A feasibility study was undertaken for the measurement of the resonance at ${\mathit{E}}_{\mathit{r}}$=545 keV in the ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$(p,γ${)}^{14}$O reaction, using intense radioactive ion beams. The analog resonance at ${\mathit{E}}_{\mathit{r}}$=512 keV in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p,γ${)}^{14}$N was chosen as a test case, leading to improved knowledge of the resonance parameters. Thin- and thick-target yields were obtained with ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ beams on an extended gas target and a polyethylene foil, respectively. In addition, thin and thick targets of enriched ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ were irradiated with proton beams. Normalization problems arising with mixed ion beams ${(}^{13}$N${/}^{13}$C) are discussed.

We have measured the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$(n,α${)}^{14}$C cross section from thermal energy to approximately 1 MeV. A bump in the data near 3 keV could be fitted by a state whose properties are consistent with a known subthreshold ${\mathit{J}}^{\mathrm{\pi }}$=$1^{\mathrm{-}}$ level at ${\mathit{E}}_{\mathit{x}}$=8.039 MeV. The cause of the 1/v cross section near thermal energy could not be determined although the known $2^{+}$ state at 8.213 MeV was found to be too narrow to contribute much to the thermal cross section. Our data are compared to measurements made via the inverse reaction. There are many differences between the two sets of data. The astrophysical reaction rate was calculated from the measured cross section. This reaction plays a role in the nucleosynthesis of heavy elements in nonstandard big-bang models. At big-bang temperatures, the experimental rate was found to be in fair agreement with the rate estimated from the previously known properties of states of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ in this region. Furthermore, using the available information from experiments, it was estimated that the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$(n,α${)}^{14}$C rate is approximately a factor of ${10}^3$–${10}^4$ times larger than the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$(n,γ${)}^{18}$O rate at big-bang temperatures. As a result, there may be significant cycling between ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ resulting in a reduction of heavy-element nucleosynthesis.

Cross sections have been measured for the reaction ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$(n,p${)}^{64}$Co at laboratory angles between 0° and 10° for incident neutron energies from 90 to 240 MeV. The ground-state cross sections together with the ${\mathrm{\beta }}^{\mathrm{-}}$ decay ft value for the transition ${}_{}{}^{64}{}_{}{}^{}\mathrm{Co}$(g.s.)${\to }^{64}$Ni(g.s.) are used to normalize the q=0 differential cross section in units of mb/sr per unit Gamow-Teller (GT) strength. This is the first absolute measurement of the A(n,p) unit cross section for a nucleus in the (fp) shell, and it may be used to calibrate the GT strength measured in other (n,p) reactions of similar mass nuclei. Since the (${\mathit{e}}^{\mathrm{-}}$,${\nu }_{\mathit{e}}$) channel involves the same nuclear matrix element as the (n,p) channel, knowledge of GT strength in these nuclei is important for supernova modeling codes which depend on knowledge of ${\mathit{e}}^{\mathrm{-}}$ capture rates of (fp)-shell nuclei to determine parameters of stellar core collapse.

Excited states of the deformed odd-odd nucleus ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ have been investigated by the following experiments: measurement of the ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$(n,γ${)}^{176}$Lu reaction with high resolution crystal spectrometers and of the ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$(n,${\mathit{e}}^{\mathrm{-}}$${)}^{176}$Lu reaction with a double focusing magnet-spectrometer. In total, 509 gamma transitions could be identified in ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$, and multipolarities were determined for 228 of these transitions. Additionally, a measurement of γ-γ coincidences after neutron capture and an investigation of the ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$(d,p${)}^{176}$Lu transfer reaction were also performed. Information on the lifetimes of relevant levels was obtained by the technique of delayed coincidences, and, in one case, by the Doppler shift attenuation method. With these results, a level scheme was established, comprising 97 energy levels connected by 270 gamma transitions. About 30 Nilsson configurations and corresponding rotational bands were identified. The comparison with model calculations indicates that the level scheme comprises all excited states with spins 1<I<8 up to 900 keV. In particular, this scheme contains transitions that connect the ${\mathit{I}}^{\mathrm{\pi }}$=$7^{\mathrm{-}}$ ground state with the $1^{\mathrm{-}}$ isomer via mediating levels at higher excitation energy. From this coupling, the excitation energy of the isomer was precisely defined to 122.855±0.009 keV. Accordingly, the neutron separation energy of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ could be revised to 6287.91±0.15 keV. Based on the fact that more than 90% of the observed intensities could be placed in the level scheme, an isomeric ratio, ${\mathrm{\sigma }}_{\mathit{p}}$(i)/${\mathrm{\sigma }}_{\mathrm{tot}}$=0.870±0.025, was deduced for the fractional population of the isomer by thermal neutron captures.

