The yield of the neutron capture reaction ${}^{232}$Th($n,\gamma$) has been measured at the neutron time-of-flight facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The reduction of the acquired data to the capture yield for resolved resonances from 1 eV to 4 keV is described and compared to a recent evaluated data set. The resonance parameters were used to assign an orbital momentum to each resonance. A missing level estimator was used to extract the $s$-wave level spacing of $D_0=17.2\pm 0.9$ eV.

The dynamical cluster-decay model (DCM) is used to study the odd-mass nuclear systems ${}^{213}$Fr${}^{*}$ (with $N=126$) and ${}^{217}$Fr${}^{*}$ (with $N=130$) formed in ${}^{19}$F + ${}^{194,198}$Pt reactions. The measured anomaly in fission anisotropy for ${}^{213}$Fr${}^{*}$ in this reaction is said to be due to either the possible role of the magic $N=126$ shell of the compound nucleus (CN) or the presence of a noncompound nucleus component, such as quasifission, in the fission cross section. Our calculations are made within the DCM for the fragments having quadrupole (${\beta }_2$) deformations with orientations of compact, hot configurations, compared with spherical as well as ${\beta }_2$–${\beta }_4$ deformed considerations. For quadrupole deformed fragments (with “optimal” orientations), the calculated fission cross-sections (as well as the evaporation residue cross-sections) match the data nearly exactly, without invoking a significant contribution from quasifission. The calculated fission mass distribution for the two systems is quite similar for either of the spherical, ${\beta }_2$-alone deformed, and ${\beta }_2$–${\beta }_4$ deformed choices of fragments. A small hump or shoulder is seen in fragment preformation yields for the deformed case (${\beta }_2$ or ${\beta }_2$–${\beta }_4$) in both the systems due to a deformed closed shell around $Z_2=36$ and a spherical magic shell around $Z_1=50$, which for ${}^{213}$Fr${}^{*}$ ($N=126$) decay is somewhat more pronounced as compared to ${}^{217}$Fr${}^{*}$ ($N=130$). Note that the magic shell of the CN proton/neutron number plays no role in DCM.

Recent studies showed that neutron pickup makes a substantial contribution to the proton optical model potential (OMP) for light, mostly halo, target nuclei. Here, we extend those studies to a more “normal” target nucleus: ${}^{40}$Ca. We present coupled reaction channel (CRC) calculations with the coupling of 30.3 MeV incident protons to deuterons and up to 12 states of ${}^{39}$Ca. The proton elastic scattering $S$ matrix from the CRC calculation is subject to $S_{lj}\to V\left(r\right)+\mathbf{l}·\mathbf{s}{V}_{\mathrm{SO}}\left(r\right)$ inversion and the bare potential of the CRC calculation is subtracted, directly yielding a local and $L$-independent representation of the dynamic polarization potential (DPP). This is appropriate for comparison with phenomenological OMPs and local OMPs derived in local density folding models. The real-central part of the DPP is repulsive and cannot be represented as a uniform normalization of the bare potential, changing the rms radius. A series of model calculations reveal the dependence of the DPP on a range of parameters illuminating (i) departures of nucleon potentials of specific nuclei from global properties, (ii) the generation of repulsion, and (iii) the requirements for all-order CRC and deuteron breakup. Light is thrown on the nonlocality of the underlying DPP.

We report here the first direct lifetime measurement of the 2${}_1^{+}$ state in ${}^{72,74}$Zn. The neutron-rich beam was produced by in-flight fragmentation of ${}^{76}$Ge at the Grand Accélérateur National d'Ions Lourds and separated with the LISE spectrometer. The 2${}_1^{+}$ state was excited by inelastic scattering and knock-out reaction on a CD${}_2$ target and its lifetime was measured by the recoil-distance Doppler-shift method with the Köln plunger device combined with the EXOGAM detectors. The lifetimes of the 2${}_1^{+}$ states in ${}^{72,74}$Zn were determined to be 17.9(18) and 27.0(24) ps, which correspond to reduced transition probabilities $B(E2;2_1^{+}\to 0^{+})=385\left(39\right)$ and 370(33) $e^2{\text{fm}}^4$, respectively. These values support the idea of a systematic maximum of collectivity at $N=42$ for Zn, Ge, and Se nuclei. In addition, the available systematics in the neighboring nuclei point toward a transition from a spherical oscillator at $N=40$ to complete $\gamma$-softness at $N=42$.

