A spherical nonlocal optical-model analysis was performed on a homogeneous set of moderate-precision neutron total cross sections for 78 elements and 14 separated isotopes. The presence of fluctuations in the cross sections prevents the effective application of the optical model for nuclei with $A<\mathrm{}45\mathrm{}$ unless the data are averaged over many experimental resolution widths. The dependence of the magnitude of the fluctuations on the ground-state spin of the target nucleus was observed. The analysis of the data for 46 spherical or soft nuclei within the regions $46<~A<~150$ and $188<~A<~206$, 2 transitional nuclei within the region $185<~A<~187$, and 19 hard-deformed nuclei within the regions $152<~A<~184$ and $228<~A<~239$ clearly indicates the effects of nuclear deformation. The spherical nonlocal optical potential of Perey and Buck describes (within 3%) the interaction of fast neutrons ($3.0<~E_n<~15.0$ MeV) with 46 spherical or soft nuclei. The analysis yields considerably less accurate (17%) results for the 19 hard-deformed nuclei. The surface thickness is approximately the same for all spherical nuclei (with the possible exception of light nuclei below $A=46\mathrm{}$), to the extent that the nonlocal optical potential has the same form as the nuclear-matter distribution. The systematic nature of the deviations of the data from the theoretical predictions leads to a conjecture which spans the mass range $45<~A<~239$.

The reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}(\alpha ,p\gamma ){}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ with incident $\alpha$-particle energies of 9 and 10 MeV has been used to investigate the properties of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ levels below 3 MeV in excitation. Using the Dopplershift-attenuation method, mean lives were obtained for 11 excited levels. These results are as follows: $\tau \left(1.22\mathrm{} \mathrm{MeV}\right)=0.084\mathrm{}\pm 0.018$, $\tau \left(1.68\mathrm{} \mathrm{MeV}\right)={0.26}_{-0.09\mathrm{}}^{+0.12\mathrm{}}$, $\tau \left(1.76\mathrm{} \mathrm{MeV}\right)=0.36\mathrm{}\pm 0.07$, $\tau \left(1.89\mathrm{} \mathrm{MeV}\right)=0.12\mathrm{}\pm 0.03$, $\tau \left(1.92\mathrm{} \mathrm{MeV}\right)=0.03\mathrm{}\pm 0.02$, $\tau \left(2.31\mathrm{} \mathrm{MeV}\right)=0.32\mathrm{}\pm 0.09$, $\tau \left(2.48\mathrm{} \mathrm{MeV}\right)={0.036}_{-0.011\mathrm{}}^{+0.014\mathrm{}}$, $\tau \left(2.60\mathrm{} \mathrm{MeV}\right)=0.11\mathrm{}\pm 0.03$, $\tau \left(2.73\mathrm{} \mathrm{MeV}\right)=0.11\mathrm{}\pm 0.03$, $\tau \left(2.80\mathrm{} \mathrm{MeV}\right)=0.04\mathrm{}\pm 0.02$, and $\tau \left(2.87\mathrm{} \mathrm{MeV}\right)=0.05\mathrm{}\pm 0.02$, all in psec. In addition multipole mixing ratios were obtained for several transitions. Arguments are given for a spin assignment of $J=\frac{7}{2}$ to the 2.31- MeV level.

Activation cross sections at an incident neutron energy of 14.4±0.3 MeV are measured for the ($n,2n$), ($n,p$), and ($n,\alpha$) reactions on isotopes of As, Br, Rb, and Sr, by using the mixed-powder method and $\gamma$ detection by Ge(Li) spectrometer. The use of a stoichiometric chemical compound as an alternative to the mixed-powder technique, where one of the constituents serves as the neutron flux monitor, is investigated and is recommended, whenever applicable, over all other methods for measurement of relative activation cross sections.

It is shown by explicit calculations that the adiabatic treatment of certain deuteron breakup channels predicts differential cross sections for ($d,p$) and ($p,d$) reactions, involving 20-MeV deuterons and a wide range of targets, similar to results obtained with the distorted-wave method but with large suppression of the contributions from low partial waves. An improved fit to angular distributions is obtained in many cases.