On the basis of the improved level scheme of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ it is demonstrated that the stellar s-process production as well as the stellar beta decay rate of that nucleus depend strongly on temperature. This behavior results from the completely different half-lives of the ground state and the isomer; since these states are coupled by induced transitions in the hot stellar photon bath, the effective half-life of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ is drastically reduced. The $5^{\mathrm{-}}$ state at 838.64 keV was identified as the most efficient mediating level. Consequently, ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ can no longer be considered as a chronometer for the age of the s process; instead, it can be interpreted as an s-process thermometer yielding a temperature range between 2.4×${10}^8$ to 3.6×${10}^8$ K.

A level scheme of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ up to ∼1400 keV excitation energy is deduced from a γ-γ coincidence experiment and previously published particle transfer data. 170 γ-ray transitions are placed between 85 levels. We identify 27 previously unknown levels and 131 previously unknown transitions in ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$. With this γ-ray data we place the energy of the isomer at 122.9 keV. A level at 838.5 keV (${\mathit{J}}^{\mathrm{\pi }}$=$5^{\mathrm{-}}$, ${\mathit{t}}_{1/2}$<10 ns) is found to decay with substantial strength to both the ground state ($7^{\mathrm{-}}$, 4.08×${10}^{10}$ yr) and the 122.9 keV isomer ($1^{\mathrm{-}}$, 3.7 hr). The presence of this level guarantees the thermal equilibrium of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}_{}^{\mathit{g},}{}_{}{}^{}$m for T≥3×${10}^8$ K and therefore during s-process nucleosynthesis. The resulting temperature sensitivity of its effective half-life rules out the use of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ as an s-process chronometer. The use of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ to determine s-process temperatures is discussed.

Two-proton correlation functions constructed via an event-mixing analysis are compared to recently published correlation functions for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${+}^{27}$Al reaction at E/A=75 MeV, which were constructed by generating the denominator from single-particle spectra. For the present case, the two techniques yield virtually identical results.

A search for ${\mathrm{\pi }}^0$’s arising from the spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ using the LAMPF ${\mathrm{\pi }}^0$ spectrometer has yielded no evidence for this process. We obtain an upper limit of 1.4×${10}^{\mathrm{-}11}$ with a 90% confidence level for the branching ratio of ${\mathrm{\pi }}^0$’s produced at rest in the spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$.

The SU(3) Elliott model is used to study the thermal description of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. This solvable model allows us to work in the canonical ensemble and still be able to define an order parameter, the expectation value of the intrinsic quadrupole moment, to investigate the occurrence of phase transitions.

We consider a chemical nonequilibrium model to describe the pion production in Ar+KCl and La+La collisions at initial energies ${\mathit{E}}_{\mathrm{lab}}$=0.5–1.8 GeV/nucleon. The excess of low-energy ${\mathrm{\pi }}^{\mathrm{-}}$ is interpreted as the manifestation of positive chemical potential of ${\mathrm{\pi }}^{\mathrm{-}}$ at the thermal freeze-out. We find that in collisions between nuclei with large atomic numbers the chemical potential of ${\mathrm{\pi }}^{+}$ is smaller than that of ${\mathrm{\pi }}^{\mathrm{-}}$. This leads to the prediction of much less excess of low-energy ${\mathrm{\pi }}^{+}$, than as measured in the ${\mathrm{\pi }}^{\mathrm{-}}$ case, in heavy-ion collisions at bombarding energies in the region of 1 GeV/nucleon.