The penetration probability across an arbitrary nucleus-nucleus potential barrier is studied by using transfer matrix approach, including continuous variations of effective mass. The calculated penetration probabilities for reaction ${}^{16}$O+${}^{208}$Pb are closed to those of WKB and modified Numerov calculations based on the Bass potential. With the transfer matrix approach, the influence of the effective mass on the penetration probability are simultaneously investigated. The calculations imply that the effective mass is an important quantity for studying the hindrance of fusion cross sections of some reactions at deep sub-barrier energies. The fusion cross sections of heavy-ion fusion reactions and the resonance phenomena due to double-hump barriers are also studied with this approach.

Light clusters are included in the equation of state of nuclear matter within the relativistic mean-field theory. The effect of the cluster-meson coupling constants on the dissolution density is discussed. Theoretical and experimental constraints are used to fix the cluster-meson couplings. The relative light cluster fractions are calculated for asymmetric matter in chemical equilibrium at finite temperature. It is found that above $T=5$ MeV deuterons and tritons are the clusters in larger abundances. The results do not depend strongly on the relativistic mean-field interaction chosen.

The inclusive ${}^{93}$Nb($\vec{p}{,}^3$He) reaction to the continuum was investigated at an incident energy of 160 MeV. Emission-energy distributions for cross sections as well as analyzing powers were explored. A range of scattering angles from 15${}^{\circ }$ to 60${}^{\circ }$ (lab.) was covered and ${}^3$He emission energies from $\approx 30$ MeV to the kinematic limit were measured. As in our earlier work, the experimental distributions were compared with a multistep direct theory in which a reaction mechanism based on two-nucleon pickup is employed. Reasonable agreement between experimental double-differential cross sections and analyzing powers and the theoretical expectation was obtained. This work, together with published results for the same reaction at a lower projectile energy, allows the incident-energy dependence of the cross section and analyzing power distributions to be explored.

A generalized version of the fusion by diffusion model is proposed, in which evolution from dinuclear to mononuclear regimes is taken into account in terms of the coupled Langevin equations in the three-dimensional collective space of neck, radial, and asymmetric degrees of freedom. By simulating numerically these dynamic equations, the probability distribution of $s_{\mathrm{inj}}$, the separation between the surfaces of two approaching nuclei at the injection point in the asymmetric fission valley, is obtained. From the injection points, the system starts its climb uphill over the saddle point in the presence of thermal fluctuation; thus for very heavy systems the injection-point distance is a very critical constituent in the calculations of fusion probability. The present model is applied for the study of the mass asymmetric system ${}^{58}\mathrm{Fe}+{}^{208}$Pb. The excitation function for the ${}^{208}$Pb(${}^{58}$Fe,$n$)${}^{265}$Hs reaction is calculated and compared with the experimental data. By comparing the theoretical results with and without taking the asymmetric degree of freedom into account, we have arrived at the conclusion that nucleon flow between the asymmetric reaction partners in the early stage of the fusion process plays an important role in the formation of superheavy nuclei in the cold fusion reactions.

The neutron-adding ($d,p$) reaction was carried out in inverse kinematics to investigate the single-neutron overlap with the ${}^{19}$O ground state. Eight states in ${}^{20}$O were populated with measurable strength and a $Q$-value resolution of approximately 175 keV FWHM was achieved. Cross sections, angular distributions, spectroscopic factors, and $T=1$ diagonal two-body matrix elements were deduced. Results are discussed in terms of shell-model calculations confined to the $0d_{5/2}$, $1s_{1/2}$, and $0d_{3/2}$ orbitals.

