The cross sections for charged-pion photoproduction from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($0^{+}$, g.s.) leading to the four low-lying bound states $J^P=2^{-}, 0^{-}, 3^{-}, 1^{-}$; $T=1\mathrm{}$ in ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}$ are calculated in the Woods-Saxon basis. Two-particle-two-hole correlations in the ground-state wave function of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ are taken into account. Calculations in the Woods-Saxon basis yield more realistic results for the cross sections near the first pion-nucleon resonance region, where high momentum transfers occur, than those obtained in the conventional harmonic-oscillator basis.

A nonperturbative derivation of the Brueckner approximation to the ground-state energy of nuclear matter (with standard choice of hole and particle energies) is given within the framework of the method of correlated basis functions. The structure of the factor-cluster (FIY) expansion of the expectation value of the Hamiltonian with respect to a trial function incorporating short-range correlations in a general fashion, is analyzed for a uniform extended medium of fermions. With a special choice of correlated wave function, the Brueckner approximation is extracted from the FIY expansion by selective summation of two-body combination terms to all orders in the smallness parameter $\kappa$ associated, in this case, with both Brueckner-Bethe-Goldstone and FIY energy expansions. A reexamination of the numerical comparison of conventional Brueckner and Jastrow methods carried out earlier for two simple models of nuclear matter leads to the conclusion that it is inadvisable, at least in a Jastrow calculation satisfying the average Pauli condition, to incorporate the $O\left(\kappa \right)$ contribution of the analog of the dispersion correction of reaction-matrix theory without at the same time including the $O\left(\kappa \right)$ contribution of the analog of the Bethe-Faddeev term. For the uniform extended medium for the Jastrow choice of wave function, there is a formal cancellation of these two three-body contributions, the scale of this cancellation being governed by the size of $\kappa$. In the numerical example considered, $\kappa$ is about 0.22 and the cancellation goes something like +14 MeV-15 MeV=-1 MeV. These findings, when juxtaposed with the standard Brueckner results for the simple models in question, suggest that a departure from the standard prescription of hole and particle energies in reaction-matrix theory may be necessary when $\kappa$ is sizeable-as in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and the high-density neutron gas, as well as equilibrium nuclear matter described with some potentials.

The total and differential cross sections for ${\pi }^{-}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ elastic scattering in the 3-3 resonance region are calculated using the first-order optical potential derived from the multiple-scattering theory of Kerman, McManus, and Thaler. In order to include the 3-3 resonance and generate a reasonable off-shell behavior of the $\pi$-nucleon transition matrix, a separable model is used to construct the $\pi$-nucleon transition matrix. The optical potential also includes a proper transformation of the $\pi$-nucleon transition matrix from the $\pi$-nucleon to the $\pi$-nucleus c.m. frames. The results are compared with recent ${\pi }^{-}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ elastic-scattering data and with earlier ${\pi }^{-}$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ calculations.

The mechanism of the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(h, p){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ has been studied by measuring the alignment of the 10 bound states of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, at 32 incident energies in the range $3\le E_h\le 11$ MeV. These alignments were measured by the angular-correlation technique, using a collinear geometry with detection of the outgoing protons at 0° as well as at 180°. The theoretical alignments which have been calculated both by the direct-interaction model and by the compound-nucleus statistical model, and which are quite different in these two models for levels of natural parity, are almost constant with energy. However, experimentally, strong fluctuations of the alignment have been observed. For the incident energies used in this work, where the mechanism is usually considered intermediate between these two extreme models, it seems that the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(h, p){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ proceeds predominantly by the compound nucleus ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$. The giant-resonance structure, or the predominant [$p\otimes {}_{}{}^{14}{}_{}{}^{}\mathrm{N}$] configuration of this nucleus, at the high excitation energies reached in this reaction, can explain theoretically the measured alignments.

The low-energy total cross section for the photodisintegration of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ is discussed in a sequential-decay model. Satisfactory agreement between theory and experiment is obtained from threshold to $\gamma$-ray energies of about 12 MeV in an essentially parameter-free model.

