Comparison of cluster and shell model wave functions of deformed32S states

The 786 keV beta-286keV gamma angular correlation in the ground state decay of¹⁴⁹Pm is measured for the first time, using the conventional slow-fast scintillation assembly. Integral correlation results characterize the involved beta transition to be of first-forbidden non-unique type. The present results combined with the other experimental parameters, strongly support a 9/2^? spin-parity character to the 286 keV level in¹⁴⁹Sm. The energy independence of the reduced correlation coefficient as found in this work shows the validity ofξ-approximation for the 786 keV beta transition in¹⁴⁹Pm and is also consistent with the logft value and spectrum shape reported by earlier authors.     

Fluorescence nucléaire de 115In

Continuous radiation (bremsstrahlung) from a 2 MeV electron accelerator has been used to excite seven nuclear levels in ¹¹⁵In, at 1133, 1291, 1449, 1464, 1487, 1498 and 1610 keV. Mean-life values were calculated for the first five levels and the δ² ratio was also determined for those at 1133 and 1464 keV.     

Properties of the 635.4 keV level in171Tm

The properties of some high excited states of¹⁷¹Tm have been studied using Ge(Li) detectors. The directional angular correlation measurements for 277.4-210.5 keV cascade are in agreement with the spins of the 635.4 keV© and 912.8 keV(5/2) levels. The magnetic momentμ=(1.15±0.21)μ _N of the 635.4 keV level was determined by integral perturbed angular correlation (IPAC) in external magnetic field.     

Winkelkorrelations- und Lebensdauer-Messungen am59Co

γγ angular correlations and delayed β-γ coincidences have been measured in the decay of⁵⁹Fe to⁵⁹Co.M1 andE2 transition probabilities were determined for the 143, 192, and 335 keV transition by measuring the 192–1099 keV, 335–1099 keV and 143–1292 keV correlations, and the half lives of the 1292 and 1434 keV levels. Theg-factor of the 1292 keV state was derived to beg=+1.09 ± 0.08 from the perturbation of the 143–1292 keV γγ angular correlation in ferromagnetic⁵⁹CoFe and⁵⁹CoNi samples. The results are discussed in terms of the weak coupling model.     

On the yrast two proton-two neutron hole states in208Po

High-spin levels in²⁰⁸Po, populated in the²⁰⁸Pb(α,4n)-reaction, were studied usingα-particles in the energy region 41–51 MeV. The energies of levels above the 6⁺ level have an uncertainty of about 10 keV due to the fact that the 8⁺→6⁺ transition has not been observed so far, but this transition has previously been established to be converted neither in theK-shell nor in theL-shells. It was found that the yrast cascade ofγ-rays from a 19⁺ level at 5896+ε keV feeds levels of lower spin which all can be explained as originating from two proton-two neutron hole configurations. In the higher part of the cascade it is mainly the neutron holes which change their configuration, while the lower part of the cascade is dominated by changes in the proton configuration. The yrast levels in the angular momentum regionJ=8–19 vary practically linearly with energy in the region 1.5–6 MeV. No isomeric traps were found above the 11^? level at 2699+ε keV.     

Low-lying energy levels in 166Ho

The properties of some low-excited states of ¹⁶⁶Ho have been studied using thin, high resolution Ge detectors. The relative intensities of γ-lines were determined. The directional angular correlation measurements for the 28.23–54.24 keV cascade are in agreement with the 1^?(M1)2^?(E2)0^? spin sequence. The magnetic moment μ = 0.068 ± 0.010 μ_N of the 54.24 keV level was determined by integral perturbed angular correlation (IPAC) in an external magnetic field. This value can be explained by the configuration mixing due to the Coriolis interaction.     

Gamma-gamma angular correlations in105Rh

Gamma-gamma angular correlation measurements have been performed on the cascades 393-263 keV, 413-263 keV, and 316–469 keV emitted in¹⁰⁵Rh after theΒ-decay of¹⁰⁵Ru. From the measured angular correlation coefficients the spins of the states at 469 keV, 785 keV, and 806 keV and the multipolarities of the involved gamma-rays are determined.     

g-factor of the 91.5 keV state in 151Sm

The g-factor of the 91.5 keV state in ¹⁵¹Sm has been measured by the TDPAC method using γγ cascades following the β-decay of 28 h ¹⁵¹Pm. The result is g = ?0.21±0.01. The anisotropy of the angular correlation for the 232.2-25.7 keV cascade is measured to be A = +0.058±0.006. From this an M1/E2 mixing ratio of δ² = 0.008±0.002 for the 232.3 keV transition is concluded. No attenuation of the anisotropy of the angular correlation is observed for aqueous solution sources of SmC1 in excess of hydrochloric acid. Spin and parity assignments for excited states in ¹⁵¹Sm are presented.     

