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The heaviest N = 127 even-odd isotone 219U was produced in a fusion evaporation reaction employing 40Ar ions bombarding 183W target. Fusion evaporation residues were separated in flight by the gas-filled recoil separator Spectrometer for Heavy Atoms and Nuclear Structure and subsequently identified using a recoil-α correlation method. The α-decay properties of 219U were measured with improved precision, and two new α-decay lines were observed and assigned as the decays from the ground state of 219U to the (5/2-) and (3/2-) states of 215Th, respectively. The systematics for the α decay of the N = 127 even-odd isotones as well as the low-lying nuclear structure of their N = 125 daughter nuclei are discussed. [ABSTRACT FROM AUTHOR]

The new neutron-deficient isotope 205Ac was synthesized in the complete-fusion reaction 169Tm(40Ca, 4n)205Ac. The evaporation residues were separated in-flight by the gas-filled recoil separator SHANS in Lanzhou and subsequently identified by the α-α position and time correlation method. The α-decay energy and half-life of 205Ac were determined to be 7.935(30) MeV and 20+97-9 ms, respectively. Previously reported decay properties of the ground state in 206Ac were confirmed. [ABSTRACT FROM AUTHOR]

The new neutron-deficient isotope 216U was produced in the complete-fusion reaction 180W(40Ar,4n)2l6U. The evaporation residues were separated from the primary beam in flight by the gas-filled recoil separator Spectrometer tor Heavy Atoms and Nuclear Structure. The activities have been identified by the α-α position and time correlation measurements. Two cc-decaying states with Ea = 8384(30) keV, Tl/2 = 4.72+4.72-1.57 ms for the ground state and E&3945; = 10582(30) keV, T1/2 = 0.741.34-0.29 ms for an isomeric state were identified in 216U. [ABSTRACT FROM AUTHOR]

A new, very short-lived neutron-deficient isotope 222Np was produced in the complete-fusion reaction 187Re (40Ar, 5n) 222Np, and observed at the gas-filled recoil separator SHANS. The new isotope 222Np was identified by employing a recoil- α correlation measurement, and six α -decay chains were established for it. The decay properties of 222Np with E α = 10 016 (33) keV and T1/2 = 38 0 + 260 - 110 ns were determined experimentally. The α -decay systematics of Np isotopes is improved by adding the new data for 222 Np, which validates the N = 126 shell effect in Np isotopes. The evolution of the N = 126 shell closure is discussed in the neutron-deficient nuclei up to Np within the framework of α -decay reduced width. [ABSTRACT FROM AUTHOR]

A new short-lived neutron-deficient isotope 220Np was synthesized in the fusion-evaporation reaction 185Re(40Ar,5n)220Np at the gas-filled recoil separator SHANS. Based on the measurement of the correlated α-decay chains, the decay properties of 220Np with Eα=10040(18) keV and T1/2=25+14-7 μs were determined, which are in good agreement with theoretical predictions. From the new experimental results coupled with the recently reported α-decay data of 219,223Np, the α-decay systematics for Np isotopes around N=126 was established, which allows us for the first time to test the robustness of the N=126 shell closure in Z=93 Np isotopes. The results also indicate that, in the region of nuclei with Z≥83, the proton drip line has been reached for all odd-Z isotopes up to Np. [ABSTRACT FROM AUTHOR]

Using the fusion-evaporation reaction ^{106}Cd(^{58}Ni,4n)^{160}Os and the gas-filled recoil separator SHANS, two new isotopes _{76}^{160}Os and _{74}^{156}W have been identified. The α decay of ^{160}Os, measured with an α-particle energy of 7080(26) keV and a half-life of 201_{-37}^{+58}  μs, is assigned to originate from the ground state. The daughter nucleus ^{156}W is a β^{+} emitter with a half-life of 291_{-61}^{+86}  ms. The newly measured α-decay data allow us to derive α-decay reduced widths (δ^{2}) for the N=84 isotones up to osmium (Z=76), which are found to decrease with increasing atomic number above Z=68. The reduction of δ^{2} is interpreted as evidence for the strengthening of the N=82 shell closure toward the proton drip line, supported by the increase of the neutron-shell gaps predicted in theoretical models.

A new α-emitting isotope ^{214}U, produced by the fusion-evaporation reaction ^{182}W(^{36}Ar,4n)^{214}U, was identified by employing the gas-filled recoil separator SHANS and the recoil-α correlation technique. More precise α-decay properties of even-even nuclei ^{216,218}U were also measured in the reactions of ^{40}Ar, ^{40}Ca beams with ^{180,182,184}W targets. By combining the experimental data, improved α-decay reduced widths δ^{2} for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N=126 are deduced. Their systematic trends are discussed in terms of the N&#95;{p}N&#95;{n} scheme in order to study the influence of proton-neutron interaction on α decay in this region of nuclei. It is strikingly found that the reduced widths of ^{214,216}U are significantly enhanced by a factor of two as compared with the N&#95;{p}N&#95;{n} systematics for the 84≤Z≤90 and N<126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the π1f&#95;{7/2} and ν1f&#95;{5/2} spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

A new, very short-lived neutron-deficient isotope ^{222}Np was produced in the complete-fusion reaction ^{187}Re(^{40}Ar,5n)^{222}Np, and observed at the gas-filled recoil separator SHANS. The new isotope ^{222}Np was identified by employing a recoil-α correlation measurement, and six α-decay chains were established for it. The decay properties of ^{222}Np with E&#95;{α}=10016(33)  keV and T&#95;{1/2}=380&#95;{-110}^{+260}  ns were determined experimentally. The α-decay systematics of Np isotopes is improved by adding the new data for ^{222}Np, which validates the N=126 shell effect in Np isotopes. The evolution of the N=126 shell closure is discussed in the neutron-deficient nuclei up to Np within the framework of α-decay reduced width.