Remarkable results have been published recently on the \(\beta\) decay of \(^{56}\)Zn. In particular, the rare and exotic \(\beta\)-delayed \(\gamma\)-proton emission has been detected for the first ...time in the \(fp\) shell. Here we focus the discussion on this exotic decay mode and on the observed competition between \(\beta\)-delayed protons and \(\beta\)-delayed \(\gamma\) rays from the Isobaric Analogue State.
Recently, a set of nine nonmagic nuclei with anomalous values of the B(E2) ratio B{sub 4/2}{identical_to}B(E2;4{sub 1}{sup +}{yields}2{sub 1}{sup +})/B(E2;2{sub 1}{sup +}{yields}0{sub 1}{sup +}) < 1 ...were identified. Such values are outside the range allowed by current collective models. In the present work, the B(E2;4{sub 1}{sup +}{yields}2{sub 1}{sup +}) values for two of these nuclei, {sup 98}Ru and {sup 180}Pt, were re-measured to determine if the current literature values for these nuclei are correct. {sup 98}Ru was studied in a {sup 27}Al({sup 98}Ru,{sup 98}Ru*) Coulomb excitation experiment in inverse kinematics, while the lifetime of the 4{sub 1}{sup +} state in {sup 180}Pt was measured in a {sup 122}Sn({sup 62}Ni, 4n){sup 180}Pt recoil distance method (RDM) experiment. For both nuclei, the remeasured B{sub 4/2} values are well above 1, removing the deviations from collective models.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Phys.Rev.Lett.98:132502,2007 Calculations of nuclear masses, using nuclear density functional theory, are
presented for even-even nuclei spanning the nuclear chart. The resulting
binding energy ...differences can be interpreted in terms of valence
proton-neutron interactions. These are compared globally, regionally, and
locally with empirical values. Overall, excellent agreement is obtained.
Discrepancies highlight neglected degrees of freedom and can point to improved
density functionals.
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.
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.
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.
Storage-ring mass spectrometry was applied to neutron-rich \(^{197}\)Au projectile fragments. Masses of \(^{181,183}\)Lu, \(^{185,186}\)Hf, \(^{187,188}\)Ta, \(^{191}\)W, and \(^{192,193}\)Re nuclei ...were measured for the first time. The uncertainty of previously known masses of \(^{189,190}\)W and \(^{195}\)Os nuclei was improved. Observed irregularities on the smooth two-neutron separation energies for Hf and W isotopes are linked to the collectivity phenomena in the corresponding nuclei.
Calculations of nuclear masses, using nuclear density functional theory, are presented for even-even nuclei spanning the nuclear chart. The resulting binding energy differences can be interpreted in ...terms of valence proton-neutron interactions. These are compared globally, regionally, and locally with empirical values. Overall, excellent agreement is obtained. Discrepancies highlight neglected degrees of freedom and can point to improved density functionals.
KPD 1930+2752 is a short-period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period just over two hours. The companion is most likely a white dwarf and the ...total mass of the system is close to the Chandresakhar limit. In this paper we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign from 2002. From 355 hours of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 \(\mu\)Hz (periods between 326 and 157 s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD 1930+2752 for identifying pulsation modes via multiplet structure and a tidally-induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short-period (\(\approx 16\) h) amplitude variability, rotationally split modes, tidally-induced modes, and some pulsations which are geometrically limited on the sdB star.
PG 1159-035, a pre-white dwarf with T_eff=140,000 K, is the prototype of both two classes: the PG1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data ...obtained with the Whole Earth Telescope (WET) showed a rich frequency spectrum allowing the identification of 122 pulsation modes. In this work, we used all available WET photometric data from 1983, 1985, 1989, 1993 and 2002 to identify the pulsation periods and identified 76 additional pulsation modes, increasing to 198 the number of known pulsation modes in PG 1159-035, the largest number of modes detected in any star besides the Sun. From the period spacing we estimated a mass M = 0.59 +/- 0.02 solar masses for PG 1159-035, with the uncertainty dominated by the models, not the observation. Deviations in the regular period spacing suggest that some of the pulsation modes are trapped, even though the star is a pre-white dwarf and the gravitational settling is ongoing. The position of the transition zone that causes the mode trapping was calculated at r_c = 0.83 +/- 0.05 stellar radius. From the multiplet splitting, we calculated the rotational period P_rot = 1.3920 +/- 0.0008 days and an upper limit for the magnetic field, B < 2000 G. The total power of the pulsation modes at the stellar surface changed less than 30% for l=1 modes and less than 50% for l=2 modes. We find no evidence of linear combinations between the 198 pulsation mode frequencies. PG 1159-035 models have not significative convection zones, supporting the hypothesis that nonlinearity arises in the convection zones in cooler pulsating white dwarf stars.