The neutron spectra produced by the ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}\mathrm{}(p,n)\mathrm{}{}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}\mathrm{}(p,n)\mathrm{}{}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}(\alpha ,n){}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(\alpha ,n){}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$ reactions were measured at five angles between 15 and 135° for proton energies between 7.8 and 14.7 MeV, and for $\alpha$ energies between 11.5 and 22.7 MeV. Spectra at low energies were used to obtain the spin-weighted level density of the residual nuclei ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$. Comparison of these spectral shapes with those obtained at higher energies made possible a separation of the higher-energy spectra into compound and noncompound contributions.

The deduced compound-nuclear cross sections to given groups of levels were related to the integrals of the level densities of the residual nuclei; the variation of these cross sections with energy was used to extend the level-density measurements beyond the neutron binding energy. A constant-temperature level-density form is found to be appropriate for ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$ up to residual excitation energies of 14 MeV. Values of the moment of intertia of the residual nuclei were extracted from the magnitude of the asymmetry of the compound-nuclear angular distributions. The characteristics of the noncompound portion were compared with those expected from direct- and pre-equilibrium-reaction mechanisms. It is concluded that no convincing evidence for a pre-equilibrium component is observed in the ($\alpha ,n$) spectra; the ($p,n$) data show behavior consistent with contributions from both pre-equilibrium- and direct-reaction mechanisms. A value of approximately 160 keV was obtained for the widths of the participating doorway states from a model-dependent calculation based on the magnitude of the pre-equilibrium ($p,n$) cross section.

The capture $\gamma$-ray spectrum resulting from thermal-neutron capture in ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ has been measured using a 30- and a 10-${\mathrm{cm}}^3$ Ge(Li) detector, and angular-correlation measurements were carried out using NaI(Tl) detectors. Some 16 $\gamma$ lines corresponding to transitions between levels of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, and 9 $\gamma$ lines corresponding to transitions between levels of ${}_{}{}^{51}{}_{}{}^{}\mathrm{Ti}$ were observed. The neutron separation energies of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{51}{}_{}{}^{}\mathrm{Ti}$ were determined to be 10.938 ± 0.008 and 6.377 ± 0.007 MeV, respectively. The following assignments of spins for some levels (in MeV) of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ and the first excited level of ${}_{}{}^{51}{}_{}{}^{}\mathrm{Ti}$ were made: 1.555 ($2^{+}$), 2.675 ($4^{+}$), 4.151 [$2^{+}$, $3^{+}$, $4^{+}$, ($5^{+}$)], 4.178 ($2^{+}$, $3^{+}$, $4^{+}$), 4.887 [$2^{+}$, $3^{+}$, $4^{+}$, ($5^{+}$)], 5.195 ($2^{+}$, $3^{+}$, $4^{+}$), 5.382 [$2^{+}$, $3^{+}$, $4^{+}$, ($5^{+}$)], 5.948 [$3^{+}$, $4^{+}$, ($5^{+}$)] for ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ and 1.164 (${\mathrm{½}}^{-}$) for ${}_{}{}^{51}{}_{}{}^{}\mathrm{Ti}$. There are some indications that only the $3^{-}$ capture-state spin contributes to the population of the low-lying levels in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$. The results of a comparison between the measured strengths of exciting the ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ levels in the ($n,\gamma$) and ($d,p$) reactions are discussed.

The threshold photoneutron cross sections for ${}_{}{}^{206,207,208}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{56,57}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{52,53}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{24,25,26}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ have been measured to about 1 MeV above the ($\gamma ,n$) threshold. Cross sections are presented and analyzed for the parameters of over 200 resonances. The results bear on several phenomena of interest in nuclear physics; these include $E1\mathrm{}$ strength functions, analog states, doorway states, the $M1\mathrm{}$ giant resonance, and nonresonant neutron capture.

