Fissioning nuclei and fission fragments, nuclear fragments emerging from energetic collisions, or nuclei probed with various external fields can emit one or more pre-equilibrium neutrons, protons, and potentially other heavier nuclear fragments. I describe a formalism which can be used to evaluate the pre-equilibrium neutron emission probabilities and the excitation energies of the remnant fragments.

The fusion evaporation residue (ER) excitation function has been measured for ${}^{35,37}\mathrm{Cl}+{}^{181}\mathrm{Ta}$ reactions at energies above the Coulomb barrier. The measurements were performed using the HYbrid Recoil mass Analyzer at IUAC, New Delhi. Comparable ER cross sections have been observed in both reactions and there is no isotopic dependence. Measured ER cross sections were compared with theoretical calculations employing the dinuclear system model at projectile and target nuclei interaction and statistical model for the deexcitation of the formed compound nucleus. Larger ER cross sections at the complete deexcitation cascade of the formed compound nucleus are noticed in both reactions at higher excitation energies $(E^{*}>80 \mathrm{MeV})$ over the calculated results. Fusion probability varies from $95\%$ to $40\%$ in the excitation energy range of the study. No appreciable difference in the fusion probability is noticed in the two reactions. Comparison of our results with other reactions populating ${}^{216}\mathrm{Th}$ shows a very strong entrance channel dependence.

The $\lambda$ and $m_{\beta \beta }$ mechanisms of neutrinoless double beta decay ($0\nu \beta \beta$) occur with light neutrino exchange via $W_L-W_R$ and $W_L-W_L$ mediation, respectively. In the present study, we calculate the nuclear matrix elements (NMEs) for the $m_{\beta \beta }$ and $\lambda$ mechanisms of $0\nu \beta \beta$, which has origin in the left-right symmetric model with right-handed gauge boson at TeV scale. The NMEs are calculated for one of the $0\nu \beta \beta$ decaying isotope ${}^{48}\mathrm{Ca}$ in the interacting nuclear shell-model using the GXPF1A effective interaction of $pf$ shell. The NMEs are calculated in both closure and nonclosure approaches using four different methods: closure, running closure, running nonclosure, and mixed methods. All the NMEs are calculated incorporating the effects of the finite size of nucleons and the revisited higher-order terms such as pseudoscalar and weak magnetism terms of the nucleon currents. Inclusion of the short-range nature of nucleon-nucleon interaction in Miller-Spencer, CD-Bonn, and AV18 parametrizations is also taken care of. We have used closure energy $\langle E\rangle =0.5$ MeV, which is near to the optimal value of closure energy that is extracted by examining the dependence of NMEs with closure energy in closure and mixed methods. The comparative dependence of the running closure and running nonclosure NMEs with the spin-parity of the allowed states of intermediate nucleus ${}^{48}\mathrm{Sc}$, the coupled spin-parity of the two initial decaying neutrons and the final two protons, the cutoff excitation energy of ${}^{48}\mathrm{Sc}$, and the cutoff number of states of ${}^{48}\mathrm{Sc}$ are examined. The neutrino momentum and radial distribution of different types of NMEs are explored. It is found that there is a significant enhancement in $M_{qGT}$-type NMEs, which originates from the large momentum distribution for the inclusion of the higher-order pseudoscalar term of the nucleon currents.

Half-lives and potential barriers of cluster radioactivity are investigated in the framework of the generalized liquid drop model (GLDM). We focus on the calculation of the preformation factor for heavy and superheavy nuclei within a redefined preformed cluster method, in which the decay constant is the product of the preformation factor, assault frequency, and penetration probability. The preformation factor is obtained from the penetrability of the potential internal barrier. The assault frequency has been estimated using classical methods and the penetration probability is calculated by the Wentzel-Kramers-Brillouin (WKB) method from tunneling through the GLDM potential barrier. The optimal mass inertia was selected for $\alpha$ decay and cluster emission by comparison of theoretical half-lives and experimental ones. The calculated preformation factor follows the preformation law formulas $S\left(A_C\right)=S{\left(\alpha \right)}^{\left(A_C-1\right)/3}$ [Phys. Rev. Lett. 61, 1930 (1988)], and the theoretical half-lives show better agreement with experimental data, including the new isotopes ${}^{219}\mathrm{Np}$ [Phys. Lett. B 777, 212 (2018)] and ${}^{220}\mathrm{Np}$ [Phys. Rev. Lett. 122, 192503 (2019)]. The predictions of cluster radioactivity half-lives are provided for heavy and superheavy nuclei, which will be useful for the detection and identification of these nuclei in the future.

