The average number of prompt neutrons ($\overline{\nu }$) emitted in the spontaneous fission of ${}_{}{}^{257}{}_{}{}^{}\mathrm{Fm}$ has been measured to be 3.97 ± 0.13 (based on $\overline{\nu }=3.72\mathrm{}$ for ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$). This result and the known values of $\overline{\nu }$ for other nuclei that undergo spontaneous fission are transformed into excitation-energy values and compared with the liquid-drop predictions regarding the excitation-energy dependence on the fissionability parameter.

Measurements have been made of the relative intensities of internal-conversion electron lines produced by the 42.9-keV pure $E2\mathrm{}$ transition in ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}$. These observations of the $L_1$, $L_2$, $L_3$, $M_2$, $M_3$, $N_2$, $N_3$, $O_2$, $O_3$, and $P_{2,3}$ lines were made with a source of $\alpha$-decaying ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$. Results are found to be in reasonable agreement with theoretical values even for the outer shells, in which the atomic-screening effects are very large.

The statistical theory of fission has been used in previous works to calculate the energy and angular distributions of the long-range $\alpha$ particle emitted in fission. It is now applied to calculate the probability of long-range $\alpha$-particle-accompanied fission relative to binary fission. For thermal-neutron fission of ${\mathrm{U}}^{235}$ the calculated rate is 1 $\alpha$-particle-accompanied fission in 461 binary fissions, which agrees well with the experimental value of 1 in 449. Concerning the mechanism, the large amount of energy required (more than 24 MeV) to emit an $\alpha$ particle at the scission point comes mainly from the reduction of the Coulomb energy between the main fragments through an over-stretched form of deformation. The balance of energy shows that the total excitation energy in $\alpha$-particle-accompanied fission is reduced by about 4.5 MeV compared with binary fission. According to the statistical theory this reduces the relative probability by several hundred fold.

Energy levels and differential cross sections for the ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}(\alpha ,d){}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ reaction have been determined at an incident bombarding energy of 42 MeV. Two-nucleon distorted-wave Born-approximation (DWBA) analysis was performed for the ground and first excited levels of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ in order to obtain a normalization for the ($\alpha ,d$) and ($d,\alpha$) reactions. The results of calculations using this normalization were compared with data for the 1.097-MeV $7^{+}$ level of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ excited in the ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}(d,\alpha ){}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ reaction and for the first excited state of ${}_{}{}^{206}{}_{}{}^{}\mathrm{T}1\mathrm{}$ excited in the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(d,\alpha ){}_{}{}^{206}{}_{}{}^{}\mathrm{Tl}$ reaction. This latter comparison confirmed an earlier agrument that cross sections to the low-lying ${}_{}{}^{206}{}_{}{}^{}\mathrm{T}1\mathrm{}$ levels are considerably enhanced over pure two-hole configuration estimates. The normalized DWBA was then used to study higher-lying two-particle—one-hole excited states in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$.

Energetics of the fission of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$ induced by 8.5- and 13-MeV protons and of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ induced by 12-MeV protons have been studied by means of a three-parameter experiment in which the time of flight of one fragment and the energies of both fragments are measured. The average number of neutrons emitted from the individual fragments and from both fragments together are obtained as functions of fragment mass and total kinetic energy. The number of neutrons emitted per fragment generally increases with increasing fragment mass, and the "sawtooth" shape characteristic of neutron emission in low-excitation fission is still apparent, although the relative depths of the minimum in each of the present cases is reduced. A comparison of the number of neutrons emitted as a function of fragment mass for 8.5- and 13-MeV proton-induced fission of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$ shows that excitation energies of the light fragments change only slightly, while those of the heavy fragments increase significantly with increasing bombarding energy. The largest change occurs in the mass region at about 132 amu, where the doubly-closed-shell configuration $Z=50\mathrm{}$, $N=82\mathrm{}$ occurs. Pre- and post-neutron-emmission fragment mass distributions are obtained, together with the fragment energy distributions and mass-versus-energy correlations. Energy balance is studied by comparing the total energy available for fission into a given mass pair with the sum of the fragment excitation energies, calculated from neutron emission data and mass tables, and the measured fragment kinetic energies. The results are discussed within the framework of simple theoretical fission models.

The value of the reduced transition probability $B(E2,0^{+}\to 2^{+})$ and the static quadrupole moments of the first $2^{+}$ states of ${\mathrm{Nd}}^{144,146,148}$ were determined. The results are discussed in terms of the variable-moment-of-inertia model.