$\beta$-delayed proton and $\gamma$-ray measurements have been used to study the decay of ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{33}{}_{}{}^{}\mathrm{Ar}$. Their half-lives have been measured as 109.0 ± 1.0 and 173.0 ± 2.0 msec, respectively, and absolute $\mathrm{ft}$ values have been determined for their $\beta$-decay branches. Precise level energies have been measured in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ and ${}_{}{}^{33}{}_{}{}^{}\mathrm{Cl}$, and an earlier discrepancy concerning energies in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ has been resolved. The $log\mathrm{ft}$ value for the superallowed decay branch of ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$ has been measured to be ${3.29}_{-0.07\mathrm{}}^{+0.04\mathrm{}}$, which indicates an isospin purity of ≥95% for the lowest $T=\frac{3}{2}$ state in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$. In addition, the antianalog configuration is located in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ and is shown to be the most probable source of the small isospin mixing present in the analog state in that nucleus. The $log\mathrm{ft}$ value measured for the superallowed decay branch from ${}_{}{}^{33}{}_{}{}^{}\mathrm{Ar}$ was 3.34 ± 0.05, a value which suggests an impurity of ∼10% in the lowest $T=\frac{3}{2}$ state in ${}_{}{}^{33}{}_{}{}^{}\mathrm{Cl}$. There is circumstantial evidence that this mixing occurs with four $T=\frac{1}{2}$ states which lie within 350 keV of the analog state.

Coulomb excitation of the first excited state of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ has been investigated by means of a coincidence experiment using a position-sensitive detector. Interpreting the data according to the semiclassical theory and correcting for quantal effects, we obtained a reduced transition probability of $B(E2; 0^{+}\to 2^{+})=0.042\mathrm{}\pm 0.002 e^2{\mathrm{b}}^2$ and a static quadrupole moment of $Q_{2^{+}}=-0.305\mathrm{}\pm 0.064 e\mathrm{b}$.

Lifetimes or, alternatively, limits for lifetimes of low-lying levels in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ have been obtained employing the Doppler-shift-attenuation method. The levels were excited by the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}\mathrm{}(t,p)\mathrm{}{}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ reaction and measurements were made of the $\gamma$-ray spectrum in coincidence with reaction protons. Measured mean lifetimes, or limits, [$E_x\left({\tau }_m\right)$, in MeV (psec)] for the first six levels of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ are: $1.402\left({3.3}_{-1.0\mathrm{}}^{+2.2\mathrm{}}\right)$, 1.762 (<0.05), 2.228 (<0.08), 2.875(<0.15), 3.071 (<0.05), and 3.191 (0.21 ± 0.10). A partial level scheme of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ for excitation energy $E_x<~4.5$ MeV based on previously reported information is presented. Properties of these levels are interpreted according to the Nilsson model on the basis of (1) a direct-reaction investigation and (2) $\gamma$-ray angular-correlation investigations as previously reported. The properties of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ are shown to be consistent with a prolate deformation characterized by $\eta \approx +3\mathrm{}$.

A detailed statistical-model analysis has been carried out of recently reported proton and $\alpha$ spectra for the complex nuclear reactions ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ (55 MeV, lab) and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$ + ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ (43 MeV, lab). In both systems the compound nucleus ${}_{}{}^{75}{}_{}{}^{}\mathrm{Br}_{}^{*}{}_{}{}^{}$ is formed with the same excitation energy of 50 MeV, but the distribution of angular momentum is expected to be significantly different. Observed differences in the experimental spectra were accordingly interpreted in terms of assumed differing angular momentum distributions. In our calculations it was found possible to achieve agreement with the data within experimental error for plausible but widely differing sets of important but unknown systemic properties, viz., the distribution of angular momentum in the ${}_{}{}^{75}{}_{}{}^{}\mathrm{Br}_{}^{*}{}_{}{}^{}$, and the level densities to high excitation of the several nuclei involved. However, it was always found necessary to include the effect of the proximity of the closed proton shell at $Z=28\mathrm{}$. The behavior of the calculated $\alpha$ emission for individual nuclei shows important differences of detail between reasonable sets of input data, although for all such sets the production ratio [(total protons) / (total $\alpha$ particles)] decreases with increasing angular momentum of the compound nucleus. We feel it is significant that one of the data sets giving satisfactory agreement with experiment included level densities calculated numerically up to the high energies involved using a realistic shell model. These calculations have already been shown to give values in agreement with reliable experimental level densities, which are, however, only available for lower energies. Since additional data on the same system are needed to reduce the ambiguities, specific suggestions for further experiments are offered, and examples of how such experiments can be useful are worked out.

