This comment on a recent Physical Review Letter by Noble points out that the assumptions used by Noble are not valid for the reaction considered. Hence, the anomaly in the angular distributions remains to be explained.

In response to a letter by Young, Blatt, and Seyler, we point out the equivalence rather than the mutual exclusion of the ${\mathrm{He}}^3-t$ and $d-\alpha$ descriptions of ${\mathrm{Li}}^6$.

A continuum wave function, improperly normalized in previous work, is corrected. Expressions for the probability of internal ionization of the atomic $K$ shell, accompanying $\beta$ decay and electron capture, are given explicitly including all factors.

$\alpha$-particle scattering by ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ has been studied in the energy range 18.9 to 30 MeV, using the Minnesota MP tandem Van de Graaff accelerator. The target consisted of 40 μg/${\mathrm{cm}}^2$ of oxygen in the form of LiOH on a 20-μg/${\mathrm{cm}}^2$ carbon backing. Absolute cross sections were determined with an oxygen gas target. Excitation functions were measured in 20-keV steps at eight angles over the entire energy range, using computer control of the accelerator's analyzing magnet. The center-of-mass angles were selected to be zeros of the Legendre polynomials $P_1$ to $P_8$ for elastic scattering. Inelastic scattering to the 6.05-6.13-MeV doublet in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ was also studied. Elastic differential cross sections were measured at 20 energies between 18.9 and 23.0 MeV. Nonstatistical structure is observed in the excitation functions. The spins and parities of the resonances are tentatively assigned on the basis of the elastic excitation functions. A phase-shift analysis of the differential cross sections has unambiguously identified $J^{\pi }=9^{-}$ resonances at 20.70 MeV ($\Gamma =120\mathrm{}$ KeV) and 21.10 MeV ($\Gamma =80\mathrm{}$ keV) in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. They may be the $9^{-}$ members of the lowest-two negative-parity rotational bands in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, which are expected to be near 20 MeV.

Measurements have been made of the radiative widths of the lowest energy resonances in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Maxwellian-averaged capture cross sections calculated for $kT=30\mathrm{}$ keV indicate that ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ could not have been significant neutron poisons in $s$-process nucleosynthesis.

A three-fluid model of nuclei is introduced, the three fluids being the protons, the neutrons of the same orbitals as protons, and the excess neutrons, to account for the fact that the excess neutrons interact less strongly with the protons than do the neutrons which occupy the same space-spin states as the protons. Calculations of proton and neutron density distributions, of isotope shifts, and of isospin impurities have been carried out. The giant-dipole phenomenon is also studied in the present model. It is found that considerable improvement is achieved in the results for the proton density distribution and for the isospin impurities as compared with the two-fluid model. The other results are found to be consistent with previous calculations.

The longitudinal and transverse form factors were determined separately as functions of the excitation energy from 15 to 40 MeV in the momentum-transfer range 0.75-1.56 ${\mathrm{F}}^{-1\mathrm{}}$. For some of the form-factor spectra the measurements were extended up to an excitation energy of 100 MeV and the results were compared with the quasielastic model presented by de Forest. The $q$ dependence of the experimental form factors for levels were compared with the predictions of the particle-hole model and with the intermediate-coupling model. We have then found the levels with the following excitation energies (MeV), spins, and parities: 18.1 ($1^{-}$), 18.6 ($3^{-}$), 19.6 ($4^{-}$), 20.0 ($2^{+}$), 20.6 ($3^{+}$), 21.6 ($3^{-}$), 22.0 ($1^{-}$), 22.7 ($1^{-}$), and 23.8 ($1^{-}$). We have also found new evidence of the possibility of the spin-isospin mode for the 22.7-MeV ($1^{-}$) excitation.

Accurate cross-section measurements are presented for $d-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ elastic scattering at 12.000 MeV.

