Search

High spin band structures of neutron-rich $^{152--158}\mathrm{Pm}$ isotopes have been obtained from the measurement of prompt $\ensuremath{\gamma}$ rays of isotopically identified fragments produced in fission of $^{238}\mathrm{U}+^{9}\mathrm{Be}$ and detected using the VAMOS++ magnetic spectrometer and EXOGAM segmented Clover array at GANIL and also from the high statistics $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ data from the spontaneous fission of $^{252}\mathrm{Cf}$ using Gammasphere. The excited states in $^{157}\mathrm{Pm}$ and those above the isomers in even-$A$ Pm isotopes $^{152,154,156,158}\mathrm{Pm}$ have been identified for the first time. The spectroscopic information on the rotational band structures in odd-$A$ Pm isotopes has been extended considerably to higher spins and the possibility of the presence of reflection asymmetric shapes is explored. The configuration assignments are based on the results of cranked relativistic Hartree-Bogoliubov calculations. From the systematics of bands in odd-$A$ Pm isotopes and weak population of opposite parity bands, octupole deformed shapes in neutron-rich Pm isotopes beyond $N=90$ seem unlikely to be present.

Level schemes of even–even neutron-rich 88-92 Kr and 86 Se have been investigated by measuring triple-γ coincidence data from the spontaneous fission of 252 Cf with the Gammasphere detector array. The level scheme of 88 Kr has been extended up to 7169 keV state. Several new excited states with new transitions have been identified in 90,92 Kr and 86 Se . Spins and parities have been assigned to levels in these nuclei by following regional systematics and angular correlation measurements. The level structures of the N = 52, 54, Se , Kr , and Sr isotones are discussed.

The high spin states of neutron-rich 103Nb, 107Tc and 109Tc nuclei in A∼110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of 252Cf with the Gammasphere detector array. In 103Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In 107Tc and 109Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified. The two-phonon bands are first observed in odd-Z nuclei. The characteristics for these band structures have been discussed.

We have used our analysis of γ-γ-γ data (5.7 × 1011 triples and higher folds) taken with Gammasphere from prompt γ rays emitted in the spontaneous fission of 252Cf to study the collective bands in 104,106,108Mo. The one-phonon and two-phonon γ-vibrational bands and known two-quasiparticle bands in neutron-rich 104,106Mo were extended to higher spins. The one-and two-phonon γ-vibrational bands have remarkably close energies for transitions from the same spin states and identical moments of inertia. Several new bands are observed and are proposed as quasiparticle bands in 104,106Mo, along with the first β-type vibrational band in 106Mo. The quasiparticle bands have essentially constant moments of inertia near the rigid-body value that indicate blocking of the pairing interaction. Candidates for chiral doublet bands in 106Mo are strong. These are the first reported chiral vibrational bands in an even-even nucleus.

Neutron-rich radioactive ion beams available from the HRIBF allow a variety of measurements around the 132Sn region, including Coulomb excitation and single-nucleon transfer. The B(E2;0+ → 2+) values for first 2+ excited states of even-even neutron-rich 132-136Te and 126-130Sn have been measured by Coulomb excitation in inverse kinematics. Neutron transfer onto a 134Te beam from 9Be and 13C targets, to populate single-particle states in 135Te, has also been studied. Gamma rays from the 13C(134Te, 12C) reaction were used to identify the νi13/2 state in 135Te, at an energy of 2109 keV. These and other results, and plans for future experiments with these neutron-rich beams, are presented.

Neutron-rich radioactive ion beams available from the HRIBF allow a variety of measurements around the 132Sn region, including Coulomb excitation, fusion-evaporation, and neutron transfer. The B ( E 2 ; 0 + → 2 + ) value for first 2+ excited states of even-even neutron-rich 132–136Te and 126–134Sn have been measured by Coulomb excitation in inverse kinematics. The results are discussed in terms of the shell model and the quasiparticle random phase approximation. Neutron transfer onto a 134Te beam, from 9Be and 13C targets to populate single-particle states in 135Te, has also been studied. Gamma rays from the 13C(134Te, 12C) reaction were used to identify the ν i 13 / 2 state in 135Te, at an energy of 2109 keV. These and other results, and plans for future experiments with these neutron-rich beams, are presented.

Ternary fission of 252Cf was studied at Gammasphere using eight ΔE×E particle telescopes. Helium, beryllium, boron, and carbon light charged particles (LCPs) emitted with kinetic energy more than 9, 21, 26, and 32 MeV, respectively, were identified. The 3368-keV γ transition from the first 2+ excited state in 10Be was found and the population probability ratio N(2+)/N(0+) = 0.160 ± 0.025 was estimated. No evidence was found for 3368-keV γ rays emitted from a triple molecular state. For the first time, charge distributions are obtained for ternary fission fragments emitted with helium, beryllium, and carbon LCPs.

