The available experimental data concerning the unpolarized cross section for the Compton scattering on the nucleon at low energy are compared with the predictions of the heavy baryon chiral perturbation theory (HBChPT) at the order $q^3$.

A study of the reaction ${\pi }^{+}+d\to p+p$ has been performed in the energy range of 18–44 MeV. Total cross sections and differential cross sections at six angles have been measured at 15 energies with an energy increment of 1–2 MeV. This is the most systematic data set in this energy range. No structure in the energy dependence of the cross section has been observed within the accuracy of this experiment.

The total photoabsorption cross section for ${}^4$He has been measured for the first time over a wide photon energy range (200 MeV$<~E_{\gamma }<~$800 MeV). By using the large acceptance detector DAPHNE at the tagged photon facility of the MAMI microtron in Mainz high precision results with small systematic errors were obtained. This measurement shows that ${}^4$He has a behavior similar to heavy nuclei and, in particular, a reduction of the cross section with respect to the lighter nuclei is found for $E_{\gamma }>$600 MeV.

Using baryon chiral perturbation theory (B$\chi$PTh), explicitly including the $\Delta$(1232) and $N^{*}$(1440) baryon resonances only, we compute for incoming ${\pi }^{\pm }P$ channels with kinetic energy under 400 MeV, total cross sections, angular distributions, and various final state correlation functions and compare these with available experimental data in this energy range. Threshold isospin amplitudes are extracted from the calculated fully covariant perturbative amplitudes. No attempt is made to fit this data. The necessary input parameters were all taken from separate experimental data. The results appear to be generally encouraging for $\mathrm{B}\chi \mathrm{PTh}$.

Inelastic electron scattering from ${}^3$He is studied in the kinematic region of pion production. Inclusive processes with polarization of the electron probe and of the ${}^3$He target are described in the plane wave impulse approximation. The question to what extent polarized ${}^3$He can serve in this kinematic regime as a substitute for unavailable neutron spin targets is discussed.

Transition potentials for elastic $p$-$d$ scattering and the coupled processes $p$+${}^3$He $\to$ $p$+${}^3$He and $n$+${}^3$He $\to$ $d+d$ are derived in the Faddeev-Yakubovsky framework with special emphasis on leading order terms, which are expected to be valid at intermediate energies. In addition, equations for the fragmentations ${}^3\mathrm{He}\mathrm{}(p,ppp)n$ and ${}^3$He$\mathrm{}(p,pp)d$ are derived within the same framework. Again leading order terms for intermediate energies are considered.

The process $\gamma +t\to n+d$ is treated by means of three-body integral equations employing in their kernel the $W$-matrix representation of the subsystem amplitudes. As compared to the plane wave (Born) approximation the full solution of the integral equations, which takes into account the final state interaction, shows at low energies a 24% enhancement. The calculations are based on the semirealistic Malfliet-Tjon and the realistic Paris and Bonn $B$ potentials. For comparison with earlier calculations we also present results for the Yamaguchi potential. In the low-energy region a remarkable potential dependence is observed, which vanishes at higher energies.

We propose a three-potential formalism for the three-body Coulomb scattering problem. The corresponding integral equations are mathematically well behaved and can succesfully be solved by the Coulomb-Sturmian separable expansion method. The results show perfect agreements with existing low-energy $n$-$d$ and $p$-$d$ scattering calculations.

We apply the strong $\pi \mathrm{NN}$ form factor, which emerges from the Skyrme model, in the two-nucleon system using a one-boson-exchange (OBE) model for the nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ interaction. Deuteron properties and phase parameters of $\mathrm{NN}$ scattering are reproduced well. In contrast to the form factor of monopole shape that is traditionally used in OBE models, the Skyrme form factor leaves low-momentum transfers essentially unaffected while it suppresses the high-momentum region strongly. It turns out that this behavior is very appropriate for models of the $\mathrm{NN}$ interaction and makes it possible to use a soft pion form factor in the $\mathrm{NN}$ system. As a consequence, the $\pi N$ and the $\mathrm{NN}$ systems can be described using the same $\pi \mathrm{NN}$ form factor, which is impossible with the monopole.

A decoupled $(\Delta I=2)$ rotational band extending to spin (47/2)$ħ$ and excitation energy 10.3 MeV has been observed in ${}^{115}$Sn using the reaction ${}^{110}$Pd${(}^9$Be,4$n)$ at a beam energy of 45 MeV. This intruder band is believed to be based upon the coupling of the $\nu h_{11/2}$ valence neutron orbital to the deformed $\left[\right(\pi g_{7/2}{)}^2\otimes (\pi g_{9/2}{)}^{-2}$] core band in ${}^{114}$Sn. Evidence also has been found for a second, nearly degenerate sequence in ${}^{115}$Sn which has the same spin and parity.

