Xiao-Hong Zhou

Observation of the Superheavy Nuclide 271 Ds

With the recent commissioning of a gas-filled recoil separator at Institute of Modern Physics (IMP) in Lanzhou, the decay properties of (271)Ds (Z = 110) were studied via the Pb-208(Ni-64, n) reaction at a beam energy of 313.3MeV. Based on the separator coupled with a position sensitive silicon strip detector, we carried out the energy-position-time correlation measurements for the implanted nucleus and its subsequent decay alphas. One alpha-decay chain for (271)Ds was established. The.. energy and decay time of the (271)Ds nucleus were measured to be 10.644 MeV and 96.8 ms, which are consistent with the values reported in the literature.

Isoscaling behavior in fission dynamics

The fission processes of 112 Sn + 112 Sn and 116 Sn + 116 Sn are simulated with the combination of the Langevin equation and the statistical decay model. The masses of two fission fragments are given by assuming the process of symmetric fission or asymmetric fission by the Monte Carlo sampling with the Gaussian probability distribution. From the analysis to the isotopic/isotonic ratios of the fission fragments from both reactions, the isoscaling behavior has been observed and investigated

Direct mass measurements of neutron-rich 86Kr projectile fragments and the persistence of neutron magic number N=32 in Sc isotopes

In this paper, we present direct mass measurements of neutron-rich 86Kr projectile fragments conducted at the HIRFL-CSR facility in Lanzhou by employing the Isochronous Mass Spectrometry (IMS) method. The new mass excesses of 52–54Sc nuclides are determined to be −40492(82), −38928(114), −34654(540) keV, which show a significant increase of binding energy compared to the reported ones in the Atomic Mass Evaluation 2012 (AME12). In particular, 53Sc and 54Sc are more bound by 0.8 MeV and 1.0 MeV, respectively. The behavior of the two neutron separation energy with neutron numbers indicates a strong sub-shell closure at neutron number N=32 in Sc isotopes.

Investigations on light proton-rich nuclei with exotic structure

Abstract One of the proton halo candidates 23Al and its isotopes are systematically investigated in the nonlinear Relativistic Mean-Field and Skyrme Hartree-Fock approaches. It is shown that there exists the energy inversion of ( 5 2 ) + (202) and ( 1 2 ) + (211) orbitals in 23Al nucleus and which may produce the large enhancement of reaction cross section comparing with its neighboring nuclei. Meanwhile, it is obvious to see that the isospin effect of the pairing correlation plays a great role to the separation energy when the Al isotopes approach to the proton drip line. In addition, the ground state and excited state of 9B, 13N are also investigated in the RMF model. There may exist the halo structure in 13N when the last proton of 13N occupies in the first excited state.

First application of combined isochronous and Schottky mass spectrometry: Half-lives of fully-ionized49Cr24+ and 53Fe26+ atoms

Lifetime measurements of β-decaying highly charged ions have been performed in the experimental storage ring (CSRe) by applying the isochronous Schottky mass spectrometry. The fully ionized Cr49 and Fe53 ions were produced in projectile fragmentation of Ni58 primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensities of stored uncooled Cr24+49 and Fe26+53 ions. The extracted half-lives T1/2(Cr24+49)=44.0(27) min and T1/2(Fe26+53)=8.47(19) min are in excellent agreement with the literature half-life values corrected for the disabled electron capture branchings. This is an important proof-of-principle step towards realizing the simultaneous mass and lifetime measurements on exotic nuclei at the future storage ring facilities.

Observation of superheavy nuclide 271Ds based on the Gas-filled separator at IMP

A gas-filled recoil separator was designed and built newly at Institute of Modern Physics (IMP) in Lanzhou. With the recent commissioning of the separator, the decay properties of 271Ds were studied via the 208Pb (64Ni, n) reaction at a beam energy of 313.3 MeV. One α-decay chain for 271Ds was established in total. The experimental result is consistent with the values reported in the literature.

Half-Lives of Low-Lying Isomeric States in 169Ta

Two low-lying isomeric states in 169Ta have been identified via 159Tb(16O, 6nγ)169Ta reaction. Their half-lives are measured to be 28 ± 5 ns for the 9/2- level and 17 ± 4 ns for the 5/2- level by using the delayed γ-γ coincidence method. These two isomeric states are considered to be the bandheads with 9/2-[514] and 1/2-[541] configurations, respectively. Possible neutron quasiparticle configuration for the ground state of 169W is discussed.

An improved method of energy calibration for position-sensitive silicon detectors *

Energy calibration of resistive charge division-based position-sensitive silicon detectors is achieved by parabolic fitting in the traditional method, where the systematic variations of vertex and curvature of the parabola with energy must be considered. In this paper we extend the traditional method in order to correct the fitting function, simplify the procedure of calibration and improve the experimental data quality. Instead of a parabolic function as used in the traditional method, a new function describing the relation of position and energy is introduced.The energy resolution of the 8.088 Me V α decay of213 Rn is determined to be about 87 ke V(FWHM), which is better than the result of the traditional method, 104 ke V(FWHM). The improved method can be applied to the energy calibration of resistive charge division-based position-sensitive silicon detectors with various performances.Energy calibration of resistive charge division-based position-sensitive silicon detectors is achieved by parabolic fitting in the traditional method, where the systematic variations of vertex and curvature of the parabola with energy must be considered. In this paper we extend the traditional method in order to correct the fitting function, simplify the procedure of calibration and improve the experimental data quality. Instead of a parabolic function as used in the traditional method, a new function describing the relation of position and energy is introduced. The energy resolution of the 8.088 MeV α decay of 213Rn is determined to be about 87 keV (FWHM), which is better than the result of the traditional method, 104 keV (FWHM). The improved method can be applied to the energy calibration of resistive charge division-based position-sensitive silicon detectors with various performances.

High-spin level structure in deformed odd-odd ~(186)Au

High-spin states in deformed odd-odd 186Au have been reinvestigated via the 172Yb(19F,5nγ) fusion-evaporation reaction.Detailed analysis of γ-γ coincidence relationships leads to a revised high-spin level scheme for 186Au.New spin values are assigned to the prolate πh9/2i13/2 and πi13/2i13/2 bands in 186Au according to the level spacing systematics as well as the existing knowledge in odd-odd neighboring nuclei.Based on the new spin assignments,both bands exhibit the characteristics of low-spin signature inversion.The properties of signature splitting for the prolate πh9/2i13/2 and πi13/2i13/2 and oblate πh-111/2νi-131/2 bands in Au isotopes have been discussed.A new rotational band built on Ix=(20+) state has been identified and assigned as the oblate πh-111/2  νi-232h-19/12 configuration.

Observation of signature inversion in the πh9/2⊗vi13/2 oblate band

High-spin states in 190Tl have been studied via the 160Gd(35Cl, 5nγ) reaction. The level scheme, consisting of the πh9/2⊗vi13/2 oblate band and a cascade with character of single particle excitations, has been established. Spin values have been firmly assigned to the oblate band in 190Tl, resulting in low-spin signature inversion in the πh9/2⊗vi13/2 oblate band for the first time. Based on the similarity of the level structure in doubly odd Tl nuclei, spin values for the oblate bands in 192–200Tl should be re-assigned, and a consistent low-spin signature inversion has occurred in these oblate deformed nuclei. The low-spin signature inversion phenomena can be interpreted qualitatively by using the 2-quasiparticle plus rotor model including p-n residual interactions.