Showing papers by "R. Wadsworth published in 1994"
TL;DR: States in the neutron-deficient 110,112Te isotopes have been populated following 58Ni+58,60Ni reactions, and a long regular cascade of transitions, indicating collective behavior, was found in 112Te extending to high spin.
Abstract: States in the neutron-deficient $^{110,112}\mathrm{Te}$ isotopes have been populated following $^{58}\mathrm{Ni}$${+}^{58,60}$Ni reactions. Gamma-ray coincidence data were acquired with the Eurogam spectrometer in conjunction with the Daresbury recoil separator and with the Chalk River 8\ensuremath{\pi} spectrometer. Although the low lying yrast states are not collective in these nuclei, a long regular cascade of transitions, indicating collective behavior, was found in $^{112}\mathrm{Te}$ extending to high spin. This structure is interpreted in terms of a deformed 4-particle 2-hole ${0}_{2}^{+}$ state coupled to rotationally aligned quasiparticles, and represents the first example of a rotational ``intruder'' band in the tellurium isotopes.
32 citations
TL;DR: Three rotational bands have been discovered in the nucleus [sup 109]Sb that extend in angular momentum to [congruent]81/2[h bar], the highest frequency so far observed in a heavy nucleus.
Abstract: Three rotational bands have been discovered in the nucleus $^{109}\mathrm{Sb}$ that extend in angular momentum to \ensuremath{\simeq}81/2\ensuremath{\Elzxh}. The rotational frequency at the highest spins reaches \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\simeq}1.4 MeV, the highest frequency so far observed in a heavy nucleus. With increasing frequency the collective moments of inertia of all three bands smoothly diminish to unexpectedly low values, ${\mathit{scrJ}}^{(2)}$\ensuremath{\sim}13${\mathrm{\ensuremath{\Elzxh}}}^{2}$ ${\mathrm{MeV}}^{\mathrm{\ensuremath{-}}1}$, approximately one-third the rigid-body value, and, contrary to expectations, the moments of inertia become nearly equal to one another and to those of rotational bands in the core nucleus $^{108}\mathrm{Sn}$.
31 citations
TL;DR: Two weakly populated rotational bands have been established in [sup 106]Sn from the [sup 54]Fe ([sup 58]Ni,[alpha]2[ital p]) reaction at 243 MeV, consistent with cranked Nilsson model calculations.
Abstract: Two weakly populated rotational bands have been established in [sup 106]Sn from the [sup 54]Fe ([sup 58]Ni,[alpha]2[ital p]) reaction at 243 MeV. One of the bands shows evidence of termination. The result is consistent with cranked Nilsson model calculations, which predict band terminations with a smooth and gradual shape change from a prolate collective to an oblate noncollective structure.
30 citations
TL;DR: The complete spectrum of γ rays following the decay of superdeformed (SD) states in 192 Hg has been extracted and reveals the decay mechanism and defines the excitation energies of the SD band.
Abstract: The complete spectrum of [gamma] rays following the decay of superdeformed (SD) states in [sup 192]Hg has been extracted. The spectrum, which comprises a quasicontinuous component and sharp lines, reveals the decay mechanism and defines the excitation energies of the SD band. The decay of SD states results from the coupling between a cold, ordered SD system with a hot, chaotic one with normal deformation.
30 citations
20 citations
TL;DR: In this article, three decoupled (ensuremath{\Delta}I=2) bands extending to over 1 MeV in rotational frequency have been observed, and the moments of inertia for these three bands are seen to decrease steadily to unexpectedly low values; this is interpreted as evidence for a novel form of band termination.
Abstract: Rotational states have been identified in $_{51}^{111}\mathrm{Sb}$ for the first time. Three decoupled (\ensuremath{\Delta}I=2) bands extending to over 1 MeV in rotational frequency have been observed. At the highest frequencies, the ${\mathit{scrJ}}^{(2)}$ moments of inertia for these three bands are seen to decrease steadily to unexpectedly low values; this is interpreted as evidence for a novel form of band termination. One of these bands is interpreted as being based on the \ensuremath{\pi}${\mathit{h}}_{11/2}$ orbital coupled to a deformed [(\ensuremath{\pi}${\mathit{g}}_{9/2}$${)}^{\mathrm{\ensuremath{-}}2}$\ensuremath{\bigotimes}(\ensuremath{\pi}${\mathit{g}}_{7/2}$)${]}_{0+}$ state of the $_{50}^{110}\mathrm{Sn}$ core. The interaction strength for the alignment of a pair of ${\mathit{h}}_{11/2}$ neutrons has been extracted and compared with calculations. Two possible quasiparticle configurations are discussed for the other decoupled bands. Two strongly coupled (\ensuremath{\Delta}I=1) bands have been identified and both shown to involve the [(\ensuremath{\pi}${\mathit{g}}_{9/2}$${)}^{\mathrm{\ensuremath{-}}1}$\ensuremath{\bigotimes}(\ensuremath{\pi}${\mathit{g}}_{7/2}$${)}^{2}$] configuration. A large number of spherical states have also been observed, which can be explained on the basis of valence protons coupled to spherical states in the $^{110}\mathrm{Sn}$ core.
