A calculational procedure based on the Huizenga-Vandenbosch formalism for the determination of isomer ratios has been developed which is applicable also at low primary excitation energies of the residual nuclei, in contrast to earlier methods. This has been accomplished by introducing level densities which are based on the shell-model level calculations of Hillman and Grover rather than a level-density formula. Furthermore, the assumption that all the neutrons are emitted with the average energy $2T$ (where $T$ is the nuclear temperature) has been replaced by a more realistic neutron spectrum. In order to test this procedure, the isomer ratio of ${\mathrm{Y}}^{87}$ from the photonuclear reaction ${\mathrm{Y}}^{89}(\gamma ,2n)$, which has its reaction threshold at 20.8 MeV, was measured for bremsstrahlung of end-point energies 23, 25.6, 28.6, and 50 MeV. The results of our method are in much better agreement with the experiment than the original Huizenga-Vandenbosch approach. The analysis indicates that a relatively large fraction of the product nuclei is formed directly in the ground state and that quandrupole transitions are an important decay mode near the threshold.

The strongly deformed even-even nuclei ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ and ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$ have been studied using the reactions ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}\mathrm{}(d,t)\mathrm{}{}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ and ${}_{}{}^{179}{}_{}{}^{}\mathrm{Hf}\mathrm{}(d,p)\mathrm{}{}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$. These reactions were performed at 12- and 14-MeV incident energy on the Florida State University super FN tandem Van de Graaff accelerator with the outgoing particles analyzed by means of a Browne-Buechner-type broad-range magnetic spectrograph. 25 states associated with two-quasiparticle rotational bands have been identified or tentatively identified in these nuclei; included are the intrinsic band heads $6^{+}$[514↓ + 512↑], $3^{+}$[514↓ - 521↓], $4^{+}$[514↓ + 521↓], and $6^{+}$[514↓ + 523↓] in ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ and the intrinsic band heads $4^{-}$[624↑ - 510↑], $5^{-}$[624↑ + 510↑], $6^{-}$[624↑ + 512↓], and $8^{-}$[624↑ + 503↑] in ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$. Coriolis-mixing calculations have been an important factor in making the state assignments.

The reactions ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}\mathrm{}(d,p)\mathrm{}$ and ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}\mathrm{}(d,t)\mathrm{}$ at an incident deuteron energy of 12.6 MeV have been investigated with an energy resolution of about 16 keV, and excitation functions for the reactions ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}(p,p_0)$ and ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}(p,p_1)$ have been measured from 9.5- to 12-MeV incident proton energies. The analysis of the analog resonances observed in the excitation functions is compared with the results of the ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}\mathrm{}(d,p)\mathrm{}$ experiment.

The ground-state wave function for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ has been calculated in the basis of 176 configurations containing all $2\hslash \omega$ excitations in addition to the doubly-closed-shell configuration. The ground state is found to be in the closed-shell configuration about 70% of the time. The rest of the intensity is highly fractionated over many of the basis configurations. The ground state is found to lie about 10 MeV lower in energy than the pure closed-shell configuration.

