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Experimental data on energy levels of the odd-odd deformed nucleus180Re obtained from radioactive-decay and heavy-ion reaction studies are analysed to deduce spin-parity and configuration assignments for the six observed rotational bands based on the selection rules for fast beta transitions, criteria for the relative-energy ordering of the triplet and singlet bandheads, two-particle-plus-rotor model calculations including Coriolis mixing, rotational energy systematics involving staggering features, and considerations of gyromagnetic ratios, signature splittings and rotational band alignments.

The level structure of178Hf is interpreted on the basis of the population of the states following178Hf (d, d′),177Hf (d, p) and179Hf (d, t) reactions. Evidence for quadrupole and octupole vibrational bands and unmixed and intermixed two-quasiparticle configurations is presented.

Using a selective fluorination method, mass-separated sources of 228Pa (separated as PaF4+ ions) were used to study the level structure of 224Ac following 2% alpha decay. The levels in 224Ac are interpreted as K=0+or- and K=3+or- parity doublet bands which are explained naturally in reflection asymmetric models. The average energy splittings between the parity doublet bands are 12.7 keV for the K=0+or- bands and 7.3 keV for the K=3+or- bands. These very small splittings are expected because of the additional polarization effects of the two odd particles in 224Ac. It is shown theoretically that the Newby shifts in all odd-odd reflection asymmetric nuclei with K=0+or- bands must have the same absolute magnitude but opposite sign in the strong coupling limit. The experimental Newby shifts in 224Ac approach this theoretical expectation.

A data set of 29 experimentally determined Newby shifts in rare-earth nuclei is examined for the reliability of each values. Using this data set, Newby shifts are obtained which are free from the Coriolis and the particle-particle coupling effects. These new empirical values help resolve the failure of a recently proposed rule for the sign of the Newby shift in the {5/2[413]p − 5/2[642]n} configuration of160Tb and the {5/2[402]p − 5/2[512]n} configuration of174Lu. Also the Newby shifts are significantly modified in two other cases namely the {1/2[411]p − 1/2[521]n} configuration in168Tm and the {1/2[541]p − 1/2[521]n} configuration in172Lu. Only marginal changes are seen in the rest of the cases in the rare-earth nuclei.

The quadrupole moments for collective structures in the odd proton (Z = 59) , and nuclei have been measured using the Doppler-shift attenuation method. New information is presented on the shape-driving behaviour of the [404] proton and [541] (, ) neutron Nilsson configurations. While the involvement of the former orbital leads to quadrupole deformations that are comparable to those observed for the so-called superdeformed bands in this mass region, the values for structures that include the 1/[541] neutron are found to lie intermediate between those observed for normally deformed and superdeformed bands.

Consideration of the expected two-quasiparticle structures and their estimated band head energies, and the selection rules for beta transition rates for the154Nd →154Pm →154Sm decays are used to deduce the configurations for the isomers and the low-spin structures in the neutron rich doubly odd nucleus 61 154 Pm93. The 2.68 m high spin isomer and the 1.73 m low spin isomer are respectively assigned the spin-parity 4+ and 1+ with the configuration {p:5/2− [532↑] +n:3/2− [521↑]} with the 2.68 m isomer lying lower in energy, and thus forming the154Pm ground state. Two-quasiparticle character of the beta-connected states in154Nd decay and154Pm decay is discussed.

It seems that the best opportunity to observe a low-energy 0+ ? 0? M0 transition would be in the most strongly octupole deformed nucleus 224Ac having the known 0? ground state and parity doublet bands with splittings of only ~7 keV. Based on the rigid rotor model fit to available experimental data a 0+ excited state at ~2 keV is suggested and possible mechanisms of the M0 transition to the ground state discussed.

The low lying level structure of 225Ra, studied with the 226Ra(d, t) reaction and 225Fr β-decay, has approximately degenerate K = 12± and K = 32± bands. Hybrid absolute values of the decoupling parameters of the K = 12± bands, intermediate between the theoretical values expected for the pure Nilsson configurations, are deduced and presented as evidence for near-stable octupole deformation in the 225Ra ground state.

