Low-lying states in ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}$ have been studied via the reaction ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}(\alpha ,n\gamma ){}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}$. A Ge (Li) $\gamma$ spectrum was measured in coincidence with neutrons to identify low-lying states and their $\gamma$ transitions. A threshold study with a Ge(Li) detector was made at bombarding energies between 5.6 to 10.0 MeV. The $n-\gamma$ and the threshold studies together with $\gamma -\gamma$ coincidences suggest the existence of states at 741 ± 1-, 1328 ± 1-, 1423 ± 1-, and 1697 ± 1-keV excitation energies. An $n-\gamma$ delayed-coincidence measurement has been done for the 741-keV $\gamma$ ray. The resulting mean life is $\tau =92\mathrm{}\pm 2$ nsec.

The magnetic excitation structures of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ have been studied by 180° inelastic electron scattering from natural targets of CaS and Ca at energies of 39 and 56 MeV. The significant feature of the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ spectrum is the fragmentation of the $\Delta T=1\mathrm{}$ magnetic dipole strength into transitions to several levels in contrast to the strong concentrations into a very few that is observed in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. In the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ spectra excitation peaks are observed at 8.13, 10.82, 11.14, 11.62, 13.37, and 13.85 MeV. Analyses of the peaks at 8.13, 11.14, and 11.62 MeV yield $M1$ ground-state transition widths ${\Gamma }_0$ of 2.8, 18.9, and 9.7 eV, respectively. Peaks in the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ spectra are observed at 5.94, 6.94, 8.43, and 10.34 MeV. The peaks at 8.43 and 10.34 MeV are found to be due to an $M2$ transition, ${\Gamma }_0=2.6\mathrm{}\times {10}^{-2\mathrm{}}$ eV, and a possible $M1$ transition, ${\Gamma }_0=7.0\mathrm{}$ eV, respectively. The analyses of the remaining peaks in the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ spectra are discussed. The ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ results are examined in terms of the theory of Kurath.

The energy levels of the positive-parity states in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Sc}$ (${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$) and ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}$ are calculated by an effective particle-hole potential determined by a least-squares fit of the low-lying levels of the negative-parity states in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. Some definite predictions are made on the spin-parity assignment for a few low-lying of ambiguous experimental spin-parity determination in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Sc}$.

The deformed Hartree-Fock method is tested for the first time in a comprehensive manner by investigating a wide range of static and dynamic nuclear properties for certain light nuclei. Intrinsic spectra are obtained for the nuclei ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$; in addition, energy-level spectra, nuclear radii, electromagnetic transition rates, electron scattering form factors, inelastic $0^{+}\to 2^{+}$ proton scattering cross sections, and excited-state quadrupole moments are calculated and, wherever possible, compared with experiment. The general results indicate that the Hartree-Fock method may legitimately be extended beyond its common use in structure studies. Both static properties and dynamic ones are reasonably well reproduced in the region where the single-determinant approximation is an acceptable starting point.

The cross-section ratio for photodisintegration to electrodisintegration was measured for targets of aluminum, iron, and tantalum bombarded with 5.0-GeV electrons. These ratios (or $F$ values) were determined for a total of six cascade-evaporation reactions in which as many as 12 nucleons are emitted from the target nucleus. The $F$ values for the six reactions average 2.1, and vary little with target mass and with the number of emitted nucleons. In addition, $F$ values were also measured for two other reactions whose mechanisms involve fragmentation and/or fissionlike processes. The average of these two $F$ values is 3.25 or about 50% larger than for the cascade-evaporation reactions.

High-resolution measurements of the deexcitation $\gamma$ rays from the ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}(n,n^{\prime }\gamma )$ reaction have been made at 0.1-MeV intervals for incident neutrons between the energies of 0.8 and 2.2 MeV. These $\gamma$ rays are assigned to energy levels up to an excitation of 1606 keV in ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}$. The level scheme is compared with that obtained in a recent resonance scattering experiment, and several new levels are proposed. Branching ratios and differential $\gamma$-ray production cross sections at 95° are determined.

The odd-$A$ Co isotopes are studied in a version of the unified vibrational model which incorporates both anharmonic and quasiparticle effects. With the $p_{\frac{1}{2}}$, $p_{\frac{3}{2}}$, $f_{\frac{5}{2}}$, and $f_{\frac{7}{2}}$ orbitals available, quasihole states are coupled to anharmonic vibrations of the corresponding Ni cores. Very good agreement is obtained with the known properties of ${}_{}{}^{57-59}{}_{}{}^{}\mathrm{Co}$ in a one-parameter fit, while the ${}_{}{}^{61-63}{}_{}{}^{}\mathrm{Co}$ calculations are essentially parameter free. The systematics of the energy levels of ${}_{}{}^{57-63}{}_{}{}^{}\mathrm{Co}$ can also be explained well by the model.

