Spin-flip probability for 7.44-MeV ($\Delta E=0.300\mathrm{}$ MeV) neutrons scattered inelastically ($Q=-1.78\mathrm{}$ MeV) from naturally occurring silicon has been measured using a $\gamma$-correlated neutron time-of-flight method. Measurements of the elastic scattering and both the $\gamma$-correlated and non-$\gamma$-correlated inelastic scattering were assumed to provide a good approximation to scattering by ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. The optical model appears to be applicable in first approximation. The inelastic differential cross section and spin-flip probability data have been compared to calculations which indicate a statistical compound-nucleus contribution of 53% and a direct-interaction (DI) contribution of 47%. The DI contribution was calculated in the distorted-wave Born approximation with: (1) a collective model and (2) a microscopic description of "valence" nucleons plus a core-polarization model. Exchange amplitudes in the microscopic calculation were small but a comparison of the calculation with the spin-flip data suggests that they may be important. The collective-model form factor does not produce agreement with the backward-angle data. The disagreement between theory and experiment suggests that the assumptions made in the analysis are approximate only.

A many-body formulation of pion-nucleus scattering in the (3,3) resonance region is presented. It is shown that the self-energy (optical potential) of a pion propagating through a Fermi gas of nucleons can be expressed as an integral over density of an effective pion-nucleon forward-scattering amplitude $f(kq;kq)\mathrm{}$ in the medium. Using a pseudoscalar pion-nucleon interaction, one finds that $f(kq;kq)\mathrm{}$ satisfies a modified form of the standard Chew-Low equation for pion-nucleon scattering. The effect of the medium is twofold: (i) The effective pion-nucleon coupling constant is quenched in the medium, and (ii) the pion-nucleon threshold of the effective amplitude is moved upwards in energy. Both effects are due to Pauli-principle restrictions on nucleons in intermediate states. Like its free-space counterpart, $f(kq;kq)\mathrm{}$ displays a resonance behavior in the (3,3) pion-nucleon channel. The resonance appears as a characteristic energy dependence in the pion-nucleus optical potential calculated from $f(kq;kq)\mathrm{}$. The resonance position in pion-nucleus scattering is determined by three competing effects, and generally differs from the free pion-nucleon (3,3) resonance energy. One finds that: (i) The quenching effect moves the (3,3) resonance up in energy and narrows its width, (ii) the dispersive effect of the nuclear medium (increase of the real part of the wave number over the free-space value) moves the resonance downward, (iii) the energy dependence of the effective radius $R+\lambda$ seen by a pion of wavelength $\lambda$ also shifts the resonance downward in energy. The net energy shift is thus a result of a rather delicate cancellation of several competing effects. Absorption cross sections for negative pions are calculated for a range of nuclei. In general, the net downward energy shift with respect to the free (3,3) resonance is found to increase with increasing mass number.

Assuming an $\alpha$-cluster structure of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, we construct ground-state wave functions (gsw) for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. We expand the gsw of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ in a product basis of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ($3\alpha$) states and relative motion of the fourth $\alpha$ particle with respect to ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. A corresponding expansion is used for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ground state. From those expansions, we get the probability amplitudes for intermediate states of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$. Those are compared with the amplitudes extracted from other calculations. Best choices of coordinate systems for the description of the virtual breakups are discussed using the concept of "democracy."

It is shown that the usual multiple-scattering treatment of nucleon-nucleus elastic scattering does not provide a complete description of the process. In particular, the replacement of the two-nucleon interaction potential by a two-body $T$ matrix (evaluated at a single parametric energy) leads to an inadequate treatment of the off-shell aspects of the multiple-scattering problem. As an example, we discuss the manner in which short-range correlations in the nuclear targets affect the off-shell behavior of the two-body scattering operators used to describe nucleon-nucleus scattering. The influence of these off-shell effects on the calculation of total cross sections is discussed.

