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The unique transition probability in chiral twin bands was predicted based on a simplified frozen alignment Particle plus Rotor (PR) model and a full PR model calculation.

High-spin states in ${}^{129}\mathrm{Nd}$ were populated in the reaction ${}^{92}\mathrm{Mo}{(}^{40}\mathrm{Ca},2pn)$ with beam energies of 170 and 184 MeV in two separate experiments. Over 140 new transitions were placed in a level scheme that consists of four rotational structures, three of which have been observed for the first time. The bands were assigned configurations based on their $B(M1)/B(E2)$ ratios (for the strongly coupled bands), aligned angular momentum, observed band crossings, and signature splitting. Evidence for of the observation of the deformation driving $\ensuremath{\nu}{i}_{13/2}[660]1/2$ orbital is presented. Signature splitting trends in the $\ensuremath{\nu}{h}_{11/2}$ bands of $A\ensuremath{\sim}130$ nuclei are investigated within the framework of the cranked shell model. Comparisons are made with observations in the $\ensuremath{\pi}{h}_{11/2}$ bands near $A\ensuremath{\sim}160.$

The chiral-twin candidate bands recently observed in {sup 136}Pm have been extended to high spins [I=(21)] using the Gammasphere {gamma}-ray spectrometer and the Microball charged-particle detector array. A more-detailed spectroscopy of the bands was possible, where the rotational alignments and B(M1)/B(E2) ratios confirm that both sequences have the {pi}h{sub 11/2}{nu}h{sub 11/2} configuration. Particle-rotor calculations of intraband and interband transition strength ratios of the chiral-twin bands are compared with experimental values for the first time. Good agreement was found between the predicted transition strength ratios and the experimental values, thus supporting the possible chiral nature of the {pi}h{sub 11/2}{nu}h{sub 11/2} configuration in {sup 136}Pm.

g-ray transitions have been identified for the first time in the near-drip-line nucleus 126 Pr, making it the lightest odd-odd praseodymium nucleus in which excited states have been reported. Evidence is presented for two rotational bands in 126 Pr, one strongly coupled and the other doubly decoupled. In addition, the preliminary reports of a band in 128 Pr are confirmed. The signature inversion phenomenon and trends in the energy staggering of the ph11/2nh11/2 bands are discussed for the Cs, La, and Pr nuclei.

Excited structures in the $Z=80,{ }^{178}\mathrm{Hg} (N=98),$ and ${}^{180}\mathrm{Hg} (N=100)$ isotopes have been investigated with the Gammasphere spectrometer in conjunction with the recoil-decay tagging technique. The present data extend the previously known ground-state bands to higher spin and excitation energy. Negative parity bands with a complex decay towards the low spin states arising from both the prolate-deformed and the nearly spherical coexisting minima have been observed for the first time in both nuclei. It is shown that these sequences have characteristics in common with negative-parity bands in the heavier even-even Hg isotopes as well as in the Os and Pt isotones. These structures are interpreted as being associated at low spin with an octupole vibration which is crossed at moderate frequency by a shape driving, two-quasiproton excitation.

High-spin states in {sup 131}Nd were populated in the reaction {sup 94}Mo({sup 40}Ca,2pn) at a beam energy of 180 MeV. Over 170 new transitions were placed in a level scheme that consists of seven rotational structures. The bands were given configuration assignments based on their B(M1)/B(E2) ratios (for the strongly coupled bands), aligned angular momentum, observed band crossings, and signature splitting. Several quasiparticle alignments were observed in the bands and compared with predictions from the cranked shell model. Three-band mixing calculations were performed in order to interpret the low-spin interaction observed in the [411]1/2 band. An examination of the signature splitting for the [541]1/2 bands in {sup 129,131,133}Nd revealed information regarding the parentage of the orbital as well as a signature inversion at higher spin. (c) 2000 The American Physical Society.

