Nuclear temperature has proved to be a useful concept in heavy ion reactions at both low (E/A<10 MeV) and high (E/A>100 MeV) bombarding energies. Experiments in the intermediate energy regime have been unable to extract a well defined value for the temperature. In this Brief Report we suggest that broad temperature distributions may be able to resolve the apparent discrepancies.

A theoretical study of the ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(n,p) reaction is performed at an incident energy of 200 MeV. The forward angle ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(n,p) spectra are calculated within a microscopic model using random phase approximation transition densities for the description of the nuclear excited states. The calculated spectra are compared to those published previously by Klein, Love, and Auerbach.

The reaction ${\mathrm{e}}^{\mathrm{-}}$${+}^{12}$C→${\nu }_{\mathrm{e}{+}^{12}}$B is studied for electron energies of 0.5, 1.5, 3.0, and 6.0 GeV. Differential cross sections as a function of outgoing nucleus angle are obtained for these energies. The differential cross sections for the 0.5 and 3.0 GeV cases are analyzed in detail and contributions from the various form factors are determined. The results of the calculation are discussed in detail.

The possibility of antiproton annihilation on a cluster of nucleons is investigated. In the model, the annihilation forms a quark-gluon plasma droplet which on expansion coagulates into mesons and baryons. The energy spectra and multiplicities of mesons as well as kaon and lambda production ratios are computed. The probability of annihilation on a pair of nucleons is about ten percent, but the lower plasma temperature reduces strangeness production.

The validity of the Otsuka-Arima-Iachello mapping procedure for a quadrupole force in a single j shell is discussed, and a comparison is made with the scheme of Bao et al.

We propose the production of polarized, ultrarelativistic, light hypernuclei to study hypernuclear magnetic moments and lifetimes.

In some formulations, application of the Lippmann-Schwinger equation to collisions in many-particle (n>2) systems naturally leads to the limits ε→0 of certain volume integrals involving Green’s functions at complex energies E+iε. The values of these limits, derived originally by Lippmann using operator techniques, are known as Lippmann’s identities. This paper evaluates the limits studied by Lippmann in a one-dimensional three-body model (due to McGuire) which has been much employed recently to test Lippmann-Schwinger formulations of scattering theory; the results verify the Lippmann identities. Also evaluated in the McGuire model are a number of related identities, not due to Lippmann, that have been derived recently via quite conventional mathematical operations which yielded a previously unsuspected relationship between Lippmann’s ε→0 limits and a class of surface integrals at infinity in configuration space, originally studied by Gerjuoy. All the results completely confirm the validity of the aforementioned mathematical operations and, by implication, also confirm the disputed conclusion that the many-particle Lippmann-Schwinger equation does not have unique solutions.

The one-nucleon ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{17}$O${,}^{16}$O) and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{17}$O${,}^{18}$F) transfer reactions have been investigated at $E_{\mathrm{lab}{(\mathrm{}}^{17}\mathrm{O})=376\mathrm{}}$ MeV. The data were analyzed in terms of the distorted-wave Born approximation. The distorted-wave Born approximation predictions reproduce fairly well the bell shape of the various angular distributions and the relative intensities of the various single-particle and single-hole transitions.

Triple-differential cross sections have been measured as a function of product mass, total kinetic energy, and center-of-mass scattering angle in reactions induced by ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Zn}$ targets at several bombarding energies between 4.6 and 7.5 MeV/nucleon. The analysis focuses on binary processes in which the product masses are substantially different from the target-projectile masses. These include the complete fusion followed by fission as well as quasifission processes in which large mass transfers occur on a short time scale. The relative contributions of these two components are estimated from the mass-angle correlations and analyzed within the extra and extra-extra push concepts. The time scale for mass transfer in quasifission reactions is derived from turning angles of the intermediate complex, and it is found that the mass drift toward symmetry shows the characteristics of an overdamped motion with a universal time constant independent of scattering system and bombarding energy. This is consistent with the one-body nuclear dissipation mechanism being responsible for the damping in the mass asymmetry degree of freedom. Also the average total kinetic energy of reaction products in quasifission is independent of temperature, supporting the one-body dissipation hypothesis.