Angular distributions of the neutron polarization for the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha , n_0){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha , n_1){}_{}{}^{12}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$ (4.43-MeV) reactions have been measured at six projectile energies in the 4.5- to 5.85-MeV interval. Large polarizations are observed for both neutron groups over the whole energy range, making both groups useful sources of polarized neutrons. The ground-state neutronpolarization angular distributions have been analyzed simultaneously with the recent cross-section data of Obst et al. using an $S$-matrix search code to make $J^{\pi }$ assignments to states in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ in the 13- to 15-MeV excitation energy range. The combined data set can be adequately described over the whole energy range by assuming the presence of at least five broad states. The $J^{\pi }$ assignments and the probable excitation energies for these states are given.

The elastic scattering of $\alpha$ particles by ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ has been studied in the bombarding energy range of 1.7-6.2 MeV. 10 excitation functions in 50-keV steps and five angular distributions near 5 MeV were measured. The elastic scattering data in the 3.5-5.0-MeV region were analyzed with the compound-nucleus theory using a computer code which evaluates the cross section in the "single-level" approximation. Analysis in terms of seven resonances reproduces many of the features of the data. Tentative spin and parity assignments are given.

Some of the low-energy properties of the three-nucleon system are calculated with two $s$-wave spin-dependent interactions, which produce almost identical ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ two-nucleon phase shifts up to a lab energy of 350 MeV. Both interactions consist of an attractive square well and a short-range repulsion. The repulsive part of one potential is a hard core, for the other it is a nonlocal, separable potential. The hard-core potential produces a triton binding energy of 8.7 MeV, a doublet scattering length of 0.84 fm, and a quartet scattering length of 6.30 fm. The corresponding parameters calculated with the partly nonlocal potential are 8.8 MeV, 0.85 fm, and 6.31 fm. These results suggest that the low-energy properties of the three-nucleon system are insensitive to the details of the short-range part of the two-nucleon interaction.

An accurate measurement of the asymmetry of the $2^{+}$→$2^{+}$ 474-keV positron group emitted by oriented ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ is reported. The ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ source, which had been ion implanted into an iron foil, was cooled to about 0.013°K by thermal contact with a demagnetized chromium potassium suplhate salt pill. The positrons were detected in a semiconductor detector telescope which reduced corrections for backscattering and $\gamma$-ray response. A complete description of the detector system and its operation is given. The accuracy of the result reported here is such that it is the first rigorous independent test of the commonly applied $\beta -\gamma$ circular-polarization-correlation technique. The asymmetry parameter was found to be $A_1=0.243\mathrm{}\pm 0.007$ which corresponds to a Fermi-Gamow-Teller mixing ratio $\frac{C_V{M}_{\mathrm{F}}}{C_A{M}_{\mathrm{GT}}}=-0.0063\mathrm{}\pm 0.0056$. This result is discussed in terms of possible second-forbidden corrections and used to derive a value for the Fermi matrix element and to determine the isospin mixing of the analog of the daughter in the parent ground state of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$.

Nuclei with odd number of protons are studied using the Hartree-Fock-Bogoliubov method. The binding energies, single-particle spectra, quadrupole moments, $B\mathrm{}\left(E2\mathrm{}\right)\mathrm{}$ values, and the pickup strengths are calculated. By comparing the results for the neighboring even nuclei one can study the sets of isotones. The nuclei with $N=26\mathrm{}$ (${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{49}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{Mn}$, and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Fe}$), $N=28\mathrm{}$ (${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{53}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Co}$), and $N=30\mathrm{}$ (${}_{}{}^{53}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, and ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$) are studied to understand the effects of the addition of a proton on the deformation, Fermi surface, fluctuations of the proton separation energies, pair separation energies, and the configuration mixing.

Protons from the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}(\alpha , p){}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ reaction were analyzed with broad-range magnetic spectrographs. Data were taken at nominal bombarding energies of 20.0 and 20.28 MeV and at observation angles ranging from 15 to 120°. 102 levels have been identified in ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ in the region of excitation from the ground state to 10.8 MeV. Uncertainties in excitation energies above 3.2 MeV have been reduced by as much as a factor of 5 from previous work and 57 previously unreported levels were observed.

