An error in the estimate of the $\Lambda -\Sigma$ coupling effects in the excited states of ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}$ and ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{He}$ is corrected and the consequences are explored.

Proton-proton bremsstrahlung cross sections at 156 MeV are calculated and compared to the Orsay experimental data. Both relativistic effects and noncoplanar effects are found to be important for forward-angle scattering. Agreement with Orsay's data is much better if these effects are included.

Details are given discussing the calculational ambiguities in deriving a neutron distribution from sub-Coulomb transfer-reaction data. This is done in the context of a recent experimental result on neutron pickup from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and the extraction of a neutron-excess radius from these data.

Doppler shifts of $\gamma$ rays emitted from excited states of nuclei slowing down in krypton gas have been measured. The particular excited states studied were chosen because they have mean lives which are well known. The measured Doppler shifts are used to gain information concerning the slowing-down properties of krypton for the recoiling ions.

We have measured the angular distributions of the neutron polarization for the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(\alpha ,n)$ reaction at $E_{\alpha }=2.075,2.25, \mathrm{and} 2.43$ MeV to determine $J^{\pi }$ assignments for states in ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ at 7.97, 8.07, and 8.197 MeV. Our analysis of $\sigma \left(\theta \right)$ and $P\left(\theta \right)$ data shows that the parity assignments reported by Schölermann for these states are ambiguous due to the spin and parity structure of the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(\alpha ,n){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reaction. The usefulness of this reaction as a source of polarized neutrons is also discussed briefly.

The situation of two closely spaced resonance levels of the same spin and parity in a single channel is investigated. The conventional $R$-matrix theory is compared to a generalized $R$-matrix theory which allows for different boundary conditions for each level. The two ${\frac{3}{2}}^{+}$ resonances near 3 MeV in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(n,n)\mathrm{}{}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction and the ${\frac{1}{2}}^{+}$ resonance dip at 2.4 MeV in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}\mathrm{}(n,n)\mathrm{}{}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reaction are investigated. With no background term $R_0$ equivalent fits to the data can be found using a wide range of boundary conditions and corresponding reduced widths. This shows that there are ambiguities in the reduced widths of levels, depending on the values of other parameters used in fitting the levels. The conventional $R$-matrix theory fits the data well and allows for inclusion of distant levels through an $R_0$ term. The inclusion of an $R_0$ term for unequal boundary conditions introduces new parameters and becomes quite complicated. Thus, we conclude that the conventional $R$-matrix theory is not only adequate to fit closely spaced resonances of the same spin and parity, but it is preferred.

A previously presented method based on the JWKB approximation for constructing a local optical potential from a complete set of complex phase shifts at a single energy is further developed. The Coulomb interaction is explicitly included. By using a pointwise rational-fraction method for numerical analytic continuation the optical potential is directly computed from the experimental phase shifts. The above procedure is applied to the elastic scattering of 104-MeV $\alpha$ particles by ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and it is found to be quite practical and reliable.

The ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^4{}_{}{}^{}\mathrm{He}$ reaction was studied at incident proton energies of 12, 14, and 16 MeV. Detection of both the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ particles in the lab defined angular distributions from about 10 to 170° c.m. The data taken as well as existing data at 8, 10, and 18.5 MeV were analyzed using a finite-range multi-interaction distorted-wave Born-approximation formalism to determine the importance of clustering in the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ nucleus as well as the importance of various reaction mechanisms. Reduced widths of 0.69 for $\alpha +d$ in a relative $s$ state, 0.04 for $\alpha +d$ in a relative $d$ state, and 0.44 for ${}_{}{}^3{}_{}{}^{}\mathrm{He}+ t$ in a relative $s$ state provided fits to the data at 12, 14, 16, and 18.5 MeV.

The $d+d\to d+p+n$ breakup reaction was studied over a range of bombarding energies $E_d=14\mathrm{}-36$ MeV. The proton and deuteron were detected at angle pairs chosen to either emphasize quasifree scattering (QFS) or the $n-p$ final-state interaction (FSI). It was found that by using a smooth cutoff for the deuteron wave function, a modified plane-wave impulse-approximation (PWIA) theory could fit the magnitude and shape of the observed QFS peaks. To fit the QFS plus FSI data only triplet FSI was needed in contrast to some earlier results that indicated a strong singlet FSI. The singlet FSI contribution to the cross sections was estimated to be less than 1% in all cases studied.

The ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}\mathrm{}(p,n)\mathrm{}{}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ reaction has been observed for the first time in the energy region from threshold to 5 MeV. Total neutron-production cross sections measured with good resolution are given. The reaction threshold is determined to be 3743 ± 6 keV. High-resolution total neutron cross sections are also given for the reaction ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}\mathrm{}(p,n)\mathrm{}{}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ from threshold to 4 MeV.

The fivefold differential cross section computed from the exact solution of the three-particle Faddeev equations for separable spin-dependent $s$-wave nucleon-nucleon interactions is compared with the data from the recent kinematically complete measurement of ${}_{}{}^2{}_{}{}^{}\mathrm{H}(p,2p)n$ reaction at 39.5 MeV in $4\pi$ geometry. The calculations agree well with the data, which includes regions of phase space where quasifree scattering and final state interactions are not the predominant reaction mechanisms.

