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.

High-spin states in Pt-190

The level structure of Pt-190 has been studied experimentally using the Yb-176 (O-18, 4n) reaction at beam energies of 88 and 95 MeV. gamma-gamma-t coincidence measurements were carried out. Based on the analysis of gamma-gamma coincidence relationships, the level scheme of Pt-190 is extended to high-spin states. A new structure built on the 3413.6 keV 14(+) state has been observed, and the vi(13/2)(-2) vh(9/2)(-1) vj (j = p(3/2) or f(5/2)) configuration is tentatively assigned to it.

Test experiments of gamma-ray linear polarization using a Clover detector

We have investigated the performance of a EXOGAM-Segmented-Clover with 16 segments as a Compton polarimeter to measure the linear polarization of gamma rays. The polarization sensitivity of the Clover detector has been measured at the energy of 1332keV through the coincidence measurements of cascade gamma-rays from Co-60. Experimental values were in good accord with our expectation.We have investigated the performance of a EXOGAM-Segmented-Clover with 16 segments as a Compton polarimeter to measure the linear polarization of gamma rays. The polarization sensitivity of the Clover detector has been measured at the energy of 1332keV through the coincidence measurements of cascade gamma-rays from Co-60. Experimental values were in good accord with our expectation.

Identification of a new band and its signature inversion in Re-174

High spin states in Re-174 are investigated via the Sm-152(Al-27, 5n gamma)Re-174 reaction and gamma-gamma coincidence relationships are analysed carefully. A new band is identified due to its spectroscopic connection with the known pi 1/2(-)[541] circle times nu 1/2(-)[521] band. This band is proposed to be the ground-state band built on the pi 1/2(-)[541] circle times nu 5/2(-)[512] configuration in view of the low-lying intrinsic states in the neighbouring odd-mass nuclei. It is of particular interesting that the new band exhibits a phenomenon of low-spin signature inversion, providing a new situation for theoretical investigations.

Low-spin signature inversion in the pi h(9/2)circle times nu i(13/2) oblate band

Excited states in Tl-188,Tl-190 have been studied experimentally by means of in-beam gamma spectroscopy techniques, and resulted in the identification of a strongly coupled band based on the pi h(9/2) circle times nu i(13/2) configuration with oblate deformation. The oblate band in doubly odd Tl nuclei shows low-spin signature inversion. It is the first experimental observation of low-spin signature inversion for a band associated with the oblate pi h(9/2) circle times nu i(13/2) configuration.

Double electron processes in collisions of partially stripped ions Cq+ (q=1-4) with helium

The multi-electron processes are investigated for 17.9-120keV/u C1+, 30-323 keV/u C2+, 120-438 keV/u C3+, 287-480keV/u C4+ incident on a helium target. The cross-section ratios of double electron (DE) process to the total of the single electron (SE) and the double electron process (i.e. SE+DE), the direct double electron (DDI) to the direct single ionization (DSI) as well as the contributions of DDI to DE and of TI to DE are measured using coincidence techniques. The energy and charge state dependences of the measured cross-section ratios are studied and discussed.

beta-delayed proton decays of Sm-133 and Yb-149

Sm-133 was produced via fusion evaporation in the reaction Ca-40+Ru-96. Its P-delayed proton decay was studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The possible spins and parities of 133Sm were extracted by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces of Sm-133 were calculated by using the Woods-Saxon Strutinsky method. Comparing the experimental and calculated results, the spins and parities Of Sm-133 were assigned to be 5/2(+) and 1/2(-), which is reconciled with our published simple (EC+beta(+)) decay scheme Of Sm-113 in 2001. In addition, our experimental data on the beta-delayed proton decay of Yb-149 reported in Eur. Phys. J., 2001, A12: 1-4 was also analyzed by using the same method. The spin and parity of Yb-149 was assigned to be 1/2-.

beta-delayed proton decays and spin assignments for Sm-133 and Yb-149

The proton-rich isotope Sm-133 was produced via the fusion evaporation reaction Ca-40 + Ru-96. Its beta-delayed proton decay was studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nucleus were determined. Comparing the observed beta-delayed proton branching ratios with statistical model calculations, the best agreement is found assuming that only one level with the spin of 3/2 in Sm-133 decays or two levels with the spins of 1/2 and 5/2 decay with similar half-lives. The configuration-constrained nuclear potential energy surfaces of Sm-133 were calculated using the Woods-Saxon-Strutinsky method, which suggests a 1/2-ground state and a 5/2(+) isomer with an excitation energy of 120 keV. Therefore, the simple(EC+beta(+)) decay scheme of Sm-133 in Eur. Phys. J.A 11,277(2001) has been revised. In addition, our previous experimental data on the beta-delayed proton decay of Yb-149 reported in Eur. Phys. J. A 12,1 ( 2 0 0 1) was also analyzed using the same method. The spin-parity of Yb-149 is suggested to be 1/2(-).