The energy levels in ${}_{}{}^{235}{}_{}{}^{}\mathrm{Np}$ have been studied through the $\alpha$ decay of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Am}$ and the electron-capture decay of ${}_{}{}^{235}{}_{}{}^{}\mathrm{Pu}$. A level was observed at 34.1 keV and assigned to the ground-state rotational band with Nilsson quantum numbers $\frac{5}{2}+\left[642\right]\mathrm{}$. Levels at 49.0, 91.6, and 146.8 keV were assigned to the $\frac{5}{2}-\left[523\right]\mathrm{}$ rotational band. The lifetime of the 49.0-keV state was measured as 6.9 nsec, and the half-life of the ${}_{}{}^{235}{}_{}{}^{}\mathrm{Pu}$ was redetermined to be 24.3 min.

Sources of 2.02-h ${}_{}{}^{138m}{}_{}{}^{}\mathrm{Pr}$ and 1.44-min ${}_{}{}^{138}{}_{}{}^{}\mathrm{Pr}$ were made by the ($p,n$) reaction on enriched ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ce}$, and sources of 5.7-h ${}_{}{}^{138}{}_{}{}^{}\mathrm{Nd}$ were produced by the ($\alpha ,2n$) reaction on enriched ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ce}$. Eighteen $\gamma$ rays plus annihilation radiation were attributed to the decay of ${}_{}{}^{138m}{}_{}{}^{}\mathrm{Pr}$, and twelve $\gamma$ rays plus annihilation radiation were attributed to the decay of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Pr}$. The level scheme of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ce}$ is discussed. Evidence is given for the existence of a ($2^{+}$) level of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ce}$ at 1510.9 keV, near the previously reported $0^{+}$ and $4^{+}$ levels at, respectively, 1477.0 and 1826.4 keV.

The nuclear decay chains beginning with the neutron-deficient isotopes ${}_{}{}^{184}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$, and ${}_{}{}^{188}{}_{}{}^{}\mathrm{Hg}$ have been studied using isotopically separated sources from the Princeton on-line isotope-separator facility. Ge(Li) and Si(Li) singles spectra and Ge(Li)-Ge(Li) coincidence spectra have been obtained and used in constructing level schemes for the corresponding platinum daughters. Systematics of experimental energy levels and ratios $\frac{B(E2,2^{\prime }\to 2)}{B(E2,2^{\prime }\to 0)}$ for all known even platinum isotopes are given.

