Alpha decay half-lives of heavy nuclei within a generalized liquid drop model

Theoretical alpha-decay half-lives of the heaviest nuclei are calculated using the experimental Q value. The barriers in the quasi-molecular shape path is determined within a Generalized Liquid Drop Model (GLDM) and the WKB approximation is used. The results are compared with calculations using the Density-Dependent, M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulae. The calculations provide consistent estimates for the half-lives of the a decay chains of these superheavy elements. The experimental data stand between the GLDM calculations and VSS ones in the most time.

Baryon magnetic moment and beta decay ratio in colored quark cluster model

Baryon magnetic moments of p, n, Sigma(+), Sigma(-), Xi(0), Xi(-) and the beta decay ratios (G(A)/G(V)) of n -> p, Sigma(-) -> n and Xi(0) -> Sigma(+) are calculated in a colored quark cluster model. With SU(3) breaking, the model gives a good fit to the experimental values of those baryon magnetic moments and the beta decay ratios. Our results show that the orbital motion has a significant contribution to the spin and magnetic moments of those baryons and the strange component. in nucleon is small.

The beta decay of N-21

The beta-delayed neutron and gamma energy spectra taken from the decay of neutron-rich nucleus N-21 were measured by using the beta - gamma and beta - n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98 MeV and with a total branching ratio of 88.7 +/- 4.2% were observed and presented. One gamma transition with an energy of 1222 keV emitted from the excited state of O-21, and four gamma transitions with energies of 1674, 2397, 2780, and 3175 keV emitted from the excited states of O-20 were identified in the 3 decay chain of N-21. The beta decay half-life for N-21 is determined to be 82.9 +/- 1.9 ms. The uncertainty of half-life is much smaller than the previous result.

Half-Lives of Superheavy Nuclei in Z=113 Alpha Decay Chain

The generalized liquid drop model (GLDM), including the proximity effects and centrifugal potential, and the cluster model with Cosh potential are used to study the half-lives of some Z=113 isotopes and their alpha-decay products.The experimental half-lives of (284)113, (283)113, (282)113and their alpha-decay products are well reproduced by the two models when zero angular momenta transfer is assumed. For (278)113 and its alpha-decay products, both the GLDM andthe cluster model could provide satisfactory results if we assume the alpha particle carry five units of angular momenta, which indicates that possible non zero angular momenta transfer and need further experimental measurements with high precision. Finally, we show that half-lives of alpha-decay are quite sensitive to the angular momentum transfers, and a formula could be used to describe the correlation between alpha-decay half-life and angular momentum transfer successfully.

beta-delayed neutron decay of N-21

The beta-delayed neutron and gamma spectra of neutron-rich nucleus N-21 using beta-gamma and beta-n coincidence measurements were presented in this paper. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio 88.7 +/- 4.2% were observed. One gamma transition among the excited states of O-21 and foury transitions among the excited states of O-20 were identified in the beta decay chain of N-21. The ungated half-life of 83.8 +/- 2.1 ms was also determined for N-21.

Efficiency calibration of neutron detector array for beta decay of exotic nuclei

The research of the in-beam efficiency calibration of Neutron Detector Array of Peking University using N-17 and C-16 beams was introduced in this paper. The efficiency of neutron wall and ball are comparable to the foreign similar devices and neutrons can be detected from low to high energies in high efficiency.

Alpha decay energies and half-lives for possibly synthesized superheavy elements

We investigate the ground state properties of some superheavy nuclei, which may be synthesized in future experiments. Special emphases are placed on the alpha decay energies and half-lives. The alpha decay energies and half-lives from different theoretical models are compared and discussed comprehensively. Through these calculations and comparisons, the optimal superheavy elements to be synthesized in future experiments are proposed theoretically.

Systematic study on alpha decay half-lives of superheavy nuclei

The a-decay half-lives of a set of superheavy nuclear isotope chain from Z = 105 to 120 have been analyzed systematically within the WKB method, and some nuclear structure features are found. The decay barriers have been determined in the quasi-molecular shape path within the Generalized Liquid Drop Model (GLDM) including the proximity effects between nucleons in a neck and the mass and charge asymmetry. The results are in reasonable agreement with the published experimental data for the alpha decay half-lives of isotopes of charge 112, 114, and 116, of the element 294118 and of some decay products. A comparison of present calculations with the results by the DDM3Y effective interaction and by the Viola-Seaborg Sobiczewski (VSS) formulae is also made. The experimental a decay half lives all stand in between the GLDM calculations and VSS formula results. This demonstrates the possibility of these models to provide reasonable estimates for the half-lives of nuclear decays by a emissions for the domain of SHN. The half-lives of these new nuclei are thus well tested from the reasonable consistence of the macroscopic, the microscopic, the empirical formulae and the experimental data. This also shows that the present data of SHN themselves are consistent. It could suggest that the present experimental claims on the existence of new elements Z = 110 similar to 118 are reliable. It is expected that greater deviations of a few SHN between the data and the model may be eliminated by further improvements on the precision of the measurements.

