Computations have been made in order to determine the optimum geometries for time-integrated angular-correlation experiments perturbed by static axially symmetric electric field gradients. Several new properties of the interaction are discussed, including planes of negative attenuation (enhancement), cases for which no interaction is allowed to occur, and new aspects of the concept of hard-core angular correlations.

The 0° excitation functions for the reaction ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha ,n){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ leading to the ground and first excited states of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were measured between 1.69- and 6.44-MeV bombarding energy, while those for the second- and third-excited-state neutron groups were measured above 2.94- and 5.94-MeV bombarding energy, respectively. Angular distributions of the ground state and first two excited-state neutron groups were measured at 17 bombarding energies between 3.21 and 6.44 MeV, and for the third-excited-state neutron group they were measured at 6.24- and 6.44-MeV bombarding energy. The magnitude of the cross sections for the ground- and first-excited-state neutron groups agrees well with the larger of the two sets of conflicting magnitudes reported in the literature. Double-differential cross sections of the continuum of low-energy neutrons were measured as a function of angle and neutron energy for 10 bombarding energies ranging from 4.86 to 6.44 MeV. The features of the continuum are consistent with the sequential decay ${}_{}{}^9{}_{}{}^{}\mathrm{Be}+\alpha \to {}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{*}{}_{}{}^{}+{\alpha }^{\prime }\to {}_{}{}^8{}_{}{}^{}\mathrm{Be}+n+{\alpha }^{\prime }$, proceeding through the 1.67-, 2.43-, and 3.04-MeV excited states in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$. The ratio of the populations of the first and second excited states in the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha ,n){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction was determined at 16 bombarding energies between 3.99 and 6.44 MeV.

The elastic and inelastic (first excited state only) scattering of pions from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is calculated by a method previously described and compared with data from 120 to 280 MeV. It is found that the agreement is comparable with other methods that have been used. An investigation of several possible sources of error in the method is also made.

Measurements of the polarization function $P\left(\theta \right)$ in $n-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ scattering have been made at neutron energies of 11.0, 17.7, 23.8, 25.7, 27.3, and 30.3 MeV with the aim of improving upon previous descriptions of the interaction, especially as regards the analyzing power. Significant differences were found at the higher energies between experimental values for $P\left(\theta \right)$ and predictions of previously existing $n-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ scattering phase shifts. The new polarization data were used with published $n-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ cross-section and polarization data in a series of single-energy phase-shift searches in an attempt to provide an improved set of phase shifts above 20 MeV.

The $E2\mathrm{}$ properties and excitation energies of low-lying states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ are calculated using the adiabatic model of a triaxially deformed rotor. The results are compared with those of recent shell-model calculations and strong similarity is found for both ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ with nearly the same deformation parameters in the adiabatic model. The strength for isovector $M1\mathrm{}$ excitation, pertinent to results of inelastic electron scattering, is also calculated using the closure sum rule.

The Hartree-Fock-Bogoliubov equations are solved for the even Sn isotopes between $A=112\mathrm{}$ and $A=124\mathrm{}$. The hypothesis that pairing restores spherical symmetry is critically examined and the interplay of the pairing and single-particle degrees of freedom are discussed.

Differential cross-section measurements are presented for the elastic scattering of 16-MeV protons from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. In general the angular range 15-160° was covered with a relative uncertainty in the cross sections of ±1%. The data are analyzed using an optical model in three ways: (1) by fitting individual data sets for each element with a nine-parameter model; (2) by fitting all the data simultaneously with a "global" search routine; and (3) by fitting individual data sets with the folding version of Greenlees, Pyle, and Tang. The lack of constraints on the spin-orbit parameters due to the absence of polarization data is overcome to some extent by procedure (2). The ambiguities associated with the spin-orbit term are investigated in some detail. The results confirm trends with mass number found at higher energies, and suggest that effects not included in the usual forms of the model are present in the interaction.

The lifetime of the 2.12-MeV $0_2^{+}$ state in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ has been measured by a $p-\gamma$ delayed-coincidence technique. This state was populated by the ($p,p^{\prime }$) reaction with 5.3-MeV protons bombarding an Ar gas target. A mean lifetime of $\tau =150\mathrm{}\pm 20$ psec was obtained for the $0_2^{+}$ state. This lifetime implies for the $0_2^{+}$ → $2_1^{+}$ transition $B\left(E2\mathrm{}\right)=42.9\mathrm{}\pm 5.7$ ${\mathit{e}}^2$${\mathrm{F}}^4$. Pairing-vibration model calculations for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ were made using experimental information regarding energies and $B\left(E2\mathrm{}\right)\mathrm{}$ strengths for the three lowest levels of both ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{38}{}_{}{}^{}\mathrm{Ar}$. Three kinds of interaction were considered: first, no interaction; second, a phenomenological quadrupole-quadrupole interaction; and third, the Kuo-Brown bare $G$ matrix elements. None of these calculations can accurately describe both the energy spectrum and the $E2\mathrm{}$ transition strengths in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$. This result may be an indication of the inadequacy of the pairing-vibration model for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$.