One- and three-quasiparticle states have been investigated in ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$ and ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$ using ($d,p$), ($d,t$), and thermal ($n,\gamma$) reactions on isotope-separated tarets of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$. The ($d,p$) and ($d,t$) studies utilized 12-MeV deuterons and a broad-range magnetic spectrograph; the ($n,\gamma$) studies used Ge(Li) and Si(Li) spectrometers. The ground-state one-quasiparticle band ${\frac{7}{2}}^{+}\mathrm{}\left[404\right]\mathrm{}$ through the ${\frac{17}{2}}^{+}$ member and four tentative three-quasiparticle bands are observed in ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$. Members of the following one-quasiparticle bands are observed in ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}:{\frac{7}{2}}^{+}\mathrm{}\left[404\right]\mathrm{}$ ground state, ${\frac{9}{2}}^{-}\mathrm{}\left[514\right]\mathrm{}$, ${\frac{5}{2}}^{+}\mathrm{}\left[402\right]\mathrm{}$, and ${\mathrm{½}}^{+}$[411]; in addition the following three-quasiparticle bands are observed in ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}:{\frac{23}{2}}^{-}[p404\mathrm{}\downarrow +n514\mathrm{}\downarrow +n624\mathrm{}\uparrow ]$, ${\frac{11}{2}}^{+}[p514\mathrm{}\uparrow +n624\mathrm{}\uparrow +n514\mathrm{}\downarrow ]$, ${\frac{13}{2}}^{+} \mathrm{and} {\frac{15}{2}}^{+}[p404\mathrm{}\downarrow +n514\mathrm{}\downarrow \pm n510\mathrm{}\uparrow ]$, $K+2\mathrm{}\gamma$ vibration built on the ${\frac{7}{2}}^{+}\mathrm{}\left[404\right]\mathrm{}$ ground state, tentatively ${\frac{17}{2}}^{+}[p404\mathrm{}\downarrow +n514\mathrm{}\downarrow +n512\mathrm{}\downarrow ]$, and tentatively ${\frac{13}{2}}^{+}$ and ${\frac{15}{2}}^{+}[p404\mathrm{}\downarrow +n514\mathrm{}\downarrow \pm n521\mathrm{}\downarrow ]$. The neutron separation energy of ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$ has been measured as 7072.7 ± 2.0 keV, and the $Q$ value for the reaction ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}\mathrm{}(d,t)\mathrm{}{}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$ as -25±15 keV. Identification of differential cross-section patterns to various members of three-quasiparticle rotational bands in both the ($d,p$) and ($d,t$) reactions indicates that this spectroscopic tool is also valuable for three-quasiparticle states. A sum rule is suggested and experimentally evaluated for the total differential cross sections in the ($d,p$) reaction to rotational members of the two different bands resulting from parallel and antiparallel coupling of the last neutron.

A model has been proposed for the fissioning nucleus which in the early stages of the fission process undergoes charge polarization into two parts, each with a number of neutrons corresponding to the ground-state $\beta$-stable nuclides for the two charges. The rest of the neutrons are then randomly distributed between the two impending fragments, as in an order-disorder process. The model is checked in detail for the thermal-neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$. The yield distributions of fission fragments having the same charge $Z$ along isotopic lines (isotopic distributions) are found to be single peaked but not exactly Gaussian. The $\overline{\nu }\mathrm{}\left(Z\right)\mathrm{}$ distribution is found to closely resemble the experimental $\overline{\nu }\mathrm{}\left(A\right)\mathrm{}$ distribution. The distribution of total isotopic yield versus $Z$, calculated from the isotopic distributions given by the model and experimental fragment-mass yield distribution, shows odd-even $Z$ effects in the form of well-defined fine structure except in the high-slope region. The isotopic distributions, taken in conjunction with total isotopic yield versus $Z$ distribution, give the usual approximately Gaussian distribution along isobaric lines (charge distribution) and provides a rationale for the variation in spread of the distributions. The variation of the mean charge $Z_p$ of the isobaric distributions is studied by plotting the parameter $Z_p-Z_{\mathrm{UCD}}$ ($Z_{\mathrm{UCD}}$ being the charge for a mass given by unchanged charge density), as a function of the mass $A$. This function obtained in the present work shows very good agreement with that calculated from published $Z_p$ values for products. The fine structure observed in this function is found to correspond to the fine structure in the fragment-mass yield distribution.

Distributions of total isotopic yield versus $Z$ for the thermal-neutron fission of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ and the spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ are also presented. In these distributions, the higher-$Z$ peak is found to be clustered around 54 (±2). The mass of 141 (±5), where the peaks in the fragment-mass yield curves are obtained, also has these $Z$'s as the most probable charges. In all these distributions, odd-even $Z$ effects are pronounced. The function $Z_p-Z_{\mathrm{UCD}}$ for the four cases studied shows vertical shift as well as horizontal shift of the peaks in the distributions with increasing charge and mass of the fissioning nucleus.