A method of describing static moments of excited states and transitions between excited states is formulated for nonmagic nuclei within the Green's function formalism. Quadrupole moments of the first 2${}^{+}$ states in tin and lead isotope chains are calculated self-consistently using the energy density functional by Fayans et al. [Nucl. Phys. A 676, 49 (2000)]. Reasonable agreement with available experimental data is obtained. Quadrupole moments of unstable nuclei including ${}^{100}$Sn and ${}^{132}$Sn are predicted. A nontrivial dependence of the quadrupole moments on the neutron excess is found which can be traced to the negative proton contributions.

Structures of excited states in ${}^{11}$B are investigated with a method of $\beta$-$\gamma$ constraint antisymmetrized molecular dynamics in combination with the generator coordinate method. Various excited states with developed cluster core structures are suggested in positive- and negative-parity states. For negative-parity states, we suggest a band with a $2\alpha$ $+$ $t$ cluster structure. This band starts from the $3/2_3^{-}$ state and can correspond to the experimental band observed recently. In positive-parity states, two $\alpha$ core cluster structures with surrounding nucleons are found. A $K^{\pi }=1/2^{+}$ band is suggested to be constructed from a remarkably developed cluster structure with a large prolate deformation. We discuss features of the cluster structure in association with molecular orbital structures of ${}^{10}$Be.

A high-precision branching-ratio measurement for the superallowed ${\beta }^{+}$ emitter ${}^{26}{\mathrm{Al}}^m$ was performed at the TRIUMF-ISAC radioactive ion beam facility. An upper limit of $⩽$12 ppm at 90$\%$ confidence level was found for the second forbidden ${\beta }^{+}$ decay of ${}^{26}{\mathrm{Al}}^m$ to the 2${}_1^{+}$ state at 1809 keV in ${}^{26}\mathrm{Mg}$. An inclusive upper limit of $⩽$15 ppm at 90$\%$ confidence level was found when considering all possible nonanalog ${\beta }^{+}$/EC decay branches of ${}^{26}{\mathrm{Al}}^m$, resulting in a superallowed branching ratio of $100.{0000}_{-0.0015}^{+0}\%$.

The cell structure of clusters in the inner crust of a cold $\beta$-equilibrium neutron star is studied within a Thomas-Fermi approach and compared with other approaches that include shell effects. Relativistic nuclear models are considered. We conclude that the symmetry energy slope $L$ may have quite dramatic effefcts on the cell structure if it is very large or small. Rodlike and slablike pasta clusters have been obtained in all models except one with a large slope $L$.

The quasistellar neutron spectrum for a thermal energy of $kT=25$ keV that can be produced via the ${}^7$Li($p,n$)${}^7$Be reaction at a proton energy of $E_p=1912$ keV has been measured using the dedicated setup for the definition of neutron fields at Physikalisch-Technische Bundesanstalt Braunschweig. The results confirm previous work with improved accuracy and resolution. Small variations in proton energy leave the spectrum essentially unchanged. This is illustrated by the example of the ($n,\gamma$) cross section of ${}^{197}$Au, where the averaged cross section for the spectrum defined in this work agrees perfectly with the result of a previous measurement.

Neutrons produced by the ${}^7$Li($p$,$n$)${}^7$Be reaction close to the reaction threshold are widely used to measure the cross section of $s$-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, future use of rf accelerators with higher intensities is planned to enable investigations on radioactive targets. Such accelerators have, however, poorer energy definition. We investigate in this work the effects of an energy-broadened proton beam on the spectrum of neutrons emitted in the thick-target ${}^7$Li($p$,$n$) reaction at $E_{\mathrm{p}}$ $=$ 1912 keV and on the experimental cross section of the ${}^{197}$Au($n$,γ)${}^{198}$Au reaction in these conditions. Measurements were made with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements using the time-of-flight technique, both with a narrow-energy proton beam (standard deviation of the distribution σ ≈ 1.5 keV) and with a broad-energy proton beam (σ ≈ 20 keV) obtained with a gold foil degrader. Neutron spectra measured with the narrow-energy proton beam are consistent with those previously reported. The angle-integrated spectrum obtained with the broad-energy proton beam more closely resembles a Maxwellian-flux distribution. The measured neutron spectra agree well with Monte Carlo simulations that include experimentally measured cross sections, two-body kinematics and proton energy loss in the target. Gold activation studies were performed for both narrow-energy and broad-energy proton beams to check the impact of the ensuing spectra on this important reference standard for activation measurements.

