Coulomb Excitation Data Research Articles

The excited states of 107Ag and 109Ag

The decay schemes for the low-lying states of 107Ag and 109Ag have been studied and revised. States of both nuclei were populated by Coulomb excitation with oxygen ions. The states of 107Ag were also populated through the β +-EC decay of 107Cd. De-excitation γ-rays were studied with Ge(Li) detectors of active volume 5.6 cm 3 and 25 cm 3. The B(E2) values were extracted from the Coulomb excitation data. The proposed level schemes are discussed in terms of a vibrational model for 107Ag and 109Ag, in which it is assumed that most of the negative parity states arise from the coupling of a p 1 2 proton to the vibrational states of the neighbouring doubly-even core nuclei.

Properties of Some Low Excited States inRu101from the Decay of 3-YrRh101

Some properties of low-lying excited states and corresponding transitions in $^{101}\mathrm{Ru}$ have been established by studying the decay of $^{101}\mathrm{Rh}({T}_{\frac{1}{2}}=3.0 \mathrm{yr})$ using scintillation spectroscopy. The three gamma rays associated with this decay with energies in keV (intensities) are 128\ifmmode\pm\else\textpm\fi{}3 (89\ifmmode\pm\else\textpm\fi{}4), 197\ifmmode\pm\else\textpm\fi{}3 (100), 320\ifmmode\pm\else\textpm\fi{}10 (24\ifmmode\pm\else\textpm\fi{}1). They de-excite levels at 128 and 325 keV. A half-life of 0.55\ifmmode\pm\else\textpm\fi{}0.03 nsec was determined for the 128-keV level and a limit of \ensuremath{\le}0.3 nsec was set for the 325-keV level using the delayed-coincidence method. The angular correlation between the 128- and 197-keV gamma rays was measured and the results fitted to the formula $W(\ensuremath{\theta})=1+(0.183\ifmmode\pm\else\textpm\fi{}0.025){P}_{2}(cos\ensuremath{\theta})$ or to $W(\ensuremath{\theta})=1+(0.181\ifmmode\pm\else\textpm\fi{}0.025){P}_{2}(cos\ensuremath{\theta})+(0.020\ifmmode\pm\else\textpm\fi{}0.034){P}_{4}(cos\ensuremath{\theta})$. When these results are combined with Coulomb-excitation data, they yield an assignment of ${\frac{3}{2}}^{+}$ for the 128-keV level with a mixing ratio $\ensuremath{\delta}$ of 0.17\ifmmode\pm\else\textpm\fi{}0.05 for the corresponding transition. Although a definitive spin assignment cannot be inferred for the 325-keV level, a spin ${\mathrm{\textonehalf{}}}^{+}$ seems the more probable, with $\ensuremath{\delta}=\ensuremath{-}({{0.15}_{+0.12}}^{\ensuremath{-}0.19})$ for the 197-keV mixed transition.

Messung von nanosekunden-lebensdauern an niveaus deformierter kerne

Lifetime measurements were performed in the ns range in the spherical nuclei ( 95Mo, 99Tc, 141Pr), spheroidal odd-mass nuclei ( 153Eu, 161Dy, 175Lu, 181Ta) and spheroidal even-mass nuclei ( 156Gd, 160Dy, 170Yd, 182W), using delayed coincidences. Total conversion coefficients for 2 + → 0 + rotational transitions calculated from lifetime and Coulomb excitation data agree with the theoretical values within 5% on the average. No striking evidence of a change in the equilibrium shape of the 153Eu nucleus in the 97 keV state could be found. The ground state of 156Eu is ascribed to the configuration 0 +( p 5 2 +[413], n 5 2 +[642]) . In 175Lu different values for the lifetime of the 343 keV level resulted from delayed coincidences and resonance fluorescence measurements. A discussion of the influence of high-energy transitions in 182W shows that earlier measurements gave too large values for the lifetime of the 1290 keV level. RADIOACTIVITY 95Tc, 99Mo, 141Ce, 153Sm, 153Gd, 156Eu, 160Tb, 161Tb, 170Tm, 175Hf, 181Hf, 182Ta; measured βψ−, ψψ−, ψce-delay. Deduced cc. 95Mo, 99Tc, 141Pr, 153Eu, 156Gd, 160, 161Dy, 170Yb, 175Lu, 181Ta, 182W levels; deduced T 1 2 J, π. Natural targets.

Half-life measurements of excited states in Ta 179 and Tm 167

Nuclear structure data pertaining to all nuclei with mass number A = 179 (Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl) have been compiled and evaluated, and incorporated into the ENSDF database. This evaluation for A = 179, which considers data available by 15 November 2008, supersedes the previous complete publication (E. Browne, Nuclear Data Sheets 55, 483 (1988), cutoff September 1987) and the update-mode publication (C. Baglin, Nuclear Data Sheets 72, 617 (1994), cutoff date September 1994), as well as the subsequent evaluations of Ta, Ir and Tl by C. Baglin (literature cutoff dates January 2000, October 1998 and February 2001, respectively). The newly evaluated literature provides new Coulomb excitation data for Hf, transfer reaction data for Hf and Ta, new information on Au and Hg from α decay and significant (HI,xnγ) reaction data for Hf, Ta, Re, Au and Hg. At the time of the 1994 evaluation, no γ-ray information was available for Au or Hg; that situation has now changed dramatically, although additional work on details of the low-lying structure of Au could be instructive.