The production of internal bremsstrahlung accompanying $\beta$ decay from radioactive nuclei of ${\mathrm{Sr}}^{90}$-${\mathrm{Y}}^{90}$ has been studied. The $\beta$-active source of ${\mathrm{Sr}}^{90}$-${\mathrm{Y}}^{90}$ is fixed to the source holder of an experimental chamber with good collimating arrangement. The internal bremsstrahlung is detected by a scintillation counter of good resolution and known efficiency, and a differential spectrum is obtained using a single-channel pulse analyzer. After making all necessary corrections, the probability of internal bremsstrahlung in $\frac{\mathrm{photons}}{m{c}^2}$ per $\beta$ disintegration is obtained. The experimental probability is compared with the theoretical probability obtained from the theories of Knipp, Uhlenbeck, and Bloch; Nilsson; and Lewis and Ford. At higher energy, where the contribution due to ${\mathrm{Sr}}^{90}$ is negligible, the experimental probability for ${\mathrm{Y}}^{90}$ is compared with the theories of Felsner, and Ford and Martin. The experimental probability at higher energy is much less than the theory predicts, in contradiction to the measurement of the previous workers.

The observed muonic-atom isomer shifts in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ and ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ are analyzed in terms of a single particle or hole coupled to collective vibrations of the nuclear core by means of the weak-coupling Hamiltonian of Bohr. The isomer shift is a delicate effect which is sensitive to certain details of nuclear structure. Although the data for these two nuclei are limited, they strongly suggest two conclusions: (1) that vibrational excitation is not strictly volume conserving, but results in a slight increase of nuclear volume; and (2) that the proton core reacts significantly to changes in state of the valence particle, in a way which is not accounted for by the present model. This reaction is found to be stronger in the case of a valence neutron than in the case of a valence proton. In addition, the Ford-Wills radial-moment analysis is found to be adequate for the analysis of isomer shifts, though the refined method of Barrett is superior. As a byproduct of this work, nuclear wave functions are obtained which may be useful for other applications.

The average emission times of $K$ x rays emitted from ${\mathrm{U}}^{236}$ fission fragments and the multiplicities of $K$ x rays from ${\mathrm{Cf}}^{252}$ fission fragments of specified atomic numbers have been determined. The average emission times of $K$ x rays from ${\mathrm{U}}^{236}$ fragments were determined by detecting the x rays in the two cases of the emitting fragments moving towards and away from the x-ray detector in the time ranges of 110 and 1000 nsec after fission. The most striking delayed $K$ x-ray emitter is found to be ${}_{52}{}^{}{}_{}{}^{}\mathrm{Te}$, wherein (79±5)% of the $K$ x rays are emitted in the time interval 110-1000 nsec. Information about the cascade emission of $K$ x rays from ${\mathrm{Cf}}^{252}$ fission fragments of specified atomic numbers was obtained by measuring the energy spectra of coincident $K$ x rays with two Si(Li) x-ray detectors operated in coincidence with each other and with fission. From the analysis of these spectra the first and second moments of the x-ray emission distribution function were determined. A noteworthy feature of these results is that there exists a significantly large probability for a cascade emission of $K$ x rays in several cases. The cascade emission is found to be, in general, more predominant in the heavy-fragment group as compared to the light-fragment group. In the heavy group, a strong odd-even effect is reflected on the cascade-emission probability. The observed effect on the average $K$ x-ray yield per fragment, if only those events are selected in which the complementary fragment charge has emitted a $K$ x ray, is also discussed.

The elastic scattering of ${}_{}{}^{16,18}{}_{}{}^{}\mathrm{O}$ by ${}_{}{}^{116,120}{}_{}{}^{}\mathrm{Sn}$ has been studied at energies near the Coulomb barrier. Angular distributions were measured at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=57.97\mathrm{}$ MeV and excitation curves at 75, 80, 85, and 90° from 45 to 68 MeV and from 54 to 67.5 MeV for ${}_{}{}^{16,18}{}_{}{}^{}\mathrm{O}$ scattered by ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, respectively. A single angular distribution was taken at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=48.53\mathrm{}$ MeV for the scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ by ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$. An optical-model analysis was used to parametrize the data, and evidence is presented for a change in radius between ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and for a change of diffuseness between ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$.