Collective structures in ${}^{178}\mathrm{Pt}$ have been investigated with $\ensuremath{\gamma}$-ray spectroscopic techniques following mass selection. The present data expand considerably the level scheme of this nucleus. A new collective structure has been identified and the known bands have been extended to higher spins. Firm spin and parity assignments have been made to many levels. Of particular interest are the negative parity bands which are interpreted in terms of structures associated with octupole vibrations crossed at moderate spin by two-quasiparticle excitations. The systematics of the $\ensuremath{\alpha}$-decay reduced widths in Pt nuclei has also been investigated. The differences of a factor of about 2 between the widths for the odd- and the even-$A$ isotopes is attributed to changes in neutron pairing associated with the blocking effect. The trend is reproduced in calculations based on the Lipkin-Nogami pairing model.

The yrast sequence in ${}^{183}\mathrm{Tl}$ has been studied for the first time in recoil-mass selected \ensuremath{\gamma}-ray spectroscopic measurements. A rotational-like cascade of seven transitions is established down to the band head with probable spin and parity ${(13/2}^{+}).$ Unlike in the adjacent odd-mass Tl nuclei, prompt \ensuremath{\gamma} decay from the yrast band to a lower lying weakly deformed (oblate) structure is not observed. These features are consistent with the predicted drop of the prolate band head in ${}^{183}\mathrm{Tl}$ compared to ${}^{185}\mathrm{Tl}.$ The implications for the prolate energy minimum in odd-mass Tl nuclei at the neutron ${i}_{13/2}$ midshell $(N=103)$ are discussed.

Two excited well-deformed bands have been observed in the semi-magic nucleus (58)Ni. One of the bands was observed to partially decay by emission of a prompt discrete alpha particle that feeds the 2949 keV 6(+) spherical yrast state in the daughter nucleus (54)Fe. This constitutes the first observation of prompt alpha emission from states lying in the deformed secondary minimum of the nuclear potential. gamma-ray linking transitions via several parallel paths establish the spin, parity, and excitation energy of this deformed band in (58)Ni.

High-spin states in the ${}^{94,95,96}\mathrm{Tc}(N=51,$ 52, and 53) nuclei have been investigated using the ${}^{65}\mathrm{Cu}{+}^{36}\mathrm{S}$ reaction at a beam energy of 142 MeV. More than 60 new transitions have been identified and placed in their level schemes, which now extend up to spin $J\ensuremath{\approx}22\ensuremath{\Elzxh}$ and excitation energies ${E}_{x}\ensuremath{\approx}12$ MeV. Spherical shell-model calculations have been performed using different model spaces. A restricted model space, using ${}^{88}\mathrm{Sr}$ as the core and the $\ensuremath{\pi}{(p}_{1/2}{,g}_{9/2})$ $\ensuremath{\nu}{(d}_{5/2}{,s}_{1/2})$ valence orbitals, reproduces the experimental excitation energies up to $J\ensuremath{\approx}14\ensuremath{\Elzxh}.$ The higher-angular-momentum states are dominated by the excitation of a ${g}_{9/2}$ neutron across the $N=50$ magic core, as indicated by large-basis shell model calculations.

Lifetimes of high-spin states in the $N=52\ensuremath{-}54 \mathrm{Ru}$ nuclei have been investigated via the ${}^{65}\mathrm{Cu}{(}^{36}\mathrm{S}{,pyn)}^{96,97,98}\mathrm{Ru} (y=4,3,2)$ reactions using the recoil-distance Doppler-shift technique. The data were collected in coincidence mode. Lifetimes have been extracted for both the positive- and the negative-parity states in ${}^{96}\mathrm{Ru}$ and ${}^{98}\mathrm{Ru}$ and for the positive-parity states in ${}^{97}\mathrm{Ru}.$ The levels studied have lifetimes in the range 2--31 ps. The observed reduced transition probabilities $B(E2)$ and $B(M1)$ are compared with the predictions of the shell model. Theoretical implications of these results are discussed.

Using the GAMMASPHERE array in conjunction with the Fragment Mass Analyzer, the level structure of the near drip-line nucleus {sup 178}Hg has been considerably expanded with the recoil-decay tagging technique. Of particular interest is a new rotational band which exhibits a complex decay towards the low spin states arising from both the prolate-deformed and the nearly spherical coexisting minima. It is proposed that this band is associated at low spin with an octupole vibration which is crossed at moderate frequency by a shape driving, two quasiproton excitation. (c) 1999 The American Physical Society.

