Based on the Q(p/alpha) values deduced from the linear extrapolations along isotopic chains and on the universal decay law, the proton- and alpha-decay partial half-lives are calculated for odd-Z, even-N neutron-deficient Bi-Pa isotopes. Eight proton-emission states in five new isotopes are suggested, including the 1/2(+) and 9/2(-) states in Bi-183, the 1/2(+) and 7/2(+) states in 187,189At, the 1/2(+) state in Fr-193, and the 9/2(-) state in Ac-199. The calculated half-lives for the 1/2(+) states in Bi-183 and At-187 are around 100 ns, too short to be studied using the recoil separator setups, which strongly encourages the development of new experimental techniques and devices to search for new submicrosecond proton-emitting nuclei.

The near-symmetric complete fusion reaction 78Kr + 107Ag -> 185Bi & lowast; was studied at the gas-filled recoil separator SHANS with an attempt to synthesize the extremely neutron-deficient proton-unbound 182,183Bi isotopes. No decay events which could be attributed to them were observed. The two- and three-particle evaporation residues 180,179Hg (alpha p, alpha pn) and 183,182Pb (pn, p2n) were identified. Their production cross sections have been measured at two bombarding energies. Based on the yields of 182,183Pb in the present work and the systematics of the ratios between the cross sections of p(x-1)n and xn evaporation channels for the most neutron-deficient odd-Z nuclei above lead, the upper limits for the half-lives of 182,183Bi were estimated to be less than 0.3 mu s.

High-spin states of 67Ga have been studied via the 58Ni(12C, 3p) 67Ga fusion-evaporation reaction at a beam energy of 50.4 MeV. Three negative-parity bands and three positive-parity bands in 67Ga are established. The observation of one new E3 transition linking the positive-parity pi 1g9/2 band and negative-parity pi 2p3/2 band provides evidence of octupole correlations in 67Ga. The characteristics of octupole correlations in the 67Ga are discussed in terms of the reflection-asymmetric triaxial particle rotor model and microscopic relativistic mean field + Bardeen-Cooper-Schrieffer model.

The prompt and delayed γ -ray spectra of 187Tl was studied via the 142Nd(50Cr, 3p2n)187Tl fusion-evaporation reaction at a beam energy of 255 MeV. An enhanced level scheme of 187Tl was established. The collective bands with one-quasiparticle configurations from the 2f_7/2 , 1h_9/2 , 1h_11/2 and 1i_13/2 orbitals and high-lying structures with possible three-quasiparticle configurations are investigated in terms of the tilted axis cranking covariant density functional theory. At low excitation energy, the rotational bands with one-quasiparticle configurations reflect coexistence of three shapes: prolate, triaxial, and oblate. The possible shapes of two microsecond isomers at high excitation energy are proposed.

The & alpha; decay of 222U was reinvestigated using a general least-square superpulse fitting algorithm dedicated to resolving pileup signals in the decay of very short-lived nuclei. The & alpha;-particle energy of 222U was revised to be 9246(8) keV, and the precision was improved significantly compared with previous result. Using the present & alpha; energy, the anomaly in the systematics of the & alpha;-decay reduced width 82 observed at 222U in the NpNn scheme is solved, all the 82 values converge into a smooth and narrow band with NpNn up to & AP;90 in the northeast of 208Pb.

The alpha decay of the neutron-deficient 190At isotope was observed following the 103Rh(90Zr, 3n) 190At reaction at Argonne National Laboratory. The reaction products were separated from the beam using the Argonne Gas-Filled Analyzer and implanted into a double-sided Si strip detector. The spatial and temporal correlations between implanted nuclei and subsequent alpha decays towards the known daughter isotope 186Bi were used to identify and characterize 190At nuclei. Two possible decay scenarios are proposed for the 190At -> 186Bi decay.

The isomer depletion of ^{93m}Mo was recently reported [Chiara et al., Nature (London) 554, 216 (2018)NATUAS0028-083610.1038/nature25483] as the first direct observation of nuclear excitation by electron capture (NEEC). However, the measured excitation probability of 1.0(3)% is far beyond the theoretical expectation. In order to understand the inconsistency between theory and experiment, we produce the ^{93m}Mo nuclei using the ^{12}C(^{86}Kr,5n) reaction at a beam energy of 559 MeV and transport the reaction residues to a detection station far away from the target area employing a secondary beam line. The isomer depletion is expected to occur during the slowdown process of the ions in the stopping material. In such a low γ-ray background environment, the signature of isomer depletion is not observed, and an upper limit of 2×10^{-5} is estimated for the excitation probability. This is consistent with the theoretical expectation. Our findings shed doubt on the previously reported NEEC phenomenon and highlight the necessity and feasibility of further experimental investigations for reexamining the isomer depletion under low γ-ray background.

