Reorientation effect measurements of 122Te and 130Te

Coulomb excitation probabilities of the first 2 ⁺ states of ¹²²Te and ¹³⁰Te have been determined. The measurement was performed by resolving the inelastically and elastically scattered ⁴He and ¹⁶O projectiles using eight surface barrier detectors between 44° and 173°. Quadrupole moments Q₂⁺ as well as B(E2, 0⁺ → 2⁺) values were deduced. The Q₂⁺ found for the positive sign of the 2₂⁺ interference term are ?0.46±0.05 e · b and ?0.15±0.10 e · b for ¹²²Te and ¹³⁰Te respectively.     

Reorientation effect measurements in 124Te, 126Te and 128Te

Coulomb excitation probabilities of the first 2⁺ states of ¹²⁴Te, ¹²⁶Te and ¹²⁸Te have been determined. The measurement was performed by resolving the inelastically and elastically backward scattered ⁴He and ¹⁶O projectiles using an annular surface barrier detector. Quadrupole moments (Q₂₊) as well as the B(E2, 0⁺ → 2⁺) values were extracted by analyzing the excitation probabilities with the Winther-de Boer multiple Coulomb excitation program. The Q₂ deduced for the positive sign of the 2⁺ interference term are ?0.41 ± 0.08 e · b, ?0.144 ± 0.11 e · b and ?0.12 ± 0.09 e · b for ¹²⁴Te, ¹²⁶Te and ¹²⁸Te, respectively.     

Giant-resonance excitation by 130 MeV 3He

Energy spectra of 130 MeV ³He scattered from ²⁴Mg, ⁹⁰Zr, ¹²⁰Sn and ²⁰⁸Pb have been measured. The spectra exhibit a pronounced giant resonance (GR) structure in the excitation energy region around $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{≈ 63A}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}\text{MeV}$. The GR angular distributions as well as those corresponding to the first 2⁺ levels in ²⁴Mg and ¹²⁰Sn have been obtained for angles 7° ≦ θ_L ≦ 35°. Distorted wave calculations using the optical model parameters fitting the elastic data resulted in good fits to the 2⁺ levels. For ²⁴Mg, ⁹⁰Zr and ¹²⁰Sn the shapes of the GR angular distributions are well fitted by L = 2 curves alone. However, for ²⁰⁸Pb both L = 2 and L = 4 curves give fits of comparable quality.     

Magnetic moment of the 2− state in 92Nb

The g-factor of the $\text{[π(2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}^1\text{v(2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}{}^1\text{]}{}_2\text{?}$ state in⁹²Nb(τ = 6.2 μsec) was determined by means of perturbed angular distribution methods using the ⁹²Zr(p, n)⁹²Nb reaction in a liquid alloy. The extracted $\text{v(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ magnetic moment is discussed in terms of the core-polarization effect.     

The electric quadrupole moment of the 6+ state of 112Sn

The spectroscopic quadrupole moment of the isomeric 6⁺' (2552 keV) state of ¹¹⁷Sn has been derived from TDPAD measurements in a Cd metal host target at 500 K as $\text{Q}{}_{\mathrm{<mtext>I</mtext>}}\text{(6}{}^{\mathrm{+}}\text{,}{}^{112}\text{Sn}\text{) = ± 0.29(6)}\text{b}$. The calibration of the effective field gradient for Sn in Cd at 500 K, given by Herrlander et al. has been used. A comparison of the results with shell model estimates makes a mixed configuration of $\text{|(}\text{g}\text{7}\text{2}\text{)}{}^{\mathrm{?2}}\text{6}{}^{\mathrm{+}}\text{〉)}\text{and}\text{(}\text{g}\text{7}\text{2}{}^{\mathrm{?1}}\text{d}\text{5}\text{2}{}^{\mathrm{?1}}\text{)6}{}^{\mathrm{+}}\text{〉)}$ for the 6⁺ state most likely.     

Level structure of123, 125I from the 122, 124Te(3He,d) reactions

The energy levels of ¹²³I and ¹²⁵I have been studied in the ^{122, 124}Te(³He, d)^{123, 125}I reactions at 24 MeV bombarding energy. The reaction products were analysed with an Enge split-pole magnetic spectrograph. A total of 57 levels below 3.3 MeV in ¹²³I and 79 levels below 4.1 MeV in ¹²⁵I were observed. Angular distributions were measured and compared with DWBA calculations to obtain orbital angular momentum transfers and spectroscopic strengths. The results were compared to previous radioactive decay studies and to theoretical energy level calculations.     

Measurement of the quadrupole moments of the first 2+ states of 130Ba and 134Ba

The quadrupole moments of the first 2⁺ states of ^130,134Ba were measured using the reorientation precession technique. Prolate deformations were determined for both nuclei. The quadrupole moments found were Q = ?0.33 ± 0.24 b and ?0.31 ± 0.24 b for ¹³⁰Ba and ¹³⁴Ba, respectively.     

