Changes in the decay constant of the isomer ${\mathrm{Nb}}^{90m}$ were measured. We found that $\frac{({\lambda }_{\mathrm{Nb}\left(\mathrm{fluoride}\mathrm{complex}\right)\mathrm{}}-{\lambda }_{\mathrm{Nb}})}{{\lambda }_{\mathrm{Nb}}}=(-3.9\mathrm{}\pm 0.8)\times {10}^{-2\mathrm{}}$, $\frac{({\lambda }_{{\mathrm{Nb}}_2{\mathrm{O}}_5}-{\lambda }_{\mathrm{Nb}})}{{\lambda }_{\mathrm{Nb}}}=(-1.9\mathrm{}\pm 0.5)\times {10}^{-2\mathrm{}}$. The Nb (fluoride complex) result confirms the value previously obtained by Cooper et al., which had been questioned because of the negative result obtained by Weirauch et al. in a similar measurement. Some possible causes of this high sensitivity to chemical environment are discussed.

Levels in ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$ were investigated by the ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}({}_{}{}^3{}_{}{}^{}\mathrm{He}, d)$ reaction and by the decay of 25-min ${}_{}{}^{145}{}_{}{}^{}\mathrm{Gd}$. At the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ energy used, i.e., 40.33 MeV, the angular distributions for the stripping reaction were found to be highly structured. This fact permitted reliable assignments of transferred orbital angular momenta to the residual levels. Singles $\gamma$-ray spectra for the decay of ${}_{}{}^{145}{}_{}{}^{}\mathrm{Gd}$ were measured with a 20-${\mathrm{cm}}^3$ Ge(Li) detector. The two sets of experimental data were then used to propose the following sequence of ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$ levels: 0 (${\frac{5}{2}}^{+}$), 330.1 (${\frac{7}{2}}^{+}$), 716 (${}_{}{}^{-}{}_{}{}^{}\frac{11}{2}$), 808.4 (${\mathrm{½}}^{+}$), 1041.9 (${\frac{3}{2}}^{+}$), 1599.9 (${\frac{7}{2}}^{+}$), 1757.9 (${\frac{3}{2}}^{+}$), 1844.7 ($\frac{3}{2}, {\frac{5}{2}}^{+}$), 1880.6 (½, ${\frac{3}{2}}^{+}$), 2112.0 ($\frac{3}{2}, {\frac{5}{2}}^{+}$), and a (${\mathrm{½}}^{+}$), ($\frac{3}{2}, {\frac{5}{2}}^{+}$) doublet at ∼ 2480 keV. The salient features of this level scheme are that (1) the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $d$) reaction predominantly populates the first five energy levels, and (2) the decay from ${}_{}{}^{145}{}_{}{}^{}\mathrm{Gd}$ (${\mathrm{½}}^{+}$ proceeds mainly to the levels at 1757.9 and 1880.6 keV and not to the single-particle states at 808.4 and 1041.9 keV. The present results were compared with experimental systematics available for $N=82\mathrm{}$ isotones and with the implications of a recent shell-model calculation for nuclei in this region.

The half-life of the 59.03-keV $3^{-}$ level of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Pr}$ was measured to be 7.2±0.3 min. The decay schemes of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ce}$ and the isomers of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Pr}$ have been investigated using Ge(Li) detectors. From the results of the $\gamma$-ray studies, we propose a (0.05±0.03)% $\beta$-decay branch from ${}_{}{}^{144m}{}_{}{}^{}\mathrm{Pr}$ to the $3^{-}$ level at 1510 keV in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$. The $\gamma$-ray spectra and decay scheme of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ce}$ are in accord with the electron-conversion work of Geiger, Graham, and Ewan.

Two methods of obtaining distorted-wave form factors which provide fits to the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}(p, d)$ reaction are investigated. Both apply a radial damping term to a Woods-Saxon eigenfunction. One method employs a correction for the density dependence of the interaction along with the usual local-energy-approximation correction terms for nonlocality and finite range. The other method applies a simple empirical two-parameter damping term. The calculations are compared with data for $1p_{\frac{1}{2}}$ and $1p_{\frac{3}{2}}$ neutron transfers at energies from 25 to 45 MeV.

A correction is reported to the mass-formula predictions for the onset of delayed neutron emission using the formula of Garvey and Kelson. The predictions of the Garvey-Kelson and Seeger mass formulas are given for delayed-neutron-emission thresholds which have been recently reported in elements not included in the original report.