New excited states built on the 11/2− isomeric states are identified in neutron-rich 121,123Cd, respectively, with gammasphere by measuring three-and higher-fold prompt coincidences following the spontaneous fission of 252Cf. The new data suggests that the 11/2− isomers in the odd-A Cd isotopes with N ≥ 75 have spherical shape similar to those in Te. It is suggested that the backbending observed at ω ≈ 0.445 MeV in 121Cd is because of the alignment of the h11/2 neutron pair.

High-spin levels of [Formula: see text]Mo have been reinvestigated by analyzing the high statistics [Formula: see text]-[Formula: see text]-[Formula: see text] and [Formula: see text]-[Formula: see text]-[Formula: see text]-[Formula: see text] coincidence data from the spontaneous fission of [Formula: see text]Cf taken with the Gammasphere detector array. Two bands and 30 new transitions have been identified. A potential energy surface calculation has been performed. The calculation confirmed the 3/2[Formula: see text][411] configuration of the ground state band and 5/2[Formula: see text][532] for the 346[Formula: see text]keV excited band, as assigned in the previous work. The two newly established bands were proposed to be one- and two-phonon [Formula: see text] vibrational bands coupling to the 5/2[Formula: see text][532] Nilsson orbital, respectively. Triaxial projected shell model calculations have been applied to explain the level structure and are found in good agreement with experimental data.

Analysis of high statistics triple coincidence fission γ data from 252Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for 82Ge, 118,120,122Cd and 114,115Rh. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. These Cd isotopes may have triaxial deformations. High-spin level schemes of 114,115Rh have been established for the first time. The existence of a relatively large signature splitting and an yrare band shows typical features of a triaxially deformed nucleus. Possible excited deformed rotational bands are observed, for the first time, in 82Ge. From the multipole mixing ratio measurement, the ground state configurations of 109,111Ru, as well as excited states in 103,107Mo and 111Ru were determined.

Excited high spin states in 211At, 212Rn, 213Fr and 214Ra with N = 126 are reorganized and interpreted in terms of the stretched weak coupling of an octupole 3− phonon. Nearly identical sequences of levels with ΔI = 3 and the parity change are found, for the first time, up to 25− for 20 states of 214Ra, up to 35− for 36 states of 212Rn and up to 53/2+ for 16 states of 213Fr. The stretched weak coupling of an octupole phonon is extended up to the highest excitation energy of 11355 keV for 212Rn which has the largest experimental B(E3) value of 44.1(88) W.u. for the 11− → 82+ transition. The stretched weak coupling of an octupole 3− phonon needs to be considered when single particle configurations are assigned to high spin states. Average octupole excitation energies of 657(51) keV for 211At, 1101(28) keV for 212Rn, 667(25) keV for 213Fr, and 709(25) keV for 214Ra are obtained. The calculated level enegies are in a good agreement with the experimental level energies within the error limit of 4.3%.

The emission of {sup 10}Be in ternary cold neutronless spontaneous fission of {sup 252}Cf is observed with the Gammasphere consisting of 72 detectors. The {gamma} ray corresponding to the decay of the first 2{sup +} state in {sup 10}Be is observed in coincidence with the {gamma} rays of the fission partners of {sup 96}Sr and {sup 146}Ba . The yield to the first excited state of {sup 10}Be in the {sup 96}Sr- {sup 146}Ba split is the order of 4.0{times}10{sup {minus}4} per 100 fission events. {copyright} {ital 1998} {ital The American Physical Society}

Excited high spin states in 136Xe, 137Cs, 138Ba, 140Ce and 142Nd with N = 82 are reorganized and interpreted in terms of the weak coupling mode of an octupole 3− phonon. Nearly identical sequences of levels with ΔI = 3 and Δπ = yes built on 17/2+ and 23/2− states are found, for the first time, up to 29/2+ and 35/2−, respectively, for 22 states of 137Cs . Also, nearly identical sequences of levels with ΔI = 3 and Δπ = yes built on the 6+ and 9− states are found, for the first time, up to 14+ and 17−, respectively, for 18 states of 136Xe, up to 14+ and 17−, respectively, for 24 states of 138Ba and up to 11+ and 14−, respectively, for 14 states of 140Ce. New spins and parities are assigned, tentatively, to the high spin states of these nuclei based on the weak coupling mode of an octupole 3− phonon. The weak coupling of an octupole 3− phonon needs to be considered when single particle configurations are assigned to high spin states. Neutron particle-hole states (νh 11/2 −1 f 7/2 +1 ) with weak coupling of an octupole 3− phonon are proposed, for the first time. The νh 11/2 −1 f 7/2 +1 excitation energies (E ext(1p1h)) are nearly constant with increasing of Z. One-phonon excited states in 136Xe, 137Cs, 138Ba and 140Ce have the stretched weak coupling configurations of ΔI = 3. But one-phonon excited states in 142Nd show the non-stretched weak coupling configurations of an octupole phonon with ΔI = 3 and 2.