The deformation driving {nu}i{sub 13/2} [660]1/2 structure has been identified for the first time in {sup 131}Nd. It is the lightest Nd (Z=60) isotope in which a band based on this intruder orbital has been reported. A crossing between the [411]1/2 band and the [660]1/2 sequence takes place near {h_bar}{omega}{approx}0.34 MeV with a large interaction strength ({vert_bar}V{vert_bar}{sub max}=47 keV). Thus, a smooth transition from the normal to the highly deformed minimum is established in {sup 131}Nd. thinsp {copyright} {ital 1999} {ital The American Physical Society}

High-spin states in ${}^{125}\mathrm{La}$ have been populated using the ${}^{94}\mathrm{Mo}{(}^{40}\mathrm{Ca},2\ensuremath{\alpha}p)$ reaction at a beam energy of 180 MeV. Four of the five previously known rotational structures have been extended to higher spin $(Il~\frac{71}{2})$ and excitation energy. In addition, three new sequences were observed, two of which form a strongly-coupled band. This latter structure is likely based on the [404]9/2 proton orbital, which is associated with strong deformation driving behavior in nearby Pr and Pm nuclei. A systematic examination of the crossing frequencies based on the rotational alignment of ${h}_{11/2}$ protons and ${h}_{11/2}$ neutrons is also presented. The dependence of the crossing frequencies on deformation and Fermi surface can be inferred based on experimental observation and evidence for reduced proton and possibly neutron pairing fields is presented.

Excited states in the N = Z+1 nucleus Y-79 Were identified using the reaction Si-28(Fe-54, p2n)Y-79 at a 200 MeV beam energy and an experimental set up consisting of an array of Ge detectors and the Recoil Mass Spectrometer at Oak Ridge National Laboratory. With the help of additional gamma-gamma coincidence data obtained with Gammasphere, these gamma-rays were found to form a strongly-coupled rotational band with rigid-rotor-like behavior. Results of conventional Nilsson-Strutinsky cranked shell model calculations, which predict a deformation of beta(2)similar to 0.4, are in excellent agreement with the properties of this band. Similar calculations for the neighboring N = Z and N = Z + 1 nuclei are also in good agreement with experimental data. This suggests that the presence of the putative T = 0 neutron-proton pairing does not significantly affect such simple observables as the moments of inertia of these bands at low spins. (Less)

The yrast sequence in 183Tl has been studied for the first time in recoil-mass and decay tagged γ-ray spectroscopic measurements. A rotational-like cascade of seven transitions is observed down to the bandhead with spin 13/2+. In contrast to adjacent nuclei, links from the yrast band to a lower lying weakly deformed (oblate) structure are not observed. It appears that the prolate energy minimum in 183Tl drops significantly compared to 185Tl and minimizes below the neutron i13/2 midshell (N⩽102). Possibilities for the decay out of the band in 183Tl are discussed.

Thanks to an experimentation, this research studies nonconscious effects of two broadcast sponsorships on attitude toward a new brand. This brand sponsors two quasi-identical broadcasts: there is almost only one difference between them, their emotional content. Effects are recorded with indirect measures. The impact of humorous broadcast sponsorship (with two exposures) on brand is manifest and positive. The sad broadcast has no influence: the intensity of emotions has produced irrelevant thoughts which prevent the processing of the closing credits sponsor billboard. Results are in line with the new familiarity-misattribution model. No automatic transfer of semantic attributes from broadcasting to brand image is observed.

