Prescission neutron multiplicities in fusion-fission reactions of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$${+}^{237}$Np, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$${+}^{232}$Th, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{232}$Th, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{232}$Th, lying on either side of the Businaro-Gallone mass asymmetry (${\mathrm{\alpha }}_{\mathrm{BG}}$), have been measured. The present data along with those available in literature for compound systems spanning the fissility range from 0.70 to 0.84 were analyzed in a consistent manner to deduce fusion-fission time scales for all systems. From the systematic behavior of all the data, the three components of total dynamical fusion-fission delay, namely, transient delay, saddle-to-scission delay, and formation delay, have been deduced. It is found that the formation delay depends on the entrance channel mass asymmetry relative to Businaro-Gallone point. The variations of the fusion-fission time scales with fissility, ratio of fission barrier to temperature, and entrance channel mass asymmetry have been studied.

The recoil range distribution of the radioactive evaporation residues in the reaction of 63 and 77.5 MeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ with ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ and that of 68 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ have been measured using the recoil catcher technique followed by gamma spectrometry. The linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The data are compared with Monte Carlo simulation of recoil range distributions of products formed by complete fusion to extract the contribution of incomplete fusion in the individual channels. The observations are discussed in the framework of existing models.

Proton and α-particle correlations with evaporation residues were measured over the complete angular range in the interaction of 450–MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ beam with a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target. Comparisons of the data with predictions of the statistical model and expectations for complete fusion from the kinematics provide clear and consistent evidence of incomplete fusion due to preequilibrium emission of both protons and α particles from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target. However, there is conflicting evidence both for and against preequilibrium emission from the projectile.

The spectral function of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(e,e’p${)}^{15}$N reaction has been measured in quasielastic parallel kinematics. Momentum distributions are extracted for transitions to several discrete states, with emphasis on the low-lying positive parity states of ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$. Spectroscopic factors and bound state wave functions are deduced from a DWIA analysis employing five different optical potentials. Coupled channels effects are investigated for the first four states of ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ and are found to be minimal. The spectroscopic results of the 1/$2^{\mathrm{-}}$ ground state and the first 3/$2^{\mathrm{-}}$ excited state indicate a 28%±5.4% reduction of the valence 1p shell strength with respect to the IPSM sum rule limit for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The spectroscopic strength for knockout of protons from the 2s1d shell, integrated up to a missing energy of 40 MeV, is found to be 0.269±0.033. The distribution of proton spectroscopic strength is determined from a multipole decomposition of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ spectral function.

Prescission and postscission multiplicities of protons and α particles are measured in the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{159}$Tb reaction. The observed prescission multiplicities are enhanced compared to statistical model predictions and the presaddle delay time of around 0.5×${10}^{\mathrm{-}20}$ sec is needed to reproduce both prescission proton and α particle multiplicities. This value is too small to account for the prescission neutron data measured by Newton et al., suggesting a long saddle-to-scission time. The measured postscission multiplicities of protons and α particles indicate that fission fragments are rather colder than the statistical model predictions, but slightly hotter than the estimation from the obseved prescission and postscission neutron multiplicities.

The angular distributions of the elastic scattering and ${(}^3$He,α) cross sections for 37.9 MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ particles incident on target nuclei ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ were analyzed from the standpoint of possible presence of the refractive effects in one-nucleon transfer reactions. The analysis of experimental data is given in the framework of the distorted wave Born approximation using external microscopically calculated form factors. The presence of the rainbowlike mechanism in both elastic and reaction channels was observed. The effect is apparent mainly for transitions where strong orbital mismatching occurs.

The study of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{12}$C${\to }^{12}$C${+}^{12}$C+α reaction performed at E${(}^{16}$O)=113 MeV shows evidence for the excitation of resonant states of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, eventually decaying in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C channel, with a width of about 500 keV. From the angular correlation of the two emitted ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions a value J=14 is obtained for the spin of two resonances at 35.1 and 36.3 MeV excitation energy. This allows for an intepretation in terms of quasimolecular states of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$. The data are compared with previous results obtained at 85 MeV incident energy, and the role of the angular momentum transfer in the reaction process is discussed.

The emission of light charged particles in the photofission of ${}_{}{}^{230,232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{233,234,235,238}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$, and ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ has been studied with bremsstrahlung with end-point energy of 12, 15, and 20 MeV. The light charged particles are measured using a setup consisting of eight ΔE-E particle identification detector telescopes. The kinetic energy distributions and the emission probabilities of tritons and long-range alpha particles were determined. The presence of photoprotons obscures the identification of ternary protons while ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ particles were observed clearly, however, with insufficient statistics to allow meaningful conclusions concerning their energy distribution or emission probability. The average kinetic energy of the ternary tritons and α particles and the width of the triton kinetic energy distributions seems to be practically independent of the compound nucleus excitation energy or ${\mathit{Z}}^2$/A. Only the width of the long-range alpha particle kinetic energy distribution shows a slight increase with increasing ${\mathit{Z}}^2$/A of the compound nucleus. Our results point toward a slight increase of the ternary alpha particle yield with increasing excitation energy of the compound nucleus. As already observed by Wild et al. for spontaneously fissioning nuclei, this yield shows a clear correlation with 〈Q〉-〈${\mathit{E}}_{\mathrm{tot}}^{\mathrm{*}}$〉, where ${\mathit{E}}_{\mathrm{tot}}^{\mathrm{*}}$ is the total kinetic energy, suggesting that the light charged particle emission probability is determined by the deformation of the system at scission, and that, for the compound nucleus excitation energy studied in our experiments, the excitation energy transferred to the compound nucleus remains in the system as internal heat, and is not transformed into deformation energy.

