Particle-gamma-ray coincidence spectra from the ${}_{}{}^{110}{}_{}{}^{}\mathrm{Pd}$(t,pγγ${)}^{112}$Pd and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$(t,pγγ${)}^{102}$Mo reactions were measured with enriched ${}_{}{}^{110}{}_{}{}^{}\mathrm{Pd}$ and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ targets bombarded by 16-MeV tritons to obtain more complete level structures for ${}_{}{}^{112}{}_{}{}^{}\mathrm{Pd}$ and ${}_{}{}^{102}{}_{}{}^{}\mathrm{Mo}$. The resultant ground state band of ${}_{}{}^{112}{}_{}{}^{}\mathrm{Pd}$ and that of ${}_{}{}^{120}{}_{}{}^{}\mathrm{Xe}$ are used in the interpretation of coexistence in ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$. The possible observation of backbending in ${}_{}{}^{102}{}_{}{}^{}\mathrm{Mo}$ is used to investigate the A dependence of backbending over a wider mass region.

The reaction ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$(p,γ${)}^{23}$Mg has been investigated in the energy range $E_p$=0.4–1.27 MeV using a radioactive ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ target. Upper limits for the γ yield have been determined for transitions to states in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$ up to $E_x$=4.4 MeV. The upper limits for the expected resonances in this energy range are more than an order of magnitude weaker than previously predicted. These upper limits are compared with shell model calculations.

Neutron-hole states in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}$ were studied by means of the ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$${(}^3$He,α${)}^{87}$Sr reaction at 36 MeV. Angular distribution measurements were carried out from 3° to 41° (lab) and analyzed with the zero-range distorted-wave Born approximation method. Spectroscopic factors have been determined for about 50 discrete levels in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}$ located below 6 MeV excitation energy and for the three lowest isobaric analog states 2p(3/2, 1f(5/2, and 2p(1/2 observed around 11 MeV. Many l=1 and l=3 discrete levels are observed in the 3–6 MeV excitation energy range. In addition, a large part of the 1f-2p strength is found to lie in the higher-lying continuum up to 13 MeV (about 10% and 40% for the l=1 and 3 contributions, respectively). The distribution of the 1f-2p neutron-hole strength is compared to previous data on neighboring nuclei ${}_{}{}^{89}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Mo}$. In addition, angular distributions for some low-lying high-spin states in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}$ are nicely reproduced by coupled-channel calculations which assume pure two-step (inelastic plus g(9/2 transfer) processes. Spin-parity assignments are proposed for the levels at 1.92 MeV (${(7/2\mathrm{}}^{+}$), 2.16 MeV (${(11/2\mathrm{}}^{+}$), 2.55 MeV (${(9/2\mathrm{}}^{\mathrm{-}}$), and 2.60 MeV (${(13/2\mathrm{}}^{\mathrm{-}}$), on the basis of this coupled-channel analysis.

Laser-stimulated enhancement of neutron widths for p-wave resonances near neutron binding energies is investigated. This study intends to clarify a long-standing disagreement about the possibility of observing the effect of laser-induced nuclear reactions. A formula for calculating the induced neutron width has been derived based upon the Einstein theory of emission and absorption of photons. In comparison with the previous ones, the width now is expressed in terms of some model-independent and measurable parameters such as the partial radiative width, thus making estimations more reliable. The published measurements on this subject have been analyzed and compared with present calculations. The prospect of experimentally observing this effect in the near future is also discussed.

A dynamical polarization potential is defined taking into account the effects on the elastic channel due to the excitation of vibrational collective modes, described within the random-phase approximation. The probability amplitudes for exciting these modes are evaluated by integration along classical trajectories determined by the real part of the nucleus-nucleus potential with energy and angular momentum loss. Calculations performed for the ${}_{}{}^{40}{}_{}{}^{}$Ca${+}^{40}$Ca system show that, at high bombarding energy (E/A=44 MeV), both the real and the imaginary parts of the polarization potential arise mainly from the excitation of the high-lying modes. At energies near the Coulomb barrier, the calculated elastic cross section is in good agreement with the experimental data. The inclusion of the real part of the polarization potential improves this agreement.

Proton transfer to unbound states was studied within the framework of the standard distorted-wave Born approximation formalism by using the form factors of their bound isobaric analog states. The results of the present analyses have shown that the spectroscopic factors obtained by substituting the form factors of the parent analog states for the unbound states in the distorted-wave Born approximation calculations are frequently not reliable.

The vector analyzing powers for the ${}_{}{}^1{}_{}{}^{}\mathrm{H}$(d→,γ${)}^3$He and ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p→,γ) ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ reactions have been measured near threshold ($E_{\gamma }$=7.5 MeV). The angular distribution of the cross section was also measured for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p,γ${)}^3$He reaction. The ratio of the analyzing powers is sensitive to the presence of S=(3/2 capture strength. It was found that a 10% contribution to the capture by M1 radiation (predominantly S=(3/2) is required to explain the data.