Bandcrossing in 31 rotational bands of 25 different odd-A nuclei in the rare-earth region has been analysed by using a two-band mixing formalism with a constant band interaction within the framework of the effective decoupling picture. The interband interaction strengthV between the one-quasiparticle band and the three-quasiparticle band exhibits a variation with the neutron number which is not different from the oscillatory behaviour observed in even-even nuclei and does not show signs of any appreciable phase shifting as predicted by theory. However, the overall range of variation ofV is greater than that observed in even-even systems.

Configuration assignments are derived for the observed energy levels in the odd-odd deformed nucleus170Lu99 based on the calculations of the two-particle band head energies for a zero range residual interaction, the beta-feeding characteristics, and the observed features for similar bands in the neighbouring nuclei. In particular, specific assignments are given for theJπ=1+ levels at 198.4 keV, 349.0 keV and 785.5 keV. The ambiguities with respect to the assignments for theKπ=3− bands are discussed. A new isomer withJπ=7+ and half-life of several seconds is predicted around (225±25) keV and experiments are suggested to identify it.

The low-lying level structures of 190 Os and 192 Os have been investigated by the (t, α) proton pick-up reaction with 15 MeV tritons. In both nuclides this reaction strongly excites the I , K π = 4,4 + levels which were previously interpreted as two-phonon γ-vibrational states. The large two-quasiproton amplitude which seens to be implied by these results is inconsistent with the two-phonon description. However, the cross sections for these states are correctly predicted when the levels are assumed to be hexadecapole vibrations.

Quasi-band structures in nuclei near double closed shells are shown to be well described by the aligned coupling scheme wave functions. This alignment of nucleons in their magnetic substates occurs for nuclei such as 40 Ar, 56 Fe and 41 K which are presented as examples.

Extensive agreement is found between the experimental levels in 28 Si and the combined SU3-Hartree-Fock and the Nilsson-Strutinsky theoretical treatments. Of particular interest is a K = 0 + band representing a third shape with ϵ ∼ 0.45 and γ ∼ 15° which coexists with the previously known oblate and prolate bands. This new band crosses the prolate and oblate bands in the vicinity of J π = 8 + producing a strong backbend.

New high spin states in 25Mg have been located above the neutron threshold using the 12C(14N, pγ)25Mg reaction at E=23.5 MeV. The members of the ground state rotational band (Kπ=52+ have been tentatively identified up to 152+. The yrast 152+ (not a member of the ground state band) and 172+ states have also been tentatively assigned. These results support the interpretation of the new 172+ state and the previously known yrast 132+ state as fully aligned prolate configurations, i.e., prolate particle-hole states with K=I and γ=-120°.

An analysis of the rotational structure of the K = |Ω p − Ω n | bands in the odd-odd nuclei from the rare earth region reveals an odd-even staggering in the level energies. Such an odd-even effect is present, sometimes very prominently, in almost all the K − bands with K values ranging from 1 to 4. We find that complete Coriolis coupling calculations are able to explain most of the staggering in the four nuclei studied. However, the K = 2 + and K = 4 − bands in 182 Re cannot be explained satisfactory.

The level structure of 221Fr has been reinterpreted in terms of the 1 2 ± , 3 2 ± and very tentative higher-lying 3 2 ± parity doublet bands predicted for the 87th proton in an axially symmetric, reflection asymmetric field with ϵ3=0.08. Decoupling parameters of the K= 1 2 ± parity doublet bands are large and of opposite sign and approaching an absolute value of ∼3.8. The alpha decay hindrance factors of states in 221Fr imply anomalously large mixing between the parity mixed Nilsson orbitals with the approach of shell model spectroscopy.

Experimental evidence in 227 Ra is presented for parity-mixed, parity-doublet 3 2 ± and 1 2 ± bands (beginning at the ground state and 120.71 keV respectively) on the one hand, and the parity-unmixed reflection symmetric band 5 2 + [633] (beginning at 1.74 keV) on the other. These coexistent spectroscopies can be explained by an intermediate coupling calculation in which a quasiparticle is coupled to a rotor core which has an intrinsic K =0 reflection asymmetric degree of freedom.

The particle-core coupling mechanism is studied for odd-A nuclei in the transitional region. Basis wave functions are constructed by projecting eigenstates of angular momentum out of deformed intrinsic states. It is shown that the present model becomes identical with the I3ohr-l\1ottelson strong coupling model in the large deformation limit. Energy spectra, B(E2) values and quadrupole moments are calculated for the La-isotopes.