The electromagnetic current ${\mathrm{j}}_2^{\mathrm{OPE}}$ due to the exchange of a charged pion between a neutron and a proton is rederived by comparing the bremsstrahlung matrix element computed from the Schrödinger equation with that obtained from the lowest-order Feynman diagrams. No account is taken of renormalization effects or nucleon resonances. The operator $\int d^{3}x{\overrightarrow{\mathrm{j}}}_2^{\mathrm{OPE}}\left(\overrightarrow{\mathrm{x}}\right)e^{-i\overrightarrow{\mathrm{k}}·\overrightarrow{\mathrm{x}}}$ which is needed for neutron-proton bremsstrahlung calculations is evaluated, and an approximation to it obtained as an expansion in powers of (photon energy)/(pion mass), keeping the first two terms. This is expected to be considerably more accurate than expanding the bremsstrahlung matrix element itself in powers of $k$. The second term in the expansion contributes to ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}\leftrightarrow {}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ transitions and may become significant even for small values of $\frac{k}{\mu }$. As a preparation for actual calculations the operator is rewritten in terms of irreducible tensors. The treatment of nonlocalities other than charged-pion exchange is discussed briefly.

States of ${}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$ up to 2 MeV in excitation were studied with 8-12-keV resolution by ($d$,$t$) and ($d$,$\alpha$) experiments, and interpreted in terms of two-hole configurations. ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(d, t)$ angular distribution and spectroscopic factors were obtained at 14.0- and 15.75-MeV bombarding energy. Six low-lying levels not detected in earlier (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$\alpha$) experiments were resolved. The summed spectroscopic ($C{}_{}{}^2{}_{}{}^{}S$) strength obtained for the five strong $l=1\mathrm{}$ transitions was $\frac{2}{3}$ of the sum-rule limit in contrast to previous (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$\alpha$) results which exceeded it. Successful distorted-wave Born-approximation (DWBA) predictions for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(d, \alpha ){}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$ angular distributions permitted the assignment of 15 $L$ values and corresponding $J^{\pi }$ limits for the final states, about half of which had not been resolved in previous particle-transfer work. Levels dominated by ${\left(f_{\frac{5}{2}}{g}_{\frac{9}{2}}\right)}^{-1\mathrm{}}$ and ${\left(p_{\frac{3}{2}}{g}_{\frac{9}{2}}\right)}^{-1\mathrm{}}$ configurations were identified by comparison with previous data for ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$. Higher-spin states dominated by the ${g_{\frac{9}{2}}}^2$ configuration were not seen, as expected; however, a comparison of measured and "absolute" microscopic DWBA cross sections for known two-hole states showed evidence of strong configuration mixing. Additional evidence for a $2^{-}$,($2^{+}$) doublet at 706 keV excitation was found.

NUCLEAR REACTIONS ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}(d, t){}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$, $E=14.0, 15.75$ MeV, measured $\sigma (E_t, \theta )$, ${}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$ level energies; resolution 8 keV. DWBA analysis, deduced $l$,$s$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(d, \alpha )$-${}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$, $E=17.0\mathrm{}$ MeV, measured $\sigma (E_{\propto }, \theta )$; resolution 12 keV. Microscopic DWBA analysis, deduced $L$ transfers, enhancement factors.

The ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ $\epsilon$ decay and the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ reaction with beam energies between 5.5 and 8.4 MeV have been used with Ge(Li) spectrometers to study the properties of $\gamma$ rays from states of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ below 2.86 MeV excitation. From ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ $\epsilon$ decay both the $\gamma$-ray spectrum and $\gamma -\gamma$ coincidences were studied. $\gamma -\gamma$ coincidences, $\gamma$-ray excitation functions, $\gamma$-ray angular distributions, and absolute cross sections were measured for the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ reaction. An $\epsilon$ decay scheme for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$, which includes six $\gamma$ rays, and an energy-level diagram for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$, which includes 35 $\gamma$ rays (14 of which are reported for the first time) from 20 excited states, are presented. Comparison of the data from ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ with predictions of the statistical compound-nuclear model have resulted in spin assignments (in parentheses) for the following states (energies in keV) of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$: 158.4(3), 576.6(5), 829.7(4), 970.3(2), 1009.2(5), 1114.6(3), 1450.8(0), and 1720.3(1). Branching ratios are presented for 14 $\gamma$ rays from these eight states and multipole mixing ratios are given for 12 of these $\gamma$ rays (10 are predominantly $M1\mathrm{}$). The data are consistent with a spin-4 assignment to the ground state. Contrary to previous suggestions, evidence from all experiments indicates that only one state (believed to be the antianalog of the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ ground state) exists in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ in the neighborhood of 1451 keV excitation. The level energies, $\gamma$-ray multipole mixing ratios, and $\gamma$-ray branching ratios agree, in general, with shell-model predictions of McGrory.

