Optical measurements of a clean, $2-\mu \mathrm{C}$ ${}^{233}\mathrm{U}$ sample were made to verify light emission from gamma ray decay of the first excited nuclear level in ${}^{229}\mathrm{Th}$. The results showed that the light observed in earlier studies was likely to be caused by alpha-particle induced fluorescence of air. In vacuo, no light emission was discernable. The ${}^{229}\mathrm{Th}$ system, therefore, does not appear to provide the level of access for studying atomic-nuclear interactions suggested by the previous measurements.

The ground-state band of the $Z=102\mathrm{}$ isotope ${}^{254}\mathrm{No}$ has been identified up to spin 14, indicating that the nucleus is deformed. The deduced quadrupole deformation, $\beta =0.27\mathrm{}$, is in agreement with theoretical predictions. These observations confirm that the shell-correction energy responsible for the stability of transfermium nuclei is partly derived from deformation. The survival of ${}^{254}\mathrm{No}$ up to spin 14 means that its fission barrier persists at least up to that spin.

Two bolometers composed of tin absorbers and neutron transmutation doped (NTD) Ge thermistors have been fabricated in preparation for experiments in nuclear and subnuclear physics. Both detectors fully resolve the two $K_{\alpha 1}$ and $K_{\alpha 2}$ lines of ${}^{55}\mathrm{Mn}$. The deconvolved FWHM resolution in this energy region ranges from 4.5 to 5.7 eV, for different published values of intrinsic widths and asymmetries of these lines, the best ever obtained at this energy with any energy dispersive detector. The $K_{{\beta }^{\prime }}$ satellite peak is analyzed for the first time in a measurement with an energy dispersive spectrometer.

The extremely weak $l$-forbidden ${1d}_{3/2}\to {2s}_{1/2}$ magnetic dipole ( $M1\mathrm{}$) transition from the ground state of ${}^{32}\mathrm{S}$ to a $J^{\pi }{=1\mathrm{}}^{+}$ state at $E_x=7.003\mathrm{MeV}$ was investigated by 165° and 180° electron scattering. The extracted strength of $0.0040\left(5\right){\mu }_N^2$ represents the smallest $B\left(M1\mathrm{}\right)\uparrow$ value ever measured in electron scattering. A combined analysis with the isospin-analogous Gamow-Teller (GT) decays of the $J^{\pi }{=1\mathrm{}}^{+}$ ground states of ${}^{32}\mathrm{Cl}$ and ${}^{32}\mathrm{P}$ is performed. Empirical corrections of Brown and Wildenthal to the magnetic operators reasonably account for the data. Corrections derived from microscopic approaches are less successful pointing towards a fundamental, not yet understood problem in the description of the effective $M1\mathrm{}$ and GT operators.

The very neutron deficient $Z=N+1\mathrm{}$ nuclei ${}_{39}^{77}\mathrm{Y}$, ${}_{40}^{79}\mathrm{Zr}$, and ${}_{42}^{83}\mathrm{Mo}$ have been observed for the first time following the fragmentation of a ${}^{92}\mathrm{Mo}$ beam. In contrast, no evidence was found for the existence of ${}_{41}^{81}\mathrm{Nb}$ and ${}_{43}^{85}\mathrm{Tc}$. The observation of ${}_{39}^{77}\mathrm{Y}$ is of particular interest in light of the instability of the odd-proton, $Z=N+1\mathrm{}$ systems, ${}_{35}^{69}\mathrm{Br}$, ${}_{37}^{73}\mathrm{Rb}$, ${}_{41}^{81}\mathrm{Nb}$, and ${}_{43}^{85}\mathrm{Tc}$, and may be explained as a consequence of the shape polarizing effect of the highly deformed, prolate $Z=N=38\mathrm{}$ core. The experimental results are discussed within the framework of the shell-correction model, which together with proton-decay calculations allow an estimate of the proton separation energies of these highly exotic systems to be calculated.

The tunneling process that governs the decay from superdeformed to normal-deformed nuclear states is shown to be enhanced by several orders of magnitude ( ${10}^4–{10}^6$) if the normal-deformed states are chaotic at the moment of decay out. The onset of (long-range) chaos may imply that the tunneling enhancement increases with decreasing angular momentum. Experimental signatures are discussed.

Angular correlations of prompt $\gamma$ rays in binary and light-charged-particle (LCP)-accompanied spontaneous fission of ${}^{252}\mathrm{Cf}$ were measured with a $4\pi$-crystal-ball NaI(Tl) $\gamma$-ray spectrometer. For ${}^3\mathrm{H}$, ${}^4\mathrm{He}$, ${}^6\mathrm{He}$, Li, and Be accompanied fission, $\gamma$-ray angular distributions were deduced with respect to the motion both of the fragments and the LCPs. There is no indication for a change of the fragment spin alignment by the LCP release or for a correlation between the LCP direction and a bending motion at scission, as was argued in previous investigations. Consequences for the understanding of fragment spin formation are briefly discussed.