Data on inclusive dielectron production are presented for the reaction $p+p$ at 2.2 GeV measured with the high acceptance dielectron spectrometer (HADES). Our results supplemented data obtained earlier in this bombarding energy regime with the dilepton spectrometer (DLS) and HADES. The comparison with the 2.09 GeV DLS data is discussed. The reconstructed $e^{+}{e}^{-}$ pair distributions are confronted with simulations, revealing an excess yield at invariant masses around 0.5 GeV/$c^2$. Inclusive cross sections of neutral pion and $\eta$ production are obtained.

We derive the sub-subleading two-pion exchange contributions to the three-nucleon force which appear at next-to-next-to-next-to-next-to-leading order in chiral effective field theory. In order to determine the low-energy constants, a complete analysis of pion-nucleon scattering at the subleading-loop order in the heavy-baryon expansion is carried out utilizing the power counting scheme employed in the derivation of the nuclear forces. We discuss the convergence of the chiral expansion for this particular three-nucleon force topology and give the values of the low-energy constants which provide the most realistic description of the three-nucleon force when the chiral expansion is truncated at next-to-next-to-leading order.

The continuum-discretized coupled channels (CDCC) method is a well established theory for direct nuclear reactions which includes breakup to all orders. Alternatively, the three-body problem can be solved exactly within the Faddeev formalism which explicitly includes breakup and transfer channels to all orders. With the aim to understand how CDCC compares with the exact three-body Faddeev formulation, we study deuteron-induced reactions on (i) ${}^{10}$Be at $E_{\mathrm{d}}=21.4,40.9\mathrm{and}71$ MeV; (ii) ${}^{12}$C at $E_{\mathrm{d}}=12\mathrm{and}56$ MeV; and (iii) ${}^{48}$Ca at $E_{\mathrm{d}}=56$ MeV. We calculate elastic, transfer, and breakup cross sections. Overall, the discrepancies found for elastic scattering are small with the exception of very backward angles. For transfer cross sections at low energy, $\sim$10 MeV/u, CDCC is in good agreement with the Faddeev-type results and the discrepancy increases with beam energy. In contrast, breakup observables obtained with CDCC are in good agreement with Faddeev-type results for all but the lower energies considered here.

Over the last several years, the surrogate reaction technique has been successfully employed to extract ($n,f$) and ($n,\gamma$) cross sections in the actinide region to a precision of $\sim$5$\%$ and $\sim$20$\%$, respectively. However, attempts to apply the technique in the rare earth region have shown large (factors of 2–3) discrepancies between the directly measured ($n,\gamma$) and extracted surrogate cross sections. One possible origin of this discrepancy lies in differences between the initial spin-parity population distribution in the neutron induced and surrogate reactions. To address this issue, the angular momentum transfer to the high excitation energy quasicontinuum region in Gd nuclei has been investigated. The ($p,d$) and ($p,t$) reactions on ${}^{154,158}$Gd at a beam energy of 25 MeV were utilized. Assuming a single dominant angular momentum transfer component, the measured angular distribution for the ($p,d$) reactions is well reproduced by distorted-wave Born approximation (DWBA) calculations for $\Delta L=4$ $\hslash$ transfer, whereas the ($p,t$) reactions are better characterized by $\Delta L=5$ $\hslash$. A linear combination of DWBA calculations, weighted according to a distribution of $L$ transfers (peaking around $\Delta L=4$–5 $\hslash$), is in excellent agreement with the experimental angular distributions.