Spontaneous-fission isomers have been searched for among the recoil products from the following reactions: ${\mathrm{Bi}}^{209}$ + ${\mathrm{H}}^1$, ${\mathrm{Bi}}^{209}$ + ${\mathrm{H}}^2$, ${\mathrm{Bi}}^{209}$ + ${\mathrm{He}}^4$, Pb + ${\mathrm{H}}^2$, ${\mathrm{Pb}}^{206}$ + ${\mathrm{He}}^4$, Ir + ${\mathrm{N}}^{14}$, ${\mathrm{Tm}}^{169}$ + ${\mathrm{N}}^{14}$, ${\mathrm{Gd}}^{154}$ + ${\mathrm{He}}^4$, and ${\mathrm{Pr}}^{141}$ + ${\mathrm{N}}^{14}$. The major products were ${\mathrm{Po}}^{198-208}$, ${\mathrm{Bi}}^{199-208}$, ${\mathrm{Dy}}^{149-151}$, At, and Os. In no case have isomers been observed unambiguously. Limiting cross sections for fission isomers are ≅${10}^{-31\mathrm{}}$ to ${10}^{-33\mathrm{}}$ ${\mathrm{cm}}^2$ compared to product cross sections of ${10}^{-24\mathrm{}}$ to ${10}^{-25\mathrm{}}$ ${\mathrm{cm}}^2$. The limiting isomer ratios are ≅${10}^{-6\mathrm{}}$ to ${10}^{-8\mathrm{}}$ for decay periods of a fraction of a nanosecond to many hours. These ratios are generally less than ≅1 to 0.01% of the corresponding ratios for fission isomers in heavier nuclei.

The decay of ${}_{}{}^{84}{}_{}{}^{}\mathrm{Br}$ to levels in ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ was investigated using Ge(Li) and NaI(TI) $\gamma$ detectors. On the basis of energy, intensity, and coincidence measurements a new decay scheme including 20 levels is proposed. Out of a total of 51 $\gamma$ rays observed, all but 3 were placed in the level scheme. The level scheme includes states at 1837, 2489, 3870, 3879, and 4189 keV not seen in previous decay studies. Spin assignments were made for most levels based on our $\gamma$-intensity measurements and $log\mathrm{ft}$ values. The level scheme is compared with the results of recent ($\alpha ,2n\gamma$) and ($p,t$) reaction studies.

Angular distributions in the range 10-60° have been measured for the reaction ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ca}(\alpha ,d){}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ at $E_{\alpha }=25\mathrm{}$ MeV. The lowest final states populated are those of odd angular momentum $J^{\pi }=1^{+}, 3^{+}, 5^{+}, \mathrm{and} 7^{+}$ belonging to the configuration ($\nu f_{\frac{7}{2}}^{}{}_{}{}^{-1\mathrm{}}\pi f_{\frac{7}{2}}$). As expected, the even-$J$ states $J^{\pi }=2^{+}, 4^{+}, \mathrm{and} 6^{+}$ of this configuration are only very weakly excited. Angular distributions for several additional states up to 4.2-MeV excitation in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ were also measured. The cross sections for these higher states are an order of magnitude lower than would be estimated from normalizing the microscopic distorted-wave calculations to the low-lying states.