20 citations
TL;DR: Using all the available data on lifetimes and branching ratios, and assuming pure magnetic dipole transitions, transition probabilities are deduced and results are consistent with weakly oblate collective structures involving high-[ital K] proton configurations coupled to rotationally aligned neutrons.
Abstract: Lifetimes of states in four of the oblate dipole bands in $^{197,198}\mathrm{Pb}$ have been measured with the recoil distance technique. Using all the available data on lifetimes and branching ratios, and assuming pure magnetic dipole transitions, we deduce transition probabilities. The results are consistent with weakly oblate collective structures involving high-K proton configurations coupled to rotationally aligned neutrons. Comparsions are made to the theoretical estimates of the D\"onau and Frauendorf semi-classical model and the tilted axis cranking (TAC) model.
16 citations
TL;DR: In this article, two new structures, made of competing ΔI=1 and ΔI = 2 transitions have been observed and their connexions with the low-lying levels established.
Abstract: The192Hg nucleus was populated in the160Gd(36S, 4n) reaction at a beam energy of E=159 MeV. Emittedγ-rays were detected with the EUROGAM array comprising 43 Compton-suppressed large volume Ge detectors. The level scheme of192Hg has been extended up to an excitation energy of E=10.4 MeV and spin I=34 ħ. Two new structures, made of competing ΔI=1 and ΔI=2 transitions have been observed and their connexions with the low-lying levels established. Their lowest levels are located at 6.304 MeV and 6.879 MeV excitation energy. The experimental results are compared with mean-field HF+BCS calculations. It is proposed that the new structures originate from deformation-aligned quasi-proton excitations π(i13/2 * h9/2)K=11 andπ (h9/2)
K=8
2
, coupled to rotation-aligned quasi-neutron ν(i13/2)n and quasi-proton π(h11/2)2 excitations.
15 citations
TL;DR: In this paper, the lifetime of the superdeformed band in 192Hg was measured using the Doppler-shift attenuation and the recoil distance methods for the high-spin and low-spin regions, respectively.
15 citations
TL;DR: Analysis of the data has revealed the presence of two new weakly populated decoupled bands in $^{134}\mathrm{Pr}$, one of these bands has been linked into the normal-deformed states and is thought to be built on a \ensuremath{\pi}(${\mathit{h}}_{11/2}$${)}^{2}$\ensure math{\bigotimes}\ensureMath{
u}$ (${\ mathit{f
Abstract: The nuclei $^{132,134}\mathrm{Pr}$ have been investigated using the $^{100}\mathrm{Mo}$${(}^{37}$Cl,xn) reactions at a beam energy of 155 MeV. Gamma rays were detected with the Eurogam array. Analysis of the data has revealed the presence of two new weakly populated decoupled bands in $^{134}\mathrm{Pr}$. One of these bands has been linked into the normal-deformed states and is thought to be built on a \ensuremath{\pi}(${\mathit{h}}_{11/2}$${)}^{2}$\ensuremath{\bigotimes}\ensuremath{
u}(${\mathit{f}}_{7/2}$,${\mathit{h}}_{9/2}$) configuration. The second band has been interpreted as being based on a \ensuremath{\pi}(${\mathit{h}}_{11/2}$${)}^{3}$\ensuremath{\bigotimes}\ensuremath{
u}${\mathit{i}}_{13/2}$ intruder configuration within the second ${\mathrm{\ensuremath{\beta}}}_{2}$\ensuremath{\simeq}0.3 prolate minimum. The known decoupled band in $^{132}\mathrm{Pr}$ (5n reaction channel) and the highly deformed band in $^{130}\mathrm{La}$ A(\ensuremath{\alpha}3n) have also been extended. The structure of all of these bands is discussed together with similar bands in nieghboring odd-odd nuclei.
12 citations
TL;DR: In this article, a comprehensive level scheme related to these structures has been built and first members of rotational bands built on K=8 and K=11 two-proton oblate states have been identified.
Abstract: Two regular dipole gamma -ray cascades have been observed in 194Pb. A comprehensive level scheme related to these structures has been built and first members of rotational bands built on K=8 and K=11 two-proton oblate states have been identified. From the excitation energies, spin values, behaviours of the moments of inertia and alignments, and from the comparison with the isotone 192Hg, multiparticle configurations can be attributed to three high-spin structures of 194Pb built respectively on the 4966 keV, 4334 keV and 6198 keV levels: ( pi 9/2(505) pi 13/2(606))(vi13/2)2, ( pi 9/2(505) pi 13/2(606))(vf5/2vi13/2), ( pi 9/2(505) pi 13/2(606)) (vf5/2(vi13/2)3). Within this interpretation, the regular dipole bands correspond to the presence of two or three i13/2 decoupled neutrons.
TL;DR: In this paper, a new superdeformed band is reported in 193Hg which has properties consistent with it being based on the unfavoured N = 7 (π, α) = (−, + 12) intruder orbital.
TL;DR: The level scheme of 138Sm has been extended up to Ipi =(32+) using gamma-ray coincidence data collected with the Eurogam array as discussed by the authors, where a strongly coupled band was also established and interpreted as a collectively rotating oblate structure.