A search has been made for excited states in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ by investigating proton-induced reactions on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. The investigation consisted of two parts. In the first part, a kinematically incomplete experiment, the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and $\alpha$-particle continua from the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p,{}_{}{}^3{}_{}{}^{}\mathrm{He})$ and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p,\alpha )$ reactions at an incident proton energy of 45.0 MeV have been studied for structure due to excited states in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, respectively. The ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and $\alpha$-particle spectra were measured from 15 to 90° (lab) in steps of 5° using a $\Delta E-E$ detector telescope. The ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ spectra exhibit clearly discernible peaks due to the 20.2-MeV ($0^{+}$, $T=0\mathrm{}$) and 21.4-MeV ($0^{-}$, $T=0\mathrm{}$) excited states in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. In the $\alpha$-particle spectra no structure has been observed that could be interpreted as due to excited states in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ for excitation energies up to 17.5 MeV. An upper limit of 30 μb/sr could be set for the excitation of states in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ having a width $\lesssim 1.0$ MeV. In the second part, a kinematically complete experiment, a study has been made of the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p,\alpha d)p$ reaction at an incident proton energy of 45.0 MeV. This investigation was carried out to study final-state interactions and, in particular, to search for a possible $p-d$ final-state interaction corresponding to a resonance in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. Coincidence spectra from the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p,\alpha d)p$ reaction were measured in coplanar geometry with the $\alpha$-particle detector set at 50° (lab), while the deuteron-detector telescope was moved in steps of 10° from -100 to -50° (lab), and with the $\alpha$-particle detector set at 30° (lab) and the deuteron-detector telescope at -100 and -80° (lab). The measured coincidence spectra show a prominent $p-\alpha$ final-state interaction corresponding to the ground state of ${}_{}{}^5{}_{}{}^{}\mathrm{Li}$. No other strong $p-\alpha$ final-state interaction was observed. The coincidence spectra do not exhibit a $p-d$ final-state interaction corresponding to a $T=\frac{1}{2}$ resonance in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ of excitation between 5.5 and 20 MeV.

The process of absorption in $K$-mesonic atoms is studied with special emphasis on the role of the $Y_0^{*}\mathrm{}\left(1405\right)\mathrm{}$ resonance. An effective $t$-matrix method is developed to incorporate the effects of the resonance. Detailed calculations of the absorption process, based on an independent-particle model of the nucleus, were made for selected nuclei. The results of these calculations are compared with available x-ray and emulsion data for moderate to heavy nuclei.

The neutron total cross section of deuterium has been determined with 1-2% accuracy at 27 energies between 1.5 and 27.5 MeV in order to investigate a 5% discrepancy in earlier measurements. The hydrogen total cross section was measured concurrently as a check on the accuracy of the method. The deuterium results agree with earlier Los Alamos data below 4 MeV and with Hanford data between 4 and 13 MeV, but disagree with these earlier measurements at other energies.

A momentum-dependent potential is developed to generate nuclear single-particle spectra in agreement with experiment. The parameters of the model are obtained by fitting to experimental data on nuclides with masses greater than 160. The heavy-element neutron single-particle spectrum is compared with the spectrum generated from a Woods-Saxon potential. The potential is applied to the problem of computing the single-particle spectra of nuclides in the mass-300 region.