The level structure of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ has been investigated in the reaction ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}({}_{}{}^3{}_{}{}^{}\mathrm{He},t){}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ at $E\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)=23\mathrm{}$ MeV. Angular distributions for the ($\nu f_{\frac{7}{2}}^{}{}_{}{}^{-1\mathrm{}}\pi f_{\frac{7}{2}}$) states have been measured from 10 to 90° in 5° steps and from 100 to 140° in 10° steps with a split-pole spectrograph and compared with microscopic distorted-wave calculations (including a tensor force for the transitions into states having odd angular momentum $J$). In addition, a number of strongly excited states are seen at and above 3-MeV excitation energy, and angular distributions for these have been taken from 10 to 50° in 5° steps. Comparison with distorted-wave calculations suggests several candidates for states belonging to odd-parity multiplets, which would be expected in this region of excitation from the configurations ($s_{\frac{1}{2}}^{}{}_{}{}^{-1\mathrm{}}{f}_{\frac{7}{2}}$) and ($d_{\frac{3}{2}}^{}{}_{}{}^{-1\mathrm{}}{f}_{\frac{7}{2}}$). Possible candidates for the expected even-parity states belonging to ($f_{\frac{7}{2}}^{}{}_{}{}^{-1\mathrm{}}{p}_{\frac{3}{2}}$) and ($f_{\frac{7}{2}}^{}{}_{}{}^{-1\mathrm{}}{f}_{\frac{5}{2}}$) are also tentatively identified.

Neutron spectra produced by the (${}_{}{}^3{}_{}{}^{}\mathrm{He},n$) reaction on targets of ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, and ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ have been obtained for bombarding energies of 10.5 and 15 MeV. Peaks were observed in the forward-angle spectra but disappear for angles larger than 30°, leaving a structureless continuum. Examination of the energy dependence in the region corresponding to residual excitations of between 3 and 8 MeV shows better agreement with the calculation assuming a knockout reaction mechanism than that assuming a stripping reaction, although the peaks seen in the forward-angle spectra correspond to stripping reactions. The Griffin formula for calculating densities of particle-hole states is compared with values obtained from combinations of a specific single-particle level scheme; good agreement is found.

A technique was developed for measuring the average number of $\gamma$ rays, $N_{\gamma }$, emitted in the decay of residual nuclei left by specific nuclear reactions as a function of excitation energy. It was used with ($p,p^{\prime }$) reactions induced by 17- and 12-MeV protons, and with ($d,p$) reactions induced by 12-MeV deuterons, each with seven target nuclei of different types. $N_{\gamma }$ increases with excitation energy up to 10 MeV, and is generally below 4 in this range. Variations between light and heavy nuclei; between ($d,p$) and ($p,p^{\prime }$) reactions; between ($p,p^{\prime }$) reactions at 17 and at 12 MeV; between odd-even, even-odd, and even-even nuclei in the same mass and energy regions, etc. were investigated, and their interpretations are discussed.

Isospin sum rules for photonuclear reactions are derived; they relate the strengths of the two isospin components of the giant resonance to the isoscalar, isovector, and isotensor radii of the nucleus. The connection between these radii and both the number and correlations of excess neutrons is discussed. A semiempirical formula for the fraction of the dipole strength in the $T+1\mathrm{}$ giant resonance is derived and various experimental data are discussed in the light of the results obtained using this equation.

The $E2:M1\mathrm{}$ multipole mixing ratio of the ${\frac{5}{2}}^{-}\to {\frac{3}{2}}^{-}$ and $2^{+}\to 2^{+}$ transitions between the second and first excited states in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, respectively, have been measured. The nuclear-orientation sources were prepared by diffusing cobalt activity into iron. Nuclear polarization was obtained by cooling the sample to 25 mK using a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ dilution refrigerator and applying sufficient external magnetic field to saturate the iron. The value $\delta =0.120\mathrm{}\pm 0.002$ was obtained for the 122-keV transition in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ by a nuclear-orientation measurement. The ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$ $\gamma \gamma$ angular-correlation results used (a) NaI(Tl)-NaI(Tl) and (b) Ge(Li)-NaI(Tl) detector combinations and gave consistent results: (a) $A_{22}=0.460\mathrm{}\pm 0.013$, $A_{44}=0.150\mathrm{}\pm 0.021$; (b) $A_{22}=0.45\mathrm{}\pm 0.04$, $A_{44}=0.08\mathrm{}\pm 0.09$. The orientation experiment yielded $A_2=0.33\mathrm{}\pm 0.03$. These values give $\delta =0.69\mathrm{}\pm 0.05$ for the 865-keV transition. From a knowledge of the temperature of the orientated nuclei the Fermi to Gamow-Teller matrix element ratio of the two $2^{+}$-$2^{+}$ electroncapture and ${\beta }^{+}$ transition from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ were obtained. For the transition to the 1675-keV level $\lambda =0.07\mathrm{}\pm 0.06$ and to the 810-keV level $\lambda =0.04\mathrm{}\pm 0.06$. The mixing ratio measurements remove existing possible ambiguities and illustrate the very useful advantages of combining nuclear-orientation and angular-correlation methods.

