The bound state populations of ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ fragments emitted from ${}_{}{}^{26}{}_{}{}^{}\mathrm{Al}$ compound nuclei formed in the reaction of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ have been measured. At bombarding energies in the range of 87.5–112 MeV, these populations are consistent with emission from the thermally equilibrated compound nucleus when the rotational energy of the compound system is taken into account. The results demonstrate for the first time that nuclear excited state populations reflect the temperature of compound nuclei which reach statistical equilibrium. At higher bombarding energies the population distributions remain constant which signals the onset of non-compound nucleus reactions.

The projectile fragments from 1.88 GeV/nucleon ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ collisions with light (CR-39 plastic) and heavy (Cu) nuclei were analyzed in a CR-39 chamber with spacers. No decay of projectile fragments in space was observed. No anomaly was clearly observed for interactions, of projectile fragments in the CR-39 chamber. The overall normalized cross sections ${\sigma }^{\mathrm{*}}$ was 1.13±0.07±0.06 in CR-39 for projectile fragments emitted by collisions of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ with Cu and CR-39 targets, though ${\sigma }_{\mathrm{CR}\mathrm{?}\left(\mathrm{h}\mathrm{y}39\mathrm{}{}^{\mathrm{*}}\right(6\mathrm{}\mathrm{\le }\mathrm{z}\mathrm{\le }11}$) of 1.42±0.25±0.13 was obtained for projectile fragments of lower charge (6≤z≤11) from light target nuclei (CR-39).

Possible alternative interpretations of the Lippmann-Schwinger integral equation for multiparticle (n>2) systems are investigated and are shown to be equivalent if integrals which occur are uniformly convergent, as is reasonable. At real energies E, the derivation of the Lippmann-Schwinger equation from the Schrödinger equation involves various surface integrals at infinity in configuration space. It is shown that the values of these surface integrals are related to the values of certain volume integrals at complex energies (E+iε) in the limit ε→0, originally examined by Lippmann. It is further proved that a number of these surface integrals vanish together, a result which—though plausible—previously had to be assumed. The results of this paper confirm previous studies showing that the solutions to the multiparticle Lippmann-Schwinger equation need not be unique. Because of certain convergence difficulties which can occur, the analysis of this paper is not wholly valid for ‘‘three-body’’ collisions (defined as collisions involving three independently incident aggregates of the fundamental particles comprising the multiparticle system), or for the even more complicated collisions involving n>3 incident aggregates.

The reactions ${}_{}{}^{92}{}_{}{}^{}$,94,95,96,97,9 ${}_{}{}^8{}_{}{}^{}$,100Mo(p,xn) have been studied with $E_{\mathrm{p}=25.6\mathrm{}}$ MeV protons for neutron angles 3?(de≤${\mathrm{CTHETA}}_{\mathrm{n}\mathrm{\le }177}$°. In the preequilibrium region the angle integrated, inclusive neutron energy spectra show pronounced pairing effects that seem to be correlated with the ground state deformation. The angular distributions show more backward yield than predicted by semiclassical preequilibrium models. A quantitative description is obtained with a quantum-mechanical statistical multistep model including three steps of direct and compound plus subsequent equilibrium emission. Both components are calculated consistently with a Yukawa-type residual interaction of strength $V_0$=25 MeV.

Nuclear spallation reactions are treated as two step processes involving energy deposition and subsequent evaporation. The first step is calculated in Glauber’s multiple scattering formalism with modification for direct knockout processes. Evaporation is treated by following the mean yield of particles from the residual nucleus taken as an excited Fermi gas with ground state provided by the semiempirical mass formula. The spallation mass yield is derived to be an exponential in the mass of the fragments. The amplitude of the exponential and its slope depend on the projectile energy and target mass. Experimental data are well reproduced without free parameters.

