Cross sections at six angles between 0° and 19° in the center-of-mass system have been measured for the ground-state transition in the reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(n,p${)}^{13}$B at ${\mathit{E}}_{\mathit{n}}$=118 MeV. The 0° cross section gives a value of 186±25 MeV ${\mathrm{fm}}^3$ for the volume integral of the spin-isospin component of the central part of the effective N-N interaction. The theoretical value is 161 MeV ${\mathrm{fm}}^3$ at 100 MeV. A distorted-wave impulse-approximation calculation for the angular distribution of the ground-state transition, (1/$2^{\mathrm{-}}$,1/2) to (3/$2^{\mathrm{-}}$,3/2), compares well with the measurement. The 0° measurement is compared with other (n,p) and (p,n) measurements on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ to test the universal proportionality of these cross sections to the inverse β decay. A falloff in the proportionality constant in going to low energy is confirmed. © 1996 The American Physical Society.

High spin states in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Sn}$ have been established up to 9.1 MeV in excitation energy and to a spin of 43/$2^{\mathrm{-}}$ħ with the reaction ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$${(}^{19}$F,p3n${)}^{109}$Sn at a beam energy of 88 MeV. In-beam measurements involved γ-γ coincidences and directional correlation of oriented states. A negative-parity band consisting of stretched E2 transitions has been established. This band has been identified as the favored signature branch of the decoupled ${\mathrm{h}}_{11/2}$ neutron coupled to the deformed π(${\mathrm{g}}_{9/2}^{\mathrm{-}2}$⊗${\mathrm{g}}_{7/2}^2$) core configuration. © 1996 The American Physical Society.

Properties of the scaled factorial moments are analytically studied within the framework of the Landau mean field approach. Dependences of the moments on resolution are found to be different for first-order and second-order phase transitions. It is suggested that the moments ln${\mathit{F}}_{\mathit{q}}$ should be fitted to powers of X≡${\mathrm{\delta }}^{1/3}$ in the range of high resolution in order to extract information about the phase transition in a parameter independent way. It is also shown that the order of the phase transition could be determined by the relative sign of the fitted coefficients to those calculated theoretically. © 1996 The American Physical Society.

Nuclear transparencies for the fundamental process γn→${\mathrm{\pi }}^{\mathrm{-}}$p on ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been calculated using nucleon configurations obtained from realistic ground-state wave functions by the Monte Carlo method. Comparisons between nuclear transparency results using nucleon configurations and the correlated Glauber approximation are made in the case of (e,${\mathit{e}}^{\prime }$p) on ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Furthermore, nuclear transparencies for the γn→${\mathrm{\pi }}^{\mathrm{-}}$p and (e,${\mathit{e}}^{\prime }$p) processes have been calculated including a color transparency effect. © 1996 The American Physical Society.

In a recent Rapid Communication [Phys. Rev. C 53, R553 (1996)] experimental hard-photon correlations have been compared to Boltzmann-Uehling-Uhlenbeck (BUU) calculations. It is concluded that the data are best described with a single photon source at the beginning of the reaction and that photons coming from the late evolution of the system are just an artifact of the BUU approach. In this Comment we discuss some arguments used by the authors and their conclusions, and demonstrate that BUU calculations, properly compared to data, are consistent with the previously established interpretation of hard photons being emitted from two distinct sources. © 1996 The American Physical Society.

The ${}_{}{}^1{}_{}{}^{}\mathrm{H}({}_{}{}^6{}_{}{}^{}\mathrm{He}, {}_{}{}^6{}_{}{}^{}\mathrm{Li})n$ reaction was studied at 0° with the NSCL A1200 fragment separator in the energy loss mode. A ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ secondary beam at $\frac{E}{A}=93\mathrm{}$ MeV was used to measure the Gamow-Teller and Fermi strengths between the ground state of ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ and the ground and excited states of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, in inverse kinematics. At 0° the ground-state cross section is measured to be $\frac{d{\sigma }_{\mathrm{GS}}}{\left(d\Omega \right)}=43\mathrm{}\pm 16$ mb/sr, which is dominated by systematic error in the secondary beam flux. The ratio of Gamow-Teller to Fermi strength is not sensitive to this error and is found to be (87±6)% of that expected from ($p, n$) systematics and $\beta$ decay. Angular distributions have been measured between 0° and 10° in the center of mass.