Prompt and delayed γ-ray spectroscopy of the neutron-deficient, semi-magic isotope 187Pb has been performed using the recoil-decay and isomer-decay tagging techniques at the Argonne Gas-Filled Analyzer. A new 5.15(15)-μs isomeric state at only 308 keV above the spherical 3/2− ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2−[514] Nilsson state in the isotone 185Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in 187Pb is proposed to originate from the same configuration. The retarded character of the 308-keV (7/2−)→3/2gs− transition with a deduced B(E2)=5.6(2)×10−4 W.u. can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The excitation energy of the isomer is surprisingly low, being roughly half of the excitation energies of the known 0+ intruder bandheads in the neighboring 186,188Pb isotopes. The combined results of the present work and the previous α-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of 187Pb, which is well reproduced by the potential-energy surface calculations.

The neutron-deficient Bi-188 and Po-188 isotopes have been studied by gamma-ray spectroscopy using the recoil-decay tagging technique with the Argonne Gas-Filled Analyzer. A new 0.25(5)-mu s isomeric state and a prompt cascade formed by 319-, 366-, and 462-keV gamma rays have been established on top of the (10-) alpha-decaying isomer in Bi-188. The first excited (2+) state in Po-188 was identified, its excitation energy of 242(2) keV continues the nearly constant trend for the first 2+ states in 190,192,194Po. The state is most likely a member of a prolate rotational band built on the ground state, albeit mixing with other coexisting configurations cannot be excluded. The new results obtained in the present work provide new information to shape coexistence in bismuth and polonium isotopes near the neutron midshell at N = 104. In this mass region, a reduction in the prompt gamma-ray yield obtained with recoil decay tagging was observed for a few nuclides, and the possible reasons are presented.

The low-lying states of Eu-146 populated in the decay of the 9(+) isomer were studied. The gamma-ray intensities were reanalyzed employing germanium detectors, and the lifetimes of the 6(1)(-) and 6(2)(-) states were measured using the mirror symmetric centroid difference (MSCD) method with fast-timing LaBr3(Ce) scintillator detectors. The B(M1) values of the 6(1)(-) -> 5(1)(-) and 6(2)(-) -> 5(1)(-) transitions were deduced, and all observed states were interpreted as members of the pi d(5/2)(-1)nu f(7/2) and pi g(7/2)(-1)nu f(7/2) multiplets. In particular, the 5(1)(-) level is shown to be dominated by the pi d(5/2)(-1)nu f(7/2) configuration, solving the discrepancy in its configuration assignment proposed in previous works. These experimental results were compared with the shell model calculations using several different effective interactions. The systematics of low-lying structure in the N = 83 isotones Pr-142, Pm-144, and Eu-146 was established.

The decay of the 13/2+ isomeric state in 183Hg was observed for the first time following the α decay of the 13/2+ isomer in 187Pb produced in the 142Nd(50Cr, 2p3n) reaction. Using α−γ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) μs. This isomer is proposed to deexcite by an unobserved low-energy M2 transition to the known 9/2− member of a strongly prolate-deformed 7/2−[514] band, followed by a 105-keV M1 transition to the bandhead. A lower limit of B(M2) ≥ 0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2+ isomer in 181Hg, suggesting both are cases of shape isomers. The B(M2) systematics of neutron transitions across the nuclear chart is discussed.

Fine structure in the α decay of 223U was observed in the fusion-evaporation reaction 187Re(40Ar, p3n) by using fast digital pulse processing technique. Two α-decay branches of 223U feeding the ground state and 244 keV excited state of 219Th were identified by establishing the decay chain 223U →α1 219Th →α2 215Ra →α3 211Rn. The α-particle energy for the ground-state to ground-state transition of 223U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62−10+14 μs. Evolution of nuclear structure for N = 131 even-Z isotones from Po to U was discussed in the frameworks of nuclear mass and reduced α-decay width, a weakening octupole deformation in the ground state of 223U relative to its lighter isotones 219Ra and 221Th was suggested.

Short-lived \(\alpha \) emitters with N = 128–131 and Z = 91–93 were studied in the fusion reaction ^40Ar + ^187Re using the digital pulse processing technique at the gas-filled recoil separator Spectrometer for Heavy Atom and Nuclear Structure (SHANS). Two new isotopes ^223,224Np were identified and the decay of 220 Pa was re-investigated through temporal and spatial correlations. The pileup signals were resolved by using the digital pulse processing technique. An \(\alpha \) decay with half-life of \(T_{1/2} = 2.15(_{52}^{100})\) μs and energy of \(E_{\alpha } = 9477(44)\) keV was attributed to ^223Np. Two \(\alpha \)-decay branches with half-life of \(T_{1/2} = 38(_{11}^{26})\) μs, \(\alpha \) energies of 9137(21) and 8868(60) keV were assigned to ^224Np, decaying to two excited states in ^220Pa. The results of ^223Np disprove the existence of a Z = 92 subshell closure.

With the charged-particle decay spectroscopy extended to the proton drip-line region, half-lives of nuclei of interest decrease rapidly. Consequently, severe signal piling-up resulting from the implanted ions and their successive decays in position sensitive detectors become more and more common. To extract the spectroscopic information from the pile-up pulses with good accuracy, a digital pulse analysis algorithm is presented in this paper and validated with the alpha decay of Th-219 and the internal conversion electron decays of Ra-210,Ra-211 isomers, all of which have similar to mu s half-lives. The results show that with proper baseline correction, standard pulse construction and plateau-region fitting etc., the spectroscopic information of overlapping signals with time separation down to 80 ns and amplitude of individual pile-up pulse down to 70 keV, can be readily extracted.

