The lifetimes of three low-lying states in the superdeformed (SD) yrast band of ${}^{194}$Hg were measured applying the recoil-distance Doppler-shift method. As the deduced transition quadrupole moments $Q_t$ are equal within the experimental uncertainties to those extracted from a Doppler-shift attenuation method (DSAM) measurement for the high-lying states of the band, the assumption that the decay out of SD bands does not strongly affect the structure of the corresponding states is corroborated. By a simple mixing model, the decay can be described assuming a very small admixture of normal-deformed (ND) states to the decaying SD states. The deduced ND mixing amplitudes for the yrast SD bands in ${}^{192,194}$Hg and ${}^{194}$Pb are presented along with average transition quadrupole moments for the lower parts of the excited SD bands in ${}^{194}$Hg.

The low energy octupole states in ${}^{134}$Ba were examined using the inelastic scattering of 22 MeV protons. Strong fragmentation of the low energy octupole strength, which was observed in ${}^{196,198}$Pt and was identified as a signature of the O(6) dynamical symmetry limit of the interacting boson approximation (IBA), does not occur in ${}^{134}$Ba, which has been proposed to have O(6) structure. The model calculations demonstrate that there is, in fact, little difference in the structure of the low-lying positive parity levels between certain nuclei in a U(5)$\to$SU(3) (vibrator$\to$rotor) transition and an O(6) nucleus $(\gamma$-soft nucleus), but that the octupole fragmentation has an enhanced sensitivity to the $d$-boson composition of the wave functions and thereby reveals differences in structure that are not easily discernible with other observables.

The fusion-fission process in heavy systems is analyzed by the Smoluchowski equation with the finite-range droplet model potential of no pocket and the temperature-dependent shell correction energy which generates the pocket around the spherical shape. The evaporation residue cross sections of superheavy elements have been shown to have an optimum value at a certain initial temperature, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature.

An analytical solution of the self-consistent Vlasov equation is presented. The time evolution is entirely determined by the initial distribution function. The largest Lyapunov exponent is calculated analytically. For special parameters of the potential a positive Lyapunov exponent is possible. This model may serve as a check for numerical codes solving self-consistent Vlasov equations. The here presented method is also applicable for any system with an analytical solution of the Hamilton equation for the form factor of the potential.

A physical prescription to improve the accuracy of few-body Glauber model calculations of reactions involving loosely bound projectiles is presented in which the eikonal phase shift function of each projectile constituent is modified to account for curvature of its trajectory. Noneikonal effects due to both nuclear and Coulomb interactions are treated on an equal footing. The proposed method is assessed quantitatively by comparison with full quantum mechanical calculations in the case of ${}^{11}$Be+${}^{12}$C elastic scattering, treated as a three-body ${}^{10}$Be+$n$+target problem, at energies of 25 and 49.3 MeV/nucleon. Calculated cross-section angular distributions which include the noneikonal modifications are shown to be accurate to larger scattering angles, and for lower incident projectile energies.

The contribution to the optical potential from the breakup reaction $(\alpha {-}^3$He) in the elastic scattering of 172 MeV $\alpha$ particles from ${}^{62}$Ni is investigated in a phenomenological fashion. A breakup part of the optical potential is introduced and the partial wave amplitudes of this part are compared with published values of the breakup probabilities for this reaction.

Second minimum structures have been observed for the first time in the doubly odd nucleus ${}_{59}^{132}$Pr. Two new bands are interpreted as based on the $\pi g_{9/2}\left[404\right]9/2\otimes \nu i_{13/2}\left[660\right]1/2$ configuration and a third as the $\pi h_{11/2}\left[532\right]5/2\otimes \nu i_{13/2}\left[660\right]1/2$ configuration. Signature splitting effects observed in the $\pi {(g}_{9/2}{)}^{-1}$ bands provide new information regarding the positive parity proton orbitals at large deformation. Results from the extracted $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios are consistent with a large deformation for the $\pi {(g}_{9/2}{)}^{-1}$ bands.

The resolution of reaction filters for intermediate-energy heavy-ion collisions based upon charged-particle and neutron multiplicity measurements with 4π coverage is compared for ${}^{112}\mathrm{Sn}{+}^{112}\mathrm{Sn}$ and ${}^{124}{\mathrm{S}\mathrm{n}+}^{124}\mathrm{Sn}$ collisions at $E/A=40\mathrm{}$ MeV. The quality of event characterization is inferred from the azimuthal correlations of α particles emitted at intermediate rapidity and from the Z distributions of projectilelike fragments emitted at forward angles. For central and midimpact parameter collisions, the associated charged-particle multiplicity appears to provide better impact-parameter selection than the associated neutron multiplicity.