The first reported measurements of the $\beta$ decay, half-life, and mass of ${}_{}{}^{31}{}_{}{}^{}\mathrm{Al}$ are presented. The new activity was produced by the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}({}_{}{}^{18}{}_{}{}^{}\mathrm{O}, \alpha p){}_{}{}^{31}{}_{}{}^{}\mathrm{Al}$ reaction using 41-MeV incident ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ ions, and was transferred pneumatically to a remotely located station where delayed $\gamma$ rays and $\beta$ rays were counted with Ge(Li) and NE 102 detectors, respectively. $\gamma$-ray energies (in keV) and relative intensities for the ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$ daughter transitions are 621.81±0.30 (9.94±0.65), 752.23 ±0.30 (18.5±0.8), 1564.49±0.30 (17.3±1.6), 1694.73±0.30 (58.9±1.6), and 2316.64±0.40 (72.8±1.8). The ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$ excitation energies (in keV) and relative $\beta$ branching intensities are 752.24±0.30 (<3.0), 1694.78±0.30 (49.0±1.7), and 2316.73±0.40 (100±2.5). A tentative $\beta$- ray transition to a state at $E_x=2787.7\mathrm{}\pm 0.8$ keV is also observed. Upper limits on the strength of some possible $\gamma$-ray transitions following $\beta$ decay to higher levels are given. ${}_{}{}^{31}{}_{}{}^{}\mathrm{Al}$ decays with a half-life of 644±25 msec. By measuring the energy spectra of $\beta$ rays populating the second and third excited states of ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$ the mass excess of ${}_{}{}^{31}{}_{}{}^{}\mathrm{Al}$ has been measured to be -15008±100 keV. The mass excess of ${}_{}{}^{34}{}_{}{}^{}\mathrm{P}$ has been remeasured by a similar technique to be -24 550±90 keV, and this value has been used to revise previous predictions for the masses of ${}_{}{}^{33}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{35}{}_{}{}^{}\mathrm{P}$. The masses of several $T_z=\frac{5}{2}$ and $T_z=3\mathrm{}$ nuclides in the $2s-1d$ shell are compared with theoretical estimates. The $\beta$-decay measurements for ${}_{}{}^{31}{}_{}{}^{}\mathrm{Al}$ are shown to be in poor agreement with simple collective-model calculations, and in good agreement with recent detailed shell-model calculations.

Proton-$\gamma$ coincidence techniques have been used to measure, by the Doppler-shift attenuation method, the lifetimes of the nine bound states of ${}_{}{}^{33}{}_{}{}^{}\mathrm{P}$ below 4.3-MeV excitation energy, via the ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}(t, p\gamma ){}_{}{}^{83}{}_{}{}^{}\mathrm{P}$ reaction, at triton bombarding energies of 2.5 and 3.1 MeV. More accurate excitation energies have also been obtained for these states. For the first nine excited states in ${}_{}{}^{33}{}_{}{}^{}\mathrm{P}$ the measurements lead to the following energies (keV) and lifetimes (psec): 1431.5±0.3 (0.60±0.10), 1847.3±0.3 (0.80±0.15), 2537.6±0.5 (0.070±0.012), 3275.5±1.0 (0.21±0.04), 3490.2±1.0 (0.11±0.02), 3626.6±1.0 (0.17±0.08), 4048±1 (0.085±0.030), 4194±3 (0.15±0.05), and 4225±1 (0.39±0.10). The decay modes and branching ratios for these states have also been measured. These results restrict the spin and parity of the listed states (MeV) to the following assignments $\left(J^{\pi }\right):3.28\mathrm{} (\frac{3}{2}, {\frac{5}{2}}^{+})$, $3.63 \left({\frac{7}{2}}^{+}\right)$, $4.05 \left({\frac{5}{2}}^{\mathrm{}(+)\mathrm{}}\right)$, $4.19 \left({\frac{5}{2}}^{+}\right)$. For some transitions better limits have been set on the $\delta$ mixing ratios previously measured. The ${}_{}{}^{33}{}_{}{}^{}\mathrm{P}$ spectrum obtained is compared to other results and to applicable shell-model calculations.

