The radiative capture reactions ${}_{}{}^3{}_{}{}^{}(\mathit{p}$,γ${)}^4$He and ${}_{}{}^3{}_{}{}^{}(\mathit{n}$,γ${)}^4$He are studied within the framework of a microscopic multichannel resonating group model. Employing a charge symmetric nuclear force we find different thresholds for the mirror channels due to the Coulomb force. These differences in term together with channel coupling effects lead to marked variations between observables of the two mirror reactions. We demonstrate that all types of experimental data can be reproduced by our calculation except for the controversial integrated (n,γ) cross section data.

We present an analysis of six-quark basis states constructed from molecular-type single-particle orbitals. In the present work, we employ a nonrelativistic constituent quark model with one-gluon exchange approximated by a spin-spin interaction. The orbitals are constructed from appropriate combinations of two-center Gaussians. The calculations are performed in the limit of zero separation, and is deemed relevant to short distances. We study the contributions of configurations which are natural in the molecular basis but had been neglected previously in cluster model calculations. We find a dramatic lowering of the energy due to these configurations.

Differential cross sections of elastic scattering of deuterons on the target nuclei ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ were measured at $E_d$=58.7 MeV and $E_d$=85 MeV. ‘‘Best-fit’’ parameters in terms of the phenomenological optical model were extracted from the data including in addition differential cross section and analyzing power data from the literature. A set of global optical potential parameters is derived.

The fine structure of the $g_{9/2}$ isobaric analog state in ${}_{}{}^{55}{}_{}{}^{}\mathrm{Co}$ at 8.46 MeV has been reexamined in the inelastic scattering and capture channels. Excitation functions were measured in the proton energy range 3.45–3.48 MeV for the γ decays of the $2^{+}$ and $4^{+}$ states of ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ and for capture to 16 bound states of ${}_{}{}^{55}{}_{}{}^{}\mathrm{Co}$. Three ${(9/2\mathrm{}}^{+}$ fragments, at 3.461, 3.465, and 3.474 MeV, were identified from their decay to the 6.068 MeV antianalog state and confirmed by angular distribution measurements. The spreading width of the analog state is about 6 keV. Incidental spectroscopic information obtained in the course of the measurements includes a previously unobserved weak decay branch of the ${(9/2\mathrm{}}^{+}$ antianalog state.

Strong transitions to high spin states are observed in the study of the (α,d) reaction at 218 MeV on closed shell heavy nuclei. It is shown that the highest spin valence valence n-p strength in the residual nuclei ${}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$, ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sb}$, ${}_{}{}^{146}{}_{}{}^{}\mathrm{Eu}$, and ${}_{}{}^{210}{}_{}{}^{}\mathrm{Bi}$ is shared between a first strongly excited fragment and higher lying groups. The valence plus outer shell (${\nu }_{13/2}$×π${\mathit{h}}_{11/2}$${)}_{12}^{\mathrm{-}}$ strength is tentatively identified in ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sb}$.

Electron scattering cross sections have been measured for the $0^{+}$, $2^{+}$, $4^{+}$, and $6^{+}$ levels of the ground state rotational band of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$ for effective momentum transfers between 0.3 and 2.9 ${\mathrm{fm}}^{\mathrm{-}1}$. The charge and transition charge densities for these states have been inferred from a combined analysis of electron scattering, muonic atom, and Coulomb excitation data. These densities are compared to the predictions of a mean field theory that describes this nucleus by a triaxial microscopic calculation in the Hartree-Fock-Bogoliubov approximation using a density-dependent force. The densities have been determined with a precision that is sufficient for the comparison of theoretical calculations with the measured densities to be sensitive to the pairing and surface properties of the effective interaction.