If an atomic collision is accompanied by a deep inelastic nuclear reaction with a time delay ΔT, a phase change which affects the ionization probability $P_K$ of the target- and projectile-like products is introduced between the incident and outgoing ionization amplitudes. In a deep inelastic nuclear reaction, the nuclear reaction time ΔT is monotonically related to the total kinetic energy loss (-Q) of the reaction products. Therefore a measurement of $P_K$ as a function of Q then yields ΔT. The K-shell ionization probability $P_K$ has been measured in the deep inelastic reactions U + U and U + Pb at a beam energy of 1785 MeV as a function of the total kinetic energy loss -Q. $P_K$ was determined for Q values down to -190 MeV. After subtraction of the ionization induced by the internal conversion of γ rays, a strongly Q-dependent $P_K$ is found, in qualitative agreement with theoretical predictions. From the data we infer a nuclear reaction time of approximately 1×${10}^{\mathrm{-}21}$ s at Q=-100 MeV. The observed reaction times agree fairly well with the predictions of the classical nuclear reaction models used to describe deep inelastic scattering processes.

High-spin states have been populated in ${}_{}{}^{136}{}_{}{}^{}\mathrm{Nd}$ using the ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}$${(}^{24}$Mg,4nγ${)\mathrm{}}^{136}$Nd reaction. Several rotational bands have been observed based on two- and four-quasiparticle configurations. The ground-state band backbends sharply at a frequency ħω=0.34 MeV due to the alignment of a pair of $h_{11/2}$ protons. Both signatures of a negative parity side band based on a π$h_{11/2}$⊗π$g_{7/2}$ configuration were observed to backbend at a frequency ħω=0.44 MeV, again due to the alignment of a pair of $h_{11/2}$ protons. All these bands are prolate because of the stabilizing influence of the $h_{11/2}$ quasiprotons on the γ-soft core. In addition to the $h_{11/2}$ proton alignment in the ground-state band, a rotational band is observed built on a second ${10}^{+}$ state, which involves the alignment of a pair of $h_{11/2}$ neutrons. An alignment of neutrons from the upper $h_{11/2}$ midshell drives the nucleus towards a collectively rotating oblate (γ=-60°) shape. Both signatures of a band based on a ν$h_{11/2}$⊗ν$g_{7/2}$ configuration were observed, also possibly oblate. The observation of both neutron and proton low-frequency alignments is consistent with cranked-shell model calculations and theoretical estimates of the prolate-oblate energy difference for this nucleus.

We have carried out simulations of central collisions between two heavy ions by the classical molecular dynamics method. The ions used in these simulations are bound spheres of charged argon atoms, and the chosen mass numbers for the collisions are 108 on 108, 65 on 65, and 16 on 200. A few hundred collisions are studied for five energies chosen to span fusion-fission, multifragmentation, and total vaporization reactions. We have also studied the disassembly of hot liquid drops containing 216 and 130 particles. By comparing collisions and disassembly we establish the formation of equilibrated hot matter in the collisions. The density of the hot matter formed appears to be ∼80% of the equilibrium density, and its temperature depends upon the beam energy. All the beam energy thermalizes in equal mass collisions; however, a large fraction of it is lost in pre-equilibrium emission in the asymmetric 16 on 200 collisions. Mass yields and energy spectra of the particles emitted in collisions and disassemblies are reported, and the role of the liquid-gas phase transition is discussed. The yield of small clusters having $A_c$<30 particles is approximately given by the & power law. The ${\tau }_{\mathrm{eff}}$ depends on the energy of the collision, and has a minimum value of ∼1.7 as observed in nuclear fragmentation reactions.

We have studied the low-energy ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,γ${)\mathrm{}}^4$He reaction based on a microscopic description of the nuclear wave functions. Our study reproduces the experimental reaction cross sections at E≤3 MeV; it allows for an extrapolation of the data to energies relevant for big-bang nucleosynthesis resulting in a cross section about 35 times higher than given in present compilations. Our results indicate a D-state admixture in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ground state of ≊5–7 %.

Excitation functions have been measured for different fragments produced in the ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$${(}^{19}$F,x)y reactions between 135 and 143.25 MeV incident energy in 250 keV steps. Cross section fluctuations correlated in atomic number and detection angle are observed with a coherence width of 200–500 keV. Lifetimes have been deduced and are of the order of a complete nuclear rotation. The data can be explained in terms of quasimolecular configurations and/or an orbiting situation in a dinuclear system.