Excited states of neutron-rich nucleus {sup 82}Ge were studied from the spontaneous fission of {sup 252}Cf. Eleven new transitions and seven new levels in {sup 82}Ge were identified by using X(Dy)-{gamma}-{gamma} and {gamma}-{gamma}-{gamma} triple coincidences. Possible excited deformed rotational bands are observed, for the first time, in this nuclear region. Coexistence of the spherical ground and deformed excited shapes is proposed in {sup 82}Ge. These deformed rotational bands can be formed by two-particle, two-hole excitations with the 0{sup +} pairing energy states of the {nu}9/2[404]{sup -2} x 1/2[431]{sup 2} configuration across the N=50 closed shell.

High-spin excited states in the neutron-rich nucleus $^{115}\mathrm{Rh}$ have been identified for the first time by studying prompt $\ensuremath{\gamma}$ rays from the spontaneous fission of $^{252}\mathrm{Cf}$ with the Gammasphere detector array. A new yrast band and a sideband are built in $^{115}\mathrm{Rh}$. This level scheme is proposed to be built on the $7/{2}^{+}$ ground state. The existence of a large signature splitting and an yrare band in $^{115}\mathrm{Rh}$ shows typical features of a triaxially deformed nucleus. The rigid triaxial rotor plus particle model is used to interpret the level structure of $^{115}\mathrm{Rh}$. The level energies, the $\ensuremath{\gamma}$ branching ratios, the large signature splitting in the yrast band, and the inverted signature splitting in the yrare band in $^{115}\mathrm{Rh}$ are reproduced very well. Strong $K$ mixing occurs in $^{115}\mathrm{Rh}$ at high spin.

High-spin excited states in the very neutron-rich nucleus $^{114}\mathrm{Rh}$ have been studied by examining the prompt $\ensuremath{\gamma}$ rays emitted in the spontaneous fission of $^{252}\mathrm{Cf}$ with the Gammasphere detector array. A high-spin level scheme of $^{114}\mathrm{Rh}$ has been established for the first time with 13 new levels. The level scheme is proposed to be built on a ${7}^{\ensuremath{-}}$ state. The existence of a relatively large signature splitting and an yrare band show features which may indicate triaxial deformation. The phenomenon of signature inversion has been observed in $^{114}\mathrm{Rh}$ at $I=12 \ensuremath{\hbar}$. The observed signature inversion of $^{114}\mathrm{Rh}$ is interpreted successfully in terms of the triaxial projected shell model. Theoretical calculations suggest that the negative-parity, yrast band of $^{114}\mathrm{Rh}$ has the two-quasi-particle configuration of $\ensuremath{\pi}{g}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$, consistent with the systematics of odd-odd Rh isotopes. The signature inversion at spin $12 \ensuremath{\hbar}$ may be attributed to the change of rotational mode, from quasi-particle aligned rotation at low spins to collective rotation at high spins.

High-spin levels of the neutron-rich $^{114}\mathrm{Ru}$ have been investigated by measuring the prompt $\ensuremath{\gamma}$ rays in the spontaneous fission of $^{252}\mathrm{Cf}$. The ground-state band and one-phonon $\ensuremath{\gamma}$-vibrational band have been extended up to 14${}^{+}$ and 9${}^{+}$, respectively. Two levels are proposed as the members of a two-phonon $\ensuremath{\gamma}$-vibrational band. A back bending (band crossing) has been observed in the ground-state band at $\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{\approx}$ 0.40 MeV. Using the triaxial deformation parameters, the cranked shell model calculations indicate that this back bending in $^{114}\mathrm{Ru}$ should originate from the alignment of a pair of ${h}_{11/2}$ neutrons. Triaxial projected shell model calculations for the $\ensuremath{\gamma}$-vibrational band structures of $^{114}\mathrm{Ru}$ are in good agreement with the experimental data. However, when using the oblate deformation parameters, both of the above-calculated results are not in agreement with the experimental data.

High-spin excited states in the neutron-rich nucleus $^{140}\mathrm{Cs}$ were re-investigated from the spontaneous fission of $^{252}\mathrm{Cf}$ with the Gammasphere detector array. Seven new transitions at low and moderate spin and 13 at high spin were observed in $^{140}\mathrm{Cs}$ and the level scheme of $^{140}\mathrm{Cs}$ was extended to 3794 keV with a new sideband. Spins and parities were assigned to levels based on angular correlation measurements and the systematics in the $N=85$ isotones.

The g factor of the 15/2{sup -} state in {sup 137}Xe was measured for the first time by using a newly developed technique for measuring angular correlations with Gammasphere. Spins and parities were assigned to several levels in the N=83 isotones {sup 135}Te, {sup 136}I, {sup 137}Xe, and {sup 138}Cs. The calculated g factor in the shell-model frame is in good agreement with the measured one in the present work. Shell-model calculations also support our spin-parity assignments.