A model is formulated for the prediction of medium energy γ rays in light-ion-induced collisions. We assume a semidirect reaction whereby the giant dipole resonance is excited in the preequilibrium relaxation process. Detailed balance is used to invert experimental photon absorption cross sections to a γ-ray emission rate, and this emission rate is incorporated into the hybrid model for pre- equilibrium decay. Comparisons of calculated and experimental γ-ray spectra from 14 MeV neutron-induced reactions give reasonably good agreement, as do comparisons with 27 MeV ${}_{}{}^3{}_{}{}^{}\mathrm{-}$ and α-induced reactions. An npγ bremsstrahlung calculation underpredicts these same data by a large amount. Our findings are consistent with an interpretation that the giant dipole resonance collective excitation may be induced by single particle-hole transitions in the preequilibrium relaxation process, and may contribute to the high-energy tail of observed γ-ray emission spectra.

A measurement of the circular polarization $P_{\gamma }$ of the 1081 keV γ-ray in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ is reported. The result is $P_{\gamma }$=(2.7±5.7)×${10}^{\mathrm{-}4}$. The reaction used was ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${(}^3$He,p${)}^{18}$F with a 3.4 MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ beam of an intensity of 7 μA impinging on a windowless water target. The circular polarization was measured with a four-prong transmission-type Compton polarimeter. The measurement of the analyzing power of the polarimeter is presented. Gamma rays were detected by means of 130 ${\mathrm{cm}}^3$ p-type germanium detectors placed behind the prongs. Four independent data acquisition channels were used: pile-up losses at a counting rate of 60 kcps were kept lower than 15%, owing to the use of trapezoidal shapers. Systematic effects of instrumental origin are discussed and found to give negligible contributions with respect to the statistical uncertainty. The calculation of the asymmetries is performed using different estimators; an extensive comparison of the various methods is presented. The result of the experiment, when averaged with those of the other experiments on ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ carried out until now, gives a grand average $P_{\gamma }$=(1.2±3.9)×${10}^{\mathrm{-}4}$. This result is compared with recent theoretical estimates.

The projectile-like fragment excitation energy in the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ho}$ reaction at 9 MeV/nucleon has been obtained by applying a light particle evaporation calculation to data obtained from coincidence measurements of projectile-like and target-like fragments. It is found that the excitation energy per nucleon is greater for the projectile-like fragment than for the target-like fragment at energy losses less than 200 MeV and that the excitation energy per nucleon is shifted increasingly toward the target-like fragment as a function of increasing energy loss. This shift is found to depend strongly upon the net amount and direction of mass exchange. The variance of the excitation energy about the mean value was also obtained with the result that this variation is approximately a constant fraction of the total excitation energy above an energy loss of 75 MeV.

We analyze quantum electrodynamic pair creation from vibrating nuclear ‘‘quasimolecules’’ which may occur in collisions of heavy ions. We find that higher-order processes, which can be phenomenologically relevant for sufficiently long lived systems, can result in coincident narrow peaks even for subcritical systems. The Z dependence of the energy of the peaks can be much softer than that predicted for positrons from ‘‘sparking’’ of the vacuum. Our results may be relevant to peaks which have been observed at the Gesellschaft für Schwerionenforschung (GSI).

The spectra of pions and light fragments at laboratory angles from 10° to 89° were measured in 0.8A GeV La+La collisions. Event multiplicity was also measured to select central collisions. For inclusive data, the slope of the pion spectrum at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}=90\mathrm{}\mathrm{°}}$ for La+La is as steep as that for Ar+KCl while the slope of the proton spectrum at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}=90\mathrm{}\mathrm{°}}$ becomes less steep with increasing mass number of the colliding nuclei. Furthermore, the ${\pi }^{\mathrm{-}}$ yield is about half of the geometrical estimate while total nuclear charge yield agrees well. Since the yield ratio of ${\pi }^{\mathrm{-}}$ to total nuclear charge at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}=90\mathrm{}\mathrm{°}}$ is significantly larger for high multiplicity events than for inclusive data, it appears that pion absorption by spectator nucleons is important. An azimuthal correlation of charged particle emission was also observed, which is consistent with collective flow of nuclear matter. The coalescence relation between protons and composite fragments holds for inclusive data in La+La collisions.