An analysis of the predictions of the intranuclear cascade model of Yariv-Fraenkel is made by means of global variables (flow angle and transverse momentum distributions). Signatures for the flow effect in the reaction are studied and the distributions of the shape of the events are determined, using the sphericity and coplanarity as shape parameters. The dependence of the results on two parameters of the model is investigated: the rearrangement of the particles in the Fermi sea after each particle-particle collision and the nuclear potential. The influence of the evaporation particles on the flow angle is checked. A comparison with the experimental results of the plastic ball/plastic wall group is made, using a simulation filter in order to take the experimental acceptance of the detector into account. The dependence of the flow angle on the mass of the colliding ions and on the bombarding energy is also studied. We find that the model predicts finite flow angles of the emitted particles. Slow rearrangement and a central potential cause larger flow angles. However, in all cases we find that the most probable calculated flow angle is smaller than the experimental one.

${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$${(}^{14}$C,xnypzαγ) reactions were used to extend our knowledge of the high-spin states of ${}_{}{}^{47}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{47}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{45}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$. The decay schemes were constructed from γγ-coincidence data and γ-ray angular distributions and excitation functions. The angular distributions also provided information on spin-parity assignments and multipole mixing ratios. Lifetime information was extracted from analysis of the γ-ray Doppler shifts observed in both the angular distribution and γγ-coincidence data. Assuming the probable $J^{\pi }$ assignments are correct, the yrast schemes for all five nuclei extend to the highest spin allowed for ($f_{7/2}$${)}^{A\mathrm{-}40}$. Results are compared to shell-model predictions generated in three different configuration spaces: ($f_{7/2}$), ($d_{3/2}$,$f_{7/2}$), and the full (f,p) shell.

The modification of the Faddeev equations including three-nucleon forces is presented in a perturbational approach for arbitrary orders in the three-nucleon force. We report our results for the triton bound state energy using the Reid-soft-core and Paris potential and the Tucson-Melbourne two-pion-exchange three-body force. Furthermore, we show that only a small number of the ${\mathrm{N}}^2$ channel to channel contributions are important for the energetic shift caused by the three-nucleon potential.

Complete angular distributions are presented (${\mathrm{theta}}_{\mathrm{c}.\mathrm{m}.\mathrm{}=9\mathrm{}\mathrm{?}(\mathrm{de}–}$90°) for the reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$${(}^{13}$C, α${)}^{22}$Ne in the energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}=6.25\mathrm{}–}$9.125 MeV. The data exhibit significant nonstatistical behavior and have been fitted to a linear Legendre polynomial sum using a least-squares procedure. A second procedure makes a grid search to find a best fit to an amplitude squared equation. The correlations with structures in other C+C systems are discussed.

The heavy fragments emitted in the ${}_{}{}^{40}{}_{}{}^{}$Ar${+\mathrm{}}^{68}$Zn reaction have been studied at ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ energies of 14.6, 19.6, 27.6, and 35 MeV/nucleon. Fusion-evaporation and fusion-fission components resulting from complete and incomplete fusion were observed, and cross sections have been measured for both components at the four energies. The velocity distributions of the evaporation residues have been analyzed and the linear momentum transferred to the compound system deduced. Compared to other results, the momentum transfer appears to depend on the asymmetry of the system and on the projectile mass. The mass, excitation energy, and temperature of the compound nuclei formed have been determined. Fusion disappears slightly above 35 MeV/nucleon, which corresponds to a compound nucleus excitation energy of 500 MeV (5.9 MeV/nucleon) and to a temperature of 6.8 MeV. The results are discussed in terms of various theoretical models.

Using a CR-39 plastic track detector, it is proved that the low energy light fragments (5≤Z≤26) produced in the interaction of 84 MeV/nucleon ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ with a Pb target originate predominantly from the binary breakup. The characteristics of light fragments and their corresponding heavy partners have been determined. The dependence of measured parameters on the atomic numbers of light fragments is observed. The obtained values of the velocity of the c.m. system of fragments indicate that high longitudinal momentum transfer to the target is characteristic for this reaction channel. The data are consistent with the assumption that at the energy used in this experiment the projectile is stopped in the target nucleus.