With a very high statistics data set with 5.7×1011 triple and higher fold γ coincidences from the spontaneous fission of 252Cf, a wealth of fascinating new collective motions in nuclei with A = 100–112 have been observed. Nothing was known previously about one‐ and two‐phonon γ‐bands in odd‐A nuclei. We discovered the first one‐and two‐ phonon γ vibrational bands in an odd N‐even Z nucleus, 105Mo. The energies of the one‐ and two‐ phonon bands in 104Mo, 105Mo, 106Mo and 108Mo were recently studied and are remarkably similar in energies. The first chiral doublet bands in e‐e nuclei were observed in triaxial 106,108Mo and 110,112Ru while such chiral band in 108Ru are perturbed by its γ‐soft shape. The experimental evidences, including our recent angular correlation studies are presented along with what these new bands are telling us about the evolving collective structures and deformation in this region.

The high spin states of neutron‐rich nuclei in A∼110 region have been carefully investigated by measuring prompt γ‐γ‐γ coincident measurements populated in the spontaneous fission of 252Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one‐phonon‐ and two‐phonon γ‐vibrational bands in odd‐A 103Nb, 105Mo and 107Tc, the chiral doublet bands in even‐even 106Mo, 110Ru and 112Ru, and the pseudospin partner bands with in 108Tc. The characteristics of these band structures have been discussed.The high spin states of neutron‐rich nuclei in A∼110 region have been carefully investigated by measuring prompt γ‐γ‐γ coincident measurements populated in the spontaneous fission of 252Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one‐phonon‐ and two‐phonon γ‐vibrational bands in odd‐A 103Nb, 105Mo and 107Tc, the chiral doublet bands in even‐even 106Mo, 110Ru and 112Ru, and the pseudospin partner bands with in 108Tc. The characteristics of these band structures have been discussed.

High spin excited states in the neutron-rich nuclei $^{137}\mathrm{I}$ and $^{139}\mathrm{Cs}$ were investigated from a study of the prompt $\ensuremath{\gamma}$ rays emitted in the spontaneous fission of $^{252}\mathrm{Cf}$ with the Gammasphere detector array. Ten new excited levels with $18$ new deexciting transitions were observed in $^{139}\mathrm{Cs}$ and the level scheme of $^{139}\mathrm{Cs}$ was extended up to $4670$ keV. Spins and parities of levels in $^{139}\mathrm{Cs}$ were firmly assigned up to $25/{2}^{+}$. Three new levels were found in $^{137}\mathrm{I}$. Shell model calculations were performed to interpret the experimental results. A good agreement between theory and experiment in both nuclei was found.

The multipole mixing ratios of $\ensuremath{\Delta}I=1$ transitions between levels in rotational bands built on single-particle states in odd neutron nuclei are dependent on the configurations of the states. In particular, the mixing ratio can be used to distinguish between several possible single-particle configurations if interpreted with the particle-axial-rotor model. This work features the first determination of the ground-state configurations of $^{109,111}\mathrm{Ru}$. The single-particle structures of the ground states of $^{101}\mathrm{Zr}$ and $^{103,105,107}\mathrm{Mo}$ as well as excited states in $^{103,107}\mathrm{Mo}$ are also investigated, with a new result found in $^{107}\mathrm{Mo}$.

High spin states in {sup 134}I were identified for the first time based on measurements of prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at Gammasphere. Five excited levels with five deexciting transitions were observed. The mass number was assigned based on the intensity of transitions in the complementary Rh fragments. Angular correlations for the first two transitions in {sup 134}I and for high spin states in {sup 133,135,136}I were performed, but were not sufficient to firmly assign the spins and parities in {sup 134}I.

The conclusions obtained from an early simulation study of the primary event in the vision process are reexamined by simulating the dynamics of the primary photoisomerization reaction in bacteriorhodopsin using a detailed molecular model for the protein-chromophore complex. The calculated photoisomerization time is of the same order of magnitude as that predicted by the early simulation and found in recent experimental studies. Several simulations with different conditions indicate that the isomerization process involves an efficient transfer of energy from the reaction coordinate to other degrees of freedom and is better described by a damped-motion model than by an inertial model. The damped motion is expected to give a significant quantum yield for both the cis→trans and trans→cis cases only if the minimum of the excited state potential surface is located above the ground state maximum (unless the excited state surface is extremely shallow or if the inertial effects associated with the surface crossing process are very large). The present study suggests that the observed quantum yield should not be analyzed by one-dimensional models but by multidimensional microscopic simulations that consider the surface crossing process and the subsequent ground state relaxation processes.