The data of an earlier paper presenting the results of 180° electron scattering from ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ have been reexamined using more refined data-treatment techniques. Present results favor an assignment of $2^{-}$ for $T=1\mathrm{}$ states at 12.91 and 13.37 MeV with estimates for radiation widths ${\Gamma }_0$ of 0.11 and 0.13 eV, respectively. Revised transition widths for the $1^{+}$, $T=1\mathrm{}$ states at 9.94 and 10.70 MeV are found to be 7.6 and 17.6 eV, respectively, in better agreement with results of other workers.

Employing the effective matrix elements of Kuo and Brown, of Auerbach, and of Cohen et al., the low-energy $1^{+}$ and $3^{+}$ levels in even-$A$ nickel isotopes are studied within the framework of the modified Tamm-Dancoff approximation. Their properties and reduced transition rates are examined.

High-energy photonucleon emission probabilities in ${\mathrm{O}}^{16}$ and ${\mathrm{C}}^{12}$ have been studied by (a) the standard direct-emission model and (b) the standard direct-emission model modified to incorporate the ground-state correlation. The calculation has been made for the 90° differential cross section, integrated cross section, angular distributions at a few energies, and 45° polarization. Inclusion of the ground-state correlation improves the agreement between the theoretical results and the observations. This, along with the sensitivity of the absolute magnitude of the photonucleon cross section to the extent of the correlation, may be exploited to study the composition of the wave functions of the target and the residual nucleus.

Three polarization distributions over the angular range from 15° to 135° (lab) have been obtained for neutrons produced in the ${\mathrm{Be}}^9(d, n){\mathrm{B}}^{10}$ reaction. Polarization distributions were obtained for deuteron bombarding energies of 1.56, 2.064, and 2.48 MeV. Polarization measurements were made for up to five neutron groups corresponding to transitions to the ground- and the 0.72-, 1.74-, 2.15-, and 3.58-MeV states of ${\mathrm{B}}^{10}$. A liquid-helium time-of-flight coincidence neutron polarimeter was used to make the measurements. In general, the polarization of the neutrons from the ground state is negative at forward angles and positive at back angles for deuteron bombarding energies from 1.56 to 2.48 MeV, whereas the polarization of the neutrons from the excited states is positive for forward angles and negative for back angles, the exception being neutrons from the 1.74-MeV level in ${\mathrm{B}}^{10}$. The maximum polarization observed is about 35%.

For any given two-body Hamiltonian, there exists a large class of unitarily equivalent Hamiltonians that lead to the same scattering phase shifts at all energies. The purpose of this paper is to exhibit typical saturation curves for reasonable equivalent potentials. The binding energy per particle changes by several MeV in either direction, and the saturation minimum shifts to higher or lower density as the binding increases or decreases. Softening the potential increases the binding. The separation approximation for the reaction matrix provides qualitative insight into these effects. Our exact calculations start with simple local $s$-wave potentials with either a hard core or a Yukawa core. The binding energy per particle is calculated in the Brueckner approximation with self-consistent single-particle energies below the Fermi level. For our examples we use unitary transformations that differ from the identity by a short-range operator of rank 2 and transformations induced by distortions of the radial scale. The latter class of transformations alters the core radius and produces potential terms that are linear in the square of the momentum.

The ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(d, d^{\prime }){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ reaction to the first excited state of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(2.31 MeV, $0^{+}$, 1) was investigated for isospin nonconservation. Angular distributions were taken for nine incident deuteron energies between 5 and 10 MeV. The symmetries observed in the angular distributions indicate a predominantly compound-nuclear reaction mechanism. The observed violation arises most probably from "Coulomb mixing" in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ compound nucleus. The measured cross-section ratio of the first to the second (3.95 MeV, $1^{+}$, 0) excited state of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ varied from 3 to 1% for deuteron energy increasing from 6 to 10 MeV. The region of excitation of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ between 26.0 and 31.0 MeV was investigated by measuring the excitation function for inelastic deuteron scattering to the second excited state of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ for deuteron energies between 5.9 and 12.2 MeV at a laboratory angle of 60°. Gross structure was observed at excitation energies of 27.2 and 29.6 MeV in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The presented data are compared with photoabsorption data for this range of excitation energy.

In this paper, it is shown that comparison between the magnetic dipole cross sections obtained from photon and electron disintegration experiments is a meaningful test for the determination of the importance of the exchange currents in nuclei. The proof is obtained by explicit use of the Foldy-Osborn invariants. A detailed discussion is given of the kinematical situation in which the test should be applied.