Recently measured fission fragment angular anisotropies for the reaction ${}^{12}$C + ${}^{232}$Th show unusual behavior compared to other reactions of ${}^{12}$C, ${}^{16}$O, and ${}^{19}$F on actinide targets at energies below the fusion barrier. As a result, doubts have been raised about the hypothesis that large sub-barrier anisotropies are due to the occurrence of quasifission when the projectiles collide with the tips of the deformed actinide target nuclei. To investigate this inconsistency, fission fragment angular distributions for this reaction were measured to high precision in the bombarding energy range 57–75 MeV. Fission following transfer reactions was identified and rejected at all angles using the deduced velocity vector of the fissioning nuclei. Cross sections and anisotropies for full momentum transfer fission were determined, and the fusion barrier distribution was extracted. These data support the interpretation that the dependence of the competition between quasifission and fusion fission on the orientation of the deformed actinide nucleus can explain the large sub-barrier anisotropies.

The octupole characteristics of excited SD bands in ${}^{190,192,194}$Hg are discussed. In particular we show that for ${}^{194}$Hg, the odd spin sequence is favored at lower spins—in agreement with the assumption these bands contain significant octupole character. The data are compared with a model in which $K$=2 octupole vibrations are predicted to be favored at the low frequencies.

Angular distributions of the analyzing powers ${\mathrm{iT}}_{11},$ $T_{20},$ and $T_{22}$ for ${}^1\mathrm{H}(d\to ,\gamma {)}^3\mathrm{He}$ at $40<~E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~110$ keV and the angular distribution of the analyzing power $A_y$ for ${}^2\mathrm{H}(p\to ,\gamma {)}^3\mathrm{He}$ at $70<~E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~210$ keV have been measured for the first time. In addition, absolute differential cross sections for proton-deuteron capture have been determined for $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=$ 75, 108, 133, and 173 keV. Thick ice or heavy ice targets and two large-volume, high-purity Ge $\gamma$-ray detectors were used. Results are in general agreement with an exact three-body calculation utilizing a realistic nucleon-nucleon potential. The vector-polarization observables are found to be especially sensitive to meson-exchange-current effects. The extracted $S\left(0\right)\mathrm{}$ value for proton-deuteron capture is $\sim 25\%$ lower than that presently used in astrophysical calculations. An expression for the thermonuclear reaction rate below 10 GK is given.

Measurements of the $\mathrm{pp}$ spin correlation coefficients $A_{\mathrm{xx}},$ $A_{\mathrm{yy}},$ and $A_{\mathrm{xz}}$ and analyzing power $A_y$ for $\mathrm{pp}$ elastic scattering at 197.8 MeV over the angular range $4.5°$–$17.5°$ have been carried out. The statistical accuracy is approximately $\pm 0.01$ for $A_{\mathrm{mn}}$ and $\pm 0.004$ for $A_y,$ while the corresponding scale factor uncertainties are 2.4% and 1.3%, respectively. The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring (IUCF Cooler) and a circulating beam of polarized protons. The target polarization $\mathrm{}(Q=0.79\mathrm{})\mathrm{}$ is switched in sign and in direction $\mathrm{}(x,y,z)\mathrm{}$ every 2 s by reversing a weak guide field (about 0.3 mT). The forward-scattered protons are detected in two sets of wire chambers and a scintillator, while recoil protons are detected in coincidence with the forward protons by silicon strip detectors placed 5 cm from the proton beam. The background rate from scattering by the walls of the target cell is $(0.2\mathrm{}\pm 0.2)$% of the good event rate. Analysis methods and comparisons with $\mathrm{pp}$ potential models and $\mathrm{pp}$ partial wave analyses are described.

We provide a unified description of (i) scalar-isoscalar exchange in the nucleon-nucleon interaction, (ii) the pion-nucleon sigma term, and (iii) the scalar form factor of the nucleon. Our analysis requires that we specify a parameter that appears in the description of a nucleon valence-quark “core.” Other parameters are fixed either by our analysis of the Nambu–Jona-Lasinio model, or with reference to a recent lattice simulation of QCD in which the scalar form factor of the nucleon was calculated. We find that our model has some predictive power. Once the parameters are fixed, we find that we reproduce the values of the scalar form factor of the nucleon, as determined in the lattice simulation. We also predict the strength of the scalar-isoscalar NN potential for the particular one-boson-exchange model considered here, where the effects of (virtual) Δ excitation are treated in an explicit fashion. However, the overall strength of the force obtained in this work is sensitive to the approximations used in the calculation.

