁸Ra than in lighter radium isotopes.