Spin des 921 keV-Zustandes in99Tc

The angular correlation of the⁹⁹Tc 739-181 keV gamma-gamma cascade has been measured in a liquid molybdenium source. The result was:A ₂=0.0930 ± 0.0028,A ₄=?0.0095 ± 0.0042. The spin of the 921 keV level was determined to 3/2⁺. The mixing ratio of the 739 keV gamma-transition was measured to δ (E2/M1)=5.9 _?0.3 ^+0.4 .     

83mKr, a potentially powerful PAC probe

In the decay of ⁸³Rb to ^83mKr and the subsequent decay to the ⁸³Kr ground state a 553–9.4 keV γ-γ and a 17.85–9.4 keV e^?-γ cascade are populated. The intermediate 9.4 keV 7/2^?+? state with a half-life of 154 ns is a perfect candidate for the application of the perturbed angular correlation (PAC) technique. Thus, it is possible to investigate the lattice environment of the implanted probes via the electric quadrupole interaction of the 9.4 keV 7/2^?+? state with the electric field gradient produced by the host lattices. Details of the production of this new PAC probe and planned measurements will be discussed.     

The magnetic moment of the lowest 3/2− state in57Co

The reaction⁵⁴Fe(α, n)⁵⁷Ni has been used to implant⁵⁷Co isotopes in ferromagnetic iron. Theg-factor of the lowest 3/2^? state is determined using the internal field in a constant angle reversed field method. The angular correlation of the 127–1,378 keV cascade is also measured. The result of the angular correlation measurement together with reaction data is consistent withp _3/2 andp _1/2 single particle assignments to the lowest 3/2^? resp. 1/2^? state. In view of this statement the quenching of the magnetic moment is discussed.     

The properties of 116in excited states

Gamma and conversion electron spectra from the ¹¹⁵In(n, γ)¹¹⁶In reaction in the energy range 20–700 keV and 20–850 keV respectively have been measured with bent crystal and magnetic spectrometers. Gamma-gamma coincidences in the energy range 50–500 keV have been investigated with Ge(Li)-Ge(Li) arrangement. Proton spectra from the 12 MeV deuteron-induced (d, p) reaction taken at the University of Pittsburgh Tandem Van de Graaf accelerator were reanalysed. The ¹¹⁶In level scheme consisting of 56 levels in the energy range 0–1.4 MeV has been constructed. Parity is determined for all the levels introduced. Unique spin values are assigned to 37 levels. The information obtained was used to place limits to the J-values for the rest of the levels. The main components of the wave function are established for 23 levels, considered to be components of p-n multiplets in which the proton hole and odd neutron are in in one of the Z = 28 → 50 and N = 50 → 82 shell states, respectively. Energy splittings of p-n configurations by residual interactions taken as a combination of short range Wigner and singlet forces have been calculated. It is noted that many excited states cannot be described in the framework of two-quasiparticle configurations.     

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.     

The spin of the 2,198 keV level in74Ge and multipole mixing ratios of gamma transitions in the decay of74As

Directional-correlation measurements of several cascades in the⁷⁴As decay have been made with a NaI — Ge(Li) detectors system. In the⁷⁴Ge the following cascades were measured: 608–596 keV, 994–1,204 keV, 994-(608)-596 keV and 887-596 keV. The corresponding results give a unique spin assignment of 2 for the 2,198 keV level and determine theE2/M 1 mixing ratios ofδ(608)=3.4±0.4 andδ(994)=?(2.8 ± 0.2). In the⁷⁴Se it was measured the 635-635 keV cascade. The result obtained assigned the spin of the 1,270 keV level as 2 and fixed the E2/M1 mixing ratio of δ(635)=?(2.6 ± 0.2). Also aγ-intensity study has been made to determine the branching ratios of the transitions that deexcite the 1,270 keV level in⁷⁴Se. From these data aI(635)/I(1,270)=12.5 ± 5.0 is obtained.     

β-γ-Zirkularpolarisationskorrelation an Ga72

The β-γ circular polarization asymmetry for the β 948—γ 2202 keV transition in Ga⁷² has been measured using the polarimeter developed at Karlsruhe. The result of the measurement isA=?0.203±0.035. From this result and γ-γ angular correlation measurements of other authors we are able to deduce the spin of the 3036 keV level in Ge⁷² to 2^?. The multipolarity of the 2202 keV γ-rays in Ge⁷² is found to beE1.     