Three superdeformed bands have been observed in the nucleus ${}^{144}$Eu with the GAMMASPHERE spectrometer in its early implementation phase. The reaction used was ${}^{122}$Sn${(}^{27}$Al,5${n)}^{144}$Eu at a beam energy of 142 MeV. All three bands are identified as single-neutron excitations with respect to ${}^{143}$Eu. One band is a confirmation of a previously suggested candidate. It is assigned as the yrast sequence based on the $\pi 6^1\nu 7^1$ configuration, and is believed to undergo an interaction with the $\nu$[514]9/2${}^{-}$ orbital. The other two bands are assigned as signature partners based on the $\pi 6^1\nu {6\mathrm{̃}}^1$ configuration, where $6\mathrm{̃}$ corresponds to a mixed [651]1/2${}^{+}$/ [642]5/2${}^{+}$ state. The partner that contains the $\alpha$=-1/2 signature component of the $6\mathrm{̃}$ orbital is identified from a band crossing that occurs in related bands in ${}^{145}$Gd and ${}^{146}$Gd. Alignment plots suggest that the interaction strength becomes stronger as the mass number increases.

The gamma decay of high spin yrast states in ${}^{83}$Y up to $I^{\pi }{=59/2\mathrm{}}^{+}$ and ${53/2}^{-}$ have been observed using the reaction ${}^{58}$Ni${(}^{29}$Si,$3p)$ at 110 MeV and the Gammasphere Early Implementation Array. The level scheme has been substantially extended due to the observations of several new transitions in all of the bands. A sequence of transitions feeding into the positive parity yrast band above $I^{\pi }{=47/2\mathrm{}}^{+}$ seems to be consistent with a noncollective oblate structure expected at these high spins. A similar cascade is found in the data for ${}^{84}$Zr. A new forking of the favored negative parity band is found which may be due to neutron alignment polarizing the core to a different shape. This suggests that the “isomeric” band in ${}^{83}$Y, for which one more connecting transition was found, is of a similar nature to other high-$K$ bands found in this region. Lifetime measurements in the unfavored negative parity band are consistent with cranking calculations which predict a nearly oblate shape with a deformation parameter ${\beta }_2\approx 0.2$. A qualitative analysis of line shapes at very high spins suggests the persistence of collectivity in the yrast sequence to the highest excitations seen.

The ${}^{29}$Si$(p,\gamma )$ reaction has been studied in the range $E_p=1.00\mathrm{}$–1.75 MeV. Three previously unknown states in ${}^{30}$P were identified, and one state previously assigned to ${}^{30}$P was identified as a state in ${}^{14}$N. Gamma-ray strengths were determined for the three new levels, and branching ratios were measured for 17 resonances. Revised $J^{\pi };T$ assignments were made for nine of these states.

The short-lived isomeric states in the $T_Z$=1 nuclei, ${}^{94m}$Pd $[T_{1/2}$=0.6(1) $\mu$s] and ${}^{96m}$Ag $[T_{1/2}$=0.7(2) $\mu$s], were identified among the fragmentation products of the ${}^{112}$Sn $(63A$ MeV) + ${}^{\mathrm{nat}}$Ni (93.5 mg/cm${}^2)$ reaction at GANIL. The separation and identification of the reaction products was done by means of the Alpha and LISE3 magnetic spectrometers combined with time-of-flight, energy-loss, and total kinetic energy measurements. Evidence for isomeric states in ${}^{80}$Y, ${}^{98}$Cd, and ${}^{102}$Sn was also obtained.

The structure of the high spin states above the 28${}^{-}$ isomer in the odd-odd ${}^{152}$Ho nucleus was investigated using the GASP $\gamma$-ray spectrometer coupled to the recoil mass spectrometer CAMEL. The ${}^{152}$Ho nucleus was populated through the ${}^{120}$Sn${(}^{37}$Cl,5$n)$ fusion reaction at a beam energy of 187 MeV. A complex level scheme above that isomer was established up to an excitation energy of 13 MeV and $I\approx$ 40$ħ$. No rotational bands were observed.

Gamow-Teller (GT) states with $J^{\pi }$ = 1${}^{+}$ excited by a $\mathrm{}(p,n)\mathrm{}$-type charge-exchange reaction on $N=Z$ nuclei with ground-state isospin $T=0\mathrm{}$ have isospin $T=1\mathrm{}$, while $M1\mathrm{}$ states excited by inelastic scattering of electrons or protons can have either $T=0\mathrm{}$ or $T=1\mathrm{}$. The latter are the isobaric analog states of the GT states. By comparing the GT states observed in the good-resolution ${(}^3\mathrm{He},t)$ reaction at 150 MeV/nucleon with the $M1\mathrm{}$ states observed in inelastic electron and proton reactions, the isospin structure of the $1^{+}$ states in ${}^{28}\mathrm{Si}$ has been determined. From an analysis of the strengths of corresponding $1^{+}$ states observed in the ${(}^3\mathrm{He},t)$ and ${(e,e}^{\prime })$ reactions, the spin and orbital contributions to the $M1\mathrm{}$ excitations have been deduced.