The isoscalar giant resonance region has been investigated in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$, and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ nuclei by inelastic scattering of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ particles at small angles where the quadrupole and monopole states can be distinguished through their angular distributions. A monopole resonance is observed in the three nuclei, exhausting, respectively, 23%, 85%, and 110% of the E0 energy weighted sum rule.

The giant quadrupole resonance and the low-lying quadrupole transition have been investigated in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$, ${}_{}{}^{120}{}_{}{}^{}$,124Sn, ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ by inelastic scattering of 108.5 MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ particles at very small angles. Anomalous rise of the giant quadrupole resonance cross section is observed to 0°. Distorted-wave Born approximation calculations are reported. Possible interpretations of the anomalous effect are discussed.

We present spectroscopic factor calculations for one-proton transfer reactions populating positive- and negative-parity states of ${}_{}{}^{105}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$, and ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$, performed within the framework of the interacting boson-fermion model. The results are compared with experimental data for both stripping and pickup reactions.

Results are presented for high-energy gamma-ray production in light-ion induced reactions. Energy spectra and angular distributions were measured for high-energy gamma rays ($E_{\gamma }$>20 MeV) from the reactions ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ on C, Zn, and Pb at E/A=53 MeV, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ on C, Zn, and Pb at E/A=25 and 53 MeV. The gamma-ray energy spectra are roughly exponential, and for ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ at E/A=53 MeV extend out to the full available energy (∼100 MeV). The angular distributions of the gamma rays are slightly forward peaked in the laboratory frame, but are symmetric about 90° when transformed to the nucleon-nucleon center-of-mass frame. For the carbon target data the angular distribution in the nucleon-nucleon frame shows a substantial dipole component. This suggests that the major high-energy gamma-ray production mechanism is bremsstrahlung from first collisions of projectile and target nucleons.

The energy spectra of α particles emitted from (p,α) reactions on ${}_{}{}^{112}{}_{}{}^{}\mathrm{Cd}$, ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, Sb, ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$, and ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ with 18 MeV protons have been measured in order to clarify the shell and odd-even effects in the preequilibrium processes of (p,α) and (n,α) reactions. From the experimental results, it was found that there exist no appreciable shell and odd-even effects on target nuclei in the gross (p,α) energy spectra lower than 20 MeV in the preequilibrium process. They can be explained well by the α knockout model using the effective Q values which are shell independent. The fine structures of the energy spectra for the (p,α) reactions on nuclei around atomic number 50 can be qualitatively explained using the three-nucleon pickup model under the assumption that the states excited in the (p,α) reaction are formed by the coupling of two-neutron-hole states excited in the reaction such as the (p,t) reaction and one-proton-hole states excited in the reaction such as the (d${,}^3$He) reaction. The similar three-nucleon pickup model can explain qualitatively the fine structures of the energy spectra for the (n,α) reactions on nuclei around neutron numbers 50 and 82.

Average s-wave resonance spacings were derived from high-resolution proton resonance data for 11 odd-Z nuclei in the mass range A=41–67 and compared with the average s-wave spacings obtained from neutron resonances for their odd-N isobars. After careful correction for missing levels the neutron and proton results are consistent; proton resonance data can be used to increase the data base for nuclear level densities. After correction to a common excitation energy, the spacings show a correlation with the shell correction energy $E_{\mathrm{shell}}$, especially for A=41, 55, and 59, where data exist for three isobars with quite different shell correction energies. The dependence of the average level spacing D¯ on $E_{\mathrm{shell}}$ is approximately exponential, in good agreement with the theoretical models of Ignatyuk et al. and Kataria et al. The data also have been used to calculate asymptotic a parameters in these two models. The mass dependence of these parameters can be described by the simple relation a=0.137A with an rms deviation of 4.3%. Attempts to describe the data within the Fermi gas model resulted in much larger fluctuations of the parameters with A and Z. Finally, the data were compared to the predictions of the microscopic Fermi gas model, using the single particle level scheme of Seeger and Perisho. At present, the quality of this description is still somewhat worse than with the phenomenological models of Ignatyuk et al. and Kataria et al.

We have investigated the ${}_{}{}^{70}{}_{}{}^{}\mathrm{Zn}$(p,t${)}^{68}$Zn reaction using a beam energy of 35 MeV. Angular distributions were extracted for 18 levels up to 4.25 MeV excitation in ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}$. Distorted-wave Born-approximation calculations have been performed and compared to each angular distribution. Because the distorted-wave Born-approximation angular distributions to the lowest $2^{+}$, $3^{\mathrm{-}}$, and $4^{+}$ states in ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}$ are found to be a poor representation of the data, we have also performed coupled-channels Born-approximation calculations for the ${}_{}{}^{70}{}_{}{}^{}\mathrm{Zn}$(p,t) reaction leading to these states.