Fine structure in the α decay of U was observed in the fusion-evaporation reaction Re(Ar, p3n) by using fast digital pulse processing technique. Two α-decay branches of U feeding the ground state and 244 keV excited state of Th were identified by establishing the decay chain U α1 −→ Th α2 −→ Ra α3 −→ Rn. The α-particle energy for the ground-state to ground-state transition of U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 56 −8 μs. Evolution of nuclear structure for N = 131 even-Z isotones from Po to U was discussed in the frameworks of nuclear mass and reduced α-decay width, a weakening octupole deformation in the ground state of U relative to its lighter isotones Ra and Th was suggested.

Fine structure in the $alpha$ decay of $^{223}$U was observed in the fusion-evaporation reaction $^{187}$Re($^{40}$Ar, p3n) by using fast digital pulse processing technique. Three $alpha$-decay branches of $^{223}$U were identified by establishing the decay chain $^{223}$U $xrightarrow{alpha_{1}}$ $^{219}$Th $xrightarrow{alpha_{2}}$ $^{215}$Ra $xrightarrow{alpha_{3}}$ $^{211}$Rn. The $alpha$-particle energy for the ground-state to ground-state transition of $^{223}$U was determined to be 8993(17) keV, 213 keV higher than the previous value. Quadrupole-octupole deformation in the ground states of $^{223}$U and its lighter isotones $^{219}$Ra and $^{221}$Th was suggested by comparison of the experimental and calculated masses. Properties of $alpha$ decays ($alpha$-particle energies, branching ratios and hindrance factors) of $^{223}$U, feeding several low-lying levels of daughter nucleus $^{219}$Th, were compared with those of its lighter $N$ = 131 isotones $^{219}$Ra and $^{221}$Th. Evolution of nuclear structure for $N$ = 129 and 131 even-$Z$ isotones from Po to U was discussed in the framework of reduced $alpha$-decay width.

Excited states in 63,65,67Mn were studied via in-beam γ-ray spectroscopy following knockout reactions from 68Fe. Similar level schemes, consisting of the 11/2−, 9/2−, 7/2− and 5/2g.s.− level sequence, connected by I→I−1 transitions, were established, the first time for 65,67Mn. Their level structures show features consistent with strongly-coupled rotational bands with K=5/2. State-of-the-art shell-model calculations with the modified LNPS effective interaction reproduce the observed levels remarkably well and suggest the dominance of 4-particle-4-hole neutron configurations for all the states. The data on the low-lying excited states of odd-mass 53−67Mn provide a textbook example of nuclear structure evolution from weak coupling through decoupling to strong coupling along a single isotopic chain on the n-rich side of the β stability line. These results help to deepen our understanding of the N=40 “island of inversion”.

The new isotope Np-224 was produced in the fusion-evaporation reaction of Ar-40 + Re-187 and identified through the evaporation residue (ER)-alpha-decay correlation measurements using the digital pulse processing technique. Two alpha-decay branches with a energies of 9137(20) and 8868(62) keV were assigned to Np-224, decaying to two excited states in Pa-220. The half-life of Np-224 was deduced to be 38(-11)(+26) mu s.

X.Y. Liu a,b, Z. Liu a,∗, B. Ding a,∗, P. Doornenbal c, A. Obertelli c,d,e, S.M. Lenzi f, P.M. Walker g, L.X. Chung h, B.D. Linh h, G. Authelet d, H. Baba c, D. Calvet d, F. Château d, A. Corsi d, A. Delbart d, J.-M. Gheller d, A. Gillibert d, T. Isobe c, V. Lapoux d, M. Matsushita i, S. Momiyama c,j, T. Motobayashi c, M. Niikura j, F. Nowacki k, H. Otsu c, C. Péron d, A. Peyaud d, E.C. Pollacco d, J.-Y. Roussé d, H. Sakurai c,j, M. Sasano c, Y. Shiga c,l, S. Takeuchi c, R. Taniuchi c,j, T. Uesaka c, H. Wang c, K. Yoneda c, Y.H. Lam a, T.H. Huang a, M.D. Sun a,b, W.Q. Zhang a,b, H.Y. Lu a,b, D.S. Hou a,b, F. Browne m, Zs. Dombradi n, S. Franchoo o, F. Giacoppo p, A. Gottardo o, K. Hadynska-Klek p, Z. Korkulu n, S. Koyama c,j, Y. Kubota c,i, J. Lee q, M. Lettmann e, R. Lozeva k,r, K. Matsui c,j, T. Miyazaki c,j, S. Nishimura c, C. Louchart e, L. Olivier o, S. Ota i, Z. Patel g, E. Sahin p, C. Santamaria d,c, C. Shand g, P.-A. Söderström c, G.L. Stefan o, D. Steppenbeck i, T. Sumikama s, D. Suzuki o, Zs. Vajta n, V. Werner e, J. Wu c,t, Z. Xu q, X.H. Zhou a, Y.H. Zhang a, H.S. Xu a, F.S. Zhang u,v