Independent yields of 139 individual secondary (appearing after neutron evaporation) fragment pairs of five different charge splits ${(Z}_L{/Z}_H=$46/52, 44/54, 42/56, 40/58, and 38/60) have been experimentally measured by detecting the coincidences between prompt $\gamma$ rays emitted in the spontaneous fission of ${}^{252}\mathrm{Cf}.\mathrm{}$ Nuclear charge and mass distributions of fission fragments that follow from the measured yields of individual fragment pairs are consistent with similar previously known more integral data. Another type of data extracted from the yields of fragment pairs is the multiplicity distributions of prompt neutrons emitted in the five above charge divisions of ${}^{252}$Cf. For the measured charge splits, about 70% of the fission events where $>~7$ neutrons are evaporated from the fission fragments occur for the Mo-Ba split of ${}^{252}$Cf. Mass and excitation energy distributions of primary Ru-Xe, Mo-Ba, and Zr-Ce fragments were deduced from a least squares fit to the yield pattern of secondary fragment pairs. For the Ru-Xe and Zr-Ce splits, the experimental data are well fitted by assuming one fission mode with average total kinetic energy $〈\mathrm{TKE}〉$ values close to the value of $〈\mathrm{TKE}〉$ known for the ${}^{252}\mathrm{Cf}$ spontaneous fission. For the Mo-Ba split, a successful fit could be obtained only with the assumption that, in addition to this “normal” fission mode, a second mode with a remarkably lower value of $〈\mathrm{TKE}〉$ of 153 MeV contributes to this charge split. This is 36 MeV lower than for the normal mode. These data indicate that in mode two the barium nuclei are hyperdeformed (3:1 axis ratio) at scission. Mean angular momentum values of Mo-Ba fission fragments observed in pairs together with various partners have been deduced from the measured populations of different spin levels of the fragment nuclei. These angular momentum values are discussed in terms of their dependence on the primary fragment excitation energy and presence of two fission modes.

Sources of ${}^{220}$Ac in secular equilibrium with ${}^{221}$Pa were produced using the reaction ${}^{209}$Bi${(}^{18}$O,$3n)$${}^{224}$Pa. The alpha decay of ${}^{220}$Ac and coincident gamma and electron spectra were used to study the level structure of ${}^{216}$Fr. The levels in ${}^{216}$Fr can be interpreted in terms of the $\pi {(h}_{9/2})$${}_{9/2}^5\nu {(g}_{9/2})$${}_{9/2}^3,$ $\pi {(h}_{9/2})$${}_0^4{(f}_{7/2}{)}_{7/2}\nu {(g}_{9/2})$${}_{9/2}^3,$ and $\pi {(h}_{9/2}{)}_{9/2}^5\nu {(g}_{9/2}{)}_0^2{(i}_{11/2}{)}_{11/2}$ shell model configurations. The alpha decay hindrance factors of the ground state to ground state transitions in the sequence ${}^{224}\mathrm{Pa}{\to }^{220}\mathrm{Ac}{\to }^{216}\mathrm{Fr}{\to }^{212}$At suggest the collapse of quadrupole-octupole Nilsson orbitals into the more degenerate shell model orbitals. The sequence of hindrance factors in this odd chain are mirrored in the corresponding odd proton and odd neutron sequences beginning with ${}^{223}$Pa and ${}^{223}$Th, respectively.

The feeding mechanism of the superdeformed bands in ${}^{147}$Gd and ${}^{148}$Gd has been studied via the ${}^{124}$Sn + ${}^{29}$Si reaction at a beam energy of 157 MeV. Using the BGO inner ball of the GASP array, high-energy $\gamma$ rays have been detected in coincidence with discrete transitions deexciting normal-deformed (ND) and superdeformed (SD) states in the final product nuclei. The slope of the measured high-energy $\gamma$-ray spectra depends strongly on the number of emitted neutrons and is somewhat lower for spectra in coincidence with SD bands than for those in coincidence with ND structures. Both observations are qualitatively reproduced by statistical model Monte Carlo calculations, which point out the importance of angular momentum effects in the emission of energetic $\gamma$ rays. The present data exclude the enhanced population of SD bands when fed through high-energy $E1\mathrm{}$ transitions.

Excited states in ${}^{182}$Pt have been studied via the heavy-ion reactions ${}^{170}$Yb${(}^{16}$O,$4n)$, ${}^{162}$Dy${(}^{24}$Mg,$4n)$, and ${}^{163}$Dy${(}^{24}$Mg,$5n)$. $\gamma$-ray coincidence measurements were performed with arrays of HPGe detectors at the McMaster University Tandem Accelerator Laboratory ${(}^{16}$O-induced reaction) and the Institut de Physique Nucléaire, Orsay ${(}^{24}$Mg-induced reactions). The ground-state rotational band has been extended to $I=26\mathrm{}ħ$, and six new band structures have been identified and assigned quasiparticle configurations. The $\gamma$-vibrational band and the band built upon the first excited 0${}^{+}$ state have also been extended. Properties of the rotational bands are compared with cranked-shell-model and total-Routhian-surface calculations. Evidence concerning shape coexistence at low spin and band crossings at high spin is discussed.