Spectra from radiative capture in $S-$ and $P-$wave resonances in ${\mathrm{Nb}}^{93}$ have been compared. Differences in these spectra are interpreted to indicate the presence of sizable two-particle—one-hole components in the capturing states. $S-$wave intensities show no correlation with ($d,p$) intensities to the same final states, but $P$-wave intensities exhibit a significant correlation. Lack of a correlation with the initial-state reduced widths rules out an appreciable channel-capture effect in this experiment. The differences in $S-$ and $P$-wave total radiation widths are discussed. Seven neutron-resonance spin assignments are made, based on the capture $\gamma$-ray spectra, and 11 new final states in ${\mathrm{Nb}}^{94}$ are observed and tabulated.

The distribution of the intensities of thermal-neutron-capture $\gamma$ rays is discussed within the framework of the statistical model. It is shown that if initial states of only one spin and parity are involved, the $\gamma$-ray intensities for most nuclides approximately satisfy the Porter-Thomas distribution, independent of how many resonances contribute to the thermal-neutron-capture cross section.

Recent precision measurements of the interfering levels in ${\mathrm{Be}}^8$ at 16.6 and 16.9 MeV are in good agreement with a simple two-level formula with interference when it is properly corrected for the effects of final-state Coulomb interactions. The widths used in the formula are $\Gamma \mathrm{}\left(16.6\right)=90\mathrm{}$ keV and $\Gamma \mathrm{}\left(16.9\right)=70\mathrm{}$ keV. It is not necessary to assume that the $T=1\mathrm{}$ components of the ${\mathrm{Be}}^8$ wave functions are excited in the reactions ${\mathrm{B}}^{10}(d,\alpha ){\mathrm{Be}}^{8*}$ and ${\mathrm{Li}}^6({\mathrm{Li}}^6,\alpha ){\mathrm{Be}}^{8*}$. Using the latter reaction, it is shown that the background is too small to have an appreciable effect on the spectral shape for the two levels.

It is proved exactly that short-range correlations enter into diagonal matrix elements of any one-body operator only in 2nd and higher order if the single-particle wave functions have been chosen self-consistently as solutions of the Hartree-Fock equations. Deviations between experimental and theoretical single-particle form factors for elastic electron scattering due to short-range correlations cannot be described by the usual Jastrow functions and generally are much smaller than hitherto assumed.

The mean lifetime of the 1.61-MeV level of ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$ has been measured by applying the recoil-distance method to the ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}(\alpha ,n){}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$ reaction. The mean lifetime was found to be 6.02 ± 0.29 nsec.

Distorted-wave calculations are compared with data from the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ reaction leading to proton-unbound levels at $E_x=7.966\mathrm{}$ MeV ($2^{\pm }$, $T=0\mathrm{}$), 8.489 MeV ($4^{-}$, $T=0\mathrm{}$), 8.617 MeV ($0^{+}$, $T=1\mathrm{}$), and 8.907 MeV ($3^{-}$, $T=1\mathrm{}$). Results show appreciable nondirect components for population of the $4^{-}$ and $0^{+}$ states. The 7.966-MeV state is suggested to have positive parity, and a definite prediction is made for its width. The spectroscopic factor for the $3^{-}$, $T=1\mathrm{}$ state approaches unity, in good agreement with theoretical calculations.

Thick targets of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ (91.7%) were bombarded with ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions accelerated in the Oak Ridge tandem Van de Graaff, and the cross section for the neutron-transfer reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$)${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ was measured from 12.5 to 20.5 MeV. The cross section measured in this energy range is due predominantly to transfer that proceed to the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ ground state, since the threshold for the reaction to populate the 6.09-MeV first excited state is 17.6 MeV. The measured excitation function was then compared with cross sections calculated from the recent distorted-wave Born-approximation (DWBA) treatment of Schmittroth, Tobocman, and Golestaneh. It was possible to find an optical potential for which the DWBA matched the observed excitation function above 14-MeV (lab) incident energy. From this fit the spectroscopic factor for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ ground state was determined. The excitation function for the compound-nucleus reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},2p){}_{}{}^{25}{}_{}{}^{}\mathrm{Na}$ was also measured for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ incident energies from 13.5 to 20.5 MeV.

This paper reports measurements made at the Cambridge Electron Accelerator of the electron-carbon scattering cross section at incident energies of 1, 1.5, 2.25, 3, and 4 GeV and at lab angles of 8.5, 12, and 18°. The measurements included quasielastic scattering and inelastic scattering through the region of the first pion-nucleon resonance. The data are compared with a spectrum generated by summing the known elastic cross section, the known cross sections for excitation of nuclear levels, and a theoretical expression for quasielastic scattering based on the Fermi model for the nucleus. The agreement is satisfactory. The meson electroproduction cross section was derived by subtracting the above calculated spectrum from the data. The total equivalent photoabsorption cross section is consistent with the cross section expected for 12 independent nucleons; the existing Fermi-model calculation does not, however, correctly predict the shape of the electron momentum spectrum. The data are also used to test the Drell-Schwartz sum rule.