Excitation energies, spins, and nuclear lifetimes have been measured in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Mg}$ by employing the reaction ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}(t, p\gamma ){}_{}{}^{28}{}_{}{}^{}\mathrm{Mg}$ at bombarding energies in the neighborhood of 2.9 MeV. Reaction-produced protons were detected in an annular Si counter at an average angle of 171°, and coincident-$\gamma$-ray spectra were obtained with both NaI(Tl) and Ge(Li) detectors at angles $120°\ge \theta \ge 0°$ $\gamma$-ray angular distributions were extracted from data obtained with the NaI(Tl) detectors, while precision $\gamma$-ray energies and Doppler-shift attenuations were extracted from the data collected with the Ge(Li) detector. The results obtained for excitation energies (keV), spins, and lifetimes (psec) are: 1473.8±0.4, 2, 1.60±0.20; 3862.9±0.7, 0, 1 or 2, 0.75±0.10; 4021.2±1.6, 4, 0.21±0.07; 4557.4±0.8, 2, <0.04; 4877±4, 2, <0.18; 5171.6±0.8, 3, 0.10±0.07; 5190.7±3.0, 1, <0.03; 5470.5±5, 2, undetermined. $\gamma$-ray branching ratios and multipole-mixing ratios were also obtained from the data, and reduced electromagnetic transition matrix elements have been extracted for all transitions observed. The results are compared with the predictions of both the triaxial rotor model of Kurath and the shell-model calculations of de Voigt and Wildenthal.

Elastic and inelastic scattering of monochromatic photons were used for studying nuclear energy levels in ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$; the photons were produced by thermal neutron capture in copper and vanadium. The decay of one resonance at 7306 keV excited by the copper $\gamma$ source and another resonance at 6874 keV excited by the vanadium $\gamma$ source were studied in detail and 30 low-lying levels were observed from the ground state up to 3.4 MeV, 17 of which are believed to be new levels in ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$. The angular distribution of some elastic and inelastic lines were measured and the following spin determinations were made (keV, $J^{\pi }$): 320, ${\frac{1}{2}}^{-}$, (${\frac{3}{2}}^{-}$); 574, ${\frac{5}{2}}^{-}$; 872, ${\frac{3}{2}}^{-}$; 1488, ${\frac{3}{2}}^{-}$, ${\frac{7}{2}}^{-}$; 1525 (½, $\frac{3}{2}$); 1891, ${\frac{3}{2}}^{-}$ (1978), (½, $\frac{3}{2}$); 2457, $\frac{3}{2}$; 2484, $\frac{5}{2}$; (2565), (½, $\frac{3}{2}$); 2660, $\frac{3}{2}$; 3051, ($\frac{3}{2}$, $\frac{7}{2}$); 3076, $\frac{5}{2}$; 3318, ($\frac{7}{2}$); 6874, ${\frac{1}{2}}^{\mathrm{}(+)\mathrm{}}$ and 7306, ${\frac{5}{2}}^{+}$, where parentheses denote uncertain $J^{\pi }$ assignments. The parity of the 7306-keV level was directly determined using a Compton polarimeter. The total radiative width of the 7306-keV level was measured and found to be $\Gamma =0.105\mathrm{}\pm 0.020$ eV. For the 6874-keV level, a positive correlation coefficient was obtained, $\rho =0.69\mathrm{}$, between the ($\gamma , {\gamma }^{\prime }$) and ($d, n$) transition strengths leading to the same final states in ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$. The levels of ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$ are compared with recent theoretical calculations.

Utilizing the recently completed cyclograaff facility, we have measured the angular distribution of the ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}(p, n){}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$ analog transition between 16 and 26 MeV. Between 21 and 26 MeV the integrated cross section decreases monotonically with increasing energy while between 16 and 21 MeV a broad resonant behavior is observed. Coupled-channel calculations, with isospin strengths linearly scaled up 1.5% per MeV from the optimum values deduced at 26 MeV, provide a good description of the measurements between 21 and 26 MeV. However, in the region of the apparent resonance the measurements are systematically higher than the calculations at the backward angles, implying a correlation between the appearance of the broad structure and the increase of cross section at the backward angles. Similarly, search routines on the isospin strengths produced a significant improvement in the fits only between 21 and 26 MeV. Between 21 and 16 MeV, the isospin strengths increase to account for the increasing total cross section but the quality of the fits is essentially unchanged. Thus, the most likely explanation for the resonant behavior is not an energy dependence of the isospin strengths, but the presence of an additional reaction mechanism which yields either an isotropic or symmetric incoherent contribution to the ($p, n$) analog transition.

The differential cross section for the capture reaction ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}(p, {\gamma }_0+{\gamma }_1){}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ has been measured. Significant structure is observed in the giant-resonance region. Comparison with the reaction ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}(\gamma , n){}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ indicates a splitting of the dipole strength. Possible sources of this splitting are discussed.