Transitions to the isobaric analog ground states of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ have been studied with the (${}_{}{}^3{}_{}{}^{}\mathrm{He},t$) reaction in the energy range of 21.4 to 37.5 MeV. Large variations in the shape of the experimental angular distributions were observed as a function of energy and target nucleus. These effects were poorly described by distorted-wave Born-approximation calculations based on a simplified shell-model theory. Calculations based on a generalized optical model, using different interaction terms for each nucleus, gave a somewhat better description. Interaction strengths, normalized to fit the data, required a significant decrease with increasing energy for both theoretical models. These effects were general, to a large extent independent of the optical-model parameter set used. The poor description, both in shape and in strength, of the energy dependence of the data is evidence of basic inadequacies in the theories as they are presently used.

A combined analysis of absolute in-plane and $z$-axis (spin-flip) $p-\gamma$ angular correlation measurements for $0^{+}$-$2^{+}$-$0^{+}$ transitions leads to various combinations of substate cross sections, populations, and phase angles. These quantities are compared with predictions based on reaction-mechanism theories. The test is very stringent. Measurements and analyses have been carried out for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(p,p^{\prime }\gamma ){}_{}{}^{12}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$(4.44 MeV) and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(p,p^{\prime }\gamma ){}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}_{}^{*}{}_{}{}^{}$(1.45 MeV) at $E_p=20\mathrm{}$ MeV, and for ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}(p,p^{\prime }\gamma ){}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}_{}^{*}{}_{}{}^{}$(1.41 MeV) at $E_p=19.6\mathrm{}$ MeV.

Each of the three nuclei studied exhibits the following qualitative features: (1) The total inelastic cross sections have a less pronounced structure than do the individual substate cross sections. (2) The $M=0\mathrm{}$ cross section is the most diffractionlike; the oscillations are out of phase with respect to the oscillations of the elastic cross section. (3) The sum of the $M=+2\mathrm{}$ and $M=-2\mathrm{}$ cross sections also are diffractionlike, but are not in phase with the $M=0\mathrm{}$.

Detailed comparisons with collective-model distorted-wave Born-approximation predictions are, on the whole, quite good for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, especially when the full Thomas form for the spin-dependent perturbation potential is used. The isotropic term in the in-plane angular-correlation function is particularly sensitive to the form and strength of the spinorbit coupling potential. For ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ the predictions are further improved when the strength of the spin-dependent perturbation potential is increased by setting the spin-dependent deformation equal to twice the central-potential deformation.

Attenuated Doppler shifts and particle-$\gamma$-ray angular correlations have been measured and interpreted to yield properties of electromagnetic transitions in ${\mathrm{V}}^{51}$ and ${\mathrm{Mn}}^{53}$. Mean lives have been obtained for states at 1.609, 1.813, 2.402, 2.670, and 2.699 MeV in ${\mathrm{V}}^{51}$, and for states at 1.288, 1.440, 1.619, 2.277, 2.406, 2.575, 2.641, and 2.705 MeV in ${\mathrm{Mn}}^{53}$. Possible multipole mixing ratios have been deduced for the transitions (energies in MeV) 0.378 → 0, 1.288 → 0.378, 1.619 → 0, 2.277 → 0, and 2.406 → 1.288 in ${\mathrm{Mn}}^{53}$. A possible identification of a ${\frac{15}{2}}^{-}$ state in ${\mathrm{Mn}}^{53}$ is presented. From these results and the results of other workers, transition probabilities in ${\mathrm{V}}^{51}$ and ${\mathrm{Mn}}^{53}$ have been calculated and compared (i) with one another, (ii) with a ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^n$ pure-configuration shell-model calculation, and (iii) with a mixed-configuration calculation.

The population of levels of ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$ from the decay of 17.8-min ${}_{}{}^{88}{}_{}{}^{}\mathrm{Rb}$ has been investigated by studying the ${}_{}{}^{88}{}_{}{}^{}\mathrm{Rb}$ $\gamma$ rays with a Ge (Li) Compton-suppression spectrometer and with largevolume Ge(Li) detectors. 42 $\gamma$ rays are identified as originating from ${}_{}{}^{88}{}_{}{}^{}\mathrm{Rb}$, and 31 of them are assigned to 18 levels of ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$. Discrepancies which existed among previous Ge (Li) $\gamma$-ray studies are resolved. The levels populated from ${}_{}{}^{88}{}_{}{}^{}\mathrm{Rb}$ decay are compared with the levels of ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$ populated by other reactions. The nature of the levels is discussed in terms of two-hole and two-particle-four-hole excitations and collective modes of excitations.