Nuclear levels in ${}_{}{}^{188}{}_{}{}^{}\mathrm{Re}$ have been investigated using the following experimental techniques: measurement of neutron-capture $\gamma$-ray transitions with energies between 4.8 and 6.0 MeV using a Ge(Li) pair spectrometer; study of ($d,p$) spectra using 12-MeV deuterons and a broad-range magnetic spectrograph; measurement of ($n,\gamma$) spectra between 45 and 830 keV with a bent-crystal spectrometer; coincidence studies of the ($n,\gamma$) radiation using two Ge(Li) detectors, including a study of short-lived isomeric states using delayed-coincidence techniques; and observation of the $\gamma$ rays following $\beta$ decay of ${}_{}{}^{188}{}_{}{}^{}\mathrm{W}$ using a Ge(Li) detector. A nuclear level scheme for ${}_{}{}^{188}{}_{}{}^{}\mathrm{Re}$ has been constructed by combining the results of the above measurements with published data. Information, including spin and parity assignments, is presented on 36 low-lying levels. The lifetimes of five excited states are reported. The Nilsson model has been used to interpret the level structure. Assignments are proposed which involve 15 separate rotational bands. Proposed Nilsson configurations, band-head energies, and band-head lifetimes (if known) are: $1^{-}$[402↑ - 512↓], 0.0 keV; $3^{-}$[402↑ + 510↑], 169.4 keV; $6^{-}$[402↑ + 503↑], 172.1 keV, 19 min; $4^{-}$[402↑ + 512↑], 182.7 keV, 18 nsec; $2^{-}$[402↑ - 505↓], 205.3 keV, 3.2 nsec; $0^{+}$[514↑ - 505↓], 207.9 keV, 3.2 nsec; $3^{+}$[514↑ - 512↓], 230.9 keV, 21 nsec; $2^{-}$[402↑ - 510↑], 256.9 keV; $1^{-}$[402↑ + 503↑], 290.7 keV; $4^{-}$[402↑ + 501↑], 325.9 keV; $5^{+}$[514↑ + 510↑], 360.9 keV, 5.2 nsec; $3^{+}$[402↑ - 615↑], 439.7 keV; $1^{+}$[514↑ - 503↑], 482.2 keV; $1^{-}$[402↑ - 501↑], 556.8 keV. A $K^{\pi }=1^{-}$ band, believed to be predominantly a $\mathrm{}|K-2\mathrm{}|\mathrm{}$ $\gamma$-vibrational band, is observed at 582.2 keV. The measured ($d,p$) reaction cross sections are compared with theoretical calculations based on these assignments. The $\beta$-decay measurements have revealed a previously unknown $\beta$ branch from the ${}_{}{}^{188}{}_{}{}^{}\mathrm{W}$ ground state to a $I^{\pi }=0^{+}$ level at 207.9 keV. This $0^{+}$ → $0^{+}$ transition ($logft=9.9\mathrm{}$) is discussed in terms of isobaric analog state mixing. Results of a calculation which uses a parametrized residual neutron-proton interaction to predict the parallel-antiparallel splitting energies and $K=0\mathrm{}$ even-odd shifts in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Re}$ and ${}_{}{}^{188}{}_{}{}^{}\mathrm{Re}$ are presented and compared with experiment.

The angular correlations of $\gamma$ rays from ($d,p\gamma$) reactions with 3-MeV deuterons to states in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{53}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Fe}$ have been measured utilizing a collinear geometry and a Ge(Li) $\gamma$-ray detector. This study was undertaken in an attempt to resolve conflicts in spin assignments between vector-analyzing-power measurements and other measurements. Results indicate $J=\frac{1}{2}$ for the 3618-keV level in ${}_{}{}^{53}{}_{}{}^{}\mathrm{Cr}$ and the 3788-keV level in ${}_{}{}^{55}{}_{}{}^{}\mathrm{Fe}$ in agreement with the vector-analyzing-power measurements. The conflict is not resolved in the case of the 3614-keV level in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$. There is a strong possibility that there are two unresolved levels in this region, one with $J=\frac{1}{2}$ and the other with $J=\frac{3}{2}$.

Isomeric cross-section ratios are measured for eight ($n,\gamma$) reactions on the target nuclei ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{79}{}_{}{}^{}\mathrm{Br}$, ${}_{}{}^{80}{}_{}{}^{}\mathrm{Se}$, ${}_{}{}^{85}{}_{}{}^{}\mathrm{Rb}$, ${}_{}{}^{103}{}_{}{}^{}\mathrm{Rh}$, ${}_{}{}^{121}{}_{}{}^{}\mathrm{Sb}$, ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$, and ${}_{}{}^{164}{}_{}{}^{}\mathrm{Dy}$ at an incident neutron energy of 25 ± 5 keV. These ratios are theoretically calculated using two models, viz., (1) the Huizenga-Vandenbosch model and (2) the $\gamma$-ray cascade model of Ponitz. A comparison of the experimental and theoretical ratios shows that the experimental values agree better with the predictions of the Ponitz model than with those of the Huizenga-Vandenbosch model. It is also observed that, on the basis of Ponitz model, the amounts of quadrupole admixtures required to reproduce experimental isomer ratios are in the range 1-25%. The present estimates of the quadrupole admixtures are in line with previous observations made at thermal energies.

The (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$) four-nucleon-transfer reaction has been performed on a ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ target using the 46-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ beam of the FN tandem Van de Graaff at Saclay. The study of the reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{F}\mathrm{e}-$ (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ shows that the four-nucleon transfer occurs via a direct surface reaction, well described by the quasielastic process formalism due to Frahn and Venter, which is based on the diffractional model. The transfer-reaction cross sections are peaked at the grazing angle where the elastic scattering begins to deviate from the pure Rutherford law. A distorted-wave Born-approximation investigation of nuclear properties of levels reached by (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$) four-nucleon transfer has been performed using the SETILL code based on the generator-coordinate framework. The $Q$-value dependence of the cross section, as well as the configuration mixing effects, has been estimated. The cases of other $1f-2p$-shell nuclei have been also investigated.