Angular distributions for ($p, n$) transitions to isobaric analog states of ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ targets have been measured at proton energies of 22, 30, and 40 MeV. The data have been compared with results of macroscopic distorted-wave Born-approximation calculations employing various form factors: pure volume, pure surface, and mixtures of real volume with imaginary surface. The comparisons show that: (i) The surface interaction describes the data rather well, particularly at the lower energies, whereas the volume interaction is adequate only at 40 MeV; (ii) complex mixtures of volume and surface give good descriptions of most of the data if the mixture is a variation of the isospin part of the Becchetti-Greenless potential with either increased surface-to-volume ratio or increased imaginary radius; (iii) use of the unmodified Becchetti-Greenless geometry gives a poor fit to much of the data; (iv) the strength of the isospin interaction decreases with increasing energy, in general agreement with other charge-exchange work. Most of the decrease here occurs between 22 and 30 MeV. This is true for the surface interaction and for each of the two complex interactions.

The properties of the low-lying states of the argon isotopes ${}_{18}{}^{39}{}_{}{}^{}\mathrm{Ar}_{21}^{}{}_{}{}^{}$, ${}_{18}{}^{40}{}_{}{}^{}\mathrm{Ar}_{22}^{}{}_{}{}^{}$, ${}_{18}{}^{41}{}_{}{}^{}\mathrm{Ar}_{23}^{}{}_{}{}^{}$, and ${}_{18}{}^{42}{}_{}{}^{}\mathrm{Ar}_{24}^{}{}_{}{}^{}$ are predicted by use of both the ${\left(\pi d_{\frac{3}{2}}\right)}^{-2\mathrm{}}{\left(\nu f_{\frac{7}{2}}\right)}^n$ model and the extended ${\left(\pi d_{\frac{3}{2}}\right)}^{-2\mathrm{}}{(\nu f_{\frac{7}{2}}, \nu p_{\frac{3}{2}})}^n$ description. The $n-n$, $p-p$, and $n-p$ interactions are taken from data on neighboring nuclei. With the extended model, reasonable agreement with experiment is obtained for the spectra. $E2\mathrm{}$ and $M1\mathrm{}$ transitions rates are examined. All $M1\mathrm{}$ transitions are predicted to be substantially inhibited, as is observed experimentally. Several experiments are suggested.

We examine the elastic scattering of slow neutrons by a standing electromagnetic wave. It is shown that the real part of the coherent scattering amplitude arises essentially from the interaction of the induced electric dipole moment in the neutron with the electric field of the wave. The imaginary part of the coherent scattering amplitude arises from the interference between the magnetic dipole and spin-orbit interaction terms.

Cross sections for electron elastic scattering from ${}_{19}{}^{39}{}_{}{}^{}\mathrm{K}$ and ${}_{20}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are given for the momentum-transfer range from 0.6 to 3.4 ${\mathrm{fm}}^{-1\mathrm{}}$. The data were analyzed by means of a phase-shift code using phenomenological Fermi charge distributions modified with small undulations. The difference of the ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ distributions has been compared with a $1d_{\frac{3}{2}}$ proton distribution and with other nuclear models.

The elastic and inelastic scattering of $\alpha$ particles by ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ has been investigated at an incident energy of 139 MeV. The elastic cross sections have been analyzed in terms of the optical model using a six-parameter Woods-Saxon potential. The data for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ are sufficient to eliminate the discrete ambiguity in the strength of the potential; the single potential which fits the data has a well depth of 116 MeV and a volume integral $\frac{J}{4A}$ of 298 MeV ${\mathrm{fm}}^3$. For ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ the discrete ambiguity could not be resolved. This outcome is consistent with recently developed criteria for experimental data necessary to resolve the discrete ambiguity. A discussion of the discrete ambiguity, in particular the $A$ dependence, is given, and it is shown that measurements at higher energies are required to resolve the ambiguity for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The inelastic cross sections for transitions to the 1.45-MeV ($J^{\pi }=2^{+}$), 2.46-MeV ($4^{+}$), 4.47-MeV ($3^{-}$) states in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and the 2.62-MeV ($3^{-}$) state in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been analyzed with distorted-wave Born-approximation (DWBA) calculations using collective-model form factors. The results are consistent with previous analyses of lower-energy data.