Magnetic moment measurements of the first-excited 2+ states in even Nd isotopes

The g-factors of the first-excited 2⁺ states of ^{144, 146, 148}Nd were deduced from precession measurements in which the excited nuclei recoil through (TF IMPAC) or stop in (IMPAC) magnetized iron. The transient and static hyperfine fields which are active in these cases have been calibrated. The results for the g-factors, combined with previous data which were reanalyzed in the present work, are: g₁₄₄ = 0.15 ± 0.02, g₁₄₆ = 0.25 ± 0.04, g₁₄₈ = 0.32 ± 0.04. The g-factor for ¹⁴⁴Nd, which is abnormally low for a collective 2⁺ state, cannot be accounted for theoretically.     

Magnetic moment of the 10−, 2.53 ms state in 208Bi measured by in-beam NMR-PAD

The g-factor of the 10^? isomeric state in ²⁰⁸Bi has been measured by the method of inbeam NMR-PAD. From the experimental value $\text{¦g¦= 0.2666(27)}$ the magnetic moment of the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ neutron hole state is deduced. The result is compared with experimental values of neighbouring nuclei and theoretical predictions.     

Nuclear polarization of high-spin levels and the sign of the quadrupole moment of 54Fe(10+)

The determination of the sign of the quadrupole deformation at high spins requires an observation of the electric quadrupole interaction of polarized isomers in single crystals of non-cubic metallic hosts. The ⁵⁴Fe(10⁺) isomer was polarized, subsequent to its population by the (¹²C, p2n) reaction, by passage through an array of tilted carbon foils. The isomers were then recoil implanted into single crystals of zinc and cadmium and the tune differential modulations of the angular distribution of decay γ-rays were observed. Nuclear polarization values of P_I = 0.08(3)?0.18(5) were found for 13–17 polarizing foils, respectively, and a positive sign of the quadrupole moment was deduced. An improved value was established for the quadrupole moment: $\text{Q[}{}^{54}\text{Fe}\text{(10}{}^{\mathrm{+}}\text{)] = + 29.7(4) e ·}\text{fm}{}^2$, in agreement with current shell-model predictions.     

Multiple coulomb excitation of 167Er

The ground-state rotational band in ¹⁶⁷Er has been investigated through multiple Coulomb excitation with a 160 MeV ³⁵Cl beam. Excited states up to $\text{25}\text{2}{}^{\mathrm{+}}$ were established by measuring γγ coincidences and γ-ray angular distributions. Gamma-gamma angular correlations were also measured. Nuclear lifetimes of levels up to spin $\text{23}\text{2}$ have been determined from Doppler-broadened γ-ray lineshapes, and B(M1) and B(E2) values of intra-band transitions deduced. Considerable signature dependence was observed for level energies and M1 transition probabilities. A Coriolis band-mixing calculation was carried our for comparison with the experimental results. The measured M1 transition probabilities are compared to calculations based on a particle-rotor model, a cranking model, and a microscopic model with quantum-number projection.     

The quadrupole moment of the 40 ps fission isomer in 236Pu

A quadrupole moment of 37_?8⁺¹⁴ b has been deduced for the 40 ps shape isomer in ²³⁶Pu. The value has been derived from a measured delayed fission fragment angular distribution with an anisotropy of 1.48 ± 0.15 for the isomeric decays at 30°. The deformation of the second minimum expressed by the axes ratio of a spheroid is found to be 2.0 ± 0.3.     

Static quadrupole moments of the first excited states of 200Hg and 202Hg

The static quadrupole moments Q_2⁺ and B(E2; 0⁺ → 2⁺) values of the 2⁺ first excited states of ²⁰⁰Hg and ²⁰²Hg have been determined using the reorientation effect in Coulomb excitation. An annular silicon surface-barrier detector was used to detect backscattered ⁴He, ¹²C and ¹⁶O projectiles. It is found that for ²⁰⁰Hg, Q_2⁺ = +1.07 ± 0.19 e · b(+0.98 ± 0.19 e · b) for destructive (constructive) interference from the 2^+′ state, and B(E2; 0⁺ → 2⁺) = 0.853 ± 0.007 e² · b². For ²⁰²Hg, we find Q_2⁺ = +1.01 ± 0.13 e · b (+0.87 ± 0.13 e · b) and B(E2; 0⁺ → 2⁺) = 0.605 ± 0.005 e² · b². The Q_2⁺ value obtained for ²⁰⁰Hg is in agreement with previous work, but that for ²⁰²Hg is not. The results obtained are compared with the predictions of various nuclear models, and the mass dependence of Q_2⁺ in the region 182 ≦ A ≦ 206 is examined.     