The presence of $\Delta I=2\mathrm{}$ staggering in the three known superdeformed (SD) bands of ${}_{}{}^{194}{}_{}{}^{}\mathrm{Hg}$ has been reexamined in a new experiment with Gammasphere. A relative precision of better than 60 eV was achieved for most transition energies. Staggering plots were extracted and their statistical significance was analyzed. No clear evidence was found for an extended regular $\Delta I=2\mathrm{}$ staggering in the three SD bands of ${}_{}{}^{194}{}_{}{}^{}\mathrm{Hg}$. However, statistically significant deviations from a smooth reference were observed in the two excited SD bands. Different scenarios are discussed but no firm conclusion about the origin of the observed deviations can be drawn.

Ternary fission in the reaction ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ + ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ at $E_{\mathrm{lab}}=200\mathrm{}$ MeV has been observed. Intermediate mass fragments (IMF: $3<~Z<~8$) with unique energy and angular distributions have been measured consistent with emission from the neck zone during fission. The widths of the energy spectra are relatively constant for neck fragments with $Z>~4$, suggesting little variability in the scission configurations. A linear dependence of $〈E〉$ on $Z$ is observed for the neck IMFs. The observed trend is compared with a Coulomb trajectory model.

Lifetimes of excited states in ${}_{}{}^{126}{}_{}{}^{}\mathrm{Ba}$ have been measured with high precision by means of the GASP spectrometer using the coincidence recoil distance technique. The reaction ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}({}_{}{}^{30}{}_{}{}^{}\mathrm{Si}, 4n){}_{}{}^{126}{}_{}{}^{}\mathrm{Ba}$ at a beam energy of 130 MeV was used. The data were analyzed with the differential decay-curve method (DDCM). The obtained transition quadrupole moments disagree with the predictions of the asymmetric rotor model (ARM), the interacting boson model (IBM), and the general collective model (GCM). They give evidence for a sudden dynamic shape change in ${}_{}{}^{126}{}_{}{}^{}\mathrm{Ba}$ between the $4^{+}$ and ${10}^{+}$ levels of the ground-state band.

Elastic photon scattering cross sections on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured in the energy range 27-108 MeV. These data are inconsistent with a conventional interpretation in which the electric and magnetic polarizabilities of the bound nucleon are unchanged from the free values and the meson-exchange seagull amplitude is taken in the zero-energy limit. Agreement with the data can be achieved by invoking either strongly modified polarizabilities or a substantial energy dependence to the meson-exchange seagull amplitude. It is argued that these seemingly different explanations are experimentally indistinguishable and probably physically equivalent.

A photon scattering experiment was performed on the $\gamma$-soft nucleus ${}_{}{}^{134}{}_{}{}^{}\mathrm{Ba}$ with photon energies of $E_{\gamma }<4.1\mathrm{}$. Around 3 MeV excitation energy a fragmented $1^{+}$ scissors mode as well as the ${(2^{+}\otimes 3^{-})}_{1^{-}}$ two-phonon dipole state were identified. The dipole excitation strengths were measured. The excitation strength of the scissors mode in this $\gamma$-soft nucleus is well reproduced by an empirical $M1\mathrm{}$ sum rule that generalizes the "${\delta }^2$ law" to nuclei without axial symmetry. The IBM-2 describes the mixed-symmetry states in ${}_{}{}^{134}{}_{}{}^{}\mathrm{Ba}$ and their decay pattern. A large $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratio for the $1^{+}$→$2_1^{+}$ decay of the scissors mode to the $2_1^{+}$ state is predicted by the IBM-2. The new result from ${}_{}{}^{134}{}_{}{}^{}\mathrm{Ba}$ together with a similar previous observation in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pt}$ corroborates the scissors mode as a typical excitation mode of $\gamma$-soft nuclei.

