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.     

Gamma transitions between low-lying levels in 119Sn

We have carried out measurements on the decay of ¹¹⁹In isomers and the ¹¹⁸Sn(n, γ) reaction to supplement Coulomb excitation measurements on ¹¹⁹Sn. In addition to the 311.39 keV isomeric transition in ¹¹⁹In, we observed 13 γ-rays in ¹¹⁹Sn from the decay of the 2 min and 18 min ¹¹⁹In isomers. These γ-rays have been incorporated into a level scheme of ¹¹⁹Sn with levels at 0, 23.867, 89.54, 787.01, 920.5, 921.4, 1089.5, 1187.76, 1249.67, 1304.44 and 1354 keV. Conclusive evidence for the existence of a 920.5–921.4 keV, $\text{3}\text{2}{}^{\mathrm{+}}\text{-}\text{5}\text{2}{}^{\mathrm{+}}$ level doublet was obtained from capture γ-ray measurements of resonance energy neutrons.     

The decay of mass-separated 99g,mAg

The decays of neutron-deficient 15 s ⁹⁹Ag and 124 s ^99gAg nuclides have been investigated at the Leuven Isotope Separator on-line facility. Sources were produced by the ⁹²Mo(¹⁴N, 2p5n) and ${}^{\mathrm{<mtext>nat</mtext>}}\text{Zr}\text{(}{}^{14}\text{N}\text{, x}\text{n}\text{)}$ reactions. Positron, conversion electron, X- and γ-ray singles spectra together with γ-γ coincidence measurements have been performed on mass-separated samples. The $\text{1}\text{2}$^? isomeric level in ^{99)Ag decays with a 163.6 keV isomeric transition to a $\text{7}\text{2}$+ level at 342.6 keV. Of the 106 γ-rays observed in the $\text{β}{}^{\mathrm{+}}\text{EC}$ decay of the 99Ag ground state, 68 γ-rays (92 % of the γ-ray intensity) have been placed in a proposed level scheme. The relative variation of the $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}\text{and}\text{1}\text{2}$?} levels in odd-mass Ag isotopes has been calculated using a residual proton-neutron delta interaction. The occurrence of decoupled bands in the odd Pd isotopes is discussed. Detailed calculations for ⁹⁹Pd have been carried out in the framework of the Nilsson model (strong-coupling wave functions) using a strong Coriolis band mixing. Energy spectra for high-spin states, wave functions and low-lying non-yrast levels (below E_x = 1 MeV) are also discussed.     

Study of the 45Sc(n, γ) reaction

Primary and secondary γ-rays from the ⁴⁵Sc(n, γ) reaction were measured at four resonances, two of them of p-wave (460.6 and 1060.4 eV) and the others of s-wave (3290 and 4330 eV) character. High accuracy measurements at near the thermal region (0.14-7.65 eV) resulted in an improved set of primary γ-ray energies and level energies above 1 MeV. We obtain a neutron binding energy $\text{B}{}_{\mathrm{<mtext>n</mtext>}}\text{(}{}^{45}\text{Sc}\text{) = 8760.5(2)}\text{keV}$. Absolute intensities of primary capture γ-rays were derived by comparison to the resonance capture in gold at 4.91 eV. El and Ml radiation strengths were observed to be about equal. No correlation of any kind [either between (n, γ) or (d, p) strengths or between adjacent s- and p-wave capture] was observed. The primary γ-ray spectrum following the capture of polarized neutrons in oriented and unoriented ⁴⁵Sc nuclei was studied. A combined χ² analysis of these two experiments resulted in 21 unique spin assignments and many spin restrictions. The fraction of spin J = 3^? in thermal capture was determined to be (92 + 5)%. From the observed transition rates to final states of known spin, J = 3 assignments result for the two p-wave resonances studied.     

