The energy and angular distributions of the α particles from the ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$(n,xα) and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$(n,xα) reactions for 14.1 MeV incident neutrons were measured by means of a multitelescope system. The results concerning total helium production are in good agreement with existing helium accumulation measurements, whereas the angular distributions reported in the literature for the ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$(n,α) reaction could not be confirmed. The results are analyzed in the framework of the statistical model of nuclear reactions. Comparison of such calculations with the measured α-emission cross sections allows the extraction of nuclear level densities for ${}_{}{}^{52}{}_{}{}^{}\mathrm{V}$ and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$, the residual nuclei reached in the reactions studied, in the energy region up to the neutron binding energy, and for ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, the residual nuclei reached by neutron emission, for energies around 11 MeV. The level densities derived in this way agree very well with the prediction of the back-shifted Fermi-gas model for the level density parameters of Strohmaier and Uhl. For ${}_{}{}^{52}{}_{}{}^{}\mathrm{V}$ and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$ there is also excellent agreement with the level densities derived from average s-wave neutron resonances. The spin cutoff factors derived from the α-particle angular distributions indicate that there is no reduction of the effective moment of inertia below the rigid body value.

We perform detailed theoretical and empirical investigations of the real part of the optical-model potential for protons with energy 9≤E≤12 MeV and targets with mass number 44≤A≤72, in order to clarify earlier claims that in this domain the potential depth presents a peculiar dependence upon the target mass number A, asymmetry parameter α, and isospin T. We compile several radial moments of the empirical potentials and compare them with those predicted by a nuclear matter approach based on Reid’s hard core nucleon-nucleon interaction. We find that this theoretical model is in good agreement with the empirical properties. In particular, the theoretical potential depends upon T for fixed α. This is due to the dependence upon A of its isoscalar component. The calculated potential is found to have approximately a Woods-Saxon shape with a fixed geometry, except in the surface tail where the theoretical model is, in any case, unreliable.

Differential cross sections for the elastic scattering of tagged, monochromatic photons have been measured on a separated target of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ between 12 and 30 MeV. The interpretation of these data implies that the total photoabsorption cross section in the region of the giant dipole resonance of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ is nearly identical to that of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, except shifted slightly higher in energy. Fore-to-aft ratios of differential cross sections are ambiguous as to the existence of a giant quadrupole resonance between 20 and 30 MeV. This ambiguity is due in part to the influence of poorly known exchange effects and in part to uncertainties in the Delbrück amplitude. Upper limits are placed on the relative photon-decay branch of the giant dipole resonance and isovector giant quadrupole resonance to the lowest $2^{+}$ and $3^{\mathrm{-}}$ states, respectively. These limits are well above those predicted by current models for the coupling of giant resonances to surface vibrations.

Cross sections for the formation of ${}_{}{}^{91}{}_{}{}^{}\mathrm{Y}$ in the interactions of 17.0 to 19.2 MeV neutrons with niobium were measured radiochemically. The major contributing process is the ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$(n${,}^3$He${)}^{91}$Y reaction. Hauser-Feshbach calculations on the first-chance emission of a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ particle show that the contributions of statistical processes are small. The ratio of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ to ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ emission increases rapidly beyond 17.5 MeV. This behavior is interpreted in terms of reaction energies, level structures of the isobars formed, and the intrinsic nature of the two processes involved.

Differential cross sections and analyzing powers of elastic and inelastic scattering of polarized protons from actinide nuclei ${(}^{232}$Th and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$) have been measured for the first time. A coupled-channel analysis has been performed for $J^{\pi }$${=0\mathrm{}}^{+}$–$6^{+}$ members of the ground state rotational band. Excellent fits have been obtained up to the $6^{+}$ state. Extracted quadrupole moments of the deformed optical potential are 1.0–2.0 % larger than those of the charge distribution. This difference is significantly small, compared with the case of the previous rare-earth region nuclei at 65 MeV (4–5 %). A realistic folding calculation based on the density- and energy-dependent effective interaction was performed. The effect of the Coulomb potential through the energy dependence of the effective interaction was found to be important to reproduce quadrupole moments of the deformed optical potential, especially for the actinide nuclei. Extracted hexadecapole moments are 14–18 % larger than those of the charge densities, and the possible sources of this difference in the hexadecapole moments will be discussed.