The g-factor of the 4{sup +} state in {sup 134}Te has been measured for the first time by using a new technique developed for measuring angular correlations with Gammasphere. Also reported is the first measurement of the g-factor of the 15/2{sup +} state in {sup 135}I and the mixing ratios of several transitions. Furthermore, spins and parities are assigned to several levels in {sup 134}Te and {sup 135}I. The g-factor measurements are compared to shell model predictions and good agreement is found between experiment and theory.

The high spin excited states of neutron-rich nuclei 159 Sm and 89,91 Kr are identified for the first time from the spontaneous fission of 252 Cf. Six excited states and six y transitions in 159 Sm are reported here for the first time. Five and two new y transitions are identified in 89 Kr and 91 Kr, respectively. Level schemes in 59,91 Kr are interpreted as the 2d 5/2 neutron hole configuration weakly coupled to the neighboring even-even Kr nuclei. A possible yrast spin sequence of 11/2 - -9/2 + -5/2 + is suggested in 89 Kr. A rotational band with the proposed configuration of v5/2[523] is observed in 159 Sm.

Neutron-rich nuclei of {sup 153,155}Nd were studied from the spontaneous fission of {sup 252}Cf. Eleven and nine new {gamma} transitions were identified in {sup 153}Nd and {sup 155}Nd, respectively. Rotational bands with the configurations of {nu}5/2[642] and {nu}3/2[521] were identified in {sup 153}Nd and {sup 155}Nd, respectively. Excited states and {gamma} transitions in {sup 155}Nd are reported for the first time here.

Triple coincidences between prompt γ-rays emitted in the spontaneous fission of 252Cf were measured with Gammasphere. These data are used to measure the angular correlation of cascades of γ-rays from excited states of neutron rich fission fragments stopped in an unmagnetized iron foil. The hyperfine fields in the iron lattice cause attenuations of the angular correlations between γ-rays emitted from the excited states which have sufficiently long lifetimes. This attenuation is measured and used to calculate the g-factors of excited states in many neutron rich nuclei. © 2007 Elsevier B.V. All rights reserved.

High spin states of neutron-rich nuclei such as 133,134Te, 93Sr, 105Nb have been studied by measuring γ- γ- γ coincidences (cube), γ- γ- γ- γ coincidences (hypercube) and angular correlations from the spontaneous fission of 252Cf with the LBNL Gammasphere detector array. Four types of particle-hole bands built on the known 334.3 keV isomer in 133Te were identified. The level structure of 93Sr is interpreted, in part, as arising from the weak coupling of the 1d5/2 neutron hole to the yrast states of the 94Sr core. The g-factor of the 4+ state in 134Te was measured, for the first time, by using a new technique developed for measuring angular correlations with Gammasphere. A new level scheme of 105Nb was established. Three new collective bands were identified with a total of 14 new levels and 36 new γ transitions. In 117-122Cd, a shift to more slightly deformed structures was found where the excited levels do not fit the long held picture of one, two and three phonon bands.

Two new $\ensuremath{\alpha}$ emitters $^{109}\mathrm{Xe}$ and $^{105}\mathrm{Te}$ were identified through the observation of the $^{109}\mathrm{Xe}\ensuremath{\rightarrow}^{105}\mathrm{Te}\ensuremath{\rightarrow}^{101}\mathrm{Sn}$ $\ensuremath{\alpha}$-decay chain. The $^{109}\mathrm{Xe}$ nuclei were produced in the fusion-evaporation reaction $^{54}\mathrm{Fe}(^{58}\mathrm{Ni},3n)^{109}\mathrm{Xe}$ and studied using the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility. Two transitions at ${E}_{\ensuremath{\alpha}}=4062\ifmmode\pm\else\textpm\fi{}7\text{ }\text{ }\mathrm{keV}$ and ${E}_{\ensuremath{\alpha}}=3918\ifmmode\pm\else\textpm\fi{}9\text{ }\text{ }\mathrm{keV}$ were interpreted as the $l=2$ and $l=0$ transitions from the $7/{2}^{+}$ ground state in $^{109}\mathrm{Xe}$ (${T}_{1/2}=13\ifmmode\pm\else\textpm\fi{}2\text{ }\text{ }\mathrm{ms}$) to the $5/{2}^{+}$ ground state and a $7/{2}^{+}$ excited state, located at $150\ifmmode\pm\else\textpm\fi{}13\text{ }\text{ }\mathrm{keV}$ in $^{105}\mathrm{Te}$. The observation of the subsequent decay of $^{105}\mathrm{Te}$ marks the discovery of the lightest known $\ensuremath{\alpha}$-decaying nucleus. The measured transition energy ${E}_{\ensuremath{\alpha}}=4703\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{keV}$ and half-life ${T}_{1/2}=620\ifmmode\pm\else\textpm\fi{}70\text{ }\text{ }\mathrm{ns}$ were used to determine the reduced $\ensuremath{\alpha}$-decay width ${\ensuremath{\delta}}^{2}$. The ratio ${\ensuremath{\delta}}_{^{105}\mathrm{Te}}^{2}/{\ensuremath{\delta}}_{^{213}\mathrm{Po}}^{2}$ of $\ensuremath{\sim}3$ indicates a superallowed character of the $\ensuremath{\alpha}$ emission from $^{105}\mathrm{Te}$.