The isotope ${}^{83}\mathrm{Kr}^m$, a 1.8-h isomer of stable ${}^{83}\mathrm{Kr}$, has become a standard for the calibration of tritium $\beta$ decay experiments to determine neutrino mass. It is also widely used as a low-energy electron source for the calibration of dark-matter experiments. The nominally monoenergetic internal conversion lines are accompanied by shakeup and shakeoff satellites that modify the line shape. We draw on theoretical and experimental information to derive a quantitative description of the satellite spectrum of the $K$-conversion line.

The dependence on applied electric field (0–40 kV/cm) of the scintillation light produced by fast electrons and $\alpha$ particles stopped in liquid helium in the temperature range of 0.44 K to 3.12 K is reported. For both types of particles, the reduction in the intensity of the scintillation signal due to the applied field exhibits an apparent temperature dependence. Using an approximate solution of the Debye-Smoluchowski equation, we show that the apparent temperature dependence for electrons can be explained by the time required for geminate pairs to recombine relative to the detector signal integration time. This finding indicates that the spatial distribution of secondary electrons with respect to their geminate partners possesses a heavy, non-Gaussian tail at larger separations and has a dependence on the energy of the primary ionization electron. We discuss the potential application of this result to pulse shape analysis for particle detection and discrimination.

An emerging direction in nuclear medicine is the coupling of a therapeutic isotope with an imaging isotope to form a so-called theranostic pair, which allows one to quantitatively track and image the delivery of the therapeutic isotope. ${}^{90}\mathrm{Y}$ is used in several therapy applications and a convenient candidate imaging partner is the positron emitter ${}^{86}\mathrm{Y}$. A 27.6 MBq source of ${}^{86}\mathrm{Y}$ was produced at the University of Wisconsin and assayed with the Gammasphere array at Argonne National Laboratory. Over 200 $\gamma$-ray transitions were identified, more than double that which was previously known. The positron emission probability inferred from the present level scheme leads to 27.9(12)%, an important $(\approx 14\%)$ reduction with respect to the previously recommended value.

An inclusion of the sharp resonant $0_3^{+}$ state of ${}^{16}\mathrm{O}$ and the first excited $2_1^{+}$ state of ${}^{12}\mathrm{C}$ in a study of $s$-wave elastic $\alpha \text{−}{}^{12}\mathrm{C}$ scattering at low energies is investigated in an effective Lagrangian approach. The elastic scattering amplitude is separated into two parts: one is for the sharp resonant $0_3^{+}$ state of ${}^{16}\mathrm{O}$ parametrized by the Breit-Wigner formula, and the other is for the nonresonant part of the amplitude parametrized by effective range expansion. In the nonresonant part of the amplitude, a contribution from the $2_1^{+}$ state of ${}^{12}\mathrm{C}$ is included. I discuss a large correlation between a coupling for the $2_1^{+}$ state of ${}^{12}\mathrm{C}$ and an effective range parameter $Q_0$ as well as the necessity of including a vertex correction in the initial and final $\alpha \text{−}{}^{12}\mathrm{C}$ state interactions. After fixing parameters appearing in the amplitudes by using experimental data, I calculate asymptotic normalization coefficients for the ground $0_1^{+}$ state and the first excited $0_2^{+}$ state of ${}^{16}\mathrm{O}$ and compare them to previous results found in the literature.

Background: Detailed spectroscopy of neutron-rich odd-$A$ Cu isotopes is of great importance for studying the shell evolution in the region of ${}^{78}\mathrm{Ni}$. While there is experimental information on excited states in ${}^{69-73,77,79}\mathrm{Cu}$ isotopes, the information concerning ${}^{75}\mathrm{Cu}$ is very limited.

Purpose: Experimentally observed single-particle, core-coupling, and proton-hole intruder states in ${}^{75}\mathrm{Cu}$, will complete the systematics of these states in the chain of isotopes.

Method: Excited states in ${}^{75}\mathrm{Cu}$ were populated in the $\beta$ decay of ${}^{75}\mathrm{Ni}$ isotopes. The Ni nuclei were produced by the in-flight fission of ${}^{238}\mathrm{U}$ projectiles, and were separated, identified, and implanted in a highly segmented Si detector array for the detection of the $\beta$-decay electrons. The $\beta$-delayed $\gamma$ rays were detected in a HPGe cluster array. Monte Carlo shell model calculations were performed using the A3DA interaction built on the $pf{g}_{9/2}{d}_{5/2}$ model space for both neutrons and protons.

Results: A level scheme of ${}^{75}\mathrm{Cu}$ was built up to $\approx 4$ MeV by performing a $\gamma \text{−}\gamma$ coincidence analysis. The excited states below 2 MeV were interpreted based on the systematics of neutron-rich odd-$A$ Cu isotopes and the results of the shell model calculations.

Conclusions: The evolution of the single-particle, core-coupling, and proton-hole intruder states in the chain of neutron-rich odd-$A$ Cu isotopes is discussed in the present work, in connection with the newly observed level structure of ${}^{75}\mathrm{Cu}$.