Signature effects observed in rotational bands are a consequence of an inherent D2-symmetry. This symmetry is naturally broken by the mean field cranking approximation when a tilted (non-principal) axis orientation of the nuclear spin becomes stable. The possible tunneling forth and back between the two symmetry-related minima in the double-humped potential-energy surface appears as a typical bifurcation of the rotational band. We describe this many-body process in which all nucleons participate by diagonalizing the nuclear Hamiltonian within a selected set of tilted and non-tilted cranking quasiparticle states. This microscopic approach is able to restore the broken D2 symmetry and reproduce the quantum fluctuations between symmetry- related HFB states which emerge as splitting of the band energies and in parallel staggering in intraband M1 transitions., 9 pages, 4 figures

The 2+2 state in 132Te is identified as the one-phonon MSS in a projectile Coulomb excitation experiment presenting a firm example of a MSS in unstable, neutron rich nuclei. The results of shell-model calculations based on the low-momentum interaction Vlow−k are in good agreement with experiment demonstrating, the ability of the effective shell-model interaction to produce states of mixed symmetry character.

A new collective band with high dynamic moment of inertia in 158Er at spins beyond band termination has been found in addition to the two previously reported ones. The measured transition quadrupole moments (Qt) of these three bands are very similar. These three bands have been suggested to possess a triaxial strongly deformed shape, based on comparisons with calculations using the cranked Nilsson-Strutinsky model and with tilted axis cranking calculations using the Skyrme-Hartree-Fock model. In addition, three collective bands with similar high dynamic moments of inertia, tentatively assigned to 157Ho, have been observed. Thus, it is suggested that all these structures share a common underlying character and that they are most likely associated with triaxial strongly deformed minima which are predicted to be close to the yrast line at spin 50 – 70.

The 2+2 state in 132Te is identified as the one-phonon MSS in a projectile Coulomb excitation experiment presenting a firm example of a MSS in unstable, neutron rich nuclei. The results of shell-model calculations based on the low-momentum interaction Vlow-k are in good agreement with experiment demonstrating the ability of the effective shell-model interaction to produce states of mixed-symmetry character.

High-spin states of the isospin T-z = -1/2 nucleus Ni-55 have been identified for the first time by means of the reaction Si-28(Ar-36,2 alpha n) at 143 MeV beam energy. The GAMMASPHERE array together with ancillary detectors was used to detect gamma rays in coincidence with evaporated light particles. The level scheme of Ni-55 comprising four transitions is compared to its mirror partner Co-55 and shell-model calculations in the Sp shell.

Excited states in /sup 119/Xe have been populated via the /sup 95/Mo(/sup 27/Al,p2n) reaction at a beam energy of 105 MeV. The high-spin level structure is interpreted as consisting of rotational bands built on quasineutron h/sub 11/2/, d/sub 5/2/, and g/sub 7/2/ states. Although these positive-parity configurations differ from previous interpretations, most notably an earlier g/sub 9/2/ assignment, they are supported by experimental B(M1; I..-->..I-1)/B(E2; I..-->..I-2) ratios plus additional levels presented here. A backbend in the g/sub 7/2/ band is attributed to the rotation alignment of a pair of ..nu..h/sub 11/2/ quasiparticles.

The reduced $E2$ and $E4$ transition matrix elements were measured for $^{156,158}\mathrm{Dy}$, $^{162,164}\mathrm{Er}$, and $^{168}\mathrm{Yb}$ via Coulomb excitation with $\ensuremath{\alpha}$ particles at energies below those where nuclear effects are expected to contribute significantly. Charge deformation parameters ${\ensuremath{\beta}}_{2}^{c}$ and ${\ensuremath{\beta}}_{4}^{c}$ were extracted from these matrix elements by assuming the charge distribution to have a deformed Fermi distribution form with quadrupole and hexadecapole components. Values of $〈{0}^{+}\ensuremath{\parallel}(E2)\ensuremath{\parallel}{2}^{+}〉$ of 1.929, 2.161, 2.238, 2.341, and 2.402 eb were found for $^{156,158}\mathrm{Dy}$, $^{162,164}\mathrm{Er}$, and $^{168}\mathrm{Yb}$, respectively, with \ensuremath{\lesssim}1% uncertainty. The values of $〈{0}^{+}\ensuremath{\parallel}M(E4)\ensuremath{\parallel}{4}^{+}〉$ for these same respective nuclei are ${0.21}_{\ensuremath{-}0.20}^{+0.16}$, ${0.16}_{\ensuremath{-}0.15}^{+0.10}$, ${0.16}_{\ensuremath{-}0.26}^{+0.14}$, ${0.12}_{\ensuremath{-}0.13}^{+0.12}$, and ${0.19}_{\ensuremath{-}0.19}^{+0.14}$ ${\mathit{e}\mathrm{b}}^{2}$.NUCLEAR REACTIONS $^{156,159}\mathrm{Dy}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$, $^{162,164}\mathrm{Er}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$, $^{168}\mathrm{Yb}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$, ${E}_{\ensuremath{\alpha}}=12\ensuremath{-}13$ MeV; measured Coulomb excitation cross sections relative to elastic cross sections at ${\ensuremath{\theta}}_{\mathrm{lab}}=150\ifmmode^\circ\else\textdegree\fi{}$; deduced $〈{0}^{+}\ensuremath{\parallel}M(E2)\ensuremath{\parallel}{2}^{+}〉$, $〈{0}^{+}\ensuremath{\parallel}M(E4)\ensuremath{\parallel}{4}^{+}〉$, using rotational model; extracted charges deformation parameters ${\ensuremath{\beta}}_{2}^{c}$, ${\ensuremath{\beta}}_{4}^{c}$ from rotational model and Fermi charge distribution. Enriched targets.