Brueckner-Hartree-Fock (BHF) equations are derived including the correction due to treating the Pauli operator in the HF basis instead of the single oscillator basis, both for standard BHF and for a variational calculation. Calculations were done with an approximate energy denominator. The correction effects for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ are significant: about a 10% decrease in total binding energy, 12-30% decreases in single-particle energies, and up to 20% decrease in the peak of the charge-density distribution.

Using the theory of groups the many-particle average of the product of one-body operators is determined in terms of the one-body average of the products of these operators. With this all the energy moments of the noninteracting system are derived in terms of the one-particle moments. For the interacting systems the third and fourth moments are derived.

A new method for calculating finite-range distorted-wave Born-approximation matrix elements is fully developed. This method is based on plane-wave expansions of the distorted waves which allows a separability feature not found in the usual approach. A spin-orbit interaction is included for both the bound states and the distorted waves.

Consequences of the conserved isospin quantum number $T$ are developed for compound-nucleus reactions with particular emphasis on statistical cross-section fluctuations. The formalism is based on the Hauser-Feshbach and Ericson theories. The appropriate autocorrelation function in case of levels of two different isospin values in the compound nucleus contains an interference term between two Lorentzian functions that are associated with the two isospins. The formalism is applied to the statistical reactions ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}(p,p)$ and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}(p,\alpha )$, where the coherence widths in the proton and $\alpha$ channels are markedly different. This is attributed to the decay properties of states with different isospin in the compound nucleus ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$. The formalism developed for the isospin quantum number $T$ can be extended to other quantum numbers. For the case of angular momentum and parity $J\pi$ interesting consequences with respect to heavy-ion reactions are discussed.

The decay scheme of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ has been studied in detail to obtain information on the $\beta$-decay mirror symmetry properties of the mass-20 multiplet and to determine the Fermi decay strength to the $T=1\mathrm{}$ isobaric analog state in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. The ratio $\frac{{\mathrm{ft}}^{+}}{{\mathrm{ft}}^{-}}$ was determined to be 1.026 ± 0.024 for the ${\beta }^{+}$ transitions to the first excited state of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. The $\mathrm{ft}$ value for the transition to the $T=1, 10.278$-MeV level was measured to be 2992 ± 233 sec indicating that most of the Fermi strength is concentrated in this transition. A weak $\gamma$ transition from the $2^{+}$ isobaric analog state to the $2^{+}$ first excited state of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ was observed and new ${\beta }^{+}$-delayed $\alpha$ groups are reported at 3.27, 5.272, and 5.701 MeV. Theoretical $\mathrm{ft}$ values derived from the shell-model wave functions are compared with experiment.

Using the recoil-distance method the mean lifetime of the 2542-keV level in ${}_{}{}^{40}{}_{}{}^{}\mathrm{K}$ has been measured and found to be 1.5 ± 0.2 ns.

Optical-model fits with successive fixed values of real well depth $V$ to five angular distributions for ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$)${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ which include data to angles > 110° for projectile energies between 29.6 and 71.1 MeV yield ${\chi }^2$ vs $V$ plots with a deep minimum at $V\sim 130$ MeV for each data set. For the lower-energy data sets, other minima (parameter families) are observed at intervals above and below this value, but the higher-energy data sets (59.8 and 71.1 MeV) show only one unique family near $V=130\mathrm{}$ MeV. The absence of the family ambiguity for the higher-energy data sets demonstrates the importance of both large-angle and high-energy data for the removal of optical-potential ambiguities. The normalized volume integral of the real potential at $V\sim 130$ MeV is $J_R\sim 330$ MeV ${\mathrm{fm}}^3$ for each data set, and $J_R$ changes by ∼100 MeV ${\mathrm{fm}}^3$ for successive families. The unambigious value of $J_R\sim 330$ MeV ${\mathrm{fm}}^3$ for the higher-energy data sets and the near independence of $J_R$ on energy implies a similar unique value and corresponding unique family for the lower-energy data sets. This value of 330 MeV ${\mathrm{fm}}^3$ is somewhat lower than values of $J_R>400\mathrm{}$ MeV ${\mathrm{fm}}^3$ suggested by earlier studies.

Two resonances have been observed at 3.283 ± 0.003 and 3.289 ± 0.003 MeV in the ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}(p,\gamma ){}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ reaction. The corresponding excitation energies are 12.044 ± 0.004 and 12.050 ± 0.004 MeV. The $\gamma$-decay schemes and resonance strengths have been measured. On the basis of $\gamma$-ray angular-distribution and proton elastic scattering measurements the 12.044-MeV level has been assigned $J^{\pi }$, $T=4^{-},1\mathrm{}$. The 12.050-MeV level has been assigned $J=0\mathrm{}$ from $\gamma$-ray angular-distribution and correlation measurements. A proton elastic scattering experiment has yielded an upper limit of 230 eV for the total width of the 12.050-MeV level. This state is shown to be the lowest $J^{\pi }$, $T=0^{+},2\mathrm{}$ state in ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$.