The triton emission to binary fission ratio, t/B, for ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$ is not substantially higher than for the neighboring nuclei, indicating that the unpaired proton in ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$ does not influence in an important way the triton emission probability.

In a γγ-coincidence study of collisions of ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$ with 247 MeV ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ we have quantitatively identified the product nuclei formed in fusion-evaporation as well as in binary reactions. Individual binary processes were sampled through identification of numerous exit partner pairs with the help of γγ cross coincidences. The data also provide information on the angular momentum transferred to the product nuclei and on charge equilibration in the collision process. The results reveal important features of heavy-ion collisions that are difficult to obtain in measurements using charged particle detection alone.

The highest spin states in a ${\mathit{T}}_{\mathit{z}}$=1/2 nucleus have been observed in ${}_{}{}^{77}{}_{}{}^{}\mathrm{Sr}$: ${\mathit{I}}^{\mathrm{\pi }}$=(49/$2^{+}$) and (29/$2^{\mathrm{-}}$). In addition, states up to ${\mathit{I}}^{\mathrm{\pi }}$=(${22}^{+}$) have been seen in ${}_{}{}^{78}{}_{}{}^{}\mathrm{Sr}$. The α=1/2, ${\mathit{g}}_{9/2}$ band and both signature partners of the negative parity band in ${}_{}{}^{77}{}_{}{}^{}\mathrm{Sr}$ were found to be identical to the yrast band in ${}_{}{}^{78}{}_{}{}^{}\mathrm{Sr}$ with relative alignments of 1.22(7)ħ, 0.52(5)ħ(α=1/2), and 0.42(4)ħ(α=-1/2), respectively. In one of the negative parity bands, the identicality persists through the first proton band crossing. The odd spin decay sequence of the $4^{\mathrm{-}}$ band in ${}_{}{}^{78}{}_{}{}^{}\mathrm{Rb}$ is identical to the ground band of ${}_{}{}^{78}{}_{}{}^{}\mathrm{Sr}$ [3.02(3)ħ] at low spin and to the α=1/2, ${\mathit{g}}_{9/2}$ band in ${}_{}{}^{77}{}_{}{}^{}\mathrm{Rb}$ [1.11(3)ħ] at higher spins. These are the only known examples of identical bands in the neutron deficient A=80 region. The analysis indicates that the [301]3/2 Nilsson orbital is a very good spectator orbital.

The probability of filling a K-vacancy, created on the incoming part of the collision, before α-particle emission is used to time the decay of Yb compound nuclei. These nuclei were produced in the fusion reaction 250 MeV ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$${+}^{100}$Mo. In general the nuclear decays are too fast to be timed by this clock, however, α-particle emitting compound nucleus states have lifetimes sufficiently long for this technique to work when both the α-particle has low energy and the compound nucleus spin is large. This supports the existence of last, or near last, chance α-particle emission in the deexcitation of high spin compound nuclei.

High-spin states of ${}_{}{}^{187}{}_{}{}^{}\mathrm{Tl}$ populated in the ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$${(}^{35}$Cl,4n) reaction have been investigated with γ-ray coincidence techniques. Two decoupled bands feeding the oblate 9/$2^{\mathrm{-}}$ isomeric state have been established. These bands are built on π${\mathit{h}}_{9/2}$ and π${\mathit{i}}_{13/2}$ configurations associated with prolate shapes. The first observation of a low-K π${\mathit{h}}_{9/2}$ structure in an odd-A Tl nucleus is used to draw conclusions on the role of this proton orbital in stabilizing the prolate minimum seen in light Hg isotopes.

