The α decay of mass separated ${}_{}{}^{190}{}_{}{}^{}\mathrm{Pb}$ was studied at the UNISOR on-line facility and fine structure was observed, feeding the $2_1^{+}$ and $0_2^{+}$ states in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$ identified previously in β-decay and in-beam γ-ray studies. The hindrance factor of the α decay to the excited $0_2^{+}$ state in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$ is similar to that observed in ${}_{}{}^{182,184}{}_{}{}^{}\mathrm{Hg}$. The variation of the hindrance factor to the $2_1^{+}$ states in ${}_{}{}^{182,184,186}{}_{}{}^{}\mathrm{Hg}$ is discussed. © 1996 The American Physical Society.

The new neutron deficient isotope ${}_{}{}^{209}{}_{}{}^{}\mathrm{Th}$ has been produced in the reaction of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ on ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ at beam energy of 171 MeV. Evaporation residues were separated in flight from beam by a JAERI recoil mass separator, and implanted in a position sensitive strip detector. The genetic correlation of α-decay events, their energies and half-lives has been used to identify isotopes. An α-decay energy and a half-life of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Th}$ have been determined to be 8.080(50) MeV and 3.$8_{\mathrm{-}1.5}^{+6.9\mathrm{}}$ ms, respectively. © 1996 The American Physical Society.

We carried out measurements of the excitation function for the reaction ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$(p,2n${)}^{44}$Ti from 16 to 55 MeV. The results show a discrepancy with the only previous work on the subject. It was also possible to measure the cross sections for the reactions (p,pn${)}^{44}$${\mathrm{Sc}}^{\mathit{m}}$ from 16 to 55 MeV, (p,pn${)}^{44}$${\mathrm{Sc}}^{\mathit{g}}$ and (p,n${)}^{45}$Ti from 16 to 22 MeV, and (p,3pn${)}^{42}$K and (p,3p${)}^{43}$K from 40 to 55 MeV. © 1996 The American Physical Society.

We report the results of a high-resolution study of neutron resonances below 500 eV in ${}_{}{}^{166}{}_{}{}^{}\mathrm{Ho}$. We find nine previously unreported weak resonances at energies 24.79, 75.08, 119.98, 187.94, 210.86, 227.87, 235.94, 248.60, and 264.98 eV. Bayesian probability analysis of the widths indicates they are formed primarily by s-wave capture and are therefore negative-parity resonances. If they have measurable d-wave neutron widths, they are candidates for the fivefold correlation test of time reversal. © 1996 The American Physical Society.

A strong quasicontinuum ridge with a spacing of 58.1 ± 0.3 keV was observed in ${}_{}{}^{173}{}_{}{}^{}\mathrm{and}$ ${}_{}{}^{174}{}_{}{}^{}\mathrm{W}$ when populated at high spin. The ridge is a factor of 4 times more intense than that of the sum of discrete bands over the same range of rotational frequencies. The strength of the ridge may be due to the large number of nearly degenerate proton orbitals lying above the Z = 73 gap occurring at a deformation ${\mathrm{\beta }}_2$≊0.3. © 1996 The American Physical Society.

The level structure of ${}_{}{}^{132,134}{}_{}{}^{}\mathrm{Ba}$ was investigated in (p,t) transfer reactions. High resolution spectra (7–8 keV full width at half maximum) with targets from a mass separator allow us to resolve levels up to 4.0 MeV. New $0^{+}$ states are identified. The monopole transfer strength shows distributions similar to those observed for ${}_{}{}^{194,196}{}_{}{}^{}\mathrm{Pt}$. This is consistent with the O(6) limit of the interacting boson approximation (IBA-1) model, without ruling out other, more microscopically based interpretations for the low-lying structure of these nuclei. We also compare with the IBA-2 model and geometrical model calculations. © 1996 The American Physical Society.

We compare α-decay half-life calculations, using parameter values unchanged from previous work, with 88 recent measurements of neutron deficient isotopes in the region N≳82≳Z. The results generally reproduce the data to within a factor of 3 or better. Exceptions to this statement occur for decays which do not proceed by s-wave transitions, and also where no α-branching ratio has been measured. In the former cases we calculate the L values for the transitions needed to bring their half-lives into agreement with the experimental values, and for the latter we predict branching ratio values based on the mismatches between the calculated α half-lives and the measured total half-lives. Amongst the 88 reported decays there are no cases which cannot be accommodated satisfactorily within this framework. For completeness we also calculate proton emission half-lives and find excellent agreement with the two observations in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Ta}$ reported in the same experimental survey. © 1996 The American Physical Society.

The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(e,${\mathit{e}}^{\prime }$p) reaction is analyzed in a model which explicitly includes final state interactions due to the coupling of the proton and neutron emission channels. We find that the effects of the final state interactions due to charge exchange reactions are important to get a good description of the symmetry properties of the newly measured Mainz spectral functions. We discuss the possible role the off-shell effects may play for the correct interpretation of spectral functions at large positive missing momenta. © 1996 The American Physical Society.

The nucleon mean free path in nuclear matter is calculated in a σ-ω model where the coupling constants have been made density dependent in order to reproduce the saturation curve obtained in a Dirac-Brueckner calculation and the real part of the nucleon-nucleus optical potential obtained by a fit of the experimental cross sections. When the modification of the Dirac sea is taken into account in the determination of the coupling constants, the mean free path obtained is much more in agreement with the experimental data. © 1996 The American Physical Society.