We calculate the nuclear level density parameter over a wide range of nuclear mass and temperature, using a recently developed realistic model. The model calculations take into account the effects of finite size of the nucleus, the continuum states, the momentum and frequency dependence of the effective mass, and the variation of these effects with temperature. A reasonable agreement with recent experimental data is obtained.

For the ratio of the bound state radius ${\mathit{r}}_{\mathit{D}}$ to the scattering length a, an expansion of the form of (${\mathit{r}}_{\mathit{D}}$/a${)}^2$=(${\mathit{c}}_0$+${\mathit{c}}_1$x+${\mathit{c}}_2$${\mathit{x}}^2$+${\mathit{c}}_3$${\mathit{x}}^3$+...)/8, where x=α${\mathit{r}}_0$, has recently been proposed for relativistic as well as nonrelativistic cases. In this paper the expansion is reexamined for a particle obeying the Dirac equation with a nonlocal, separable potential. This model is analytically solvable and enables us to corroborate a heuristic argument which underlies the expansion for the relativistic cases.

Priority of our interpretation of the fine structure in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ radioactive decay of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ is asserted. It seems that the deformation parameter values, used in the framework of ARM to interpret properties of both ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ ground and excited states, partly allow for the qualitative interpretation of the experimental hindrance factors to the ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$ states.

We reply to the preceding Comment.

The interpretation of the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mn}$(α,d${)}^{26}$Al, isospin forbidden reaction as a successive-transfer reaction is very uncertain. The data do not support the existence of significant isospin mixing in low-lying states of ${}_{}{}^{26}{}_{}{}^{}\mathrm{Al}$.

Neutron spectra from the inverse-kinematics reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${+}^{208}$Pb at ${\mathit{E}}_{\mathrm{lab}}$/A=6.65 MeV have been measured in coincidence with nickel-like fragments. Neutron emission patterns for net pickup and stripping channels have been analyzed in terms of sequential evaporation from fully accelerated projectile-like and target-like fragments. Like at higher energies, these patterns suggest an absence of appreciable correlations between net mass transfer and excitation energy division for strongly damped collisions, at the present near-barrier energy. The overall multiplicities, as well as energy spectra and angular distributions of neutrons, are well reproduced by simulation calculations, assuming an energy division always in favor of the heavy fragment.

Excited states in ${}_{}{}^{86,88}{}_{}{}^{}\mathrm{Mo}$ have been identified using recoil-γ and γγ coincidences. Energy-level systematics of the molybdenum isotopes from the N=Z line to the N=50 shell closure are compared to their strontium and zirconium neighbors. This comparison, an estimate of the B(E2) strengths, and a Woods-Saxon cranking model have been used to suggest that the molybdenum isotopes undergo a transition from spherical to moderately deformed shapes at ${}_{}{}^{86}{}_{}{}^{}\mathrm{Mo}$.

The production of high-energy photons in an intermediate energy heavy-ion reaction (65 MeV/nucleon ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{93}$Nb) is studied by characterizing the events, which produce the photons, by the forward and backward, light and heavy, charged particle production. While the absolute yield of high-energy photons increases with increasing charged particle multiplicity, the spectral shape is found to be almost independent of multiplicity. This indicates that the fundamental photon production mechanism is insensitive to the impact parameter but that the production process is more probable for the more violent collisions. This is expected for an incoherent nucleon-nucleon bremsstrahlung mechanism but not for a statistical mechanism. This work also provides a comparison of two observables that have been suggested as impact parameter selectors: the high-energy photon yield and the charged particle multiplicity. We find that the photon yield, binned by particle multiplicity, does not scale as would be expected if both techniques truly measured the impact parameter. This observation can be explained by large fluctuations in the particle multiplicity at fixed impact parameter.

We show that the linear energy weighted M1 sum rule is proportional to the summed E2 strength in the region of vibrational, transitional, and strongly deformed even-even nuclei using the proton-neutron interacting boson model. This general relation is compared with extensive data on M1 and E2 transition strength in rare-earth nuclei truncating the M1 sum rule to states below an excitation energy of 4 MeV. The above observation also implies a quadratic dependence on deformation (δ) for the summed orbital M1 strength.