Vibrational E1, E2 and E3 transitions in deformed even nuclei

By means of a Bohr-Mottelson type of collective model, reduced E1, E2 and E3 transition probabilities are calculated for transitions involving vibrational states in deformed even nuclei. The E2 and E3 results, obtained under the assumption of uniform charge density, are used to determine the mass parameters B 2 and B 3 from Coulomb excitation data. Collective E1 transitions are treated in terms of polarization oscillations of the nuclear charge density. The E1 transition probabilities thus predicted for Sm 152, Th 232 and U 238 are found to be an order of magnitude smaller than the measured values.

Messung der Lebensdauer des 87 keV-Niveaus von 160Dy

Measuring the half-life of the first excited state of 160Dy we got T12= (2,24 ± 0,06) ns. instead of (1,8 ± 0,2) ns given by McGOWAN 1. This value is in good agreement with COULOMB-excitation data

Das gyromagnetische Verh�ltnis des 2+-Rotationsniveaus von Hf178 und weitere Untersuchungen zum Zerfall von W178

The nuclearg-factor of the 2+ rotational state of Hf178 was determined by a measurement of the rotation of the angular correlation between the gamma-group of ∼1350 keV and the 93 keV radiation in an external magnetic field of 49550 gauss. The result is: $$g_R = + 0 \cdot 356 \pm 0 \cdot 035.$$ Liquid sources of 21 days W178 (ammoniumtungstate in aqueous solution) in equilibrium with 9.3 min Ta178 have been used for these measurements. Differential angular correlation measurements showed the existence of a strong time dependent attenuation. The observed attenuation parameters are: $$\begin{gathered} \lambda _2 /\lambda = 0 \cdot 85 \pm 0 \cdot 23 \hfill \\ \lambda _4 /\lambda = 0 \cdot 74 \pm 0 \cdot 10. \hfill \\ \end{gathered} $$ The true coefficients of the angular correlation between the gamma-group of ∼1350 keV and the 93 keV radiation were derived as: $$\begin{gathered} A_2 = + 0 \cdot 330 \pm 0 \cdot 047 \hfill \\ A_4 = 0 \cdot 990 \pm 0 \cdot 060. \hfill \\ \end{gathered} $$ As they are substantially larger than previously published values a reinterpretation of the correlation function is given. The half-life of the 93 keV state was found to be: $$T_{\tfrac{1}{2}} = (1 \cdot 49 \pm 0 \cdot 05) \cdot 10^{ - 9} \sec $$ in good agreement with the coulomb excitation data.

Decays ofRh106andAg106

The gamma-ray spectra of 30-sec ${\mathrm{Rh}}^{106}$ and 8.3-day ${\mathrm{Ag}}^{106}$, which both decay to ${\mathrm{Pd}}^{106}$, have been studied with scintillation spectrometers. Three gamma-gamma angular correlations have also been measured. The results are consistent with the following level scheme for ${\mathrm{Pd}}^{106}$: 0.513(2+), 1.131(2+), 1.137(0+), 1.360 or 1.213, 1.563(2+), 1.73(2 or 3), 1.84, 1.88, 1.94(3- or 4+), 2.01, 2.052(4+), 2.09(3), 2.28, 2.305 (3 or 4), 2.352(4+), 2.46, 2.62, 2.764(5-), 2.87, and 3.08 Mev. The transition between the first and second 2+ levels was found to consist primarily of $E2$ radiation. The branching ratio obtained for the cascade to crossover gamma rays from the second 2+ level is 2.1\ifmmode\pm\else\textpm\fi{}0.3. This ratio combined with Coulomb excitation data of Stelson and McGowan gives a value of 1.0\ifmmode\pm\else\textpm\fi{}0.3 for the ratio $\frac{B(E2, {2}^{\ensuremath{'}}\ensuremath{\rightarrow}2)}{B(E2, 2\ensuremath{\rightarrow}0)}$.

Photoneutron Yields in the Rare-Earth Region

The total photoneutron yield curves for Sn, I, La, Ce, Sm, Tb, Ho, Er, Yb, Ta, Au, and Pb have been measured for x-ray energies from 7 to 40 Mev with about one percent statistical uncertainty. The Penfold-Leiss matrix was used to convert these yield curves to integrated neutron yield cross sections directly without smoothing the original activation curves. The cross sections derived from the integral curves were corrected for multiple neutron emission above the ($\ensuremath{\gamma}, 2n$) threshold using the statistical model. The widths found for the giant resonances for the closed-shell nuclei decreased from 5 Mev to 3.8 Mev in going from Sn to Pb. The widths for the elements having large nuclear deformations for most of their isotopes were considerably broader. These widths decreased slowly from 8.6 Mev for Sm to 6 Mev for Ta. These widths are consistent with the broadening of the giant resonance to be expected on the Danos model if values of the intrinsic quadrupole moment are taken from Coulomb excitation data. The neutron yield cross sections corrected for multiple neutron emission were integrated to 22 Mev. Using these integrals and defining $f$ by $\ensuremath{\int}\ensuremath{\sigma}\mathrm{dE}=0.06(\frac{\mathrm{NZ}}{A})f$, these data gave an average value of $f=1.34\ifmmode\pm\else\textpm\fi{}0.21$.