Simulations of neutron evaporation from light heavy ions are presented to illustrate experimental biases present in coincidence experiments. In particular, the case presented involves neutrons observed in coincidence with quasi-elastic boron fragments from collisions of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ with ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ at a bombarding energy of 35 MeV/nucleon. The left-right asymmetry observed experimentally in the high energy neutron spectra at angles of ±60° and ±90° cannot be reproduced together with the correct angular distribution if only a projectile-like source is assumed to create the observed spectra, and this suggests that some other process is required to explain the data. Some general features of the simulations will be compared with results of moving-source analyses.

Inclusive and coincidence measurements have been performed to study symmetric fragmentation of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ binary decay from the ${}_{}{}^{32}{}_{}{}^{}\mathrm{C}$ reaction at 280 MeV incident energy. Element distributions after binary decay were measured. Angular distributions and fragment correlations are presented. Total c.m. kinetic energy for the symmetric products is extracted from our data and from Monte-Carlo model calculations including Q-value fluctuations. This result was compared to liquid drop model calculations and standard fission systematics. Comparison between the experimental value of the total kinetic energy and the rotating liquid-drop model predictions locates the angular momentum window for symmetric splitting of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ between 33ħ and 38ħ. It also showed that 50% of the corresponding rotational energy contributes to the total kinetic energy values. The dominant reaction mechanism was found to be symmetric splitting followed by evaporation.

An in-beam spectroscopic study of ${}_{}{}^{135}{}_{}{}^{}\mathrm{Pr}$ was made using a 91 MeV ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$${(}^{19}$F,4n) reaction. Two positive parity bands were observed based on the $g_{7/2}$ proton orbital with (π,α)=(+,±(1/2)). A strongly populated negative parity (-,-(1/2)) band was also seen (based on the $h_{11/2}$ proton orbital). The unfavored (-,+(1/2)) structure may also be present. In both the positive and negative parity bands the first backbend is attributed to the alignment of two $h_{11/2}$ protons on the basis of cranked shell model calculations. The crossing frequency was found to increase in the (-,-(1/2)) band because of blocking of the $h_{11/2}$ orbital. The alignment of protons in ${}_{}{}^{135}{}_{}{}^{}\mathrm{Pr}$ causes a shift of γ towards ∼+10° with nearly collective prolate deformation. Also, there is some evidence for a second backbend and an upbend in the case of positive and negative parity bands, respectively. They could result from the alignment of the $h_{11/2}$ neutrons.

Single- and two-particle inclusive cross sections for the production of light nuclei and intermediate mass fragments, 3≤Z≤24, were measured at angles well beyond the grazing angle for ${}_{}{}^{32}{}_{}{}^{}\mathrm{induced}$ reactions on Ag at 720 MeV. Information about fragment multiplicities and reaction dynamics was extracted from measurements of light particles, intermediate mass fragments, and targetlike residues in coincidence with intermediate mass fragments. Incomplete linear momentum transfer and non-compound-particle emission are important features of collisions producing intermediate mass fragments. About half of the incident kinetic energy in these collisions is converted into internal excitation. The mean multiplicity of intermediate mass fragments is of the order of 1. Particle correlations are strongly enhanced in the plane which contains the intermediate mass fragment and the beam axis.