Candidate chiral doublet bands in the odd-odd nucleus Cs-126

The candidate chiral doublet bands recently observed in Cs-126 have been extended to higher spins, several new linking transitions between the two partner members of the chiral doublet bands are observed, and gamma-intensities related to the chiral doublet bands are presented by analyzing the gamma-gamma coincidence data collected earlier at the NORDBALL through the Cd-116(N-14, 4n)Cs-126 reaction at a beam energy of 65 MeV. The intraband B(M1)/B(E2) and interband B(M1)(in)/B(M1)(out) ratios and the energy staggering parameter, S(I), have been deduced for these doublet bands. The results are found to be consistent with the chiral interpretation for the two structures. Furthermore, the observation of chiral doublet bands in Cs-126 together with those in Cs-124, Cs-128, Cs-130, and Cs-132 also indicates that the chiral conditions do not change rapidly with decreasing neutron number in these odd-odd Cesium isotopes.

beta-delayed proton decays of Tb-140 and Dy-140 as well as the spin and parity of Dy-143

Tb-140 and Dy-141 were produced via fusion evaporation in the reaction Ca-40+Cd-106. Their beta-delayed proton decays were studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of Tb-140 and Dy-141 were extracted as 7(+/-) and 9/2(+/-), respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of Tb-140 and Dy-147 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 was also calculated by using the same method. From the NPES a 1/2(+) ground state and a 11/2(-) isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of Dy-143 reported in Eur. Phys. J., 2003, A16: 347-351.

beta-delayed proton decays and spin assignments for Tb-140, Dy-141 and Dy-143

The proton-rich isotopes Tb-140 and Dy-141 were produced via the fusion evaporation reaction Ca-40+ Cd-106. Their beta-delayed proton decays were studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nuclei were determined. Comparing the experimental data with statistical model calculations, the ground-state spins of Tb-140 and Dy-141 were found to be consistent with 7 and 9/2, respectively. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated using the Woods-Saxon-Strutinsky method, which suggest the ground-state spins and parities of Tb-140 and Dy-141 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 were calculated, which predict a 1/2(+) ground state and a 11/2(-) isomer with excitation energy of 198 keV. These findings are consistent with our previous experimental data on Dy-143 reported in Eur. Phys. J. A 16, 347 (2003).

Systematic study of properties of Hs nuclei

The ground-state properties of Hs nuclei are studied in the framework of the relativistic meanfield theory. We find that the more relatively stable isotopes are located on the proton abundant side of the isotopic chain. The last stable nucleus near the proton drip line is probably the (255)Hs nucleus. The alpha-decay half-lives of Hs nuclei are predicted, and together with the evaluation of the spontaneous-fission half-lives it is shown that the nuclei, which are possibly stable against spontaneous fission are (263-274)Hs. This is in coincidence with the larger binding energies per nucleon. If (271-274)Hs can be synthesized and identified, only those nuclei from the upper Z = 118 isotopic chain, which are lighter than the nucleus (294)118, and those nuclei in the corresponding alpha-decay chain lead to Hs nuclei. The most stable unknown Hs nucleus is (268)Hs. The density-dependent delta interaction pairing is used to improve the BCS pairing correction, which results in more reasonable single-particle energy level distributions and nucleon occupation probabilities. It is shown that the properties of nuclei in the superheavy region can be described with this interaction.

Experimental study of the beta-delayed proton decays of Er-145,Er-147

The beta-delayed proton decays of Er-145,Er-147 have been studied experimentally using the Ni-58 + Mo-92 reaction at beam energy of 383 MeV. On the basis of a He-jet apparatus coupled with a tape transport system, the beta-delayed proton radioactivities both from the nu s(1/2) ground state and the nu h(11/2) isomer in Er-145,Er-147 were observed by proton-gamma coincidence measurements. By analyzing the time distributions of the 4(+) -> 2(gamma)(+) transitions in the granddaughter nuclei Dy-144,Dy-146, the half-lives of 1.0 +/- 0.3 s and 1.6 +/- 0.2 s have been deduced for the nu h(11/2) isomers in Er-145,Er-147, respectively.

Measurement of the inelastic branch of the stellar O-14(alpha,p)F-17 reaction occurring in the explosive burning in Novae and X-ray busters

The inelastic component of the key astrophysical resonance (1(-), E-x=6.15 MeV) in the O-14(alpha,p)F-17 reaction has been studied by using the resonant scattering of F-17+p. The experiment was done at REX-ISOLDE CERN with the Miniball setup. The thick target method in inverse kinematics was utilized in the present experiment where a 44.2 MeV F-17 beam bombarded a similar to 40 mu m thick (CH2)(n) target. The inelastic scattering protons in coincidence with the de-excited 495 keV gamma rays have been clearly seen and they are from the inelastic branch to the first excited state in F-17 following decay of the 1(-) resonance in Ne-18. Some preliminary results are reported.

Properties of the beta-delayed proton decay of Ho-146

The proton-rich isotope Ho-148 was produced via the fusion-evaporation reaction Mo-92 (Ni-58, 3p1n). The beta-delayed proton decay of Ho-146 was studied by proton-gamma coincidence measurements using a He-jet tape transport system. The gamma-transitions in Tb-145 following the proton emissions were observed, and the beta-delayed proton branching ratios to the final states in the grand-daughter nucleus Tb-145 were determined. According to the relative branching ratios, the ground-state spin of Ho-146 has been proposed and the possible configuration discussed.