The disassembly of hot classical charged drops containing ∼230 and 130 particles is studied with the molecular dynamics method. The strength of the Coulomb repulsion is chosen so that these drops have a binding energy formula similar to that of nuclei. The phase diagram of neutral matter, obtained by switching off the Coulomb force, is also similar to that of nuclear matter. In addition to the total-vaporization, fragmentation, and evaporation modes of the disassembly of neutral drops, the charged drops also break by multiple and binary fission. The liquid-gas phase transition plays an important role in the multiple fission of expanding charged liquid drops. There also appears to be a window in the initial conditions in which binary fission followed by a density oscillation is the dominant mode of breakup. The multiple and binary fission breakups are due to the Coulomb forces, and they yield more massive clusters with relatively few small clusters with ∼10 particles. The higher energy fragmentation and total vaporization modes are not significantly influenced by the Coulomb forces. They are primarily due to the liquid-gas transition, and their yields decrease almost monotonically with the number of particles in the cluster.

The influence of fluctuations of the shape degree of freedom in collisions of deformed nuclei with energies between 0.8 and 2.1 GeV/nucleon is analyzed on the basis of an intranuclear cascade simulation for the strongly deformed systems ${}_{}{}^{46}{}_{}{}^{}$Ti${+\mathrm{}}^{46}$Ti and ${}_{}{}^{166}{}_{}{}^{}$Er${+\mathrm{}}^{166}$Er. While there is a considerable sensitivity of the global event variables to the orientation for polarized beams and targets, this dependence disappears in the average over all orientations for impact parameter selected and integrated events. The dependence of the nuclear stopping and thermalization on the size of the system under consideration and on the bombarding energy is also investigated.

A method is presented by which an intranuclear cascade model may be used to obtain pion source parameter predictions which can be directly compared with pion interferometry experiments. This method is applied with Cugnon’s intranuclear cascade model to extract predictions for recent pion interferometry measurements, and generally good agreement is found.

Individual evaporation channels and total fusion cross sections have been deduced for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{13}$C reaction in the center of mass energy range 7.8–14.6 MeV. This was accomplished through measurements of absolute γ-ray yields from low-lying levels of evaporation residues. Singles γ-ray spectra were obtained with a high resolution Ge(Li) detector at an angle ${\mathrm{theta}}_{\gamma }$=125° with respect to the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ beam. All excitation functions measured are devoid of any structure, in contrast with the well-known oscillations observed in ${}_{}{}^{16}{}_{}{}^{}\mathrm{C}$. The results are compared to statistical model calculations and predictions of macroscopic models.

We present a formalism for calculating three effects of nuclear dissipation on neutron emission prior to fission: (1) Kramers’s modification of the Bohr-Wheeler statistical-model result for the fission width; (2) the transient time required to build up the quasistationary probability flow over the barrier; and (3) the mean time required for the system to descend from the saddle point to scission. Each of these effects increases the average multiplicity of neutrons emitted prior to fission relative to that calculated with a standard statistical model. The multiplicity calculation includes the dependence of the ratio $a_f$/$a_{\mathrm{n}}$ of level-density parameters for fission and neutron emission upon dissipation that is imposed by the low-energy fission probability. We use this formalism to analyze recent experimental results of Gavron et al. for the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{142}$Nd→${\mathrm{}}^{158}$Er at 207 MeV, where 2.7±0.4 neutrons are emitted prior to fission compared to 1.6 neutrons calculated with a standard statistical model. This determines the limit β≲5×${10}^{21}$ ${\mathrm{s}}^{\mathrm{-}1}$ for the reduced nuclear dissipation coefficient β defined as the ratio of the dissipation coefficient to the inertia.