The excitation function and projected recoil ranges for ${}_{}{}^{211}{}_{}{}^{}\mathrm{At}$ produced through ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ reactions have been measured for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ beam energies from 190 to 270 MeV. A substantial value (25 mb) was found for the cross section at high energies. The general features of the reaction (excitation function, magnitude of the cross section, variation of recoil range versus incident energy) are very similar to the results for lighter projectiles, and show unambiguously a noncompound-nucleus process. The possibility that various transfer mechanisms may lead to ${}_{}{}^{211}{}_{}{}^{}\mathrm{At}$ is discussed with the help of a kinematic analysis.

Potential-energy surfaces and shell-correction-energy surfaces for nuclei in the $A\simeq 200$ region and for actinide ($A\gtrsim 230$) have been calculated in the improved two-center model. These surfaces are shown in a two-dimensional representation as a function of the elongation and the constriction of the nuclear shape. Both the ground-state shell corrections and the fission barriers in the $A\cong 200$ region agree well with experiment. It is found that the saddlepoint position in this region is shifted significantly towards smaller deformations compared with the liquid-drop-model prediction, this shift arising from a very pronounced valley in the shell-correction surface at the position of the liquid-drop-model saddle point. The implications of this finding for a nuclear mass formula and for the application of the liquid-drop model to fission of these nuclei are discussed. In both mass regions ($A\cong 200 \mathrm{and} A\gtrsim 230$) the shell corrections alone show pronounced structure which changes slowly with mass number. At small deformations, up to the region of the second maximum in the potential, this structure is determined by the compound-nucleus shell structure. At larger deformations this structure is shown to arise from the shell structure of the nascent fragments, thus establishing the importance of fragment shells early in the fission process for the entire mass range $A\gtrsim 200$. As a consequence of these studies the regions of validity for the liquid-drop model in describing nuclear fission are explained. Finally, it is shown that the recently observed symmetry in the mass distribution of ${}_{}{}^{257}{}_{}{}^{}\mathrm{Fm}$ is due to the approach to the nucleus ${}_{}{}^{264}{}_{}{}^{}\mathrm{Fm}$, which can split symmetrically into the two energetically strongly favored ${}_{}{}^{132}{}_{}{}^{}\mathrm{Sn}$ nuclei.

Independent and cumulative yields of about 50 rare-earth nuclides produced in the interaction of 28-GeV protons with uranium have been measured. Chain yields on the neutron-excess side of $\beta$ stability were found to have the same mass dependence as in low-energy fission. Based on the results obtained in the present study and with the aid of the published Cs isotopic distribution, charge-dispersion curves at $A\approx 147$ and $A\approx 170$ were constructed. The curve at $A\approx 147$ has two maxima, one on the neutron-deficient and one on the neutron-excess side of $\beta$ stability, separated by a deep valley; the curve at $A\approx 170$ has a single peak on the neutron-deficient side of $\beta$ stability. Corrections were made for feeding and depletion of various mass chains by $\alpha$ decay. Total isobaric yields were determined for 11 mass numbers between $A=143\mathrm{}$ and $A=171\mathrm{}$. On the basis of these results and published data at lower masses, a mass-yield curve was constructed. The apparent constancy of the neutron-deficient yields between mass 143 and mass 171 is consistent with the yield pattern of a spallation-like process. Over the mass range $50<A<\mathrm{}160\mathrm{}$, binary fission and spallation cannot account for all the observed yields. Other processes must be partially responsible for the production of these nuclides, especially at the lower masses.

The circular polarization $P_{\gamma }$ of the 279-keV $\gamma$ ray in ${}_{}{}^{203}{}_{}{}^{}\mathrm{Tl}$ and the 401-keV $\gamma$ ray in ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}$ has been measured using a Compton polarimeter and a current-measuring technique. The result for ${}_{}{}^{203}{}_{}{}^{}\mathrm{Tl}$ is $P_{\gamma }=(2\mathrm{}\pm 5)\times {10}^{-6\mathrm{}}$. For ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}$ evidence for a nonzero circular polarization, $P_{\gamma }=(-0.6\mathrm{}\pm 0.2)\times {10}^{-4\mathrm{}}$, is found. The role of the electron-capture bremsstrahlung in the case of ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}$ is discussed.