The possibility of spin-spin effects that are generated by the static quadrupole moments of two strongly deformed nuclei is investigated. Spin-spin total reaction cross sections ${\sigma }_{\mathrm{ss}}^r$ for the system ${}_{}{}^7{}_{}{}^{}$Li${+}^{11}$B at energies $E_{\mathrm{lab}{(}^7\mathrm{L}\mathrm{i})=30\mathrm{}–}$38 MeV are obtained in coupled-channels calculations which include all the possible sequential and mutual reorientation couplings to the two nuclei in the elastic channel. The values of ${\sigma }_{\mathrm{ss}}^r$ obtained are relatively very small, indicating that spin-spin effects of static nuclear deformation are not important for heavy ions.

The feasibility of populating high spin states using reactions induced by a 10 MeV/nucleon ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ beam on ${}_{}{}^{170}{}_{}{}^{}\mathrm{Er}$ was studied. The experiment was carried out using a multidetector array for high resolution γ-ray spectroscopy, a 14 element sum-multiplicity spectrometer and six ΔE-E telescopes. Detailed information was obtained concerning the reaction mechanisms associated with various reaction channels. Deep inelastic collisions are shown to be a promising tool for high spin spectroscopy in regions of the chart of nuclides which are not accessible by other reactions.

The time for fusion process is estimated by evaluating the time spent by the classical Coulomb trajectory and Coulomb-nuclear trajectory within the fusion formation region r<$R_F$. The parameter $R_F$ is taken from the recent works of Udagawa et al. Our estimate of fusion time extends the results of Scalia to a larger number of pairs of nuclei and energies. We find that the fusion time above the barrier obtained by using classical Coulomb-nuclear trajectories which is of the order of ${10}^{\mathrm{-}22}$ to ${10}^{\mathrm{-}21}$ s is about five times larger than the times obtained using Coulomb trajectories. We also see that fusion times for different partial waves are of the same order and do not vary much with angular momentum. We further adopt the quantum-mechanical phase-shift method used by Munzinger and Berkowitz to estimate the fusion time both below and above the barrier. In agreement with their general conclusion, we find that fusion time is oscillatory above the barrier and decreases rapidly with decrease in energy below the barrier up to certain energy. However, at still lower energy it starts increasing rapidly. The order of magnitude of oscillatory time above the barrier falls in between the times obtained using classical Coulomb trajectories and Coulomb-nuclear trajectories. But the trend in the sub-barrier region is physically not well understood. We take an alternative approach to estimate the fusion formation time below the barrier by assuming fusion to be a reverse decay process caused by the incident flux of projectiles on the target. This calculation of fusion time is done within the framework of the WKB method. We find that fusion formation time just below the barrier is of the order of ${10}^{\mathrm{-}23}$ s and starts increasing very rapidly with decrease in energy. In this case, we find that fusion formation time is larger than the corresponding time for free transit across the barrier. On the other hand, in the phase-shift method fusion time is found to be smaller than the free time in some cases. It is observed that fusion time, in general, is larger for identical nuclei than that for nonidentical pairs of nuclei.

We have measured the neutron-induced-fission cross section of the ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ isomer with cold and with thermal neutrons. Because of its short half-life (26 min), preparation of an adequate isomeric target is the major difficulty. A simple and easy-to-operate technique has been developed. The cross-section ratio of isomer to ground state is measured to be 1.61±0.44 and 2.47±0.45 for the cold and the thermal neutrons, respectively.

The pion-nucleus double charge exchange reaction is studied with special emphasis on nuclear structure. The reaction mechanism and nuclear structure aspects of the process are separated using both the plane-wave and distorted-wave impulse approximations. Predictions are made employing both the seniority model and a full shell model (with a single active orbit). Transitions to the double analog state and to the ground state of the residual nucleus are computed. The seniority model yields particularly simple relations among double charge exchange cross sections for nuclei within the same shell. Limitations of the seniority model and of the plane-wave impulse approximation are discussed as well as extensions to the generalized seniority scheme. Applications of the foregoing ideas to single charge exchange are also presented.