Cross sections for the fusion of ${}_{}{}^{28}{}_{}{}^{}\mathrm{C}$ have been measured at center of mass bombarding energies of 39, 43.5, 48, and 54 MeV. Velocity and energy spectra of reaction products having charge Z≥12 and mass number A≥24 were studied at several angles between ${\mathrm{theta}}_{\mathrm{lab}=2\mathrm{}\mathrm{°}}$ and 13°. Separation of fusion from other processes was made by comparison of kinematic calculations to measured spectra. The extracted critical angular momentum ($l_{\mathrm{cr}{}^{\mathrm{fus})}}$ of 22ħ indicates the existence of an entrance-channel-imposed limit on the high energy fusion cross section. More symmetric systems forming the same compound nucleus, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, have considerably larger limiting angular momenta. This result is consistent with the previous observation of a maximum angular momentum of 22ħ (relative to the entrance channel) for the orbiting dinuclear complex found in studies of back-angle deeply inelastic scattering of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$.

The dynamics of collisions between very heavy ions have been studied via their influence on the positron and δ-electron spectra using the Tori spectrometer, a new magnetic transport system which is able to measure positrons and electrons simultaneously. The spectra obtained in coincidence with elastic scattering agree well at all measured energies with theory based on Rutherford trajectories, while a steeper slope is observed in spectra measured in coincidence with dissipative collisions. These spectra can only be described by calculations taking into account a nuclear contact time of up to 2×${10}^{\mathrm{-}21}$ s in the collision process.

Nuclear structures of ${}_{{\mathrm{}}^{136}}{}^{}{}_{}{}^{}$,1${\mathrm{}}_{62}^{38}$Sm and ${}_{{\mathrm{}}^1{\mathrm{}}_{60}^{32}}{}^{}{}_{}{}^{}\mathrm{Nd}$ have been studied through heavy ion fusion reactions. In order to select particular reaction channels, charged particle-gamma coincidences were measured with a charged particle multiplicity filter ‘‘silicon box.’’ Yrast bands with spins up to 14 have been observed in all nuclei investigated. Lifetimes of excited states were also measured with the recoil distance method. The experimental results were compared with the interacting boson model predictions.

Nuclear spin polarization of projectile-like fragments ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ produced in ${(}^{14}$N${,}^{12}$B) reactions at around the classical grazing angle was measured as a function of reaction Q value at incident energies of 120 and 200 MeV. Large positive ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ polarization was observed in the region of small kinetic energy loss for heavy target nuclei ranging from ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ to ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Fe}$, and it was interpreted in terms of direct two-proton transfer. For the target nucleus ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, however, large negative polarization was observed in the region of small kinetic energy loss. It was found that the ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ target nucleus was situated at a crossover point for the sign of the polarization. This fact is explained by assuming coexistence of direct and frictional processes. It is found that the contribution of the frictional process tends to exceed that of the direct process with a decrease of target mass number in the region of small energy loss. In the region of large kinetic energy loss, the dominant mechanism is due to the frictional process. A friction constant of (2.4±0.5)×${10}^{\mathrm{-}22}$ MeV?${\mathrm{fm}}^2$ is deduced from the present experimental data. This value agrees in order of magnitude with that obtained from the recent study on the reaction Xe + Bi.

Fission fragment angular distributions were measured for the neutron-induced fission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ at incident energies from threshold to 6 MeV, using a white source of neutrons, time-of-flight techniques, and position-sensitive multiwire counters subtending a solid angle of nearly 2π sr. The experimental data were analyzed in incident neutron energy bins of 40 keV and angular bins of 9 deg, and compared with previous results which were available for only partial energy ranges covered by this experiment. A channel analysis yielded relative strengths for the K transition states with K=(1/2), (3/2), and (5/2) from threshold to $E_{\mathrm{n}=4.5\mathrm{}}$ MeV.

We study the (p,${\pi }^{\mathrm{-}}$) continuum spectra at intermediate energy in the local Fermi gas model, where the pion production process is described in the standard p- and s-wave two-body mechanisms. The continuum spectra are very sensitive to the surface properties of nuclei and the local Fermi gas model seems to provide a good description of the (p,${\pi }^{\mathrm{-}}$) spectra.