In the present investigation the $\alpha$ decay of the previously unknown isotopes ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tm}$ and ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$ was observed. These thulium nuclides were produced by bombarding targets of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{147}{}_{}{}^{}\mathrm{Sm}$ with 103-MeV ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions accelerated in the Oak Ridge isochronous cyclotron. Supplementary data were also obtained by irradiating ${}_{}{}^{162}{}_{}{}^{}\mathrm{Er}$ with 110-MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ particles. The experimental apparatus used in this study is based on the idea of stopping recoil products in helium gas. The stopped recoils are then swept out through a small orifice and deposited on a wheel which, after bombardment, conveys the collected radioactivity to a position in front of a Si(Au) detector for the assay of $\alpha$ activity. Three new $\alpha$ emitters were observed. Their decay characteristics and mass assignments (made on the basis of yield-curve measurements and parent-daughter relationships) are as follows: (1) ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tm}$, $E_{\alpha }=4.45\mathrm{}\pm 0.01$ MeV, $T_{\frac{1}{2}}=39\mathrm{}\pm 3$ sec; (2) ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$ (low-spin isomer), $E_{\alpha }=4.23\mathrm{}\pm 0.01$ MeV, $T_{\frac{1}{2}}=80\mathrm{}\pm 3$ sec; and (3) ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$ (high-spin isomer), $E_{\alpha }=4.46\mathrm{}\pm 0.01$ MeV, $T_{\frac{1}{2}}=19\mathrm{}\pm 3$ sec.

Using ${\mathrm{Re}}^{183}$ sources in cubic matrices of tungsten metal and tantalum metal, lower limits to the half-lives of the ${\frac{3}{2}}^{-}$ 46.5-keV and ${\frac{5}{2}}^{-}$ 99.1-keV levels of ${\mathrm{W}}^{183}$ are found to be 188 ± 4 psec and 975 ± 40 psec, respectively.

The effects of short-range nucleon correlations have been included in intranuclear-cascade calculations in an approximate manner. Comparisons are made with earlier calculations and with experiments. The agreement with experimental data on spallation reactions and spectra of emitted protons is systematically improved when the nucleon-correlation effect is included, along with refraction and reflection at potential boundaries and with a velocity-dependent potential.

In order to test a procedure for resolving the problem of discrete real-well-depth ambiguities found in optical-model analyses, $\alpha$ particles were elastically scattered from ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$, and ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$ at incident energies from 0.6 to 1.2 times the classical Coulomb-barrier height for each nucleus. The real and imaginary nuclear potential-well radii and the Coulomb radius (assuming a uniformly charged sphere) for each nucleus were taken to be $R=R_C={\gamma }_0(A_{\mathrm{Alpha}}^{\frac{1}{3}}+A_{\mathrm{Target}}^{{}^{\frac{1}{3}}})$, where ${\gamma }_0=1.22\mathrm{}$ F. A diffuseness of 0.57 F was used throughout. For three of the nuclei, only one pair of real ($U$) and volume-imaginary ($W$) potentials was found, with the real-well depth for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ showing a slight energy dependence. The potentials obtained were (in MeV): $U=23.5\mathrm{}$, $W=11.0\mathrm{}$ for ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$; $U\sim 22$, $W\sim 10.3$ for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$; $U=23.5\mathrm{}$, $W=14.5\mathrm{}$ for ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$; and $U=18.0\mathrm{}$, $W=6.0\mathrm{}$ for ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$. Analysis of angular distributions taken with 15-18-MeV $\alpha$ particles did not yield evidence of expected ambiguities in the real-well depth, so further calculations were performed in which the effect of absorption was more generally explored. The usefulness of the proposed method was found to be limited to cases where the absorption is either ineffective, or small compared with the average spacing between single-particle levels of the same spin and parity.

The prompt $\gamma$-ray spectrum resulting from capture of 2-keV neutrons in natural lead samples was measured using the 2-keV neutron beam facility of the Materials Testing Reactor. Primary capture $\gamma$-ray lines resulting from neutron capture in both ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ were observed in this spectrum. From these data, and utilizing the 477-keV prompt $\gamma$ rays resulting from the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}(n,\alpha )$ reaction as a flux monitor, cross-section values of 1.8 ± 0.5 b and 3.2 ± 1.2 mb, respectively, were obtained for capture of these 2-keV neutrons in ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$. These data also provide additional information about the level scheme of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Pb}$, including the existence of a previously unreported level at 1748.4 keV, with spin of ½ or $\frac{3}{2}$ and with probable negative parity. A value of 6731.7 ± 0.6 keV was obtained for the neutron binding energy of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Pb}$.