This paper reports an experimental comparison of $\gamma$-ray multiplicity (the average number of $\gamma$ rays emitted in the decay of residual nuclei left by nuclear reactions) for compound-nucleus and direct-reaction mechanisms. The $\gamma$-ray multiplicity was determined for ($p, p^{\prime }$) reactions with targets ${\mathrm{Sn}}^{122}$, ${\mathrm{Cd}}^{116}$, ${\mathrm{Ni}}^{64}$ [for which ($p, p^{\prime }$) reactions are direct] and ${\mathrm{Sn}}^{112}$, ${\mathrm{Cd}}^{106}$, ${\mathrm{Ni}}^{60}$ [for which ($p, p^{\prime }$) reactions are to a considerable extent compound nucleus]. Two bombarding energies, 17 and 12 MeV, were used. The $\gamma$-ray multiplicity was found to be approximately the same for compound-nucleus and direct reactions for similar targets, although there is some indication that it is slightly larger for the former in Sn and Cd at 12-MeV bombarding energy, but not at 17-MeV bombarding energy and not for Ni at either bombarding energy. The observed compound-nucleus-direct-reaction differences do not explain why the $\gamma$-ray multiplicity is larger for $\mathrm{Ni}(p, p^{\prime })$ than for $\mathrm{Sn}(p, p^{\prime })$ reactions.

Neutron transmission and self-indication measurements have been made for two of the separated isotopes of Sm ($A=152\mathrm{} \mathrm{and} 154$) and the separated isotopes of Eu ($A=151\mathrm{} \mathrm{and} 153$) at the Nevis synchrocyclotron. The measurements used a 200-m path for transmission measurements and a 40-m path for self-indication measurements, covering an energy range from approximately 1 eV to greater than 5 keV. Since these isotopes are at a region of a peak in the $l=0\mathrm{}$ strength function, mainly $s$ resonances are involved. The results for the even-even Sm isotopes show that essentially complete $s$ populations were obtained for the first 70 levels in ${\mathrm{Sm}}^{152}$ and 27 levels in ${\mathrm{Sm}}^{154}$. Values of ${\Gamma }_n$ (or $g{\Gamma }_n$ for Eu) were obtained for the observed resonances. Values of ${\Gamma }_{\gamma }$, obtained for 9, 3, 45, and 46 levels of ${\mathrm{Sm}}^{152}$, ${\mathrm{Sm}}^{154}$, ${\mathrm{Eu}}^{151}$, and ${\mathrm{Eu}}^{153}$, respectively, give $〈{\Gamma }_{\gamma }〉$ values of 65, 79, 90.0, and 94.8 meV, respectively, with most of the individual values within 20% of $〈{\Gamma }_{\gamma }〉$. The $s$ strength function is $10{}_{}{}^4{}_{}{}^{}S_0^{}{}_{}{}^{}=2.2\mathrm{}\pm 0.4, 1.8\pm 0.5, 3.2\pm 0.5, \mathrm{and} 2.3\pm 0.4$ for ${\mathrm{Sm}}^{152}\mathrm{}(n=90\mathrm{})\mathrm{}$, ${\mathrm{Sm}}^{154}\mathrm{}(n=33\mathrm{})\mathrm{}$, ${\mathrm{Eu}}^{151}\mathrm{}(n=63\mathrm{})\mathrm{}$, and ${\mathrm{Eu}}^{153}\mathrm{}(n=68\mathrm{})\mathrm{}$, where $n$ is the number of levels in the sample. Somewhat smaller $S_0$ values result for the Sm isotopes if a larger energy interval is used. Values of the mean $s$ level spacing for these isotopes of 51.8±1.5, 115±8, ∼0.7, and ∼1.1 eV, respectively, were found. Good fits are obtained with the Porter-Thomas theory for the reduced-neutron-width distributions and the Wigner formula for the nearest-neighbor level separation. Other statistical tests applied to ${\mathrm{Sm}}^{152}$ and ${\mathrm{Sm}}^{154}$, respectively, are: (a) the Dyson-Mehta $\Delta$ statistic, which is particularly sensitive to long-range order in the level spacings, $\Delta =0.40\mathrm{} \mathrm{and} 0.38$ versus ${\Delta }_{\mathrm{DM}}=0.42\mathrm{}\pm 0.11 \mathrm{and} 0.32\pm 0.11$; (b) correlation coefficients of adjacent nearest-neighbor spacings are -0.26±0.10 and -0.32±0.18 versus -0.27 predicted for an orthogonal ensemble.