We report on a four-parameter measurement of the kinetic energies E and the velocities v of correlated fragments in fast-neutron-induced fission of ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$. The influence of excitation energy on the important fragment properties such as mass, kinetic energy, and prompt neutron emission have been investigated experimentally at 0.80 and 5.55 MeV neutron energy. Our results include mean values of fragment properties before and after neutron evaporation, e.g., of fragment velocities and masses, total kinetic energies, and the respective variances. Also given are the distributions of fragment mass, of $E_k$,tot, the variance of $E_k$,tot, as well as the number of prompt fission neutrons as a function of fragment mass. These results show that shell effects are strong near threshold at $E_{\mathrm{n}=0.80\mathrm{}}$ MeV, but decrease significantly at the higher excitation energy, in qualitative agreement with the model of Wilkins, Chasman, and Steinberg. However, the observed increase in the number of prompt fission neutrons, which appears only in the heavy fragment, cannot be explained by this model.

The ground and even-parity excited states and the scattering problem of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ system are examined within the framework of the (2N+2N) and (1N+3N) cluster-coupling model with the specific distortion effect of the deuteron cluster taken into consideration. Calculations are performed by a multichannel resonating-group method using an effective nucleon-nucleon (NN) potential similar to that adopted in p+α, d+α, ${}_{}{}^3{}_{}{}^{}\mathrm{H}$+α (or ${}_{}{}^3{}_{}{}^{}\mathrm{He}$+α), and α+α systems. The results show that, because of the high compressibility of the deuteron cluster and the similarity in threshold energies for the 2N+2N and 1N+3N configurations, both the distortion effect and the channel-coupling effect are important in this system. When the 1N+3N configuration is included in the calculation, the deuteron-distortion effect turns out to be significantly weakened, owing to the fact that the 1N+3N configuration is energetically the most favored one. In addition, it is shown that such a specific distortion effect is quite small in the channel spin S=2 state of d+d scattering. With the full calculation including the distortion effect, it is found possible to reproduce well the energies of the ground state and the first-excited $0^{+}$ state; the differential cross sections for d+d, p+t, and n+h elastic scattering; the polarizations for p+t and n+h scattering; and the cross sections for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$(t,n${)}^3$He and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(p,d${)}^2$H reactions.

With the double purpose of improving the theoretical description of πd observables and of obtaining information on the ΔN interaction parameters, we add to sets of amplitudes obtained from three-body calculations of πd scattering the contributions due to the short range ΔN interaction in the intermediate state. The full amplitudes are used to fit the experimental data on differential cross section and vector analyzing power at 142, 180, and 256 MeV pion kinetic energies, while the free ΔN parameters are determined, with attention given to possible resonant forms in the $J^P$${=2\mathrm{}}^{+}$, $3^{\mathrm{-}}$, and $4^{+}$ states. Our results, for two independent sets of three-body amplitudes, show that the ΔN interaction in the ${}_{}{}^5{}_{}{}^{}\mathrm{S}_2^{}{}_{}{}^{}$ and ${}_{}{}^5{}_{}{}^{}\mathrm{P}_3^{}{}_{}{}^{}$ waves give very important additional contributions, with remarkable improvement in the description of the data. However, in the limited conditions of our experimentation, we cannot prove the existence of a clean resonant character in these interactions. The contributions of other ΔN low orbital angular momentum waves, such as ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ and ${}_{}{}^5{}_{}{}^{}\mathrm{D}_4^{}{}_{}{}^{}$, give additional improvements to the fittings, but we must be aware that quantitative conclusions about the corresponding ΔN parameters may be affected by uncertainties in the background amplitudes.

Differential cross sections and analyzing powers for proton elastic scattering from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ have been measured for proton scattering angles between 15° and 150° in the center of mass at incident proton energies of 200, 300, 415, and 515 MeV. These data, together with data from the literature, in the energy range 100–1000 MeV, have been analyzed within the framework of the Glauber multiple scattering theory. Firstly, a simple spin-independent calculation was performed using a parametrized form for the N-N scattering amplitudes. This provided reasonable agreement with the differential cross section data. Secondly, a more detailed calculation was performed incorporating spin dependence and using a complete set of N-N scattering amplitudes as determined from phase shift analyses. The agreement with the experimental data was not improved by the more detailed calculation. Possible reasons for this discrepancy are discussed.