Eight new high spin states and 23 new \ensuremath{\gamma} transitions have been identified in $^{100}\mathrm{Zr}$ from studies of $^{252}\mathrm{Cf}$ spontaneous fission with Gammasphere. A near-spherical excited band in $^{100}\mathrm{Zr}$ based on the 331.1 keV ${0}^{+}$ state is extended from ${4}^{+}$ up to ${12}^{+}$. A $\ensuremath{\Delta}I=1$ band with band-head energy of 2316.1 keV is extended.

New level schemes of odd-$Z$ $^{105,107,109}\mathrm{Tc}$ are proposed based on the $^{252}\mathrm{Cf}$ spontaneous-fission-gamma data taken with Gammasphere in 2000. Bands of levels are considerably extended and expanded to show rich spectroscopic information. Spin/parity and configuration assignments are made based on determinations of multipolarities of low-lying transitions and the level analogies to the previously reported levels, and to those of the neighboring $\mathrm{Rh}$ isotopes. A non-yrast negative-parity band built on the $3∕{2}^{\ensuremath{-}}[301]$ orbital is observed for the first time in $^{105}\mathrm{Tc}$. A positive-parity band built on the $1∕{2}^{+}[431]$ intruder orbital originating from the $\ensuremath{\pi}({g}_{7∕2}∕{d}_{5∕2})$ subshells and having a strong deformation-driving effect is observed for the first time in $^{105}\mathrm{Tc}$, and assigned in $^{107}\mathrm{Tc}$. A positive-parity band built on the excited $11∕{2}^{+}$ level, which has rather low excitation energy and predominantly decays into the $9∕{2}^{+}$ level of the ground state band, provides evidence of triaxiality in $^{107,109}\mathrm{Tc}$, and probably also in $^{105}\mathrm{Tc}$. Rotational constants are calculated and discussed for the $K=1∕2$ intruder bands using the Bohr-Mottelson formula. Level systematics are discussed in terms of the locations of proton Fermi levels and deformations. The band crossings of yrast positive-parity bands are observed, most likely related to ${h}_{11∕2}$ neutron alignment. Triaxial-rotor-plus-particle model calculations performed with $\ensuremath{\epsilon}=0.32$ and $\ensuremath{\gamma}=\ensuremath{-}22.5\ifmmode^\circ\else\textdegree\fi{}$ on the prolate side of maximum triaxiality yielded the best reproduction of the excitation energies, signature splittings, and branching ratios of the positive-parity bands (except for the intruder bands) of these $\mathrm{Tc}$ isotopes. The significant discrepancies between the triaxial-rotor-plus-particle model calculations and experiment for the $K=1∕2$ intruder bands in $^{105,107}\mathrm{Tc}$ need further theoretical studies.

Ternary fission of $^{252}\mathrm{Cf}$ was studied at Gammasphere with eight $\ensuremath{\Delta}E\ifmmode\times\else\texttimes\fi{}E$ particle telescopes. After Doppler correction, the $3368\phantom{\rule{0.3em}{0ex}}\text{keV}\phantom{\rule{0.3em}{0ex}}{2}^{+}\ensuremath{\rightarrow}{0}^{+}$ transition in $^{10}\mathrm{Be}$ was found in coincidence with the $^{10}\mathrm{Be}$ fragments with no evidence for any $\ensuremath{\gamma}$ rays not Doppler shifted for $^{10}\mathrm{Be}$ with $g21\phantom{\rule{0.3em}{0ex}}\text{MeV}$ kinetic energy. The ratio of the first ${2}^{+}$ to ground-state population probabilities was estimated as $N({2}^{+})∕N({0}^{+})=0.160\ifmmode\pm\else\textpm\fi{}0.025$. The angular distribution for $3368\phantom{\rule{0.3em}{0ex}}\text{keV}$ $\ensuremath{\gamma}$ rays indicated the spin alignment of excited $^{10}\mathrm{Be}$ nuclei preferentially is parallel or antiparallel to their momentum.

Ternary fission of 252Cf was studied at Gammasphere with using ΔE×E particle telescopes. The abundance ratio of 10Be LCP’s emitted in the excited 2+ state (E*=3368 keV) and in the ground state was found to be N(2+)/N(0+)=0.160±0.025. No evidence was found for the 3368 keV γ rays emitted from a triple molecular state. For the first time charge distributions were obtained for fission fragments emitted with helium, beryllium and carbon LCP’s.

