The mean-lifetimes, tau, of various medium-spin excited states in Pd-103 and Cd-106,Cd-107 have been deduced using the Recoil Distance Doppler Shift technique and the Differential Decay Curve Method. ...In Cd-106, the mean-lifetimes of the I-pi=12(+) state at E-x=5418 keV and the I-pi=11(-) state at E-x=4324 keV have been deduced as 11.4(17)ps and 8.2(7)ps, respectively. The associated beta(2) deformation within the axially-symmetric deformed rotor model for these states are 0.14(1) and 0.14(1), respectively. The beta(2) deformation of 0.14(1) for the I-pi=12(+) state in Cd-106 compares with a predicted beta(2) value from total Routhian surface (TRS) calculations of 0.17. In addition, the mean-lifetimes of the yrast I-pi = 15(-)/2 states in Pd-103 (at E-x=1262 keV) and Cd-107 (at E-x=1360 keV) have been deduced to be 31.2(44)ps and 31.4(17)ps, respectively, corresponding to beta(2) values of 0.16(1) and 0.12(1) assuming axial symmetry. Agreement with TRS calculations are good for Pd-103 but deviate for that predicted for Cd-107.
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A study of the $\beta$ decay of the proton-rich $T_{z}$ = -2 nucleus
$^{56}$Zn has been reported in a recent publication. A rare and exotic decay
mode, $\beta$-delayed $\gamma$-proton decay, has been ...observed there for the
first time in the $fp$ shell. Here we expand on some of the details of the data
analysis, focussing on the charged particle spectrum.
A very exotic decay mode at the proton drip-line, $\beta$-delayed
$\gamma$-proton decay, has been observed in the $\beta$ decay of the $T_z$ = -2
nucleus $^{56}$Zn. Three $\gamma$-proton sequences ...have been observed following
the $\beta$ decay. The fragmentation of the IAS in $^{56}$Cu has also been
observed for the first time. The results were reported in a recent publication.
At the time of publication the authors were puzzled by the competition between
proton and $\gamma$ decays from the main component of the IAS. Here we outline
a possible explanation based on the nuclear structure properties of the three
nuclei involved, namely $^{56}$Zn, $^{56}$Cu and $^{55}$Ni, close to the doubly
magic nucleus $^{56}$Ni. From the fragmentation of the Fermi strength and the
excitation energy of the two populated 0$^{+}$ states we could deduce the
off-diagonal matrix element of the charge-dependent part of the Hamiltonian
responsible for the mixing. These results are compared with the decay of
$^{55}$Cu with one proton less than $^{56}$Zn. For completeness we summarise
the results already published.
The ratio of B(E2) strengths between the lowest lying members of the ground state band in {sup 144}Nd, B{sub 4/2}=B(E2;4{sub 1}{sup +}{yields}2{sub 1}{sup +})/B(E2;2{sub 1}{sup +}{yields}0{sub 1}{sup ...+}), which is used to quantify collectivity in nonmagic nuclei, has been remeasured by means of Coulomb excitation. Ambiguities in literature values for this ratio have been resolved. The results are discussed in terms of the interplay of collective and single-particle degrees of freedom, and in the context of the formation of collective structures in the A=140 mass region, and more generally near (sub)shell closures. In addition, the B{sub 4/2} ratio of {sup 148}Sm has been remeasured, and the quadrupole moment of the 4{sub 1}{sup +} state is found to be on the order of 1 e b.
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Excited low-spin, nonyrast states in {sup 170,172,174}Hf were populated in {beta}{sup +}/{epsilon} decay and studied through off-beam {gamma}-ray spectroscopy. New coincidence data allowed for a ...substantial revision of the level schemes of {sup 170,172}Hf and a confirmation of the level scheme of {sup 174}Hf. The Hf isotopes represent a unique situation in which a crossing of collective intrinsic excitations occurs, enhancing significantly the effects of mixing. Using branching ratios from excited 2{sup +} states, this mixing is followed and studied. The resulting mixing matrix elements are found to be {approx}30 keV - an order of magnitude larger than estimated previously for nearby nuclei. In the case of {sup 170}Hf, the 2{sub {beta}}{sup +} and 2{sub {gamma}}{sup +} level are shown to be completely mixed.
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Excited states in {sup 192}Pt were populated in {beta}{sup +}/{epsilon} decay and studied through off-beam {gamma}-ray spectroscopy. New coincidence data give no support for several reported ...low-energy, low-spin states proposed in {beta} decay and lead to a substantially revised level scheme. The structure of {sup 192}Pt is discussed in terms of both single-space IBA-1 calculations and two-space IBA calculations with configuration mixing. Both models together suggest that it is the perhaps the 0{sub 4}{sup +} state that corresponds to an intruder excitation, resulting from the excitation of a pair of protons across the Z=82 closed shell.
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169.
The (n, gamma) campaigns at EXILL Jolie, J; Régis, J. -M; Wilmsen, D ...
Cgs15 - Capture Gamma-Ray Spectroscopy and Related Topics,
01/2015
Journal Article
Open access
At the PF1B cold neutron beam line at the Institut Laue Langevin, the EXILL array consisting of EXOGAM, GASP and ILL-Clover detectors was used to perform (n, gamma) measurements at very high ...coincidence rates. About ten different reactions were measured in autumn 2012 using a highly collimated cold neutron beam. In spring 2013, the EXOGAM array was combined with 16 LaBr3(Ce) scintillators in the EXILL&FATIMA campaign for the measurement of lifetimes using the generalised centroid difference method. We report on the properties of the set-ups and present first results from both campaigns.
Phys. Rev. Lett. 112, 222501 (2014) We report the observation of a very exotic decay mode at the proton
drip-line, the $\beta$-delayed $\gamma$-proton decay, clearly seen in the
$\beta$ decay of the ...$T_z$ = -2 nucleus $^{56}$Zn. Three $\gamma$-proton
sequences have been observed after the $\beta$ decay. Here this decay mode,
already observed in the $sd$-shell, is seen for the first time in the
$fp$-shell. Both $\gamma$ and proton decays have been taken into account in the
estimation of the Fermi (F) and Gamow Teller (GT) strengths. Evidence for
fragmentation of the Fermi strength due to strong isospin mixing is found.
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