Elastic collisions between light nuclei are investigated at medium energies using Glauber theory. It is shown that a phase variation of the nucleon-nucleon elastic scattering amplitude leads to large increases in the calculated differential cross sections, even away from the minima that would occur if there were no phase variation. The relatively small number of minima that occur with no phase variation is explained in terms of the relative lack of strong destructive interference among multiple scattering amplitudes due to their relatively slow decrease with increasing momentum transfer. The introduction of a phase variation leads to even fewer minima. Calculations with no phase variation are in marked disagreement with α ${}_{}{}^4{}_{}{}^{}$He, α ${}_{}{}^3{}_{}{}^{}$He, α ${}_{}{}^2{}_{}{}^{}$H and α ${}_{}{}^1{}_{}{}^{}$H data at 7 GeV/c and α ${}_{}{}^4{}_{}{}^{}$He data at 5.07 and 4.32 GeV/c. The presence of a phase variation leads to a substantial improvement.

The differential cross sections for the πN charge-exchange reaction, ${\pi }^{\mathrm{-}}$p→${\pi }^0$n, have been measured in an angular range corresponding to 0.99≥cos${\mathrm{theta}}_{\mathrm{c}.\mathrm{m}.\mathrm{}\ge 0.90}$ at 100.6, 106.7, 113.4, 125.2, 130.9, 136.4, and 147.1 MeV/c. A striking feature of the charge-exchange reaction at forward angles is the presence of a deep minimum near 120 MeV/c, caused by interference between s- and p-wave scattering. The parameters of this minimum, of interest both intrinsically and for applications to π-nucleus single- and double-charge-exchange reactions, are well determined by the measurements. Our data are compared with the results of existing partial-wave analyses, and the data are discussed in terms of the isospin-odd, s-wave scattering length, $a_1$-$a_3$.

A complete set of polarization transfer observables was measured for inclusive 500 MeV proton scattering from ${}_{}{}^2{}_{}{}^{}\mathrm{H}$, Ca(nat.), and Pb(nat.) at ${\mathrm{theta}}_{\mathrm{lab}}$=18.5° (q=1.75 ${\mathrm{fm}}^{\mathrm{-}1}$). The excitation energy ranged over the entire quasielastic peak from 20 to 100 MeV. Longitudinal and transverse spin-flip probabilities were extracted from the data. These have simple model-dependent connections to the spin-longitudinal and transverse response functions for the heavy targets. Detailed analysis of the data reveals no evidence for collective enhancement in the spin-longitudinal response function. The relation of this analysis to the interpretation of the European Muon Collaboration effect in terms of excess pions is discussed in detail.

It is found that the differential cross sections for ${}_{}{}^{13}{}_{}{}^{}({\pi }^{+}$,γ${)}^{13}$N ${}_{\mathrm{g}.\mathrm{s}.\mathrm{}}{}^{}{}_{}{}^{}$ for 115.5 MeV kinetic energy pions can be understood within the framework of a distorted wave impulse approximation, suggesting that core polarization and precursor effects give small contributions. It is further found that, within the limits of current nuclear photopion theory, the data for the radiative capture process are incompatible with earlier measurements for the inverse reaction ${}_{}{}^{13}{}_{}{}^{}(\gamma$,${\pi }^{\mathrm{-}}$${)}^{13}$N ${}_{\mathrm{g}.\mathrm{s}.\mathrm{}}{}^{}{}_{}{}^{}$. It is shown that the reconciliation of the two sets of data places stringent demands on possible modifications to the theory.

Angular distributions of elastic differential cross sections were obtained at 65 MeV using positive and negative pions scattered from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$. The data were compared to predictions using the Michigan State University optical potential. These predictions are not in good agreement with the data. The negative pion cross sections are more poorly described than the positive pion cross sections. The p-wave part of the potential is observed to be especially sensitive to this Coulomb-nuclear interference effect.