${}_{}{}^{36,38}{}_{}{}^{}\mathrm{Ar}(d, p)$ angular distributions at 9- and 10-MeV incident energy, for 13 neutron-unbound states in ${}_{}{}^{37,39}{}_{}{}^{}\mathrm{Ar}$, are described in terms of conventional distorted-wave Born-approximation theory using complex-energy eigenstates as form factors, and spectroscopic information is extracted which is consistent with previous studies of the bound neutron states of ${}_{}{}^{37,39}{}_{}{}^{}\mathrm{Ar}$.

Compound states of high excitation in ${}_{}{}^{25,26}{}_{}{}^{}\mathrm{Mg}$ have been observed, with good resolution, in the total neutron yield from $\alpha$-particle bombardment of ${}_{}{}^{21,22}{}_{}{}^{}\mathrm{Ne}$. Bombarding energies were from 1 to 5 MeV. Analysis of the areas under the yield curves gives $\alpha$-particle strength functions of ${\overline{S}}_{\alpha }=0.031\mathrm{}\pm 0.021$ for ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$+$\alpha$ and ${\overline{S}}_{\alpha }=0.026\mathrm{}\pm 0.012$ for ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$+$\alpha$. For astrophysical purposes these strength functions are used to extrapolate the averaged cross sections to lower energies.

The calcium isotopes ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ through ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ are described within the framework of the conventional shell model using a phenomenological effective two-body interaction. The residual interaction consists of usual $j-j$ pairing plus a surface-tensor force. ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ is assumed to be an inert core. Besides all possible configurations arising from $1f_{\frac{7}{2}}$ and $2p_{\frac{3}{2}}$ orbits, configurations of the form ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^{n1\mathrm{}}{\left(1\mathrm{}{f}_{\frac{5}{2}}\right)}^{n2\mathrm{}}$ where $n_1+n_2=n$ (the number of extracore neutrons) and $n_2=1, 2$, are also considered in the basis vector spaces. The calculated ground-state energies as well as the excited energy levels are in good agreement with the experimental values. Reproduction of single-neutron spectroscopic factors for stripping and pickup reactions is also good.

Yields for 40 nuclides have been determined in the interaction of 3- and 29-GeV protons with V. Most of the radionuclides were measured by direct $\gamma$-ray spectroscopy of the irradiated targets; stable Ne and Ar isotopes were measured by mass spectrometry; radicargon isotopes were determined both mass spectrometrically and by radioactivity measurements. Charge dispersion curves were derived from independent and cumulative yield measurements for the mass regions 22-29, 36-41, and 42-48. The curves for 29 GeV are almost identical with the corresponding ones for 3 GeV. Total isobaric cross sections were determined at many mass numbers by estimating the unmeasured cross sections, from the charge dispersion curves, and adding them to the directly measured ones. Thus mass-yield distributions were obtained. At 3 GeV the total isobaric cross section is 30 mb at mass 47 and it decreases to a minimum of 8 mb around mass 24. At 29 GeV the cross sections are slightly lower than at 3 GeV for the heavier products, down to about mass 30, and somewhat higher for the lighter products, below mass 30. The mass-yield distributions from V are similar to those determined from Cu and Ag. It is shown that the experimental results (including those from Cu) do not agree as well with the Monte Carlo cascade calculations of Metropolis et al., as has been generally supposed.

A self-consistent core-particle coupling method derived from the generalized Hartree-Fock approximation was applied to the nickel isotopes. The $0^{+}$ ground and $2^{+}$ first excited states of the even nickel isotopes are considered as cores, and the low-lying states of the odd nickel isotopes as well as the even core states are calculated self-consistently from the equation of motion in a particle-number nonconserving approximation. The static electric quadrupole moments of the first excited $2^{+}$ states, the spectroscopic factors for pickup and stripping reactions on even targets, and energies of low-lying states of the odd isotopes are calculated and compared with experiments.

Thirty levels in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ were populated by use of the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}({}_{}{}^3{}_{}{}^{}\mathrm{He}, p)$ reaction. The angular distributions of protons leading to these states were obtained with a split-pole magnetic spectrograph. In some cases a study of the angular distribution permitted the determination of the orbital angular momentum transferred by the $n-p$ pair. Coincidences between protons and $\gamma$ rays from the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}({}_{}{}^3{}_{}{}^{}\mathrm{He}, p\gamma )$ reaction were also studied to obtain the $\gamma$ decay of some levels in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$. The results of the present investigation are combined with those of previous work on ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ to assign spins and parities for some of the levels. The isobaric analog to the ground state of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$ and the corresponding antianalog state are briefly discussed.