The low-lying excited states of ${\mathrm{Pd}}^{105}$ were investigated by means of Coulomb excitation using 4.4-8.0-MeV $\alpha$-particle projectiles. The $\gamma$-ray spectrum resulting from the deexcitation of these levels was recorded at each bombarding energy with the aid of a large-volume high-resolution Ge(Li) detector. Thirteen transitions were observed that result from direct $E2\mathrm{}$ excitation of 10 excited states up to an excitation energy of 782 keV. The $B\left(E2\mathrm{}\uparrow \right)$ values from the ground state to each of these 10 levels was determined. Several $E2\mathrm{}$ transitions were found to be strongly enhanced over estimates of single-particle speed, a pattern suggestive of collective behavior. The measured $B\left(E2\mathrm{}\right)\mathrm{}$ values, together with some inferred $M1\mathrm{}$ transition speeds, are compared with predictions of a weak-coupling core-excitation model.

The technique of fluctuation averaging has been utilized with ($p,\alpha$) reactions to measure subkilovolt average widths $\Gamma$ of excited states for six medium-weight nuclei. The following compound-nucleus widths were determined: 386 ± 80, 465 ± 111, and 390 ± 100 eV at excitations of 15.24, 17.02, and 17.00 MeV, respectively, for the ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}$ compound nucleus; 114 ± 40, 150 ± 66, 206 ± 34, and 190 ± 65 eV at excitations of 17.36, 18.80, 18.90, and 20.85 MeV, respectively, for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$; 111 ± 46 and 312 ± 85 eV at excitations of 15.50 and 17.72 MeV, respectively, for ${}_{}{}^{104}{}_{}{}^{}\mathrm{Pd}$; 36 ± 30 and 101 ± 30 eV at excitations of 15.06 and 16.27 MeV, respectively, for ${}_{}{}^{108}{}_{}{}^{}\mathrm{Cd}$; 128 ± 64 eV at an excitation of 15.98 MeV for ${}_{}{}^{110}{}_{}{}^{}\mathrm{Cd}$; and ${58}_{-58\mathrm{}}^{+120\mathrm{}}$ eV at an excitation of 19.29 MeV for ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$. In all these measurements, excitation functions were measured over a span of several hundred keV in steps of 5- to 15-keV proton energy. The accurately known instrumental resolutions required by the method were primarily determined from the target thicknesses, which were about 10 keV. The required dominance of compound-nucleus reactions was obtained by the use of sufficiently low incident energies and by observations at backward angles. Excitation functions over a span of several MeV and angular distributions were measured in order to select regions of negligible direct reactions.

Comparison of these measurements with widths calculated from the statistical model of the nucleus suggests the need for reduced level densities. The measured widths show no evidence for shell effects.

A double-decay process in which the transition energy is distributed between one photon and one $K$ conversion electron was investigated in the decay of the 662-keV state in ${}_{}{}^{137}{}_{}{}^{}\mathrm{Ba}$. For the energy interval of emitted photons from 50 to 150 keV, the result of $\frac{T_{K\gamma }}{T_K}=(2.2\mathrm{}\pm 0.2)\times {10}^{-3\mathrm{}}$ was obtained. The measured energy and angular distributions are compared with the Spruch-Goertzel theory in which the process is treated as the internal Compton effect. Some deviations from the theory are observed in both distributions. The contribution of nuclear intermediate states is negligible in the range of energies which was investigated.

Simultaneous ejection of two electrons in the decay of the 662-keV state of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Ba}$ has been investigated by means of two Si(Li) detectors and a two-dimensional pulse-height analyzer. The $\mathrm{KK}$ process has been observed, while for the $K$, $L+M+\dots$ processes only an upper limit has been determined. The results obtained are $\frac{T_{\mathrm{KK}}}{T_K}=(1.8\mathrm{}\pm 0.5)\times {10}^{-4\mathrm{}}$ and $\frac{T_{K,L+M+\cdots }}{T_K}<~4.5\times {10}^{-4\mathrm{}}$. The comparison of the experimental results with the existing theories indicates that the process proceeds primarily via electronic intermediate states.