The reaction ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}\mathrm{}(p,t)\mathrm{}{}_{}{}^{139}{}_{}{}^{}\mathrm{Pr}$ at 40 MeV strongly populates collective states in the residual nucleus. The shapes of the angular distributions, taken at 5° intervals between 15 and 65°, show the inadequacies even of finite-range, two-nucleon-pickup distorted-wave Born-approximation calculations and the need for inclusion of higher-order effects.

We explore the superheavy region, using a recent two-body interaction which yields, in the Hartree-Fock framework, very good radii and good binding energies for known spherical nuclei, and also a well-ordered occupied ${\mathrm{Pb}}^{208}$ spectrum near the Fermi surface. A strong shell effect is found for elements ${114}_{184}^{298}$ and ${120}_{184}^{304}$ and a less pronounced one for ${114}_{196}^{310}$, ${114}_{228}^{342}$, ${120}_{196}^{316}$, and ${120}_{228}^{348}$. Their spectra do not lead to allowed $\beta$ transitions, and for $\alpha$ decay, ${114}_{184}^{298}$ is favored over all others except ${114}_{228}^{342}$. However, the former exhibits a greater binding energy per particle and is closer to the $\beta$-stability line predicted by the semiempirical formula.

Angular distributions of 166-MeV $\alpha$ particles scattered from the Sn isotopes 116, 118, 120, and 124 have been measured. An analysis of the elastic scattering data was performed using an optical potential calculated from an effective interaction between the $\alpha$ particle and a nuclear-matter distribution. The variation of nuclear sizes among the isotopes is considered. Assuming charge densities derived from the results of elastic electron scattering and/or mesonic atom data, values of neutron-matter radii for the tin isotopes are deduced which agree well with theoretical values. An analysis of the inelastic $\alpha$-particle scattering to the first $2^{+}$ and $3^{-}$ levels for each isotope was effected using the optical potentials calculated from the elastic scattering, the distorted-wave Born-approximation, and quasiparticle wave functions for the excited states. Electromagnetic transition rates and form factors for electron scattering were calculated with the same wave functions, and a comparison of the calculations to the experimental results provides information about the proton and neutron configurations in these isotopes.

Double ionization of the $K$ shell has been studied in the electron capture decays of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Cs}$ and ${}_{}{}^{165}{}_{}{}^{}\mathrm{Er}$ by recording coincidences between $K$ x rays emitted when the double vacancies are filled. A Si(Li) x-ray detector was used in conjunction with a NaI(T1) detector for these measurements. The results obtained for $P_{\mathrm{KK}}$, the probability per $K$ capture that a double $K$-shell vacancy is formed, were (1.33 ± 0.33) × ${10}^{-5\mathrm{}}$ for ${}_{}{}^{131}{}_{}{}^{}\mathrm{Cs}$ and (6.7 ± 3.9) × for ${}_{}{}^{165}{}_{}{}^{}\mathrm{Er}$. Both of these values are a factor of 2 smaller than previous measurements and, within the experimental uncertainties, are in agreement with predictions based on the relativistic theory of Intemann.

Measurements of the total thick-target yields of $\gamma$ rays deexciting the first $2^{+}$ excited states of ${\mathrm{Os}}^{192,190,188,186,184}$ following Coulomb excitation by helium, oxygen, and sulfur ions have been made. These measurements were compared with theoretically calculated yields in order to extract linear combinations of the static electric quadrupole moments of the $2^{+}$ states. The results were compared with the measurements of Pryor and Saladin of the absolute moments of ${\mathrm{Os}}^{192,190,188}$ in order to obtain the best combined values for these three isotopes, as well as absolute values for ${\mathrm{Os}}^{186,184}$. These values are -0.50 ± 0.20, -0.95 ± 0.19, -1.32 ± 0.43, -1.47 ± 0.54, and -2.4 ± 1.1, respectively. For the isotopes ${\mathrm{Os}}^{192,190,188,186}$ the $B(E2,0^{+}\to 2^{+})$ values determined in the experiment agree with published values to within 10%. The $B(E2,0^{+}\to 2^{+})$ value of ${\mathrm{Os}}^{184}$ was previously unknown and was determined to be 3.20 ± 0.62 ${\mathit{e}}^2$${\mathit{b}}^2$. The results are also compared with the model calculations of Kumar and Baranger and found to be in good agreement.