Collective excitations in the 123, 125I nuclei

The odd-proton nuclei ¹²³I and ¹²⁵I have been studied in the reactions ¹²¹Sb(α, 2n)¹²³I and ¹²³Sb(α, 2n)¹²⁵I, respectively. The level schemes, spin and parity assignments are based on results obtained from singles γ-ray spectra (E_α = 27 MeV) and excitation functions, from measurements of delayed γ-rays, γ-γ coincidences, internal conversion electrons and γ-ray angular distributions. High-spin positive- and negative-parity bands with energies up to 2948 keV and spins up to $\text{23}\text{2}$ in ¹²³I and with energies up to 3775 keV and spins up to $\text{27}\text{2}\text{in}{}^{125}\text{I}$ have been established. In the decay schemes of both nuclei two separated structures of levels have been observed. One group of levels shows a strong ΔJ = 2 quasirotational pattern predicted by the particle-vibration coupling model. The ΔJ = 1 sequence on a $\text{9}\text{2}$⁺ state is assigned as a rotational structure built on the axially symmetric deformed state $\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$. In ¹²³I a 28 ns isomer at 2660.0 keV has been found.     

Electromagnetic decay of a fragmented analogue state in 63Cu

The ⁶²Ni(p, p), (p, p'γ) and (p, γ) reactions were studied in the vicinity of the $\text{3}\text{2}{}^{\mathrm{-}}$ fragmented analogue of the first excited state of ⁶³Ni. The overall proton energy resolution was about 300 eV. The γ-rays were detected with both Nal(T1) and Ge(Li) detectors. Elastic and inelastic proton widths and partial and total γ-ray widths were measured for each of the fourteen fine structure states of the analogue. Statistically significant correlations were observed between the elastic proton widths, the inelastic proton widths and the total γ-ray widths.     

High spin states in 57Co

High spin states of ⁵⁷Co have been studied via prompt γ-ray spectroscopy in the reactions ⁴⁸Ti(¹²C, p2n) and ⁵⁴Fe(α, p) at 26–48 MeV and 12–24 MeV, respectively. The energies and decay modes of these levels were determined from the analysis of γ-ray singles and γ-γ coincidence spectra, excitation functions, angular distributions and correlations. The relevant lifetimes were measured by the Doppler-shift attenuation method. The new levels established in this work are at 4037, 4814 and 5918 keV with the most probable J^π assignment of $\text{15}\text{2}{}^{\mathrm{?}}$, if $\text{17}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$, respectively. The previously known level at 2524 keV was assigned to have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{?}}$. These together with the known $\text{9}\text{2}{}^{\mathrm{?}}$(1224 keV) and $\text{11}\text{2}{}^{\mathrm{?}}$(1690 keV) levels constitute the yrast states of ⁵⁷Co. The measured lifetimes of the above six levels are (in order of increasing energies) 0.085±0.030, 0.32±0.10, 0.16±0.06, 0.10_?0.07^+0.06, 1.5_?0.5⁴ and 0.17_?0.07^+0.08 ps, respectively. Comparisons with some theoretical calculations are presented.     

Angular distributions of the 2h(d, γ)4he reaction

Angular distributions of γ-rays from the ²H(d, γ)⁴He reaction have been measured at the deuteron energies E_d = 6.05, 8.96 and 11.67 MeV with a 12.7 cm × 15.2 cm NaI(Tl) crystal enclosed in a Cerenkov anticoincidence shield. A least-square fit of the angular distributions indicates that the differential cross section is proportional to sin²θ cos²θ and that the process proceeds through an E2 transition of the type ${}^1\text{D}{}_2\text{→}{}^1\text{S}{}_0$.     

High spin collective excitations in 101Ru

The energy level structure of ¹⁰¹Ru was studied using the reactions ¹⁰⁰Mo(α, 3n)¹⁰¹Ru and ¹⁰⁰Mo(³He, 2n)¹⁰¹Ru. Excitation functions, γγ coincidences and γ-ray angular distributions were measured. Three ΔI = 2 cascades proceeding to a $\text{5}\text{2}{}^{\mathrm{+}}$, $\text{7}\text{2}{}^{\mathrm{+}}$ and $\text{11}\text{2}{}^{\mathrm{?}}$ state were observed. A decay scheme is presented showing energies up to 5849 keV and spins up to $\text{35}\text{2}$. The bands are discussed within the framework of the Nilsson model with Coriolis coupling in which the recoil effect has been properly introduced.     