Spectroscopic properties that characterize shape-phase transitions in neutron-rich odd-$A$ Zr isotopes are investigated using the framework of nuclear density-functional theory and particle-core coupling. The interacting-boson Hamiltonian of the even-even core nuclei, and the single-particle energies and occupation probabilities of the unpaired neutron, are completely determined by deformation constrained self-consistent mean-field calculations based on the relativistic Hartree-Bogoliubov model with a choice of a universal energy density functional and pairing interaction. The triaxial $(\beta ,\gamma )$ deformation energy surfaces for even-even ${}^{94-102}\mathrm{Zr}$ indicate the occurrence of a transition from triaxial or $\gamma$ soft $({}^{94,96}\mathrm{Zr})$ to prolate $\left({}^{98}\mathrm{Zr}\right)$ and triaxial $\left({}^{100,102}\mathrm{Zr}\right)$ shapes. The corresponding low-energy excitation spectra of the odd-$A$ Zr isotopes are in very good agreement with recent experimental results. Consistent with the structural evolution of the neighboring even-even Zr nuclei, the state-dependent effective deformations and their fluctuations in the odd-$A$ isotopes indicate a pronounced discontinuity around the transitional nucleus ${}^{99}\mathrm{Zr}$.

The measured inclusive ${}^6\mathrm{He}$ and ${}^4\mathrm{He}$ production cross sections of Marquínez-Durán et al., [Phys. Rev. C 98, 034615 (2018)] are reexamined and the conclusions concerning the relative importance of $1n$ and $2n$ transfer to the production of ${}^6\mathrm{He}$ arising from the interaction of a 22 MeV ${}^8\mathrm{He}$ beam with a ${}^{208}\mathrm{Pb}$ target revised. A consideration of the kinematics of the $2n$-stripping reaction when compared with the measured ${}^6\mathrm{He}$ total energy versus angle spectrum places strict limits on the allowed excitation energy of the ${}^{210}\mathrm{Pb}$ residual, constraining distorted wave Born approximation calculations such that the contribution of the $2n$ stripping process to the inclusive ${}^6\mathrm{He}$ production can only be relatively small. It is therefore concluded that the dominant ${}^6\mathrm{He}$ production mechanism must be $1n$ stripping followed by decay of the ${}^7\mathrm{He}$ ejectile. Based on this result we present strong arguments in favor of direct, one-step four-neutron ($4n$) stripping as the main mechanism for ${}^4\mathrm{He}$ production.

In the present work the ${}^{165}\mathrm{Ho}(n,2n)$ reaction was studied experimentally and theoretically for the population of the ground state ($J^{\pi }=1^{+}$) of the ${}^{164}\mathrm{Ho}$ product nucleus, as well as for the population of its isomeric state ($E_{ex}=139.8$ keV, $J^{\pi }=6^{-}$). The cross sections of both the ground and isomeric state channels were measured at energies near the reaction threshold ($E_{th}=8.04$ MeV), at 10.1, 10.4, and 10.7 MeV, as well as at energies higher than 17 MeV, at 17.1, 18.1, 19.0, and 19.6 MeV. The adopted method was the activation technique relative to the ${}^{197}\mathrm{Au}(n,2n){}^{196}\mathrm{Au}$ and ${}^{27}\mathrm{Al}(n,\alpha ){}^{24}\mathrm{Na}$ reference reactions. The quasi-monoenergetic neutron beams for the near threshold energies were produced via the ${}^2\mathrm{H}(d,n){}^3\mathrm{He}$ reaction, while for the neutron beams above 17 MeV the ${}^3\mathrm{H}(d,n){}^4\mathrm{He}$ reaction was utilized. In both cases the deuteron beams were delivered by the 5.5 MV Tandem Van de Graaff accelerator of the Institute of Nuclear and Particle Physics at N.C.S.R. “Demokritos”. Additional to the experimental study, calculations were performed using the talys code (v. 1.9). The experimental data of the present work along with the previous measurements were compared with the talys results so as to investigate the reproduction of the experimental data for the different level density models of the code.

Many simulations of relativistic heavy-ion collisions involve the switching from relativistic hydrodynamics to kinetic particle transport. This switching entails the sampling of particles from the distribution of energy, momentum, and conserved currents provided by hydrodynamics. Usually, this sampling ensures the conservation of these quantities only on the average, i.e., the conserved quantities may actually fluctuate among the sampled particle configurations and only their averages over many such configurations agree with their values from hydrodynamics. Here we apply a recently invented method [D. Oliinychenko and V. Koch, Phys. Rev. Lett. 123, 182302 (2019)] to ensure conservation laws for each sampled configuration in spatially compact regions (patches) and study their effects: from the well-known (micro-)canonical suppression of means and variances to little studied (micro-)canonical correlations and higher-order fluctuations. Most of these effects are sensitive to the patch size. Many of them do not disappear even in the thermodynamic limit, when the patch size goes to infinity. The developed method is essential for particlization of stochastic hydrodynamics. It is useful for studying the chiral magnetic effect, small systems, and in general for fluctuation and correlation observables.