The new neutron-rich isotope ${}_{}{}^{208}{}_{}{}^{}\mathrm{Hg}$ was observed for the first time in the reaction products from a thick ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Pb}$ target bombarded by a 30 MeV/nucleon ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ beam. A high efficiency release, separation, and collection of Hg products were of success with a good selectivity by using a special off-line gas-phase thermochromatographic process followed by a liquid-liquid procedure which was developed in the present work. The assignment of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Hg}$ was based on the identification of its ${\mathrm{\beta }}^{\mathrm{-}}$ decay daughter ${}_{}{}^{208}{}_{}{}^{}\mathrm{Tl}$ observed in the periodically extracted Tl element sample growing in the separated Hg element product solution. In the γ spectra of the Tl samples a 2614.6-keV γ activity with a half-life ${191}_{\mathrm{-}50}^{+104\mathrm{}}$ s was observed, which could only be assigned to the daughter ${}_{}{}^{208}{}_{}{}^{}\mathrm{Tl}$ of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Hg}$ ${\mathrm{\beta }}^{\mathrm{-}}$ decay. The measured ${}_{}{}^{208}{}_{}{}^{}\mathrm{Hg}$ half-life was ${42}_{\mathrm{-}12}^{+23\mathrm{}}$ min and the average production cross section for the energy of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ beam ranging from 30 MeV/nucleon to 5 MeV/nucleon and the effective target thickness of 670 mg/${\mathrm{cm}}^2$ was deduced to be 1.$1_{\mathrm{-}0.5}^{+1.0\mathrm{}}$ μb. Moreover, in the time-successive γ spectra of the separated Hg sample, a 473.5-keV γ activity corresponding to the γ transition of $4^{+}$ to ground state ($5^{+}$) of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Tl}$ was observed and found to have the same half-life as the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Hg}$ ${\mathrm{\beta }}^{\mathrm{-}}$ decay within the error range of the present work. A theoretical discussion for the obtained half-life of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Hg}$ is given.

Three-body ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ photodisintegration was measured in the photon energy range (${\mathit{E}}_{\gamma }$) of 145–425 MeV. The total cross section for photon absorption on the np pairs in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, σ${(}^3$He(γ,np)${\mathit{p}}_{\mathrm{sp}}$), where ${\mathit{p}}_{\mathrm{sp}}$ is a spectator proton, is reported here for the first time. The ${\mathit{E}}_{\gamma }$ dependence of the σ is found to scale to that of σ${(}^2$H(γ,np)), and the ratio is determined to be σ${(}^3$He(γ,np)${\mathit{p}}_{\mathrm{sp}}$)/σ${(}^2$H(γ,np))=1.24±0.,26.

We calculate the differential cross section and the photon asymmetry of the reaction γd→${\mathrm{\pi }}^0$d for incident photon energies below 1 GeV and compare with data at θ=130°. Our formalism, based on the spectator-on-mass-shell approximation, is fully relativistic and uses the dNN vertex of Buck and Gross and a recently developed model for the elementary γN→πN amplitude that describes well the first and second resonance regions. We find large sensitivity to the small components of the deuteron wave function in the energy region of the Roper resonance. Comparison to experimental data points towards a deuteron wave function with a high probability of small components.

A staggering index for alternating parity bands in even-even nuclei is discussed. A study of parity-doublet structures shows that the critical angular momentum at which strong octupole correlations develop can be expressed by a universal relation in terms of the P factor, P=${\mathit{N}}_{\mathit{p}}$${\mathit{N}}_{\mathit{n}}$/(${\mathit{N}}_{\mathit{p}}$+${\mathit{N}}_{\mathit{n}}$).

The relativistic transport model is extended to include the kaon degree of freedom. We also take into account the density dependence of the kaon effective mass in nuclear matter and the rescattering of kaons by nucleons. We find that the inclusion of kaon self-energy due to the attractive scalar mean field leads to an enhanced kaon yield in heavy-ion collisions at subthreshold energies. Also, kaon rescatterings are found to affect significantly the final kaon momentum spectra. We compare the theoretical results with recent experimental data from the Heavy-Ion Synchrotron (SIS) at GSI.

A time-reversal-violating spin-correlation coefficient in the total cross section for polarized neutrons incident on a tensor rank-2 polarized target is calculated by assuming a time-reversal-noninvariant, parity-conserving ‘‘fivefold’’ interaction in the neutron-nucleus optical potential. Results are presented for the system n${+}^{165}$Ho for neutron incident energies covering the range 1-20 MeV. From existing experimental bounds, a strength of 2±10 keV is deduced for the real and imaginary parts of the fivefold term, which implies an upper bound of order ${10}^{\mathrm{-}4}$ on the relative T-odd strength when compared to the central real optical potential.

The potential role of charged particle resonance reactions in the study of parity nonconservation (PNC) in the nucleus is examined in light of recent statistical interpretations of PNC measurements in neutron resonances. Several PNC observables have been calculated using experimental resonance parameters for five s-d shell nuclei. Longitudinal analyzing powers in (p→,${\mathrm{\alpha }}_0$) reactions show strong dependence on energy, angle, and resonance parameters. Measurements of analyzing powers at the ${10}^{\mathrm{-}4}$ level should provide new information on parity vaiolation in the nucleon-nucleus interaction.

Improved upper limits are derived on the possible existence of the T-violating (time-reversal) part of the tensor weak coupling constants, ${\mathrm{C}}_{\mathrm{T}}$ and ${\mathrm{C}}_{\mathrm{T}}^{\prime }$. The previous measurements of the electron-neutrino directional correlation in the nuclear beta decay of ${\mathrm{He}}^6$ are analyzed for sensitivity to T-violating couplings. The results of the analysis are presented in the context of previous beta decay limits on T-violating tensor couplings and compared to somewhat similar limits from precision electric dipole moment experiments.