The electric quadrupole moment of the first excited state of 204Hg

The static electric quadrupole moment Q₂₊ and the B(E2; 0⁺ → 2⁺) value of the 2⁺ first excited state of ²⁰⁴Hg have been determined using the reorientation effect in Coulomb excitation. An annular Si surface-barrier detector was used to detect back-scattered ⁴He, ¹²C and ¹⁶O projectiles. In a subsidiary experiment, spectra were obtained from ²⁰⁴Hg(p, p')²⁰⁴Hg using Si surface-barrier detectors, and the results were used in conjunction with previously existing data to provide information on higher states of ²⁰⁴Hg which might participate in the Coulomb excitation of the 2⁺ state. From a 3-level analysis, we find Q₂₊ = +0.40 ± 0.20 e · b and B(E2; 0⁺ → 2⁺) = 0.423 ± 0.005 e² · b². These results are in good agreement with the predictions of particle-vibrational coupling calculations. The value obtained for $\text{Q}{}_{\mathrm{2+}}\text{(}{}^{204}\text{Hg)}$ is substantially smaller in magnitude than values of Q₂₊ previously determined for ^{198, 200, 202}Hg.     

The g-factors of the first 2+ states in 50, 54Cr, 54Fe and 70Ge

The gyromagnetic ratios of the first excited J^π = 2⁺ states of ^50,54Cr, ⁵⁴Fe and ⁷⁰Ge have been determined by the ion-implantation perturbed angular correlation technique (IMPAC) with ferromagnetic Gd as stopping material. The g-factors were extracted from the measured precession angles with use of known lifetimes, static hyperfine magnetic fields and transient hyperfine magnetic field data for fast ions traversing ferromagnetic lattices. The deduced values are 0.59 ± 0.10, 0.56 ± 0.10, 1.08±0.19 and 0.38±0.08, respectively. With the exception of ⁵⁴Fe all g-factors are close to the collective value. A re-evaluation of earlier IMPAC data on ^{70, 72, 74, 76}Ge with Fe as stopping material has been performed. The value obtained for ⁷⁰Ge is in good agreement with the one measured in this work.     

Magnetic moment of the 2543 keV 7+ state in 40K

The nuclear g-factor of the 2543 keV, 7⁺ state ⁴⁰K has been measured as g = 0.59 ± 0.10. Time-integral perturbed angular distributions were measured in an external magnetic field and, after implantation, in the hyperfine field at potassium in nickel. The experimental value is discussed within the $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^2\text{and}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?2}}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^2$, configurations.     

Measurement of the magnetic moment of the 7+ isomer in 198Tl

Using the atomic beam magnetic resonance method the hyperfine structure separation of $\text{1.9}\text{h}{}^{\mathrm{198m}}\text{Tl}\text{(I}{}^{\mathrm{\pi }}\text{= 7}{}^{\mathrm{+}}\text{)}$ has been measured in the ${}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ atomic ground state. From the hyperfine structure splitting the nuclear magnetic dipole moment has been deduced. The results are: Δν = 4500 (68) MHz, μ_I = 0.641(10)μ_N. This is an improvement of approximately one order of magnitude compared to a previous measurement. The quoted value of the magnetic dipole moment includes corrections for the hyperfine structure anomaly and for diamagnetic shielding.     

The elastic scattering of polarized 3He by 3He and excitation in the 6Be system

Angular distributions of the polarization in the elastic scattering of ³He by ³He have been measured at eight energies between 18 and 33 MeV, corresponding to excitation of ⁶Be between 20.5 and 28 MeV. The measurements were made using the 33 MeV polarised ³He beam at the University of Birmingham Radial Ridge cyclotron and a small gas target. The data have been analysed in terms of real and complex phase shifts. The deduced phase shift energy dependence cannot be associated with a single isolated level in ⁶Be, however an application of the two-level R-matrix formula reveals some broad L = 3 structures around E_x = 25 MeV.     

The excitation function for the 89Y(n, 2n)88Y reaction

Activation cross sections for the ⁸⁹Y(n, 2n)⁸⁸Y reaction at neutron energies between 12.6 and 17.8 MeV have been measured by using the mixed-powder method and γ-ray detection by a Ge(Li) spectrometer. Using the ²⁷Al(n, α)²⁴Na reaction for monitoring the neutron flux, the measured cross-section values for the ⁸⁹Y(n, 2n)⁸⁸Y reaction were found to be 331±32 mb, 603±58 mb, 820±79 mb, 1040±100 mb, 1072±103 mb, 1172±112 mb, 1221±117 mb and 1218±117 mb at the respective incident neutron energies of 12.6±0.1 MeV, 13.3±0.1 MeV, 14.0±0.4 MeV, 14.9±0.3 MeV, 15.1±0.3 MeV, 16.0±0.4 MeV, 16.7±0.5 MeV and 17.8±0.7 MeV. The measured values are compared with the experimental values of others and with the theoretical values obtained from calculations based on the statistical model for the formation of a compound nucleus and its subsequent emission of neutrons.