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Isochronous mass spectrometry has been applied to neutron-deficient Ni-58 projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of four short-lived T-z = -3/2 nuclides Ti-41, Cr-45, Fe-49, and Ni-53 have been measured with a precision of 20 - 40 keV. The new mass data enabled for the first time to test the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observed that the IMME is inconsistent with the generally accepted quadratic form for the A = 53, T = 3/2 quartet. We performed full space shell model calculations and compared them with the new experimental results. The main results were published in Y.H. Zhang et al., Physical Review Letters 109 (2012). Here we give details on the experiment and data analysis as well as summarize the main findings.

Masses of neutron-deficient Ni-58 projectile fragments have been measured at the HIRFL-CSR facility in Lanzhou, China employing the isochronous mass spectrometry technique. Masses of a series of short-lived T-z = -3/2 nuclides including the Cr-45 nucleus have been measured with a relative uncertainty of about 10(-6)-10(-7). The new Cr-45 mass turned out to be essential for modeling the astrophysical rp-process. In particular, we find that the formation of the predicted Ca-Sc cycle in X-ray bursts can be excluded.

Gamma rays with energies between 80 keV and 1500 keV produced by 133Ba and 152Eu standard sources are measured with the clover detector. Relative efficiencies and add-back factors are determined in both crystals and full clover modes. The add-back characteristics have been calculated using Monte-Carlo simulation code Geant4. The simulation and measurements agree very well.

The high-spin level structure of 186Au is re-investigated by means of in-beam γ-ray spectroscopy via the 172Yb(19F, 5nγ)186Au reaction. The oblate bands previously reported are revised and extended to higher-spin states. A new Iπ = (20+) excited state has been identified and assigned to the πh−111/2 ⊗ νi−213/2h−19/2 configuration. The total Routhian surface and cranked shell model calculations suggest that the πh−111/2 ⊗ νi−213/2h−19/2 band in 186Au has a non-axial deformation.

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 alpha's. 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.

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.

High-spin states in Tb-145 have been populated using the Sn-118 (S-32, 1p4n) reaction at beam energy of 165 MeV. The level scheme of Tb-145 has been established up to Ex approximate to 7.4 MeV. The level scheme shows characteristics of a spherical or slightly oblate nucleus. Based on the systematic trends of the level structure in the neighboring N = 80 isotones, the level structure in Tb-145 below 2 MeV excitation is well explained by coupling an h(11/2)valence proton to the even-even Gd-144 core. Above 2 MeV excitation, most of the yrast levels are interpreted with multi-quasi particle shell-model configurations.

High-spin states in182Au have been produced and studied via the152Sm(35Cl,5nγ)182Au reaction. The level scheme consisting of the πh 9/2⊗νi 13/2 and πi 13/2⊗νi 13/2 bands has been established for the first time. The low spin signature inversion in both bands has been found. The observed signature inversion phenomena can be interpreted qualitatively using the pairing and deformation self-consistent cranked Wood-Saxon calculations.

Excited states of125Sb have been studied using in-beam γ spectroscopy techniques via the124Sn(7Li, α2n) reaction at a beam energy of 32 MeV. A high-spin level scheme including 21 new γ-transitions and 14 new excited states have been established. Three isomers have been identified at 1970, 2110 and 2471 keV and the ranges of their half-lives have been estimated from the delayed coincidence data. The level structure of125Sb is discussed in terms of particle-core excitation coupling. With the help of empirical shell model calculations the three isomers are proposed to have three-quasiparticle πg7/2⊗v(h 11/2 s 1/2)5−, πg7/2⊗v(h 11/2 d 3/2)7− and πg7/2⊗v(h 11 2/2 )10 + configurations, respectively.

High-spin states in141Nd have been studied using in-beam γ-ray spectroscopic techniques via the130Te(16O, 5nγ)141Nd reaction. The level scheme of141Nd has been extended up to an excitation energy of 7614.5 keV including 12 new γ rays deexciting 15 new levels. According to particle-vibrator coupling and semi-empirical shell model calculations, the level structure of141Nd can be well interpreted by coupling an h11/2 neutron-hole to the respective excited states in142Nd core.