Multiple Coulomb excitation measurements have been performed with $^{16}\mathrm{O}$ projectiles on $^{168,170,172,174,176}\mathrm{Yb}$, Measured $\ensuremath{\gamma}$-ray yields were compared to the Winther-deBoer calculations in order to extract $B(E2)$ and $B(E3)$ values to vibrational and rotational states. The ${2}^{+}$ member of the $\ensuremath{\gamma}$-vibrational band was observed in all the nuclei, the ${4}^{+}$ member in three cases, and excited ${0}^{+}$ states in $^{168,170,172,174}\mathrm{Yb}$. The $B(E2;{0}^{+\ensuremath{'}}\ensuremath{\rightarrow}{2}^{+})$ values from ${0}^{+}$ states at 1228 keV in $^{170}\mathrm{Yb}$ and 1154 keV in $^{168}\mathrm{Yb}$ are in excess of one single-particle unit, the first such cases observed in Yb nuclei. $B(E3)$ values to octupole states were deduced for $^{172,174}\mathrm{Yb}$. Members of the ground state rotational band up to $I=8$ were excited in each nucleus. The measured yield of the ${8}^{+}$ state relative to that of the ${6}^{+}$ level is compared to calculations and discussed for the five nuclei studied.NUCLEAR REACTIONS $^{168,170,172,174,176}\mathrm{Yb}$($^{16}\mathrm{O}$, $^{16}\mathrm{O}^{\ensuremath{'}}\ensuremath{\gamma}$), $E=58\ensuremath{-}62$ MeV; measured $\ensuremath{\sigma}(E)$, ${I}_{\ensuremath{\gamma}}$. $^{168,170,172,174,176}\mathrm{Yb}$ deduced levels, $J$, $\ensuremath{\pi}$, $B(E2)$, $B(E3)$. Enriched targets; Ge(Li) detector.

A measurement of lifetimes in /sup 172/W by the Doppler-shift recoil-distance technique indicates a reduction of the transition quadrupole moments by about 15% for spins > or =12. This can be understood if the rotation-induced structure change is due not only to i-italic/sub 13/2/ neutrons, which is the standard theory for this region of nuclei, but also to h-italic/sub 9/2/ protons. The resulting three-band interpretation of the ''upbend'' in the yrast level sequence is supported by energy-level systematics suggesting that it is valid for a wide range of nuclei in this region.