A new potential fit to single particle levels in doubly closed shell nuclei from 16O to 208Pb is presented and the effect of a negative spin-orbit symmetry term on the single particle levels in the superheavy region is discussed.

A systematic analysis of the results of single quasiparticle-plus-rotor bandmixing calculations is presented wherein the empirically noticed characteristic effective decoupling patterns and their systematics in certain odd-A odd-Z rotational bands based onh9/2, d1/2, h 11/2 andg 7/2 orbitals are reproduced. The strategy adopted allows us to obtain an almost unique set of parameter values for a given decoupling pattern. The composition of wavefunctions in terms of core rotational angular momentum supports the idea of effective decoupling. These wavefunctions are then used to analyse the extent and nature of Coriolis coupling in these bands. It is found that either one or both parts of the Coriolis energies, diagonal and non-diagonal, are significant in most of the cases and the non-diagonal part is mainly responsible for the effective decoupling. These Coriolis effects prominently affect the intrabandB(M1) andB(E2) values and their variation with spin is discussed. An unusual feature in theB(M1) value of theh9/2 orbital based band is pointed out.

Octupole deformation has been observed for the first time in the detailed spectroscopy of an odd-odd nucleus in 154Eu. 15 parity doublet bands or band heads are observed including most of the known levels below 600 keV. El transition probabilities are enhanced by ≈ 102 compared to the normal transitions in 154Eu.

The level structure of 223Ra is reinterpreted in terms of two sets of approximately degenerate opposite parity bands with K = 3 2 ± and K = 1 2 ± . Hybrid values of the magnetic moments of the 3 2 ± states and the absolute values of the decoupling parameters are observed and are able to test the changes in Nilsson wave functions resulting from octupole deformation.

The 176 Lu(t, p) 178 Lu reaction shows two levels, at 98±40 and 1329±40 KeV, which are strongly populated by L = 0 transitions. The ratio of intensities for these two states is 0.85. This is larger than any comparable ratio of two-neutron transfer strengths in the rare-earth or actinide regions of deformation. Yet the cross sections are nearly a factor of two smaller than cross sections for comparable states in even-even nuclei. The explanation of our results requires a detailed analysis of both the shape and pairing degrees of freedom.

The reanalysis of all the experimental data on 225 Ra demonstrates the coexistence of reflection asymmetry and reflection symmetry in this nucleus. In 225 Ra as well as 227 Ra and 229 Th this phenomenon can be explained by the calculated ability of the odd particle in different orbitals to polarise the soft nuclear shapes toward smaller and larger octupole deformations.

Eigenvalues for the harmonic oscillator without l · s or l 2 terms suggest a deformed shell structure for nuclei with axes ratios 2 : 1 and deformation ϵ = 0.6 with corresponding nucleon “magic numbers” 2, 4, 10, 16, 28, 40, 60, 80 110 and 140, subject to small modifications due to spin-orbit and other correction terms. Experimental evidence of reasonably stable highly deformed structures corresponding to nucleon numbers 16, 20, 28, 40 and 60 (64) is presented. Attempts to calculate the corresponding potential energy surfaces using the Strutinsky shell correction method are described.

The energies of, and transition probabilities involving, the ground-state rotation bands of ${\mathrm{Os}}^{186}$, ${\mathrm{Os}}^{188}$, and ${\mathrm{Os}}^{190}$ are compared with a diagonalized rotation-vibration theory in which vibrations are considered to three phonon order. Agreement even in the Os transition region is found to be excellent. The theory appears to be particularly successful in predicting two phonon states in ${\mathrm{Os}}^{190}$.

The anomalous behavior of the rotational motion in high spin states of deformed nuclei is ascribed to a combination of both Coriolis-anti-pairing (CAP) and hybridization of decoupled band (HDB). Calculations suggest that the CAP effect should be most important for light nuclei, the HDB effect for actinide nuclei while the two effects should compete in the nuclear region 100 ⩽ A ⩽ 190.