The variable moment-of-inertia (VMI) model for the asymmetric shape of nuclei which allows a simultaneous analysis of the data for both the ground-state band and the $\gamma$-vibrational band in even-even nuclei is worked out. For the asymmetric rotor we use Krutov's model which is based on the assumption of rotational flow and a rotationally invariant core in nuclei and predicts a linear dependence of the moment of inertia on the deformation-a condition used by the VMI model. The calculations (using a least-squares-fitting procedure) are carried out for all the even-even nuclei which have at least two states above the ground state and two states above the $\gamma$-vibrational band head well established. The over-all comparison with the experimental data is very good. The fits to the ground-state band, however, remain essentially the same as for the VMI model.

Properties of levels in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$, and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ have been investigated both by observing the electron-capture decay of ${}_{}{}^{148}{}_{}{}^{}\mathrm{Tb}$ and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Tb}$ as well as the $\gamma$ transitions following the ($\alpha , \mathrm{xn}$) reactions on ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ targets. Decay schemes were constructed or confirmed. The angular distributions of the $\gamma$ lines with respect to the beam direction enabled spin assignments for most states. Searches for isomerism revealed lifetimes of $T_{\frac{1}{2}}=17.3\mathrm{}\pm 2.0$ nsec and $T_{\frac{1}{2}}=9.1\mathrm{}\pm 2.0$ nsec, respectively, for the $8^{+}$ 2689-keV level in ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$ and the $6^{+}$ 2981-keV state in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ and indicate a particle character for these states. An upper limit of 5 nsec was derived for the half-lives of any level reached in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$. The decay schemes of ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ are similar to those of the neighboring neutron-deficient nuclei, e.g. ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Nd}$. The low-lying negative-parity states observed may represent a collective sequence based on a $3^{-}$ state.

The ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(p, t){}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(p, t){}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ reactions were studied at a proton energy of 17.8 MeV in order to examine possible relationships between the nuclear structures of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ and ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$. From a detailed comparison of the cross sections and angular distributions observed in the two reactions, it is concluded that a number of low-lying levels in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ are built upon core excitations which can be identified with the levels of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$. The cross-section comparisons served to measure the fragmentation of the observed core strengths caused by the particle-core interaction in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$, and yielded the corresponding weak-coupling wave-function amplitudes for the low-lying ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ levels. The results show that considerable mixing occurs in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ between members of a multiplet based on the $2_1^{+}$ core excitation and the single-particle proton levels, so that the $L=2\mathrm{}$ ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(p, t){}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ cross section was not distributed according to the normal ($2J+1$) rule. The measured wave-function amplitudes are consistent with a weak-coupling structure, however, and also are consistent with ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}({}_{}{}^3{}_{}{}^{}\mathrm{He}, d){}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ measurements of the fragmentation of the single-particle proton strengths produced by the particle-core interaction.

Thin targets of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$, and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ were bombarded with protons of several energies between 7 and 13 MeV. Correlated energies of fission-fragment pairs were measured with silicon surface-barrier detectors. Fragment mass vs total kinetic energy distributions were deduced, and their systematic variation with bombarding energy was studied. It was found that the yield in the valley of the mass distributions for symmetric divisions increases with increasing excitation energy, and that the peaks move slightly toward symmetry. The average total kinetic energy for mass divisions with one fragment mass ≃ 132 amu was found to decrease with increasing excitation energy, while for other mass divisions little change was observed. The average over-all total kinetic energy was found to decrease with increasing bombarding energy, and widths of both the kinetic energy distributions and the mass distributions were found to increase somewhat. The results are discussed in terms of fragment shell effects which appear to persist to our highest excitation energy (∼18 MeV), and also in terms of the two-component fission hypothesis.

The ${}_{}{}^{130}{}_{}{}^{}\mathrm{Ba}(n, \gamma )$ cross section has been measured from 0.5 to 5000 eV with an energy resolution of 0.4%. The large epithermal resonances found in this experiment explain the anomalously high concentrations of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ found in lunar rocks, and the measured resonance parameters provide one with a quantitative tool for correlating burial depth with exposure age for lunar samples.