An isomer with a half-life of 6$\pm$1 $\mu$s has been observed in the $N=74\mathrm{}$ nucleus ${}^{138}$Gd, populated following the reaction ${}^{106}$Cd${(}^{35}$Cl,${p2n)}^{138}$Gd. The isomer decays via a 583 keV $E1\mathrm{}$ transition with a hindrance per degree of $K$ forbiddenness, $f_{\nu }$=24. This value is similar to the values measured for the $N=74\mathrm{}$ isotones ${}^{134}$Nd and ${}^{136}$Sm but markedly different from that measured for ${}^{130}$Ba. This suggests that there is some change in structure across the $N=74\mathrm{}$ isotones and possible explanations of this feature are discussed.

Inelastic ${\pi }^{\pm }$ differential cross-section measurements at a pion incident energy of 162 MeV were made for 12 ${(f}_{7/2}^{}{d}_{5/2}^{}-1)$ 6${}^{-}$ states in ${}^{32}$S, including four tentative new isoscalar states. Isoscalar and isovector magnetic structure coefficients were determined for each state by combining the pion data with previous electron scattering data. The trend of small isoscalar/isovector strength ratios continues in ${}^{32}$S, with the isovector strength being comparable to theoretical calculations, but the isoscalar strength exhausting only about 17% of an extreme-single-particle-hole model. However, this isoscalar strength is larger than that observed in other $\mathrm{sd}$-shell nuclei and exhausts 75% of large-basis shell-model predictions. The substantial fragmentation of the 6${}^{-}$ isovector strength observed in ${}^{32}$S electron scattering, but not previously observed in other self-conjugate nuclei, appears to extend to the isoscalar strength and to include substantial isospin mixing. The general systematics of isoscalar and isovector stretched state transition strengths are reviewed.

We measured ${}^{36}$Ar$(p\to {,p}_0)$ cross sections and analyzing powers for $E_p$ between 3.22 and 5.98 MeV, and used these data to deduce spin, parity, and widths of 17 levels in ${}^{37}$K. Our results, combined with existing information on ${}^{37}$Ca ${\beta }^{+}$ decay, yield information on the distribution of Fermi and Gamow-Teller strength in this decay. A $T=1/2\mathrm{}$ level lying 31 keV below the $J^{\pi }{=3/2\mathrm{}}^{+}$, $T=3/2\mathrm{}$ analog of the ${}^{37}$Ca ground state was found to have $J^{\pi }{=3/2\mathrm{}}^{+}$. The relative proton widths of the two levels imply an isospin-mixing matrix-element of $4.84\pm 0.43$ keV. This agrees with the value ${5.93}_{-0.65}^{+0.23\mathrm{}}$ keV extracted from the ${\beta }^{+}$-decay intensities to the two levels, plus the Gamow-Teller to Fermi strength ratio for the 5018 keV level. We decompose the Gamow-Teller strength in ${}^{37}$Ca decay into components feeding daughter levels with $J^{\pi }{=1/2\mathrm{}}^{+}$, ${3/2}^{+}$, or ${5/2}^{+}$, and compare the results to theory. None of the available shell-model calculations gives a satisfactory account of the data.

Lifetime measurements on the $i_{13/2}$ band built on the proton configuration ${1/2}^{+}\left[660\right]$ in ${}^{173}\mathrm{Re}$ have been carried out by the Doppler-broadened line shape method with the use of the GAMMASPHERE array in an early-implementation arrangement. Lifetimes of the stretched $E2\mathrm{}$ transitions from states of spin ${41/2}^{+}–{69/2}^{+}$ in this band were measured, and the transition quadrupole moments calculated from these lifetimes are consistent (average $Q_t=8.1\mathrm{}\pm 0.5e\mathrm{b})$ with a large and near-constant deformation $({\beta }_2\approx 0.29)$ over the frequency range of $ħ\omega =0.29\mathrm{}$–0.47 MeV. This result attests to the strong deformation-driving effect of the intruder $\pi i_{13/2}$ orbital when it lies just above the Fermi surface. From thin-target measurements, it was possible to add three new levels to this band and to determine that the experimental aligned angular momenta gradually evolve over a large frequency range and level off with a total gain characteristic of alignment by $i_{13/2}$ neutrons. Calculations carried out for diabatic configurations give a satisfactory accounting of the alignment gain. However, because of the large interaction between crossing bands, a more meaningful description of the deformation pattern in this band was achieved through calculations of the spin-adiabatic type. Both calculations are discussed and compared with the experimental results.