The reactions ${}_{}{}^7{}_{}{}^{}\mathrm{Li}({}_{}{}^3{}_{}{}^{}\mathrm{He},p){}_{}{}^9{}_{}{}^{}\mathrm{Be}\left(14.39\mathrm{} \mathrm{MeV}\right)\left(\gamma \right)$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}({}_{}{}^3{}_{}{}^{}\mathrm{He},n){}_{}{}^9{}_{}{}^{}\mathrm{B}\left(14.67\mathrm{} \mathrm{MeV}\right)\left(\gamma \right)$ have been used to study the $\gamma$-decay modes of the first $T=\frac{3}{2}$ states in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{B}$. $\gamma$ spectra from a NaI detector were recorded in coincidence with proton energy spectra from the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}({}_{}{}^3{}_{}{}^{}\mathrm{He},p)$ reaction, and with neutron time-of-flight spectra from the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}({}_{}{}^3{}_{}{}^{}\mathrm{He},n)$ reaction. In addition, the singles $\gamma$ spectrum from the 14.39-MeV state in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ was studied using a Ge-Li detector. The $\gamma$ spectrum from the Ge-Li detector gives the branching ratio $\frac{{\Gamma }_{\gamma \mathrm{}\left(2.43\right)\mathrm{}}}{{\Gamma }_{\gamma 0}}=1.19\mathrm{}\pm 0.16$ for the decay of the first $T=\frac{3}{2}$ state in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$. From the $\gamma -n$ coincidence spectrum below threshold for production of ${}_{}{}^9{}_{}{}^{}\mathrm{B}$(14.67 MeV) a $\gamma$ decay from ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(14.39 MeV) to a state in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ at $E_x=2.9\mathrm{}\pm 0.25$ MeV was found. The total width of this state was found to be $\Gamma =1.0\mathrm{}\pm 0.25$ MeV. A measurement of the strength of this $\gamma$ branch relative to that to ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(2.43 MeV) yields $\frac{{\Gamma }_{\gamma \mathrm{}\left(2.9\right)\mathrm{}}}{{\Gamma }_{\gamma \mathrm{}\left(2.43\right)\mathrm{}}}=0.30\mathrm{}\pm 0.04$. From the $\gamma -n$ spectra above the ${}_{}{}^9{}_{}{}^{}\mathrm{B}$(14.67 MeV) threshold a $\gamma$-decay spectrum from the (14.67-MeV) state in ${}_{}{}^9{}_{}{}^{}\mathrm{B}$ was obtained which shows consistency with the branching ratios obtained for ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(14.39 MeV). Combining our branching ratios with previously available information allows us to present a best set of radiative widths from the first $T=\frac{3}{2}$ levels in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{B}$. From the coincidence spectra the value for $\frac{{\Gamma }_{\gamma 0}}{{\Gamma }_{\mathrm{tot}}}$ is found to be 0.021±0.004 for ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(14.39 MeV). The ratios of the total widths $\frac{{\Gamma }_{\mathrm{tot}}\left({}_{}{}^9{}_{}{}^{}\mathrm{Be}\right(14.39\mathrm{} \mathrm{MeV}\left)\right)}{{\Gamma }_{\mathrm{tot}}\left({}_{}{}^9{}_{}{}^{}\mathrm{B}\right(14.67\mathrm{} \mathrm{MeV}\left)\right)}$ is deduced as ${1.23}_{-0.43\mathrm{}}^{+0.54\mathrm{}}$. When combined with the value for ${\Gamma }_0\left({}_{}{}^9{}_{}{}^{}\mathrm{Be}\right(14.39\mathrm{} \mathrm{MeV}\left)\right)$, these ratios yield ${\Gamma }_{\mathrm{tot}}=0.50\mathrm{}\pm 0.1$ keV (${}_{}{}^9{}_{}{}^{}\mathrm{Be}$) and ${0.4}_{-0.18\mathrm{}}^{+0.14\mathrm{}}$ keV (${}_{}{}^9{}_{}{}^{}\mathrm{B}$) for the total widths of the two states.

States in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ have been studied by 180° inelastic electron scattering with incident energies of 39 and 56 MeV. A large scattering peak is found at each bombarding energy, showing excitation of a $1^{+}$, $T=1\mathrm{}$ state at 11.2 MeV, with transition radius $R=2.53\mathrm{}\pm 0.15$ fm and radiation width ${\Gamma }_0=11\mathrm{}\pm 2$ eV. Other levels from 11 to 19 MeV are also excited.

Quasielastic electron scattering from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ is investigated with a model in which the two-nucleon interaction is described by a separable potential. Cross sections are given in the impulse approximation for the ejected proton and scattered electron detected in coincidence, and for detection of only the scattered electron. Both two- and three-body breakup of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ are considered, with final-state interactions between the spectator nucleons included in three-body breakup. Good agreement is obtained with all the electrodisintegration data, except the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ coincidence data, for wave functions derived from separable potentials which reproduce the $s$-wave two-nucleon phase shifts at low and medium energies. Rescattering corrections between the spectator particles are found to be important in calculating three-body disintegration. The need for more refined and reliable coincidence data is reaffirmed.

We show by direct calculation that the heavy-particle-transfer model of backward elastic $\alpha$-particle scattering, together with the assumption of $\alpha$-cluster structure of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, is capable of explaining the large backward peak in elastic $\alpha$ scattering from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$.

A model is proposed for following the progress of nucleon-induced nuclear reactions as a function of time. It predicts that the majority of protons and high-energy neutrons emitted from heavy targets in these reactions appear before internal statistical equilibrium has been established. However, for the 18-MeV ($p,xn$) reaction with ${\mathrm{Ta}}^{181}$ the model predicts fewer high-energy neutrons than are observed experimentally. Further, there is a difference in shape between the predicted and observed spectrum. The same differences arise when a comparison is made between the experimental spectrum and that predicted by Griffin's model for decay. It is suggested that these differences arise because both models fail to consider surface reactions explicitly.

It is also suggested that this model might best be used in conjunction with Monte Carlo cascade calculations of high-energy nuclear reactions to follow the complete equilibration of the nonequilibrated excited nuclei left after these cascades are terminated. An example of using the model for this purpose is given.