To aid fundamental studies on the polarization of electrons in beta decay, measurements were made of the spin dependence in the scattering of 14 MeV electrons from Pb as a function of scattering angle and foil thickness. The experiment made use of a beam of polarized electrons from a strained GaAsP cathode. A simple theoretical model based on plural scattering explains the observed dependence of the analyzing power on foil thickness. The results extrapolated to infinitely thin targets are in excellent agreement with theory if the finite nuclear size is taken into account.

The inherent nodal structure in the wave functions of 6-nucleon systems is investigated using group theory. The existence of a group of six low-lying states composed of mainly an $L=0\mathrm{}$ component is deduced. In addition to the $\{\}\left(4,2\right)$ spatial permutation symmetry, the $\{\}\left(2,2,2\right)$ symmetry is found to be also important for the low-lying states.

Recently reported transverse momentum distributions of strange hadrons produced in $\mathrm{Pb}\left(158A\mathrm{GeV}\right)$ on Pb collisions and corresponding results from the relativistic quantum molecular dynamics approach are examined. We argue that the experimental observations favor a scenario in which multi-strange hadrons are formed and decouple from the system rather early at large energy densities (at about $1\mathrm{GeV}/{\mathrm{fm}}^3$). The systematics of the strange and nonstrange particle spectra indicate that the observed transverse flow develops mainly in the late hadronic stages of these reactions.

A Comment on the Letter by A. Novoselsky, M. Vallières, and O. La'adan, Phys. Rev. Lett. 79, 4341 (1997). The authors of the Letter offer a Reply.

A Reply to the Comment by Yutaka Utsuno et al.

It is shown that the chemical freeze-out parameters obtained at CERN/SPS, BNL/AGS, and GSI/SIS energies all correspond to a unique value of 1 GeV for the average energy per hadron in the local rest frame of the system, independent of the beam energy and of the target and beam particles.

We examine phenomenologically the ${}^4\mathrm{He}(\mathrm{in}-\mathrm{flight}{K}^{-},{\pi }^{-})$ spectrum at $p_{K^{-}}=600\mathrm{}\mathrm{MeV}/c$ and ${\theta }_{K\pi }=4\mathrm{}°$ within distorted-wave impulse approximation calculations by using a coupled $\left(3N-\Lambda \right)+\left(3N-\Sigma \right)$ model. The result shows that there exists a pole of the ${}_{\Sigma }^4\mathrm{He}$ unstable bound state on the second Riemann sheet of the complex energy plane, and its complex eigenvalue is $E_{{\Sigma }^{+}}^{\left(\mathrm{pole}\right)}=-1.1-i6.2\mathrm{MeV}$ near the $\Sigma$ threshold. Because of the $\Sigma$ branch cut associated with opening the $\Sigma$ channel, an asymmetric peak for ${}_{\Sigma }^4\mathrm{He}$ appears with lying at 3.7 MeV below the ${\Sigma }^{+3\mathrm{}}\mathrm{H}$ threshold and the width of about 10 MeV, which is in good agreement with the recent observation.

In order to study the structure of excited states we perform a variational calculation after spin parity projection (VAP) within the framework of antisymmetrized molecular dynamics (AMD). The framework is proven to be a new powerful approach for the study of the various structures of excited states because it is free from model assumptions such as inert cores, existence of clusters, and the axial symmetry. By using finite range interactions with a density dependent term we reproduce well all the energy levels below 15 MeV in ${}^{12}\mathrm{C}$. This is the first theoretical model that reproduces many $E2\mathrm{}$ transition rates and $\beta$ decays to ${}^{12}\mathrm{C}$ successfully.

We measured simultaneously $\mathrm{pp}$ elastic and quasielastic $(p,2p)$ scattering in hydrogen, deuterium, and carbon for momentum transfers of 4.8 to $6.2(\mathrm{GeV}/c{)}^2$ at incoming momenta of 5.9 and $7.5\mathrm{GeV}/c$ and center-of-mass scattering angles in the range ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=83.7\mathrm{}°–90°$. The nuclear transparency is defined as the ratio of the quasielastic cross section to the free $\mathrm{pp}$ cross section. At incoming momentum of $5.9\mathrm{GeV}/c$, the transparency of carbon decreases by a factor of 2 from ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\simeq 85°$ to ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\simeq 89°$. At the largest angle the transparency of carbon increases from 5.9 to $7.5\mathrm{GeV}/c$ by more than 50%. The transparency in deuterium does not depend on incoming momentum nor on ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}$.

Measurements of deexcitation $\gamma$ rays in coincidence with the momentum distribution of the projectile residues produced in reactions of the type ${}^9\mathrm{Be}{(}^{28}\mathrm{P}{,}^{27}\mathrm{Si}+\gamma )X$ at energies around 65 MeV/u are used to study single-nucleon stripping to individual states. The cross sections are compared with calculations based on an eikonal model description of the reaction and the shell model. The measurements indicate that the halo character of the ground state and other detailed spectroscopic information can be derived using knockout reactions in inverse kinematics.

A Comment on the Letter by T. E. O. Ericson, et al., Phys. Rev. Lett. 75, 1046 (1995). The authors of the Letter offer a Reply.

A Reply to the Comment by M. C. M. Rentmeester, R. A. M. Klomp, and J. J. de Swart.