Predictions for spontaneous and neutron-induced fission, alpha and beta decay have been made on the basis of potential-energy surfaces for Z ⩾ 90 nuclei on the neutron-rich side of the beta stability line. In spite of their considerable quantitive uncertainties, these predictions appear to negate the possibility of superheavy element synthesis via a one- or two-step r-process from super novae. In addition artificial superheavy element synthesis by two consecutive exploding nuclear devices appears improbable from these results. Neutron induced fission seems to be even more decisive than spontaneous fission for the early termination of the r-process.

The decoupled bands of the odd-A La-isotopes are described by the angular momentum projection method. The coherent phonon state is assumed for the intrinsic wave function of the core. The present model covers the particle-vibrator and the particle-rotor coupling model. The results are in good agreement with the experimental energy spectra.

Ground state moments of inertia and collective gyromagnetic ratios of deformed even nuclei with 50

Calculations of the quadrupole (ϵ2)- octupole (ϵ3(ϵ5)) potential energy surface for nuclei beyond 208Pb indicates the presence of a very low lying secondary minimum in the oblate octupole region of deformation for certain nuclei. The well-known low-lying K = 0− bands in the RaTh region are interpreted as associated with this secondary minimum.

The band structure and mechanism of formation of odd- A decoupled rotational bands are studied using the weak coupling model of de-Shalit. The geometrical relation between the spin of the core and the particle can be shown explicitly because of the fact that the interaction matrix elements are written in terms of the angle between these two spins. This scheme is shown to be a good representation in describing decoupled bands and to have wave functions with large overlaps with those resulting from the coupling scheme introduced by Stephens.

Half-life measurements show that the lowest high-j state in 141Ce, 143Nd, 145Sm, and 147Gd, earlier assigned as an h9/2 fragment, is an i13/2 single-neutron excitation which previously was thought to lie above 3 MeV in the N = 83 nuclei.

A combination of two different potential systems involving prolate deformations is proposed to explain the intensity and energy systematics of the Nilsson states populated in 155, 157, 159 Gd by (d, p) and (d, t) reactions. In the group of states associated with the more nearly spherical potential,the absence of regular rotational patterns is attributed to the mixing of principal harmonic oscillator shells and to severe Coriolis coupling.

A s-transition with a log ft value of 9.9 has been observed between the 188 W 0 + ground state and a 0 + state at 207.9 keV in 188 Re. This highly forbidden Fermi transition can be quantitatively interpreted in terms of the mixing of the isobaric analog state of the 188 W ground state into the 188 Re ⦅π 9− 2 [514↑] − ν 9− 2 [505↓]⦆0 + state.

The intensity systematics of a series of states strongly populated in the (d,t) reaction in 91, 93, 95 and 97 neutron species in Gd, Dy and Er nuclei, as well as other information, requires considerable mixing of the 32+[651] and 32+[402] orbitals. In the case of 155Gd this ΔN = 2 mixing of states from different principal harmonic-oscillator shells results in a spliting of 162 keV between the two 32+ states. This splitting is much larger than that predicted by the Nilsson model.

A new mode associated with a high momentum transfer field is investigated. The lowest collective mode involves configurations in which the difference in principal quantum numbers, ΔN , between the components of the configurations is two.

The triaxial harmonic oscillator is found to be associated with a shell gap for nuclean number 8 corresponding to oscillator frequency ratios 3:2:1 and a deformation γ = 30°, ϵ = 0.87. The experimental positive-parity spectrum of 16O is interpreted in terms of an anharmonic ground state vibrational spectrum on which is superimposed 3:2:1 triaxial bands. The moment of inertia of the latter are found to agree well with expectations. There is also empirical evidence for an extremely deformed band at about 17 MeV, that might be associated with a 4:1 shell structure.

The low-lying energy levels of 106 Ru have been investigated with the 104 Ru(t, p) 106 Ru reaction at 15 MeV bombarding energy. Spins and parities were obtained from the measured angular distributions. The energy levels are discussed in terms of the phonon and rotational models and 106 Ru is found to be of transitional character between these limits.

The spectroscopies of 190 and 21 Ne (both eleven-neutron systems) are compared. The 1-+ [211 iJ, t+ [220il and t- [lOttl bands are observed in both nuclei. On the basis of these similarities 190 is assumed to be a prolate rotor like 21 Ne. If then the recently studied IBN ground state is also considered to be a deformed system (a one-proton hole in the 190 nucleus), both the 1- ground state spin and the sudden change in the systematics of the two-neutron binding energies can be understood.