High-spin states in 14460Nd84 observed in the (α, 2nγ) reaction

Excited states of ¹⁴⁴₆₀Nd₈₄ have been studied using the ${}^{142}\text{Ce}\text{(α,2}\text{n}\text{γ)}{}^{144}\text{Nd}$ reaction. Singles γ-ray, γ-γ coincidence spectra, angular and time distributions of γ-rays with respect to the beam bursts have been measured. Excited states up to 4.986 MeV with spin values up to 13 were populated. The majority of the observed states with spin values up to 12 can be interpreted as two-quasiparticle states. Several of the highest-spin levels can also be explained quantitatively as four-quasiparticle states. No isomeric states with a half-life longer than 1 ns have been found.     

Ground-state rotational band in 181Ta

The ground-state rotational band in ¹⁸¹Ta has been observed up to a spin of $\text{21}\text{2}{}^{\mathrm{+}}$ using Coulomb excitation with ⁸⁴Kr ions. The nuclear lifetimes of the band members have been determined from the Doppler-broadened lineshapes of the de-excitation γ-rays, and the angular distributions of the γ-rays have been measured. It is found that the E2 transition rates from higher spin states $\text{(≧}\text{17}\text{2}{}^{\mathrm{+}}\text{)}$ are retarded relative to the rotational model predictions. A suggestion is made that this retardation may be due to the Coriolis antipairing effect.     

Spectroscopy of 41K by thermal neutron capture in 40K

The γ-ray spectrum emitted after thermal neutron capture in ⁴⁰K has been studied at the ILL high flux reactor with curved crystal Bragg, pair and Ge(Li) spectometers. 585 transitions were assigned to the reaction ⁴⁰K(n, γ)⁴¹K and 490 of them were placed into a ⁴¹K level scheme; 68 new states are proposed. On the basis of γ-ray branches to states with established spin and parity, many new spin-parity assignments were made. The level energies up to 4 MeV were measured with a precision of 8–50 eV relative to the 411.8 keV ¹⁹⁸Au standard, those above 4 MeV with a precision of 50–100 eV. The spin of the capture state was found to be $\text{I =}\text{7}\text{2}$; the neutron binding energy was determined to E_B = 10095.25(10) keV. The level density of $\text{I}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{\pm }}\text{,}\text{7}\text{2}{}^{\mathrm{\pm }}\text{,}\text{9}\text{2}{}^{\mathrm{\pm }}$ states was analyzed in terms of the constant-temperature Fermi gas model. It was shown that in this spin window the level scheme is almost complete up to an excitation energy of 5 MeV.     

Étude des niveaux excités du 231Th par la désintégration α du 235U

An α-spectrum using Si(Au) detectors is obtained with a thin sample of ²³⁵U (0.0013 % ²³⁴U content). A total of thirteen lines are determined. Direct γ-spectra have been obtained with Ge(Li) and Si(Li) detectors at low energy (x_L rays), medium energy (using continuous purification in a resin column) and high energies, enabling the identification of forty-five ²³¹Th γ-rays. A γ-γ two-dimensional coincidence experiment permitted the decay scheme of levels to be established. Some of the suppositions have been verified in α-γ and γ-X_L ray coincidence experiments. Eighteen energy levels are established, seventeen being identified terms of the rotational bands $\text{5}\text{2}$⁺(633), the fundamental; $\text{7}\text{2}{}^{\mathrm{?}}\text{(743),}\text{the}\text{α-}\text{favored}\text{;}\text{5}\text{2}{}^{\mathrm{?}}\text{(75}\text{3}\text{2}{}^{\mathrm{+}}\text{(631)}\text{and}\text{1}\text{2}{}^{\mathrm{+}}\text{(631)}$ also using arguments of previous nuclear reaction work.     