The absorptive part of the optical potential is considered as a function of conserved quantum numbers such as the total angular momentum $J$. This investigation results in the introduction of a smooth cutoff in the strength of the absorptive potential as $J$ gets larger than a certain critical value. This value is typical of nonelastic channels, and the cutoff reflects poor matching between the angular momenta in the elastic channel and those in the nonelastic channels. Brief consideration is also given to other conserved or approximately conserved quantum numbers such as isobaric spin and parity. The standard optical potential is modified to include an angular-momentum dependence with a suitable cutoff, and is applied to the elastic scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ by ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei. In the energy range 15-36 MeV (c.m.), such an extended optical model gives a good description of all the gross features of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ data. A repulsive core in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ potential has been considered, but no definite evidence for it is found in the present analysis.

Asymmetries produced in the scattering of 7.8-MeV polarized neutrons have been measured to an accuracy better than ±0.020 for 12 angles ranging from 58° to 165° (c.m.). The ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha , n_0)$ reaction was employed as a neutron source with a polarization of 0.539±0.012. The measured asymmetries agree with the 8-MeV data for the charge-symmetric $p-d$ scattering, indicating that the Coulomb effects are indeed small at this energy. The data also follow the trend of the 9-MeV calculation of Purrington and Gammel.

A method has been developed which allows the effect of the short-range dynamical correlations on the nuclear-charge form factors generated in arbitrary potential wells to be taken into account. Recent highenergy experimental data on elastic electron scattering by ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been analyzed with this method. The single-particle radial wave functions have been generated in a state-dependent Woods-Saxon well whose parameters have been chosen to fit the eigenenergies to the proton separation energies, as obtained from ($p, 2p$) reactions. It is shown that only by the inclusion of correlations is it possible to reproduce theoretically the experimental charge form factor of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei. It is also pointed out that the inclusion of correlations leads to the use of potential wells which are deeper and narrower than usually assumed. The radial wave functions of the harmonic oscillator have also been used. It is shown that these wave functions also give a good reproduction of the experimental data, provided that correlations are taken into account. The effect of the center-of-mass motion on the form factors calculated in the finite well is also considered.

The $\alpha$-particle energy spectra from bombardment of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ with 9.1-MeV protons have been obtained for $2.5°\le {\theta }_{\alpha }\le 120°$. The high-energy portions of the $\alpha$ spectra are interpreted as due to the ${}_{}{}^1{}_{}{}^{}S$, $p$+${}_{}{}^3{}_{}{}^{}\mathrm{H}$ finalstate interaction through the first excited state of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at 20.06 MeV. The factored-wave-function method is used to deduce the resonance parameters of this state. Consistency in the use of this method is obtained by a plane-wave Born-approximation calculation based on triton-transfer mechanisms to account for the forward peaking in the angular distribution. Coincidence measurements between $\alpha$ particles and other charged reaction products give additional evidence for the $0^{+}$ assignment to the state and indicate the importance of the $\alpha$+${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and $\alpha$+${}_{}{}^1{}_{}{}^{}\mathrm{H}$ final-state interactions at still higher excitation energy of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ system.

It is well known that the second-order ground-state correlation energy calculated in the usual random-phase approximation (RPA) is off by a factor of 2. It has also been noted that there is a factor-of-2 discrepancy in the correlation corrections to the Hartree-Fock occupation probabilities. The reason for these phenomena is traced to the treatment of the exchange terms in the interaction matrix element. An illustration based on a simple single multipole interaction shows that the factor of 2 arises from a coherent sum of small higher-order terms. Results based on the consideration of one or a few eigenmodes at a time are seen to be free of this difficulty. The correlation energy, occupation-probability corrections, and equations of motion are reexamined in the Beliaev-Zelevinsky boson expansion, as an illustration of clearly defined higher-order treatments.

The $T=1\mathrm{}$ single-particle-hole states of ${\mathrm{C}}^{12}$ are considered on the basis of the harmonic-oscillator shell model in the particle-hole formalism developed by Lewis and Walecka. Configuration mixing is included via a Serber-Yukawa residual interaction. Resulting mixed states lying close in energy are grouped together into complexes whose inelastic-electron-scattering form factors are then compared with recent experimental data. This comparison is done mainly at large momentum transfers and large scattering angles, where the transverse excitations (and consequently the $T=1\mathrm{}$ states) dominate, and where the excitation spectrum contains only a few strongly excited features (to be related here to collective single-particle-hole states). By working at high momentum transfer, the contributions from transitions of high multipolarity can be strongly enhanced. Here all possible $T=1\mathrm{}$ single-particle-hole states of all allowed angular momenta are considered in a basis including single-particle states up to the $2s-1d$ shell. A simple square-well shell model is used to account for the quasielastic cross section in the giant-resonance region. All of the gross features of the experimental excitation spectrum for excitation energies between 14 and 30 MeV can be accounted for on the basis of this simple model.