Abstract: The level scheme of 138Sm has been extended up to Ipi =(32+) using gamma -ray coincidence data collected with the Eurogam array. The 106Cd(35Cl,3p)138Sm fusion-evaporation reaction was used at a bombarding energy of 150 MeV. Several new bands have been observed and the known bands extended to higher spin. Band crossings and shape coexistence are discussed with the aid of Woods-Saxon cranking calculations (CMS and TRS). Evidence is presented for a neutron (i132/)2 pair alignment which is predicted to drive the nucleus to a prolate shape with enhanced quadrupole deformation beta 2=0.32. A strongly coupled band was also established and is interpreted as a collectively rotating oblate structure.
TL;DR: In this paper, internal conversion coefficients have been determined from online measurement of electron and y-ray emission related to the dipole transitions in the so-called oblate collective bands in199Pb.
Abstract: Internal conversion coefficients have been determined from online measurement of electron- and y- ray emission related to the dipole transitions in the so-called oblate collective bands in199Pb.The results strongly support the M1 (or M1+E2) character of these transitions.
TL;DR: In this paper, the authors obtained new results on the192Hg superdeformed band with EuroOGAM with the 160Gd(36S,4n) reaction at 159 MeV, which is in better agreement with the Hartree-Fock-Bogoliubov calculations.
Abstract: New results on the192Hg superdeformed band have been obtained with EUROGAM. The experiment has been performed with the160Gd(36S,4n) reaction at 159 MeV. Above 800 keV the γ-ray energies differ from the previously published ones. Thus the rise of the dynamical moment of inertia\(\mathfrak{F}^{(2)} \) above ħω=0.4 MeV is no longer observed. This is in better agreement with recent cranked Hartree-Fock-Bogoliubov calculations.
TL;DR: In this article, the authors used the 186W(19F,xn)198-200Bi reaction at beam energies of 115 MeV and 105 MeV to populate the Delta I=1 rotational structures, consisting of stretched magnetic dipole transitions.
Abstract: The nuclei 198-200Bi were populated via the 186W(19F,xn)198-200Bi reaction at beam energies of 115 MeV and 105 MeV. Another experiment, aimed at investigating the high-spin-level structure of 203,204Bi, used the 198Pt(11B,xn) reaction at a beam energy of 74 MeV. Five new Delta I=1 rotational structures, consisting of stretched magnetic dipole transitions, have been observed. One of these bands is assigned to 198Bi, one to 199Bi, two to 200Bi, and one to 203Bi. The behaviour of the dynamic moments of inertia of these oblate bands is compared with other bands in neighbouring Pb and Bi nuclei.
TL;DR: The level schemes of mass A approximately 138 nuclei have been extended using data collected with the Eurogam array as mentioned in this paper, and the 35Cl+106Cd fusion-evaporation reaction was used at a bombarding energy of 150 MeV.
Abstract: The level schemes of mass A approximately 138 nuclei have been extended using data collected with the Eurogam array. The 35Cl+106Cd fusion-evaporation reaction was used at a bombarding energy of 150 MeV. Results are presented for odd-odd 138Eu and even-even 138Gd. The high-spin behaviour is discussed in terms of quasiparticle alignments of h11/2 proton and neutron pairs.
TL;DR: The high-spin structure of [sup 139]Sm has been investigated with the [sup 110]Pd([sup 34]S,5[ital n]) reaction at a beam energy of 159 MeV at the Stony Brook Tandem/Superconducting LINAC facility.
Abstract: The high-spin structure of [sup 139]Sm has been investigated with the [sup 110]Pd([sup 34]S,5[ital n]) reaction at a beam energy of 159 MeV at the Stony Brook Tandem/Superconducting LINAC facility. The TESSA3 spectrometer array was used to collect [gamma]-[gamma] coincidence data from which an extended decoupled band structure has been found. It is proposed that this band is based on the [ital i][sub 13/2] ([Omega]=1/2) neutron intruder orbital. The decay pattern, enhanced dynamic moments of inertia, and aligned spins are consistent with the [nu][ital i][sub 13/2] bands in neighboring odd-neutron nuclides. Total Routhian surface and cranked shell model calculations reproduce qualitative features of these nuclides, further supporting the proposed interpretation.
TL;DR: In this article, the population of the yrast superdeformed (SD) band of192Hg in the α4n exit channel of the 16O+184W reaction at 113 MeV beam energy was revealed.
Abstract: Recent data from the EUROGAM array have revealed the population of the yrast superdeformed (SD) band of192Hg in the α4n exit channel of the16O+184W reaction at 113 MeV beam energy. The nucleus assignment was made on the basis of the SD band transition energies, and the observation of characteristic X-rays and lowlying yrast γ-transition of192Hg in coincidence with the SD band γ-rays. Both the feeding and decay-out patterns of the observed SD band have been found similar to the ones previously measured in the (36S,4n) reaction.
TL;DR: In this paper, the multiplicity of KX-rays originating from the conversion of quasi-continuum transitions feeding non-collective discrete states in 143Eu was determined to be about 0.2 per cascade.