The fractional and independent fission yields of krypton isotopes (masses 87 to 94) and xenon isotopes (masses 137-143) produced in thermal-neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ were measured using a mass separator operating in an on-line mode with a fission source exposed to time-controlled neutron fluxes. The noble-gas isotopes were collected simultaneously at given times and each mass was measured separately. The distribution of the isotopic yields of each element was found to be Gaussian, in general agreement with Wahl's estimates. The total independent yields of krypton and xenon, as well as their complementary elements, barium and strontium, were found to indicate an odd-even effect in the element yield distribution. Even-$Z$ elements are formed in higher yields than their odd-$Z$ neighbors (20-50% higher); the even-$Z$ yields are also higher than Wahl's "normal" element yields (∼12% higher for Kr and Ba and ∼40% for Xe and Sr). Half-life values of 20 nuclides produced in the decay of krypton and xenon isotopes were measured as well.

The decay of ${}_{}{}^{162}{}_{}{}^{}\mathrm{Yb}$ was studied with samples produced by irradiating ${}_{}{}^{164}{}_{}{}^{}\mathrm{Er}$ with 52-MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ions. Mass separation of the irradiated samples provided isotopically pure ${}_{}{}^{162}{}_{}{}^{}\mathrm{Yb}$ samples for half-life and $\gamma$-ray spectra measurements. Three $\gamma$ rays (44-, 118-, and 162-keV in energy) as well as the Tm $K$ x rays were observed and the half-life of ${}_{}{}^{162}{}_{}{}^{}\mathrm{Yb}$ was determined to be 18.87 ± 0.19 min. The latter two $\gamma$ rays were found only in coincidence with Tm $K$ x rays but not with each other. From the growth and decay of the 102-keV $\gamma$ ray of ${}_{}{}^{162}{}_{}{}^{}\mathrm{Tm}$ in these same samples, the abundances of the three $\gamma$ rays and the Tm $K{\alpha }_1$ x ray were determined.

Nonelastic interactions corresponding to continuum-state transitions are calculated using the intranuclear-cascade evaporation approach. Spallation yields, energy- and angle-dependent spectra, particle multiplicities, and nonelastic cross sections are calculated for incident nucleons and $\pi$ mesons with energies below 3 GeV on complex nuclei. Comparisons with experimental data are made and, in general, the agreement is good. Discrepancies in these comparisons are discussed with respect to the deficiencies in the model.

The intranuclear-cascade codes recently discussed by Bertini were modified to include fission-spallation competition in the heavy elements during the evaporation phase of the reaction, and use an empirical, energy-independent relation for ($\frac{{\Gamma }_n}{{\Gamma }_f}$). Calculations of the reactions of protons with ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at several energies from 0.15 to 3.0 GeV, and with ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ at 0.7 GeV, have been done to illustrate the results that are obtainable with these codes. The calculations do not allow any adjustment of parameters. However, the range of applicability of the calculations, especially their extension to nuclei (with $Z\lesssim 91$) that are not very fissionable, was investigated by means of the parameter $Z_f$, below which fission was taken to be relatively unimportant. A $Z_f$ value of 91 was found to give results that agreed best with experimental data. In general, comparison with a large collection of experimental spallation yields, total fission cross sections, and particle multiplicities indicated that the calculations are able to reproduce the trends, and often the details, exhibited by the data. In the case of neutron multiplicities, only the calculations without fission effects agreed with the data, indicating that it is the energy available for evaporation, and not the fission competition, that influences neutron emission.

The 8.998-MeV resonance level excited by the ($\gamma ,{\gamma }^{\prime }$) reaction, which was previously assigned to ${}_{}{}^{150}{}_{}{}^{}\mathrm{Sm}$, is shown to belong to ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$. The level scheme of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ is given and the re-evaluated level parameters of the 8.998-MeV resonance are presented.

A simplified Hauser-Feshbach treatment of angular distributions of the ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}\mathrm{}(p,t)\mathrm{}{}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ reaction populating levels in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ up to 7.59-MeV excitation energy yields good agreement with the data for several of the states above the 1.37-MeV $2^{+}$ level. In particular, it is not necessary to invoke a direct two-step process to explain the magnitude and shape of the $3^{+}$ level at 5.22 MeV excitation as suggested by Shepard, Kraushaar, and Baer.

The nonrelativistic impulse approximation for the induced-tensor interaction has been analyzed in detail. $\mathrm{ft}$ values for mirror transitions have been calculated using electron Coulomb wave functions for the extended charge distribution and introducing higher-order corrections. 14 angular $\beta -\gamma$ correlations, the $\beta$ transition being allowed, have been analyzed, showing that this process is sensitive to the presence of the induced-tensor interaction. The amount of information about the induced tensor at present obtainable from circular $\gamma$ polarization in nuclear transitions has been investigated. A limit on the induced-tensor coupling constant has been obtained which does not contradict the evidence based on $\mathrm{ft}$ values. $\beta -\gamma$ angular correlations seem to yield evidence for the weak-magnetism term, while not excluding the existence of the induced tensor.