Low-energy $\gamma$ rays of the reaction ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}(n, \gamma ){}_{}{}^{233}{}_{}{}^{}\mathrm{Th}$ have been measured with the Risö bentcrystal spectrometer and with a Ge(Li) spectrometer at Munich. High-energy neutron-capture $\gamma$ rays from four low-energy neutron resonances have been investigated at the fastchopper facility at Brookhaven. Data on the reaction ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}(d, p){}_{}{}^{233}{}_{}{}^{}\mathrm{Th}$ were taken with an Enge split-pole magnetic spectrograph at the tandem Van de Graaff accelerator at Argonne. The combination of these data resulted in a level scheme of ${}_{}{}^{233}{}_{}{}^{}\mathrm{Th}$. Seven Nilsson configurations have been assigned to rotational bands, two of them tentatively. Spectroscopic factors have been calculated with ${\epsilon }_4$ deformation and Coriolis mixing, and compared with the experiment. The neutron binding energy in ${}_{}{}^{233}{}_{}{}^{}\mathrm{Th}$ has been determined to be 4786.5±2.0 keV.

The compound spreading widths (due to the Coulomb interaction) of ${\frac{9}{2}}^{+}$, ${\frac{11}{2}}^{+}$, ${\frac{15}{2}}^{-}$,${\mathrm{½}}^{+}$, ${\frac{7}{2}}^{+}$, and ${\frac{3}{2}}^{+}$ analog resonances in ${\mathrm{Bi}}^{209}$ are calculated within the general framework of the de Toledo Piza-Kerman scheme by relegating the giant isovector monopole contributions to the continuum space. The work emphasizes the structure of the parent states and the coupling is via [$H_c$, $T_{-}$]. The widths are found to be of the order of 20 keV, which is considerably less than the observed experimental total widths of 200-300 keV. A background of (i) configuration states (6 including the antianalog state for each analog resonance) and (ii) complex levels (e.g., 33261 states for ${\frac{9}{2}}^{+}$ are considered. The one-body Coulomb interaction represented by a uniform sphere of charge is used for (i), while the two-body Coulomb force is expanded in multipoles for (ii). In (i) the dependence on the Coulomb radius and the nuclear spreading width are also studied. For all doorways the relative importance, number, density, strength, and compound-width contributions are investigated in great detail and the results are presented in tables and histograms. In addition to certain states of type (i) the most significant complex states are those based on the ${\mathrm{Pb}}^{208}$ giant dipole doorway resonance.

A weak radiative decay from the proton-unbound level at 7.966-MeV excitation in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ has been observed by coincident detection of protons and $\gamma$ rays from the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He}, p\gamma ){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$. Using the previously known decay scheme the width ratio $\frac{{\Gamma }_{\gamma }}{\Gamma }$ is measured as (0.7±0.2)% from the observed coincidence yield. This result together with the reported value of $\frac{\omega {\Gamma }_p{\Gamma }_{\gamma }}{\Gamma }$ implies $\mathrm{}(2J+1)\mathrm{}{\Gamma }_p=12.6\mathrm{}\pm 3.6$ eV. Comparison of the present value of ${\Gamma }_p$ with measurements involving the reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He}, d){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ implies $l_p=2\mathrm{}$ for the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $d$) transition leading to the 7.966-MeV state, and consequently establishes the parity of that state as negative.

The ($p, n\overline{p}$) reaction has been measured on the lead isotopes ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and on ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. Coulomb-energy differences are extracted from the positions of the $\overline{p}$ peaks. Proton decay widths are also obtained and compared with values from resonance experiments and with a previous value from ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(p, n\overline{p})$.

Ratios of total cross sections for the ($n, 2n$) reactions with 14-MeV neutrons leading to the $J^{\pi }=4^{+}, 7^{+}, \mathrm{and} {11}^{-}$ metastable states in ${}_{}{}^{190}{}_{}{}^{}\mathrm{Ir}$ and the $J^{\pi }=2^{-}, 5^{+}, \mathrm{and} {12}^{-}$ metastable states in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ have been determined. The experimental results for ${}_{}{}^{190}{}_{}{}^{}\mathrm{Ir}$ are in agreement with the prediction of the statistical model of the compound nucleus. However, the cross section for the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}(n, 2n)$ reaction leading to the $5^{+}$ isomer in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ is at least an order of magnitude smaller than expected.

The $K$- and $L$-subshell internal-conversion coefficients of the transitions in ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ populated in the decay of ${}_{}{}^{169}{}_{}{}^{}\mathrm{Yb}$ have been measured using a double-focusing electron spectrometer and a Ge(Li) $\gamma$-ray spectrometer, with special reference to the retarded transitions, in order to look for any nuclear-structure effects. The particle parameters of the $K$ conversion electrons of the 198.0-, 177.2-, and 130.5-keV transitions in ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ and the 308.2- and 295.6-keV transitions in ${}_{}{}^{171}{}_{}{}^{}\mathrm{Tm}$ have been determined from $e^{-}-\gamma$ and $\gamma -\gamma$ angular-correlation measurements using a single-gap electron spectrometer and NaI(Tl) and Ge(Li) $\gamma$ spectrometers. A value of the penetration parameter $\lambda =6-9\mathrm{}$ for the 198.0-keV transition in ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ has been deduced from the conversion coefficients and the particle parameter. The upper limit of the penetration parameter for the 177.2-keV transition is $\lambda \le 7$ from the present measurements. The conversion coefficients and particle parameters of the other transitions in ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ and ${}_{}{}^{171}{}_{}{}^{}\mathrm{Tm}$ measured in the present work agree within experimental errors with the theoretical values with no penetration effect. The $M3\mathrm{}$ transition from the 316.2-keV level to the ground state in ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ has been found to be retarded by a factor of 90 ± 25 with respect to the singleparticle estimate.