beta(+)/EC decay and systematic analysis of Ir-176,Ir-178

The gamma rays following the beta(+)/EC decay of Ir-176,Ir-178 nuclei have been investigated using in-beam gamma-ray experiment. In addition, with the aid of a helium-jet recoil fast tape transport system, the beta(+)/EC decay of Ir-176 was further studied, the new gamma rays were proved and a low-spin isomer was proposed in Ir-176. The isomeric state was analysized according to the systematics in neighboring nuclei.

alpha decay half-lives of new superheavy nuclei within a generalized liquid drop model

The alpha decay half-lives of the recently produced isotopes of the 112, 114, 116 and 118 nuclei and decay products have been calculated in the quasi-molecular shape path using the experimental Q(alpha) value and a Generalized Liquid Drop Model including the proximity effects between nucleons in the neck or the gap between the nascent fragments. Reasonable estimates are obtained for the observed alpha decay half-lives. The results are compared with calculations using the Density-Dependent M3Y effective interaction and the Viola-Seaborg-Sobiczewski formulae. Generalized Liquid Drop Model predictions are provided for the alpha decay half-lives of other superheavy nuclei using the Finite Range Droplet Model Q(alpha) and compared with the values derived from the VSS formulae.

Alpha decay half-lives of new superheavy elements through quasimolecular shapes

The lifetimes of alpha decays of the recently produced isotopes of the elements 112, 114, 116 and the element (294)118 and of some decay products have been calculated theoretically within the Wentzel-Kramers-Brillouin approximation. The alpha decay barriers have been determined in the quasimolecular shape path within a generalized liquid drop model including the proximity effects between nuclei in a neck, the mass and charge asymmetry and the precise nuclear radius. These calculations provide reasonable estimated for the observed alpha decay lifetimes. The calculated results have been compared with the results of the density-dependent M3Y effective interaction and the experimental data. It is indicated that the theoretical foundation of the generalized liquid drop model is as good as that of the microscopic DDM3Y model, at least in the sense of predicting the T-1/2 values as long as one uses a correct alpha decay energy. The half lives of these new nuclei are well tested from the consistence of the macroscopic, the microscopic and the experimental data.

beta(+)/EC-decay study of Ir-176 neutron-deficient isotope

The beta(+)/EC decay of doubly odd Ir-176 has been investigated using Nd-146(Cl-35, 5n gamma)Ir-176 heavy ion fusion evaporation reaction at 210MeV bombarding energy. With the aid of a helium-jet recoil fast tape transport system, the reaction products were transported to a low-background location for measurements. Based on the data analysis, the previously published gamma rays in Ir-176 decay were proved, moreover, 3 new levels and 10 new gamma rays were assigned to Ir-176 decay. The new level scheme of Os-176 with low excitation energy has been established. The time spectra of typical gamma rays clearly indicate a long-lived low-spin isomer in Ir-176 nuclide.

Properties of the superheavy nuclei (288)115 and its alpha-decay chain in a generalized liquid-drop model

The properties of the nuclei belonging to the newly observed nuclei starting from (288)115 have been studied with the generalized liquid drop model connected with WKB approximation. The calculated results have been compared with the results of the DDM3Y theory and the experimental data. The half lives of this new alpha decay chain have been well tested from the consistence of the macroscopic, microscopic and the experimental data.

Properties of alpha-decay to ground and excited states of heavy nuclei

Branching ratios and half-lives of alpha-decay to the ground-state rotational bands as well as the high-lying excited states of even-even nuclei have been calculated in the framework of the generalized liquid drop model (GLDM) and Royer's formula that we improved very recently. The calculation covers the isotopic chains from Ra to No in the mass regions 222 <= A <= 252 and 88 <= Z <= 102. The agreement between the calculated results and the experimental data indicates the reliability of investigating the properties of the unfavored alpha-decay with our method, especially the improved Royer's formula, which is very valuable for the analysis of experimental data. In addition, the dependence of half-lives on excitation energies of daughter nuclei has been investigated. It is shown that the influence on half-lives becomes stronger and stronger with the increase of the excitation energies.