In the fully stripped cosmic rays, the electron capture decay of ${}_{}{}^{54}{}_{}{}^{}\mathrm{Mn}$ (${\tau }_{\frac{1}{2}}=312d$) is strongly suppressed. In this situation the ${\beta }^{-}$ decay channel dominates; however, this half-life has never been measured in the laboratory. Some lower limits have been placed on it previously. Using the cosmic-ray data from the Ulysses spacecraft high-energy telescope (HET) and a self-consistent model of the galactic transport of cosmic rays, this partial lifetime can be determined. The best-fit ${\beta }^{-}$ partial decay lifetime is dependent on the interstellar gas density, but is constrained to be between 1-2×${10}^6$ yr. This is consistent with, but much more restrictive than, earlier limits placed on the lifetime (>3×${10}^4$ and >2.95×${10}^5$ yr) from direct and indirect methods, respectively. This determination using the cosmic-ray data requires laboratory verification for which there appears to be interest.

Correlations among protons and neutral pions emitted in the reaction ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$+${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ at 95 MeV/nucleon have been studied. The analysis of the (${\pi }^0-p$) invariant-mass and relative-angle distributions shows evidences of $\Delta \mathrm{}\left(1232\right)\mathrm{}$-resonance excitation. The experimental data are in agreement with the predictions of microscopic theoretical calculations.

The quadrupole strength function of ${}_{}{}^{28}{}_{}{}^{}\mathrm{O}$ is calculated making use of the SIII interaction, within the framework of continuum-RPA and taking into account collisions among the nucleons (doorway coupling). The centroid of the giant resonance is predicted at ≈ 14 MeV, which is much below the energy expected for both isoscalar and isovector quadrupole resonances in nuclei along the stability valley. About half of its width arises from the coupling of the resonance to the continuum and about half is due to doorway coupling. This result is similar to that obtained in the study of giant resonances in light, $\beta$-stable nuclei, and shows the lack of basis for the expectation, entertained until now in the literature, that continuum decay was the main damping mechanism of giant resonances in halo nuclei.

A recently proposed correlation of quasiground band energies in collective nuclei is shown to provide a highly sensitive indicator of different classes of nuclei and to lead to an empirical analytic formula for these energies.

The collective yrast band and the high spin states of the nucleus ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$ are studied using the spherical shell model and the cranked Hartree-Fock-Bogoliubov method. The two descriptions lead to nearly the same values for the relevant observables. A first backbending is predicted at $I=10\mathrm{}\hslash$ corresponding to a collective to noncollective transition. At $J=16\mathrm{}\hslash$ a second backbending occurs, associated to a configuration change that can also be interpreted as a spherical to triaxial transition.

Within a theoretical study using both HYLANDER and RQMD, we revisit Bose-Einstein correlation measurements of $200A$ GeV S+S and $160A$ GeV Pb+Pb. Transverse flow does not show up in the Bose-Einstein measurements. The decrease of the effective transverse radius parameters with increasing transverse average momentum of the particle pair is largely due to the effect of resonance decays.

We study antikaon flow in heavy-ion collisions at SIS energies based on the relativistic transport model (RVUU 1.0). The production of antikaons from both baryon-baryon and pion-baryon collisions are included. Taking into account only elastic and inelastic collisions of the antikaon with nucleons and neglecting its mean-field potential as in the cascade model, a strong antiflow or anticorrelation of antikaons with respect to nucleons is seen as a result of the strong absorption of antikaons by nucleons. However, the antiflow of antikaons disappears after including also their propagation in the attractive mean-field potential. The experimental measurement of antikaon flow in heavy-ion collision will be very useful in shedding light on the relative importance of antikaon absorption versus its mean-field potential.