High-spin states in ${}^{180}\mathrm{Ir}$ have been investigated by means of in-beam $\ensuremath{\gamma}$-ray spectroscopy techniques with the ${}^{154}\mathrm{Sm}{(}^{31}\mathrm{P},5n\ensuremath{\gamma}{)}^{180}\mathrm{Ir}$ reaction. Excitation functions, $x\ensuremath{-}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}\ensuremath{-}t$ coincidences, DCO (directional correlation of $\ensuremath{\gamma}$ rays deexciting oriented states) ratios, and intraband $B(M1)/B(E2)$ ratios were measured. Five rotational bands have been identified and their configurations are proposed on the basis of $B(M1)/B(E2)$ ratios and by comparing the band properties with known bands in neighboring odd-mass and even-mass nuclei. The neutron $\mathrm{AB}$ crossing is observed at $\ensuremath{\Elzxh}{\ensuremath{\omega}}_{c}=0.26(1) \mathrm{MeV}$ for the $\ensuremath{\pi}{1/2}^{\ensuremath{-}}[541]\ensuremath{\bigotimes}\ensuremath{\nu}{1/2}^{\ensuremath{-}}[521]$ and $\ensuremath{\pi}{1/2}^{\ensuremath{-}}[541]\ensuremath{\bigotimes}\ensuremath{\nu}{5/2}^{\ensuremath{-}}[512]$ bands, respectively. Staggering of levels as a function of the number of neutron pairs is revealed in the $\ensuremath{\pi}{1/2}^{\ensuremath{-}}[541]\ensuremath{\bigotimes}\ensuremath{\nu}{1/2}^{\ensuremath{-}}[521]$ doubly decoupled bands of ${}^{178--186}\mathrm{Ir}.$ The gradual alignment gains at low rotational frequencies are observed in the two strongly coupled bands. Band crossings and alignments in ${}^{180}\mathrm{Ir}$ are discussed with reference to the total Routhian surface and cranked shell model calculations performed for the neighboring odd-mass nuclei.

Isochronous Mass Spectrometry (IMS) in heavy-ion storage rings is an excellent experimental method for precision mass measurements of exotic nuclei. In the IMS, the storage ring is tuned in a special isochronous ion-optical mode. Thus, the mass-over-charge ratios of the stored ions are directly reflected by their respective revolution times in first order. However, the inevitable momentum spread of secondary ions increases the peak widths in the measured spectra and consequently limits the achieved mass precision. In order to achieve a higher mass resolving power, the ring aperture was reduced to 60 mm by applying a mechanical slit system at the dispersive straight section. The momentum acceptance was reduced as well as better isochronous conditions were achieved. The results showed a significant improvement of the mass resolving power reaching $5.2 \times 10^{5}$, though at the cost of about 40\% ion loss., Comment: 6 pages, 6 figures, proceeding of EMIS2018

Isochronous mass spectrometry (IMS) of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei. In IMS experiments, masses are determined through precision measurements of the revolution times of the ions stored in the ring. However, the revolution times cannot be resolved for particles with nearly the same mass-to-charge (m/q) ratios. To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios, in our early work on particle identification, we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons. Here, the previous data analysis method is further improved by considering the signal amplitudes, detection efficiencies, and number of stored ions in the ring. A sensitive Z-dependent parameter is introduced in the data analysis, leading to a better resolution of $^{34}$Ar$^{18+}$ and $^{51}$Co$^{27+}$ with A/Z=17/9. The mean revolution times of $^{34}$Ar$^{18+}$ and $^{51}$Co$^{27+}$ are deduced, although their time difference is merely 1.8 ps. The uncorrected, overlapped peak of these ions has a full width at half maximum of 7.7 ps. The mass excess of $^{51}$Co was determined to be -27332(41) keV, which is in agreement with the previous value of -27342(48) keV., 8 pages, 6 figures