Details of the identification of $^{186}\mathrm{Tl}$ and its decay to $^{186}\mathrm{Hg}$ as investigated with an isotope separator are presented. Conversion electrons, $\ensuremath{\gamma}$, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$, and $e\ensuremath{-}\ensuremath{\gamma}$ studies establish two bands in $^{186}\mathrm{Hg}$; one built on a near-spherical ground state and one on a more strongly deformed shape with a band head at 522 keV. The levels are discussed in the framework of recent theoretical calculations.RADIOACTIVITY $^{186}\mathrm{Tl}$, $^{186}\mathrm{Tl}^{m}$ from $^{181}\mathrm{Ta}(^{16}\mathrm{O},11n)$, $E=145$ MeV; $^{182}\mathrm{W}(^{14}\mathrm{N},10n)$, $E=168$ MeV; mass separated radioactivities. Measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, ${E}_{\mathrm{ce}}$, ${I}_{\ensuremath{\gamma}}$, ${I}_{\mathrm{ce}}$, $\ensuremath{\gamma}\ensuremath{\gamma}$ coin, $e\ensuremath{\gamma}$ coin, ICC, $^{186}\mathrm{Hg}$ deduced levels, $I$, $\ensuremath{\pi}$, multipolarities.

High spin states in the odd-odd nucleus /sub

Lifetimes in the yrast sequence of $^{128}\mathrm{Ce}$ have been measured following the reaction $^{92}\mathrm{Zr}$($^{40}\mathrm{Ar}$,4n) induced by 159-MeV $^{40}\mathrm{Ar}$ ions. A Doppler-shift recoil-distance device was utilized inside a large NaI detector where the latter provided total $\ensuremath{\gamma}$-ray decay energy selection for these measurements. The $B(E2)$ values deduced for the ${2}^{+}$ through ${14}^{+}$ states indicate that in the ground band $^{128}\mathrm{Ce}$ conforms much more closely to rigid-rotor behavior than do the heavier cerium isotopes, and that in the $s$ band the shape parameters remain in the collective sector $\ensuremath{-}60\ifmmode^\circ\else\textdegree\fi{}l\ensuremath{\gamma}l0\ifmmode^\circ\else\textdegree\fi{}$, as predicted by cranked self-consistent theory.

High-spin states in $^{164}\mathrm{Er}$ have been populated by the reaction $^{150}\mathrm{Nd}(^{18}\mathrm{O}, 4n)^{164}\mathrm{Er}$. In addition to the lowest even-spin superband we present the first evidence for the lowest odd-spin and the second lowest even-spin superbands. We also observe the first example of the intersection of the $\ensuremath{\gamma}$-vibrational band with these superbands. The rotation-alignment model can explain the observed pattern of behavior.

A new method, which has been developed to isolate energy-correlated cascades from a background of uncorrelated events in the ..gamma..-ray continuum, has been applied to the /sup 16/O+/sup 64/Ni reaction at E (/sup 16/O) =80 MeV. In /sup 74/Se, the dominant reaction product, it gives 2J/h/sup 2/ approx. = 53 +- 5 and 65 +- 6 MeV/sup -1/, respectively, for the rotationallike cascades below and above a phase transition observed at I approx. = 22 units. These data also indicate that only a small portion of the decay proceeds through rotationallike cascades.

Sources of /sup 199/Po/sup m/ and /sup 199/Po/sup g/ have been produced and mass separated on line. Multiscaled spectra of ..gamma.. rays, x rays, and conversion electrons, and ..gamma..-..gamma.. and ..gamma..-x-ray coincidences were measured. The M4 isomeric transition of the (13/2)/sup +/ state of /sup 199/Po, with a half-life of 4.17 min, was observed for the first time, permitting the placement of the (13/2)/sup +/ and (5/2)/sup -/ levels above the (3/2)/sup -/ ground state. Also, the placement of the (13/2)/sup +/ state in Po together with previously reported ..cap alpha..-decay Q values made possible the location of the (13/2)/sup +/ isomeric state in /sup 195/Pb. From an analysis of ..gamma..-..gamma..-t coincidence data and energy sums, 26 transitions were placed in a decay scheme between 23 levels in /sup 199/Bi. On the basis of systematics the population of a (1/2)/sup +/ isomeric state in /sup 199/Bi was deduced. The isomeric (M4) transition to the (9/2)/sup -/ ground state was not observable in the present data; its rate is at least 390 times less than the Weisskopf single particle estimate.

The first saddle-point energies (i.e., the heights of the barriers separating “super-” and “normal-” deformed minima) are calculated as functions of spin and nuclear temperature in a few dozen rare-earth nuclei. Calculations predict systematic growth in the barriers especially at low ( I ∼20) spins when Z decreases , the strongest effect occuring in samarium and neodymium nuclei with 84⪅ N ⪅88. Consequences for observability of superdeformed states are discussed.