A new N = Z isotope: Krypton 72

Beta-delayed γ-rays have been observed from the decay of ${}^{72}\text{Kr}\text{(τ}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 16.7 ± 0.6}\text{s}\text{)}$. A decay scheme is proposed based on γ-γ and β⁺-γ coincidence measurements. The total decay energy was measured to be Q_EC = 5057 ± 135 keV. The value is compared with mass predictions.     

Electron capture decay of 245Bk (4.90 d) and 246Bk (1.80 d)

The electron capture decay schemes of ²⁴⁵Bk and ²⁴⁶Bk have been investigated by measuring the γ-ray and conversion-electron spectra of mass-separated ²⁴⁵Bk and ²⁴⁶Bk samples. The γ-ray spectra were measured with a 25 cm³ Ge(Li) spectrometer and the conversion-electron spectra were measured with a cooled Si (Li) detector. Multipolarities of most of the transitions in ²⁴⁵Cm and ²⁴⁶Cm were deduced. The half-lives of ²⁴⁵Bk and ²⁴⁶Bk were determined by following the decay of the 252.85 and 798.7 keV photopeaks and were found to be 4.90 ± 0.03 d and 1.80 ± 0.02 d, respectively. The α/(α+EC) ratio for the ²⁴⁵Bk decay was measured to be (1.2 ± 0.1) × 10^?3. On the basis of the present investigation the following non-rotational states were identified in ²⁴⁵Cm: $\text{7}\text{2}{}^{\mathrm{+}}$ [624], 0; $\text{5}\text{2}{}^{\mathrm{+}}$[622], 252.85; $\text{1}\text{2}{}^{\mathrm{+}}$ 355.95; $\text{3}\text{2}{}^{\mathrm{?}}$ vibrational, 633.65; and $\text{1}\text{2}{}^{\mathrm{+}}$[620], 740.95 keV. The $\text{3}\text{2}{}^{\mathrm{?}}$ state at 633.65 keV is int as a K_π = 2^? phonon coupled to the i$\text{7}\text{2}{}^{\mathrm{+}}$[624] single-particle state. Our measurements of ²⁴⁶Bk γ-ray and conversion-electron energies and intensities confirm previous level assignments in ²⁴⁶Cm.     

Electromagnetic decay of fragmented analogue states in 45Sc

The ⁴⁴Ca(p, γ) reaction was studied for 45 resonances for E_p = 1.6?2.2 MeV. The overall proton energy resolution was 300–350 eV; the γ-rays were detected with both NaI(T1) and Ge(Li) detectors. Partial and total γ-ray widths were measured for each of the fine structure states of the $\text{3}\text{2}{}^{\mathrm{?}}$ and $\text{1}\text{2}{}^{\mathrm{?}}$ analogue states at E_p = 1.65 and 2.04 MeV, respectively. The data are examined for correlations between the partial widths (Γ_p, Γ_p′, Γ_γi, Γ_γ^total) in different channels. The γ-ray intensities are compared with (τ, d) spectroscopic factors.     

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.     

Angular correlation study of the levels of 97Nb populated in the decay of 97Zr

The level structure of ⁹⁷Nb has been studied by measuring angular correlations of γ-rays emitted in the decay of ⁹⁷Zr. The cascades measured were (energies in keV): 355–1750, 355-(602)-1148, 254-(703)-1148, 602–1148 and 703–1148. The deduced correlations permit unique spin-parity assignments to be made for the levels at $\text{1148 (}\text{7}\text{2}{}^{\mathrm{+}}\text{), 1750 (}\text{5}\text{2}{}^{\mathrm{+}}\text{)}\text{and}\text{1852 (}\text{5}\text{2}{}^{\mathrm{+}}\text{)}\text{keV}$. Multipole mixing ratios have been deduced for the 254, 355, 602, 703 and 1148 keV transitions.