An extended time-dependent Hartree-Fock theory which incorporates the effects of nucleon-nucleon collisions into the mean field is presented and applied to head-on collisions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{16}$O at low incident energies. Particularly investigated is the influence of nucleon-nucleon collisions on the low angular momentum limit for fusion which is predicted by time-dependent Hartree-Fock calculations. It is found that the threshold energy for the low angular momentum limit is dramatically increased because of nucleon-nucleon collision effects.

We have measured the momentum distributions and the excitation energy of the p${,}^{11}$B pair in the ${(}^{12}$C${,}^{11}$B + p) reaction at 2.1 GeV/nucleon with C and ${\mathrm{CH}}_2$ targets. The cross section separates into three regions: (1) nucleon-nucleon quasi-elastic scattering, (2) nucleon-nucleon inelastic scattering, and (3) a low excitation energy and momentum transfer peak. The cross sections, by region, are as follows: (1) 8.8±2.5 mb, (2) 10.1±2.2 mb, and (3) 0.81±0.45 mb for H${(}^{12}$C${,}^{11}$B + p)X and (1) 11.1±2.4 mb, (2) 24.1±3.7 mb, and (3) 4.50±0.67 mb for C${(}^{12}$C${,}^{11}$B + p)X. The shapes of the first two regions can be fit with a nucleon-nucleon cascade model including π production. However, the cascade model prediction for the quasi-elastic component is too large by a factor of 3. The low momentum transfer peak is consistent with two mechanisms, (1) an excitation and decay via proton emission of the carbon projectile and (2) a projectile proton scattering diffractively off the C target. Finally, the Fermi momentum determined from the transverse momentum distribution is 160±11 MeV/c compared to 190±11 MeV/c from the longitudinal momentum distribution.

The neutron decay of excited states of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$ has been investigated in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{Ag}$ reaction at E/A=35 MeV. Specifically, the production of the 2.255 MeV unbound state in ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$ and the 7.456 MeV unbound state in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ have been measured. Comparison of the production of those two states to that of previously measured lower-lying excited states indicates a nuclear temperature of 3.0(4) MeV. The fraction of the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ nuclei from the neutron decay of these states is 6(2)% and 4(1)%, respectively, which is significant in that it can resolve some of the discrepancies between recent nuclear temperature measurements.

Neutron energy spectra were measured at angles between 14° and 159° in coincidence with evaporation residues as a function of linear-momentum transfer in reactions of ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ with 600 MeV ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. In addition, angular distributions and absolute cross sections for elastic scattering, fission, and evaporation residues have been measured. The preequilibrium component of the neutron spectra has been parametrized with a hot-moving-source fit. For the highest linear-momentum transfer the forward-to-backward anisotropy in the angular distribution is smallest and the quality of the fit is best. From the temperature and multiplicity of evaporated neutrons the level density parameter of nuclei with A≊180 has been determined to be a=A/(10.5±1) ${\mathrm{MeV}}^{\mathrm{-}1}$ at excitation energies of 300 to 400 MeV.

Previously experimental data on the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,γ${)\mathrm{}}^4$He reaction have been analyzed within a potential model of structureless particles to derive quantitative information about the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ground state. We have tested the applicability of the potential model by comparing cross sections calculated for a wide range of Woods-Saxon parametrizations covering those of previous studies with recent low energy ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,γ${)\mathrm{}}^4$He fusion data. We find that the results for the capture cross sections from the d+d S-wave into the D-state component of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ground state, which dominate the fusion data at E≤200 keV, are very sensitive to the parametrization of the nucleus-nucleus potential. Hence simple potential model studies seem not to be an appropriate tool for quantitative analysis of low energy ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d, γ${)\mathrm{}}^4$He fusion data.

We study the dynamics of high energy heavy ion collisions through the Vlasov-Uehling-Uhlenbeck approach. Equilibration is observed, for central collisions. It is shown that the produced entropy, the pion multiplicity, flow angle, and transverse momentum distributions saturate at the moment of maximum compression and temperature. The effects of the nuclear equation of state and the Pauli principle are investigated. For the flow angle distribution there is a 20 deg reduction of the peak flow angle due to the Pauli principle. A stiff equation of state results in a 10–20 deg increase over the soft equation of state at all energies. The transverse momentum at projectile rapidity exhibits a peak structure as a function of impact parameter b. A 40% difference between soft and hard equation of state is observed for the peak impact parameter, i.e., for intermediate multiplicities.