An excited rotational band including seven new $\ensuremath{\gamma}$ transitions was identified in ${}^{97}\mathrm{Sr}$ from $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences in the spontaneous fission of ${}^{252}\mathrm{Cf}.$ This new band, built on the 829.8-keV state, is interpreted as the $\ensuremath{\nu}9/2[404]$ rotational band with a very deformed shape. The half-life of the 829.8-keV state is determined to be 265(27) ns in the present work. The new band indicates that the emptying of the upsloping ${g}_{9/2}$ orbital with $K=9/2$ is closely related to the strong prolate shapes of some bands in the Sr and Zr regions with $A\ensuremath{\approx}100.$

The mass A = 140 products of the 54Fe (315 MeV) + 92Mo reaction were selected by a recoil mass spectrometer and studied in a recoil ‐ delayed γ‐γ coincidence experiment. A new 7 μs isomer was identified in the drip line nucleus 140Dy. Five cascading γ transitions were assigned to the decay of the Iπ = 8− {v9/2−[514] ⊗ v7/2+[404]} K isomer via the ground state band transitions. The established structure of 140Dy is discussed with reference to the fine structure in proton decay of 141Ho.

New level schemes of {sup 141}Ba and {sup 139}Xe are proposed from the analyses of spontaneous-fission gamma data from our {sup 252}Cf spontaneous fission Gammasphere runs of 1995 and 2000. By analogy with the N = 85 even-odd isotones {sup 149}Gd, {sup 147}Sm, and {sup 145}Nd, spins and parities were assigned to the observed excited states in {sup 141}Ba and {sup 139}Xe. It appears that spherical shell model neutron excitations plus octupolephonons are an appropriate basis at the lower end of the bands. Going to higher spins it is clear that the soft rotor involving valence protons as well as neutrons becomes increasingly important in the configurations. Level systematics in the N = 85 even-odd isotones from Gd(Z=64) through Te(Z=52), are discussed. The excitation systematics and smooth trends of the analogous levels support the spin and parity assignment for excited levels observed in {sup 141}Ba and {sup 139}Xe. The level systematics and the comparison with neighboring even-even isotopes indicate that quadrupole and octupole collectivity play roles in {sup 141}Ba and {sup 139}$Xe. From Gd(Z=64) through Te(Z=52), increasing excitation energies of the 13/2{sup +} states and lowering relative intensities of the positive parity bands in the N = 85 even-odd isotones may indicate that the octupole strength is becoming weaker for the isotones when approaching the Z = 50 closed shell.

Excited states in neutron-rich ${}^{133}\mathrm{Te}$ have been identified with the Gamma sphere array by measuring three- and higher-fold prompt coincidence events following spontaneous fission of ${}^{252}\mathrm{Cf}.$ Four types of particle-hole bands built on the known 334.3 keV isomer in ${}^{133}\mathrm{Te}$ are identified. The yrast and near yrast particle-hole states observed up to 6.2 MeV in ${}^{133}\mathrm{Te}$ have characteristics quite similar to those in ${}^{134}\mathrm{Te}.$ These states are interpreted as a result of coupling a neutron $\ensuremath{\nu}{h}_{11/2}$ hole to the ${}^{134}\mathrm{Te}$ core. The group of states observed above 5.214 MeV is the result of a neutron particle-hole excitation of the double magic core nucleus ${}^{132}\mathrm{Sn},$ and is a candidate for a tilted rotor band. Shell-model calculations considering ${}^{132}\mathrm{Sn}$ as a closed core have been performed and have provided guidance to the interpretation of the levels below 4.3 MeV. Very good agreement between theory and experiment is obtained for these states.

A new $7 \ensuremath{\mu}\mathrm{s}$ isomer in the drip line nucleus ${}^{140}\mathrm{Dy}$ was selected from the products of the ${}^{54}\mathrm{Fe}$ $(315 \mathrm{MeV}{)+}^{92}\mathrm{Mo}$ reaction by a recoil mass spectrometer and studied with recoil-delayed $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences. Five cascading $\ensuremath{\gamma}$ transitions were interpreted as the decay of an ${I}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ ${\ensuremath{\nu}{9/2}^{\ensuremath{-}}[514]\ensuremath{\bigotimes}\ensuremath{\nu}{7/2}^{+}[404]}$ K isomer $({T}_{1/2}=7.0(5) \ensuremath{\mu}\mathrm{s})$ via the ground-state band. The probability of proton emission from ${}^{141}\mathrm{Ho}$ to the ${0}^{+}$ ground state and to the ${2}^{+}$ excited state in ${}^{140}\mathrm{Dy}$ is discussed.