Range distributions in ${\mathrm{H}}_2$, He, Ne, and Ar, are reported for seven fission products (${\mathrm{Zr}}^{97}$, ${\mathrm{Mo}}^{99}$, ${\mathrm{Rh}}^{105}$, ${\mathrm{Pd}}^{112}$, ${\mathrm{In}}^{115}$, ${\mathrm{Te}}^{132}$, ${\mathrm{Ce}}^{143}$). The method of electrostatic collection of these products has been explored, and high collection efficiencies are observed for most products. The width of the observed distributions is resolved into a contribution from the stopping effects and a contribution from the fission process. The average range values and the stopping straggling are compared with the theory of Lindhard, Scharff, and Schiøtt. The differences between theory and experiment are ≈ 5 to 50%.

Hartree-Fock intrinsic states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ are examined to find out the extent to which they are good approximations to the exact eigenstates of the system. For this purpose the notion of width of a state is used. In terms of the width we find that by itself the Hartree-Fock approximation is not good in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, however it does provide a suitable basis to discuss the structure of the low-lying states. Our calculation of the $0^{+}$ levels confirms earlier suggestions made regarding the nature of these levels and is also in agreement with exact calculations done in a small basis space.

Range measurements of fission products (${\mathrm{Zr}}^{97}$, ${\mathrm{Mo}}^{99}$, ${\mathrm{Rh}}^{105}$, ${\mathrm{Pd}}^{112}$, ${\mathrm{In}}^{115}$, ${\mathrm{Te}}^{132}$, ${\mathrm{Ce}}^{143}$) in gases have been compared with the range-energy tables of Northcliffe and Schilling. A reevaluation of the kinetic energy deficit for symmetric fission has been made, using a modification of these range-energy relationships. Experimental measurements of range distributions of fission fragments stopped in gases have been used to determine the width of the kinetic energy distributions as a function of product mass. The values obtained are compared with those from other workers.

The lifetime of the 1314-keV 4+ level in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$ was measured by delayed coincidence using a self-comparison method. The decay of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Pm}$ to ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$ proceeds mainly via a 476-keV (4+)-618-keV (2+)-696-keV (0+) $\gamma$-ray triple cascade. By means of suitable triple-coincidence requirements, the time spectra of delayed coincidences through the 4+ and the 2+ states were obtained simultaneously but stored separately. These spectra were analyzed for their relative centroid shift, which when combined with the known lifetime of the 696-keV level, yielded a half-life for the 1314-keV level of 20.5±3.7 psec.

The ($p, t$) reaction has been studied on targets of ${\mathrm{Dy}}^{160,162,164}$ and ${\mathrm{Er}}^{166,168}$ at a proton energy of 17.5 MeV. Excited $0^{+}$ states have been strongly populated in ${\mathrm{Dy}}^{158}$ ($E_x=0.991\mathrm{}$ MeV, $\sigma =0.09\mathrm{}{\sigma }_{\mathrm{g}.\mathrm{s}.\mathrm{}}$), ${\mathrm{Dy}}^{160}$ ($E_x=1.275\mathrm{}$ MeV, $\sigma =0.16\mathrm{}{\sigma }_{\mathrm{g}.\mathrm{s}.\mathrm{}}$), ${\mathrm{Dy}}^{162}$ ($E_x=1.670\mathrm{}$ MeV, $\sigma =0.13\mathrm{}{\sigma }_{\mathrm{g}.\mathrm{s}.\mathrm{}}$), and ${\mathrm{Er}}^{164}$ ($E_x=1.248\mathrm{}$ MeV, $\sigma =0.07\mathrm{}{\sigma }_{\mathrm{g}.\mathrm{s}.\mathrm{}}$). Excited $0^{+}$ states in ${\mathrm{Er}}^{166}$ are much more weakly populated ($E_x=1.460\mathrm{} \mathrm{and} 2.187$ MeV, $\sigma =0.02\mathrm{}{\sigma }_{\mathrm{g}.\mathrm{s}.\mathrm{}}$). This result, along with similar studies of Gd and Yb nuclei, indicates that an excited $0^{+}$ state retains two-neutron-transfer coherence through the mass region between $N=88\mathrm{}$ (end of shape-transition region) and $N=96\mathrm{}$. Residual nuclei with 98 neutrons have not exhibited a strong ($p, t$) population of an excited $0^{+}$ state.