A study of the systematics of the breathing mode giant monopole resonance in the isotopic chains of Sn and Sm nuclei by means of inelastic scattering of 120 MeV alpha particles at 0° has been performed. The obtained energy systematics for spherical Sn and Sm nuclei have been employed to fit the nuclear-compressibility parameters. The data on Sn and Sm nuclei have been used in conjunction with already existing data on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ to constrain the various parameters contributing to the nuclear compressibility. The compressibility of nuclear matter $K_{\infty }$ has been deduced to be 300±25 MeV, in contrast with the commonly accepted value of 210±30 MeV. The neutron-asymmetry term has been determined to be -320±180 MeV.

Phenomenological analyses of the experimental n${\mathrm{-}}^{208}$Pb differential, total, and polarization cross sections with local optical-model potentials indicate that the radial shape of the surface absorption depends upon energy below 10 MeV: The corresponding diffuseness decreases and the radius parameter increases with decreasing neutron energy. Because of the dispersion relation that connects the real and imaginary parts of the mean field, these features imply that the real potential contains a surface component whose radial shape also depends upon energy. This radial shape is calculated numerically for typical parametrizations of the energy dependence of the surface absorption; it turns out to be quite complicated for neutron energies between 0 and 15 MeV. In this domain, the predicted differential cross sections are sensitive to the radial shapes of both the real and imaginary surface components of the mean field even though their volume integrals are exactly the same in all the investigated models. The best agreement with the experimental data is obtained for parametrizations in which the radial shape of the surface absorption depends only weakly upon energy. It is shown that good fits to the experimental data can also be obtained in the framework of models in which the radial shape of the surface absorption is independent of energy but in which the strength of the surface absorption depends upon the orbital angular momentum of the incoming neutron. Tentative physical interpretations of these features are proposed.

The n${\mathrm{-}}^{40}$Ca complex mean field is derived from a dispersive optical-model analysis of the available experimental cross sections. In this analysis the real part of the mean field contains dispersive contributions which are derived from the imaginary part by means of a dispersion relation. These dispersive contributions must be added to the Hartree-Fock potential which is assumed to have a Woods-Saxon shape, with a depth $V_H$(E) that depends exponentially upon energy. The input experimental data are 14 differential cross sections in the energy domain (5.3, 40.0 MeV), five polarization cross sections in the domain (9.9, 16.9 MeV), and the total cross section in the domain (2.5, 80 MeV).

The resulting optical-model potential is an analytic function of energy. It can thus be extrapolated towards negative energies, where it should be identified with the shell-model potential. This extrapolation yields good agreement with the experimental single-particle energies in the two valence shells of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. The model also predicts the radial shape and the occupation probabilities of the single-particle orbits and the spectroscopic factors of the single-particle excitations. In order to reproduce the experimental energies of the deeply bound 1p and 1s orbits, one must use a linear rather than an exponential energy dependence of $V_H$(E) at large negative E. It is shown that this is precisely the behavior expected from the fact that the energy dependence of $V_H$(E) actually represents the nonlocality of the original microscopic Hartree-Fock field. The model also correctly predicts the distribution of the single-particle strength of the 1d(5/2 excitation in ${}_{}{}^{39}{}_{}{}^{}\mathrm{Ca}$. The calculated distributions of the 1p strength in ${}_{}{}^{39}{}_{}{}^{}\mathrm{Ca}$ and of the 1f(5/2 strength in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ show that the available experimental information extends over less than half the expected peak, whose energy is thus poorly known experimentally. In the energy domain (2.5, 9 MeV) the predicted total cross section deviates from the experimental data; this reflects the fact that at low energy the calculated cross section is very sensitive to small modifications of the mean field.

A transport theory is developed for description of capture processes in low-energy nuclear collisions. It is based on the picture that a dinuclear molecular complex formed during early stages of the collision acts as a doorway configuration toward formation of a fully equilibrated compound nucleus, and this complex can decay into open binary channels while it evolves toward a compound nucleus. The evolution of the dinuclear molecular complex and its decay into binary fragmentation channels are determined by two coupled transport equations. The formalism, in a local equilibrium limit, is successfully applied to analyze complex fragment emission and fusion-evaporation data from collisions of Si+C, Si+N, and Mg+C.

A computation model for nuclear reaction studies which is based upon a momentum dependent interaction between quasiparticles is extended to include collisions between the nucleons. The model is first used to examine the time scales involved in fragment formation at intermediate energies, both as a function of bombarding energy and impact parameter. The distribution of excitation energies and angular momenta of the reaction products is also investigated since the model possesses stable ground states. Several reactions are chosen as examples: Ar+C at 12A MeV, and Ca+Ca at 25A, 50A, and 100A MeV. The time scale for changes in mass distribution, etc., is discussed and the need for an afterburner scheme is established.

Statistical calculations are performed to evaluate the sequential decay of highly excited primary reaction products and the resulting perturbations of the relative populations of widely separated particle unbound states in light nuclei. Previous calculations are improved upon by including more states in the primary distribution and constraining the element distribution by that measured experimentally. Emission temperatures of about 5 MeV, extracted from the relative populations of states in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^5{}_{}{}^{}\mathrm{Li}$, and ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ nuclei emitted in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Au reaction at E/A=94 MeV, are not likely due to sequential feeding from an ensemble of primary fragments characterized by much higher initial temperatures.