The isomeric decays of the 1 2 + shell-model intruder states in 199,201Bi have been investigated. In the case of 201Bi we show that the s 1 2 → h 9 2 isomeric transition is pure M4 within experimental error and is 2200 times slower than any other M4 transition observed in odd-mass nuclei. Its l-forbiddenness and the possibility of an E5 admixture and penetration effects are discussed.

An investigation of a low-frequency anomaly in the moments of inertia of the yrast sequence of /sup 172/Os has been carried out via the /sup 144/Nd( /sup 32/S,4n) reaction using a 162-MeV /sup 32/S beam. Gamma-gamma coincidence information was obtained from a large array of Compton-suppressed Ge detectors. The ordering of the yrast sequence was deduced to be the same as had been previously proposed. Self-consistent cranked shell-model calculations and three-band-mixing calculations have been performed, but show only limited success in explaining the anomaly.

The β-band and the octupole band in 152Gd have been populated up to spin 10+ and 15- respectively in the 150Sm(α, 2n)152Gd reaction. The band structures have been analyzed in terms of rotational frequencies, and it is suggested that the observed downbending effect is due to a considerable difference in the moments of inertia for the excited bands and the ground band.

Recent data on 185 Au indicate that previously published Nilsson ( kappa , mu ) parameter sets for the Au-Pt-Hg region are not able to reproduce either the bandhead energies for the odd-proton configurations or the single-particle structure of the higher-spin states in 185Au. A new set of ( kappa , mu ) parameters are deduced for the N=5 and N=6 proton shells in order to give better agreement between the calculated and experimental results. The Nilsson single-particle orbits obtained using the new ( kappa , mu ) parameters are compared with the Woods-Saxon results for this region.

High-spin states were populated in 185Au via the 170Yb(19F, 4n)185Au reaction. The shape coexistence of both prolate and oblate band structures was observed. In the prolate bands the two-quasiparticle πh 9 2 and νi 13 2 alignment processes are seen to occur at similar frequencies. The upbend observed in 184Pt is then interpreted as resulting from a double crossing involving both of these processes. Strong evidence is presented for the first identification of a low-lying f 7 2 structure in nuclei below lead.

Radioactive sources of /sup 164/Lu were produced in /sup 14/N bombardments of /sup 155/Gd. A helium-jet capillary system was used to transport product nuclei to a shielded area suitable for ..gamma..-ray counting. Both singles and coincidence measurements were made. The half-life of /sup 164/Lu was found to be 3.17 +- 0.03 min, in agreement with earlier measurements. This state in /sup 164/Lu is thought to have a low spin, most probably a value of 2; there is also some evidence for the existence of a high-spin isomer, possibly of shorter half-life, based on weak population of high-spin states in /sup 164/Yb. Fifteen levels were placed in /sup 164/Yb, 12 of them previously unknown. The 2/sup +/ and 3/sup +/ members of the ..gamma.. vibrational band are located at 863.9 and 1004.2 keV; there are also candidates for the 4/sup +/ and 5/sup +/ members. An even-odd shift in the ..gamma.. band, both in level energies and mixing parameters, is observed with a magnitude greater than in the previously studied /sup 166,168/Yb cases. A K = 0 2/sup +/ level is placed at 1073.8 keV, and its effect on the ..gamma.. band is discussed. From an analysis of the population trendsmore » of levels in /sup 164,166,168/Yb from Lu decays, we make arguments concerning the available proton and neutron Nilsson orbitals.« less

Calculations have been performed to explain in a uniform way three recently measured phenomena in the N = 88–90 region: the quenching of signature-splitting in π h 11 2 bands, the reduction of E2 transition rates after the first backbend, and the loss of collective band structure in the I = 30–40 ℏ range. The model incorporates the tendency of high-j quasiparticles to drive the nucleus to triaxial shapes.