A new 7 μs isomer in the drip line nucleus 140Dy was selected from the products of the 54Fe (315 MeV) + 92Mo reaction by a recoil mass spectrometer and studied with recoil ‐ delayed γ‐γ coincidences. Five cascading γ transitions were interpreted as the decay of an Iπ = 8− {v9/2−[514] ⊗ v7/2+[404]} K isomer via the ground state band.

New analyses of spontaneous-fission gamma data from our 252Cf Gammasphere runs of 1995 and 2000 have identified new transitions and given improved transition energy and intensity values for known transitions in even-odd fission-product nuclei just beyond the 82-neutron closed shell. New level schemes of N=83 isotones 139Ba83 and 135Te83 and of N=85 isotones 141Ba85, and 139Xe85 are established. Single-particle (hole) excitations and couplings, core excitations, and octupole excitations are assigned to these isotones. A regular sequence found in 135Te is interpreted as a shears band within the tilted-axis cranking model of Frauendorf. The level systematics of N=85 isotones indicate that the octupole excitation moves to higher excitation energy as the Z=50 shell is approached.

We identified γ transitions in several neutron‐rich nuclei near 132Sn produced in the spontaneous fission of 252Cf. These are of interest because they can test shell model calculations. These nuclei are 139Ba, 133,135Te, and 121,123Cd. Excited states in neutron‐rich 133Te exhibit four types of particle‐hole bands built on the known 334.3 keV isomer in 133Te. The yrast and near yrast particle‐hole states observed up to 6.2 MeV in 133Te have characteristics quite similar to those in 134Te. The band starting at 5.214 MeV is assigned as a neutron particle‐hole excitation of the double magic core nucleus, 132Sn and is a candidate for a tilted rotor band. Theoretical shell model calculations show good agreement with the experimental states up to 4.3 MeV. The new level scheme of 139Ba includes 11 new transitions and 10 new levels and is compared with the 83‐neutron isotone 135Te. In 135Te, a tilted rotor band, also, is proposed. Excited states built on the 11/2− isomeric states in neutron‐rich 121,123Cd are iden...

Levels in the neutron-rich, odd-mass ${}^{107}\mathrm{Ru}$ nucleus have been reinvestigated with Gammasphere by measuring high-fold, prompt coincidence events following spontaneous fission of ${}^{252}\mathrm{Cf}.$ The ground state band has been extended up to $\frac{27}{2}\ensuremath{\Elzxh}.$ The structure associated with the ${h}_{11/2}$ excitation has been confirmed and extended to higher spin. The ${h}_{11/2}$ band head has been established to lie at 301.8 keV. These results clear up differences between our earlier work and results from another experiment published recently. A new collective band based on a ${9/2}^{\ensuremath{-}}$ level has been identified for the first time. Some distinct features of the level scheme are discussed.

The decay of the neutron-rich nucleus {sup 110}Tc has been investigated using {beta}-{gamma} and {gamma}-{gamma} coincidences. The on-line mass separated source is produced by using the ion-guide technique from fission products. An extended level scheme of {sup 110}Ru has been constructed, including 20 new excited states and 36 new {gamma} transitions. The {beta} feedings, log ft values, and B(E2) ratios were extracted. A spin and parity of 0{sup +} is suggested for a level at 1137 keV in {sup 110}Ru, and the spin and parity of the previously identified 2{sub 3}{sup +} state was confirmed. Level systematics of neutron-rich even-even Ru isotopes shows that the maximum deformation is at A=112 (N=68), two neutrons more than the middle of the N=50-82 neutron shell. The experimental results are compared with theoretical values calculated by different nuclear models. (c) 2000 The American Physical Society.

Triple-γ coincidence data were used to study the γ-vibrational bands to 14+ in 104–106Mo, to 13+ in 108,110Ru and 17+ in 112Ru, and to 13+, 15+ in 112–116Pd. The even-odd spin energy level splittings show rapid variations with spin and neutron number in these nuclides. With one exception, the Sm-Pt nuclei show no such reversal and much smaller staggering.

By using different time-gated triple γ coincidence data, the half-lives (T1/2) of several short lived states in neutron-rich nuclei have been studied. The first excited states in the ground state bands often decay by delayed γ emission. By creating triple γ coincidence spectra with time windows of 8, 16, 20, 28, and 48 ns, we have studied states with half-lives below 10 ns. The estimated half-lives of 102Zr, 137Xe, and 143Ba are in reasonable agreement with previously reported values. We extract the first estimates of the half lives of the 2+ states in 104Zr and 152Ce.

Half-lives (T 1/2) of several states which decay by delayed γ transitions were determined from time-gated triple γ coincidence method. We determined, for the first time, the half-life of 330.6 + x state in 108Tc and the half-life of 19/2− state in 133Te based on the new level schemes. Five half-lives of 95,97Sr, 99Zr, 134Te and 137Xe are consistent with the previously reported ones. These results indicate that this new method is useful for measuring the half-lives.