Investigation of statistically perturbed angular correlations of154Gd and156Gd in different liquid sources

The statistical perturbations of γγ-angular correlations involving the first 2⁺ rotational state of¹⁵⁴Gd and¹⁵⁶Gd have been time differentially investigated. We used liquid sources of 3⁺ ions of Gadolinium in lN perchloric acid, 0.5 N and 1N hydrochloric acid, 1.3N and 2.6 N sulfuric acid. Influences of the various chemical surroundings on the ratio λ₄/λ₂ of the attenuation parameters have been found. A simultaneous measurement of the angular correlation of the 874 keV–123 keV cascade and the 2,098 keV–89 keV cascade of¹⁵⁴Gd and¹⁵⁶Gd, respectively, has been performed in perchloric solution. From the ratio of the attenuation parameters λ₂, obtained by this experiment, we have derived the ratio of the magneticg-factors of the first 2⁺ levels of these isotopes asg ¹⁵⁴/g ¹⁵⁶=1.11±0.08.     

Angular correlation measurements in 131Xe

An experiment is described determining the angular correlations of five γ-γ cascades in ¹³¹Xe appearing in the decay of ¹³¹I. Using a 12-channel goniometer the following results were obtained: 325.8–177.2 keV, A₂ = 0.018(11), A₄ = ?0.003(10); 318.1–404.8 keV, A₂ = ?0.18(4), A₄ = ?0.05(3); 272.5–364.5 keV, A₂ = 0.15(4), A₄ = ?0.03(3); 284.3–80.2 keV, A₂ = ?0.005(7), A₄ = 0.005(15); 318.1–324.6 keV, A₂ = 0.24(5), A₄ = ?0.01(5). The result for the 318.1–324.6 keV cascade has not been corrected for a small influence from the 318.1–404.8 keV cascade. Four E2/M1 mixing ratios are deduced from the angular correlation coefficients (energies in keV): $\text{?0.28 ≦ δ(325.8) ≦}\text{t}\text{?}\text{0.20}$, ?0.19 ≦ δ(318.1) ≦ ?0.035, ?1.5 ≦ δ (324.6) ≦ ?0.05, δ(272.5) = ?0.38(17). Transition strengths and limits to transition strengths are calculated for several transitions. The properties of negative parity states in ¹³¹Xe are investigated theoretically in a model where three neutron holes in the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ orbit are coupled to the quadrupole vibrations of the even core. The experimental energies of the lowest negative parity states and the strengths of the transitions between these states are very well accounted for by the calculation.     

Investigation of backward α-particle scattering in 24Mg and 28Si through α-γ angular correlations

Alpha-gamma angular correlations have been measured for the reaction ²⁴Mg(α, α'γ) in the energy range 15.50 to 17.00 MeV in steps of 300 keV and for ²⁸Si(α, α'γ) from 15.00 to 16.20 MeV in steps of 200 keV to provide energy averaged results. The scattered α-particles were detected for lab angles θ_α = 115°–178° in a multidetector arrangement. The coincident γ-rays were observed with a Ge(Li) detector placed at 90° in the reaction plane. Data were obtained for the 1st, 2nd and 3rd excited states of ²⁴Mg and for the 1st, 2nd, 3rd and 4th excited states of ²⁸Si. The absolute doubledifferential cross sections were analysed with Hauser-Feshbach calculations. The analyses show that compound nuclear processes are responsible for the rise of backward α-scattering in ²⁴Mg(α, α'γ)²⁴Mg and ²⁸Si(α, α'γ)²⁸Si at the energy studied.     

Messung der Linearpolarisation der 245 keV-γ-Strahlung in111Cd

A Compton polarimeter for linear polarization measurements ofγ-quanta existing of two thin NaI-crystals is described. The linear polarization correlation of the 171–245 keV cascade in¹¹¹Cd was measured. TheE2-character of the 245 keV quanta follows immediately from this correlation measurement. The mixing ratioδ of the 171 keV quanta was confirmed to beδ ₁=+0.145. The polarization sensitivity of the polarimeter is discussed.     

Die Gamma-Gamma-Winkelkorrelation der 326-177 keV-Kaskade in Xe131

The angular correlation of the 326-177 keV gamma-gamma cascade in Xe¹³¹ has been measured with 2 Ge(Li)-detectors. For the corrected correlation coefficients we obtainedA ₂=0.002±0.011 andA ₄=0.097±0.012. Estimating possible spins of 7/2, 9/2 and 7/2, 9/2, 11/2, 13/2 for the 667.0 and 341.2 keV states respectively, our experimental value agrees with the following spin sequences: 7/2^?→ 9/2^?→11/2^?, 7/2^?→11/2^?→11/2^? and 9/2^?→13/2^?→11/2^?.