Coulomb excitation by $^{4}\mathrm{He}$ ions was studied to deduce the electric quadrupole and hexadecapole reduced transition matrix elements of deformed gadolinium and hafnium nuclei. Our values of $〈{0}^{+}\ensuremath{\parallel}M(E2)\ensuremath{\parallel}{2}^{+}〉$ for $^{154,156,158,160}\mathrm{Gd}$ are 1.962(20), 2.136(7), 2.230(12), and 2.269(14) eb. For $^{176,178,180}\mathrm{Hf}$ they are 2.281, 2.204, and 2.176 eb. The values of $〈{0}^{+}\ensuremath{\parallel}M(E4)\ensuremath{\parallel}{4}^{+}〉$ for $^{156,158,160}\mathrm{Gd}$ are 0.42 \ifmmode\pm\else\textpm\fi{} 0.08, $0.34_{}^{+0.20}{}_{\ensuremath{-}0.22}{}^{}$, and $0.35_{}^{+0.09}{}_{\ensuremath{-}0.07}{}^{}$ e${\mathrm{b}}^{2}$. For $^{176,178,180}\mathrm{Hf}$ they are 0.26 \ifmmode\pm\else\textpm\fi{} 0.12, $0.23_{}^{+0.11}{}_{\ensuremath{-}0.20}{}^{}$, and $0.21_{}^{+0.11}{}_{\ensuremath{-}0.16}{}^{}$ e${\mathrm{b}}^{2}$, if positive values are taken, and -0.76 \ifmmode\pm\else\textpm\fi{} 0.15, -0.67 \ifmmode\pm\else\textpm\fi{} 0.20, and -0.65 \ifmmode\pm\else\textpm\fi{} 0.16 e${\mathrm{b}}^{2}$ if they are negative. We compare our measurements with other experimental values and with theoretical predictions of quadrupole and hexadecapole moments.

Large amplitude collective motion in nuclei is a very fascinating subject for studying the properties of finite quantum systems. Examples include oscillations between coexisting deformed shapes or the interplay of the rotating deformed field and the alignment of individual particles. In the experimental data the related phenomena manifest themselves by the characteristic pattern of level schemes and transition rates as found, for example, in the research on properties of high-spin states. Concerning the theoretical description of those features, the construction of Potential Energy Surfaces (PES) by the Strutinsky shell-correction method or by constrained Hartree-Fock calculations provides a profound background for understanding and interpreting the observed features in a microscopic way. The knowledge of such PES maps gives us detailed information on the statics of the system under study, because they predict the stability of selected quasiparticle configurations which correspond to the minimal points in the potential-energy landscape. The so-called Total Routhian Surfaces [1] describe the spatial deformation of the nuclear density distribution as function of rotational frequency. These are examples of the succesful application of theoretical PES maps and are important for the interpretation of experimental data. However, to describe, in addition, possible transitions between coexisting quasiparticle configurations, one finds it necessary to account for the full dynamics of the collective motion treated for the case of large amplitudes.

Using on-line mass separation $sup 116$I has been identified and its half-life determined to be 2.91 +- 0.15 sec. The activity was produced by the $sup 103$Rh($sup 16$O, 3n)$sup 116$I reaction and by the decay of 57-sec $sup 116$Xe. The $sup 116$I decays primarily to the ground state of $sup 116$Te and also to excited states at 678.9 and 1219.1 keV. From positron measurements, a decay energy of Q/sub E//sub C/ = 7.71 +- 0.20 MeV is assigned to $sup 116$I. $gamma$ rays of 540.2 and 678.9 keV are observed in this decay and are assigned to depopulate levels in $sup 116$Te at 1219.1 and 678.9 keV, respectively. The former is a new level with a probable spin-parity of either 2$sup +$ of 0$sup +$. From the logft values, a spin-parity assignment of 1$sup +$ is deduced for the ground state of $sup 116$I, which is interpreted to have a configuration of $pi$ (d$sub 5$/$sub 2$) $nu$ (d$sub 3$/$sub 2$). A decay energy of Q/sub E//sub C/ =4.34 +- 0.20 MeV observed from activity produced by the $sup 104$Pd + $sup 16$O reaction is assigned to $sup 116$Xe. (AIP)