We use a percolation model of nuclear fragmentation to study the possibility of observing a phase transition of nuclear matter in collisions of high-energy (> 10 GeV) protons with heavy targets. It is shown that the model is able to reproduce experimental results for inclusive mass yields, while only using very simple physical assumptions. By employing event by event analysis of the moments of the mass distributions it is shown how to extract possible signals of a phase transition and information on its specific nature. Special attention is focused on the influence of the size of the fragmenting system on our ability to observe the phase transition.

Differential cross sections and analyzing powers for the ${}_{}{}^7{}_{}{}^{}(\mathit{p}\to$,${\pi }^{\pm }$) reactions leading to discrete states of ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$, as well as to the continuum, are presented at $T_p$=280, 354, and 489 MeV. These results are compared with previously published results at 200 and 250 MeV. At fixed four-momentum transfers squared in the region 0.6>t>0.4 ${\mathrm{GeV}}^2$/${\mathrm{c}}^2$, the energy dependence of the (p,${\pi }^{+}$) and (p,${\pi }^{\mathrm{-}}$) differential cross sections is quite similar, in sharp contrast to earlier results from the ${}_{}{}^{13}{}_{}{}^{}(\mathit{p}$,${\pi }^{\pm }$) reactions. The observed variations in the (p,${\pi }^{\mathrm{-}}$) energy dependence are presumed to reflect differences in the relative importance of resonant and nonresonant amplitudes in the (p,${\pi }^{\mathrm{-}}$) reaction mechanism. The analyzing powers of the (p→,${\pi }^{\mathrm{-}}$) and (p→,${\pi }^{+}$) reactions are qualitatively very similar except for a difference in sign.

Angular distributions have been measured for ${\pi }^{\pm }$ elastic scattering at 50 MeV from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$. A target isospin dependence is observed in the ${\pi }^{+}$ angular distributions in the region of the diffraction minimum, while the effect is less pronounced for ${\pi }^{\mathrm{-}}$. The ${\pi }^{\mathrm{-}}$ angular distributions for these isotopes have a very deep minimum compared with those for ${\pi }^{+}$. The angular distributions are compared with predictions of the second-order Michigan State University potential. The potential describes the ${\pi }^{+}$ data much better than the ${\pi }^{\mathrm{-}}$ data, though qualitative agreement was obtained for both. The discrepancy between the experimental and calculated cross sections is discussed. The Coulomb distortion of the nuclear amplitude is shown to be important in the region of the diffraction minimum. The ${\pi }^{+}$/${\pi }^{\mathrm{-}}$ difference introduced by this distortion is responsible for the striking energy dependence of the cross sections near the diffraction minimum between 50 and 80 MeV and can account for the poorer agreement for ${\pi }^{\mathrm{-}}$.

The (${\pi }^{+}$,$K^{+}$) strength functions (cross sections) are systematically calculated in the distorted-wave impulse approximation for the production of light-to-heavy hypernuclei: ${}_{\mathrm{\Lambda }}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{\mathrm{\Lambda }}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{\mathrm{\Lambda }}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{\mathrm{\Lambda }}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{\mathrm{\Lambda }}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{\mathrm{\Lambda }}{}^{90}{}_{}{}^{}\mathrm{Zr}$ (and ${}_{\mathrm{\Lambda }}{}^{208}{}_{}{}^{}\mathrm{Pb}$). The quasifree continuum effects are taken into account in the frameworks of the Kapur-Peierls method and also of the continuum shell model. The characteristic feature of the (${\pi }^{+}$,$K^{+}$) reaction is to provide well-separated series of peaks with high spin corresponding to the bound and resonant Λ states, yielding information on deep-lying hyperon states in heavy nuclei as well. Reasons for this effectiveness are clarified and discussed. The calculated results are in good agreement with the recent experiments which further demonstrates that the average Λ nucleus well can be simulated by an appropriate Woods-Saxon type potential ($V_0$≊-30 MeV) over a wide mass range of hypernuclei to a good approximation.