Effective interaction and energy levels of light and intermediate nuclei (${}_{}{}^6{}_{}{}^{}\mathrm{He}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$) are calculated using the interaction of Shakin and his collaborators derived from the Yale potential following the unitary-model-operator approach. Detailed comparison is made with works of Kuo-Brown and other authors. It is found that the differences in the approximations used by different groups of workers in the evaluation of the reaction matrix elements can lead to large differences in the spectra, indicating that it is very necessary to evaluate the reaction matrix elements more precisely before applying them to nuclear-structure calculations.

Results of self-consistent calculations with Hartree-Fock (HF), Hartree-Fock-Bogoliubov (HFB), and spherical BCS approximations obtained with the central Yukawa (CY) interaction and with renormalized Kuo and Brown matrix elements for the Hamada-Johnston (HJ) interaction are reported for even Ti, Cr, and Fe isotopes. The calculated ground-state energies, corrected for Coulomb interaction amongst the extracore protons, are compared with the experimental values, and a better agreement for the HJ interaction is obtained than for the CY although they do not differ much with respect to each other. It is found that in the HFB approximation, the HJ interaction favors prolate solutions over oblate or spherical ones. Unlike the CY, the HFB approximation for $Z<N=28\mathrm{}$ nuclei with the HJ interaction does not converge to spherical minima with lowest energy. It is also seen that the pairing contribution to the spherical BCS energy minimum is considerably larger for the HJ interaction as compared to the CY. The desirability of spherical solutions for $Z<N=28\mathrm{}$ nuclei for the HJ interaction is discussed, and it is argued that it cannot be obtained by including $n-p$ pairing in the $T=1\mathrm{}$ state. Modification of the Kuo and Brown renormalized matrix elements is suggested. Results for the oblate and prolate HFB solutions for ${\mathrm{Fe}}^{58}$ with HJ interaction are discussed, as these solutions have very close energy minima.

The energy per particle of neutron matter in the density range ${10}^{13} \mathrm{to} {10}^{15} \frac{g}{{\mathrm{cm}}^3}$ was calculated self-consistently using recent nuclear potentials: the Bressel-Kerman-Rouben potential and the boundary-condition model of Feshbach and Lomon. At low densities the results are in good agreement with other calculations of the energy density of neutron matter. At higher densities, the predicted energy density depends more strongly on the specific potential used. More recent potentials yield somewhat lower pressures for neutron matter (hence a smaller mass range for neutron stars) than those predicted with the Levinger-Simmons potential which has been used as the basis for calculations of neutron-star structure.

The $\beta$ decay of ${\mathrm{Be}}^{11}$, formed in the ${\mathrm{Be}}^9\mathrm{}(t,p)\mathrm{}{\mathrm{Be}}^{11}$ reaction, has been investigated using Ge(Li) and NaI(Tl) $\gamma$-ray detectors and Si $\alpha$-particle detectors. Eight $\gamma$-ray transitions were measured including three weak $\gamma$ rays with energies of 1772, 2893, and 5019 keV not observed previously in ${\mathrm{Be}}^{11}$ decay. The relative $\gamma$ intensities show that the 5020-keV state of ${\mathrm{B}}^{11}$ is populated by a ${\mathrm{Be}}^{11}$ first-forbidden $\beta$-ray branch of 0.28% ($logft=7.94\mathrm{}\pm 0.14$), as well as by a cascade $\gamma$-ray branch of 4.1% from the ${\mathrm{B}}^{11}$ 6793-keV state. Other previously observed $\beta$-ray branches have been confirmed. Accurate energies have been obtained for the ${\mathrm{B}}^{11}$ states, including a value of 7978.1±1.9 keV for the seventh excitated state. This is 18 keV lower than in previous reports. Delayed $\alpha$ particles are also found in ${\mathrm{Be}}^{11}$ decay; the experimentally observed $\alpha$-particle spectrum is a continuum extending from an instrumental lower limit of 0.3 MeV up to about 1.0 MeV, and with a total $\alpha$-particle intensity of 3.0% per decay. These $\alpha$ particles are not in coincidence with 478-keV $\gamma$ rays from ${\mathrm{Li}}^7$. It is suggested that this $\beta$-ray branch of ${\mathrm{Be}}^{11}$ proceeds to the 9870-keV $J^{\pi }={\frac{3}{2}}^{+}$ state of ${\mathrm{B}}^{11}$ ($logft=4.03\mathrm{}\pm 0.15$) followed by $\alpha$-particle emission to the ground state of ${\mathrm{Li}}^7$, although an $\alpha$-decay branch to the 478-keV state of ${\mathrm{Li}}^7$ cannot be excluded. The new features of ${\mathrm{Be}}^{11}$ decay are discussed. It appears that the analog in ${\mathrm{B}}^{11}$ of the ground state of ${\mathrm{Be}}^{11}$ has no antianalog.