We present a new and simple method of calculating the occupation probability of the number of total harmonic-oscillator quanta for a microscopic cluster model wave function. Examples of applications are given to the recent calculations including an α+n+n model for ${}_{}{}^6{}_{}{}^{}\mathrm{He}$, an α+t+n+n model for ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$, and an α+α+n model for ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ as well as the classical calculations of an α+p+n model for ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and an α+α+α model for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The analysis is found to be useful for comparing various model wave functions by quantifying the amount of excitations across the major shell. © 1996 The American Physical Society.

The ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(p,α${)}^6$Li reaction at 45 and 50 MeV has been analyzed in the finite-range distorted-wave Born approximation (FR-DWBA) formalism including both the direct and the exchange modes, in which all one-step DWBA terms have been treated coherently. The spectroscopic factors are obtained theoretically by making use of the cluster-coupling shell-model wave functions. Numerical calculations show that the inclusion of the coherent contribution of the direct and the exchange modes is of considerable importance to give a reasonable agreement with the experimental data. © 1996 The American Physical Society.

We use scaled factorial moments (SFM’s) to analyze pseudorapidity fluctuations of nonstatistical origin in p-nucleus interactions at 800 GeV. The SFM’s are found to exhibit a power-law dependence on the pseudorapidity interval size. The anomalous dimensions ${\mathit{d}}_{\mathit{q}}$ have been calculated up to order 5. The fractional dimensions ${\mathit{D}}_{\mathit{q}}$ have been extracted from the slopes of the multifractal plots. Both the multifractal and intermittency approaches have been found to be complementary to each other. The behavior of ${\mathit{D}}_{\mathit{q}}$ and ${\mathit{d}}_{\mathit{q}}$ with order q indicates a possible self-similar random cascading mechanism for multiparticle production. © 1996 The American Physical Society.

We use a nonlocal nucleon-Δ interaction, based on a quark cluster model for the nonstrange sector, to analyze the possible existence of a resonance in the ${\mathit{J}}^{\mathit{P}}$=$0^{\mathrm{-}}$ channel with isospin 2. The employed quark cluster model has been successfully applied to the one and two nonstrange baryon properties. The nonlocal potential results to be attractive enough to generate a resonance although with a mass and width larger than the experimental predictions. There is a strong correlation between the mass and the width of the resonance due to the proximity of the nucleon-Δ threshold. © 1996 The American Physical Society.

We comment on a recent paper by Knobles, Stotts, and Udagawa [Phys. Rev. C 52, 2257 (1995)]. It is pointed out that this model is inconsistent as far as the relationship between the mean field and effective residual interaction is concerned. Furthermore, the conclusions drawn by these authors about the validity of other treatments of continuum effects are incorrect. © 1996 The American Physical Society.

A response is made to the Comment in Ref. . The discussion centers on two approaches to evaluate the nuclear response in the continuum. Both approaches approximate the damping mechanism and can be considered complementary to each other since they can be used to study different aspects of the nuclear response. The issue of self-consistency between the mean field and residual interaction is addressed along with a discussion concerning the nature of the damping in the continuum. © 1996 The American Physical Society.

Resonances in the unbound nucleus ${}_{}{}^{11}{}_{}{}^{}\mathrm{N}$ have been studied, using the resonance scattering reaction ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$+$p$. The data give evidence for three states above the ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$+$p$ threshold with energies 1.30, 2.04, and 3.72 MeV. These states can be interpreted, in a potential-model analysis, as the ground state and the first two excited states with spin-parity $\frac{1}{2^{+}}$, $\frac{1}{2^{-}}$, and $\frac{5}{2^{+}}$ arising from the shell-model orbitals $1s_{\frac{1}{2}}$, $0p_{\frac{1}{2}}$, and $0d_{\frac{5}{2}}$. A narrow state superposed on a broad structure found at higher energy could be interpreted as the mirror state of the $\frac{3}{2^{-}}$ in ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ shifted down in energy. This shift would suggest a large radius of the potential.

In the fusion-fission reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}$→${}_{}{}^{156}{}_{}{}^{}\mathrm{Dy}$→fission, performed at beam energies $E_b=216\mathrm{} \mathrm{MeV} \mathrm{and} 238 \mathrm{MeV}$, $\gamma$ rays were measured in coincidence with fission fragments. The $\gamma$-ray spectra are interpreted using a modified version of the statistical-model code cascade. From a comparison of the experimental and calculated spectra it is deduced that the nuclear viscosity is in the range $0.01<\mathrm{}\gamma <4\mathrm{}$. The extracted fission time scale is of the order of ${10}^{-19\mathrm{}}$ s.

Calculated neutron momentum distributions are presented for the reaction ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}+{}_{}{}^{12}{}_{}{}^{}\mathrm{C}\to {}_{}{}^9{}_{}{}^{}\mathrm{Li}+2n$ at a beam energy of 280 MeV/nucleon. Different assumptions were made about the average distance between the two outer (halo) neutrons of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ projectile. The purpose was to discover whether the measurement of neutron momentum distributions and fragment cross sections could provide information about the distribution of distance between the two neutrons.

Based on a perturbative QCD analysis of the deuteron form factor, a model for the reduced form factor is suggested. The numerical result is consistent with the data in the intermediate energy region. © 1996 The American Physical Society.