The analyzing-power and differential cross-section excitation functions for the reaction $p$ + ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ have been measured at 150° in the energy range from 10.0 to 14.9 MeV, which spans the thresholds of the ($p, n$) quasi-elastic and quasi-inelastic reaction channels leading to the production of the analogs in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ of the ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ target ground state and ${\frac{5}{2}}^{+}$ (1.46 MeV) excited state, respectively. A pronounced variation in the analyzing power is observed in the ($\overrightarrow{p}, d_0$) exit channel at just the energy regions where charge-exchange coupling is expected to occur due to the opening of the quasi-elastic and quasi-inelastic channels. Somewhat less expected is the change in analyzing power observed in the elastic proton channel in the vicinity of the quasi-elastic and quasi-inelastic thresholds. Sharp resonance structures are observed in the analyzing-power and differential cross-section excitation functions for the ($\overrightarrow{p}, d_0$) channel near the quasi-elastic and quasi-inelastic thresholds which are not readily observable in the elastic channel. The analyzing power for the ($\overrightarrow{p}, n\tilde{p}$) process has been measured at a number of energies in this region and found to be consistent with zero.

Results of certain Hartree-Fock calculations, previously published, were obtained utilizing a computer program which contained an error. In this note the corrected results are presented. The suggestion of $Z=120\mathrm{}$ and $N=184\mathrm{}$ as magic numbers is not changed.

The delayed-proton spectrum following the $\beta$ decay of ${}_{}{}^9{}_{}{}^{}\mathrm{C}$ (${\tau }_{\frac{1}{2}}=126.5\mathrm{}\pm 1.0$ msec) was found to consist primarily of a continuum extending from 13 to 1.5 MeV, the latter being the lowest energy observed. In addition to the previously observed peaks at 9.28 and 12.30 MeV (c.m.), possible peaks between 3 and 7 MeV have been tentatively identified.

The reaction ${\mathrm{Be}}^9({\mathrm{He}}^3, \gamma \gamma ){\mathrm{C}}^{12}$ has been reexamined near a previously reported resonance at $E_{{\mathrm{He}}^3}=1.739\mathrm{}\pm 0.007$ MeV, which was ascribed to the lowest $T=2\mathrm{}$ state in ${\mathrm{C}}^{12}$. No resonance was observed and an upper limit $\frac{{\Gamma }_{{\mathrm{He}}^3}{\Gamma }_{\gamma }}{\Gamma }<1.5\mathrm{}$ meV is established for the $T=2\mathrm{}$ resonance strength (assuming $\Gamma \le 1.5$ keV) which is $\frac{1}{5}$ of the previously reported strength.

The first $J^{\pi }=0^{+}$, $T=2\mathrm{}$ level in ${}_{}{}^{32}{}_{}{}^{}\mathrm{P}$ has been found at an excitation 5073.4±1.5 keV using the reaction ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}({}_{}{}^3{}_{}{}^{}\mathrm{He}, p\gamma ){}_{}{}^{32}{}_{}{}^{}\mathrm{P}$ at 8.02-MeV incident energy. The angular distribution has been analyzed with the distorted-wave Born-approximation formalism. Using a Ge(Li) detector, the $\gamma$-decay scheme of this level has been established. The following branching ratios to the ground state, the 1.149-, and the 2.230-MeV levels are, respectively: (5.3±0.9), (84.0±8.5), and (10.7±1.4)%. This is compared with the decay scheme of its analog state in ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$.

The low-lying $T=0\mathrm{}$ energy levels of ${\mathrm{F}}^{18}$ are calculated in the harmonic-oscillator shell model using several velocity-dependent one-boson-exchange potential models of the nucleon-nucleon interaction. In these calculations we neglect (a) the short-range correlations which, if they were included, would suppress the repulsive core; and (b) core-polarization effects, which take account of the excitations of the ${\mathrm{O}}^{16}$ core. It is found that the shell-model matrix elements are too replusive, and the energy levels lie too high. In general, good fits to the experimental levels are obtained after reducing the $\omega$-meson coupling constant to compensate for the neglect of the effects (a) and (b).

Experimental results are presented on the scattering of 200- and 300-MeV electrons by ${\mathrm{Ti}}^{46}$, ${\mathrm{Ti}}^{48}$, and ${\mathrm{Ti}}^{50}$. These results, and their analysis in terms of charge distributions, complete an earlier investigation of calcium isotopes and ${\mathrm{Ti}}^{48}$. Isotopic differences in rms radii, in agreement with other measurements, are very small, but the actual differences in charge shapes as revealed by these experiments are considerable.