Background: It has been recently suggested that hydrogen ingestion into the helium shell of massive stars could lead to high ${}^{13}\mathrm{C}$ and ${}^{15}\mathrm{N}$ excesses when the shock of a core-collapse supernova passes through its helium shell. This prediction questions the origin of extremely high ${}^{13}\mathrm{C}$ and ${}^{15}\mathrm{N}$ abundances observed in rare presolar SiC grains which is usually attributed to classical novae. In this context the ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction plays an important role since it is in competition with ${}^{13}\mathrm{N}{\beta }^{+}$ decay to ${}^{13}\mathrm{C}$.

Purpose: The ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction rate used in stellar evolution calculations comes from the Caughlan and Fowler compilation with very scarce information on the origin of this rate and with no associated uncertainty. The goal of this work is to provide a recommended ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction rate, based on available experimental data, with a meaningful statistical uncertainty.

Method: Unbound nuclear states in the ${}^{17}\mathrm{F}$ compound nucleus were studied using the spectroscopic information of the analog states in ${}^{17}\mathrm{O}$ nucleus that were measured at the Tandem-Alto facility using the ${}^{13}\mathrm{C}({}^7\mathrm{Li},t){}^{17}\mathrm{O}$ $\alpha$-particle-transfer reaction. The $\alpha$-particle spectroscopic factors were derived using a finite-range distorted-wave Born approximation analysis. This spectroscopic information was used to calculate a recommended ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction rate with meaningful uncertainty using a Monte Carlo approach.

Results: The ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction rate from the present work is found to be within a factor of two of the previous evaluation in the temperature range of interest, with a typical uncertainty of a factor $\approx 2–3$. The source of this uncertainty has been identified to come from the three main contributing resonances at $E_r^{\mathrm{c}.\mathrm{m}.}=221$, 741, and 959 keV. This new error estimation translates to an overall uncertainty in the ${}^{13}\mathrm{C}$ production of a factor of 50 when using the lower and upper reaction rates in the conditions relevant for the ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ activation.

Conclusions: The main source of uncertainty on the re-evaluated ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction rate currently comes from the uncertain $\alpha$-particle width of relevant ${}^{17}\mathrm{F}$ states.

It is shown, for the first time, how the exotic shapes due to cluster formation at high excitation energy and angular momentum are manifested through giant dipole resonance (GDR) strength function under the framework of the extended quantum molecular dynamics (EQMD) model. The results of EQMD calculation are compared with the existing experimental data of ${}^{32}\mathrm{S}$ and ${}^{28}\mathrm{Si}$ formed in the reactions ${}^{20}\mathrm{Ne}+{}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}+{}^{12}\mathrm{C}$, respectively, at high angular momenta. It is found that the EQMD predicts the general trend of the experimental GDR strength functions for ${}^{32}\mathrm{S}$ and ${}^{28}\mathrm{Si}$ by considering the ring or toroidal configuration, whereas the linear chain configurations with $\alpha$ clusters can reproduce the higher-energy peak in ${}^{32}\mathrm{S}$ and ${}^{28}\mathrm{Si}$. Thus, the direct signature of the cluster formation at high temperature and angular momentum is the observation of a GDR peak $\approx 25\mathrm{MeV}$ which cannot be predicted within the mean-field calculations. The present result highlights the role of $\alpha$ cluster states above the decay threshold, which is still an open field of investigation.

The three-neutron ($3n$) system is studied by numerical calculations with the Faddeev three-body formalism for a realistic nucleon-nucleon (NN) potential. A response function for the transition from ${}^3\mathrm{H}$ to $3n$ continuum states by an isospin excitation operator is calculated, from which no evidence of $3n$ resonance state is found. Different methods to extrapolate the $3n$ energy from bound state energies with an extra attractive effect to the NN potential are examined. While extrapolations with attractive effects by enhanced NN potentials or three-body potentials result in the nonexistence of $3n$ resonance states, one by external trapping potentials leads to a positive $3n$ energy, which may be considered as a resonance state. It is found that this contradiction is due to a general defect of the trapping method.

Three-boson Efimov physics is well known in the bound-state regime, but far less in the three-particle continuum at negative two-particle scattering length where Efimov states evolve into resonances. They are studied solving rigorous three-particle scattering equations for transition operators in the momentum space. The dependence of the three-boson resonance energy and width on the two-boson scattering length is studied with several force models. The universal limit is determined numerically considering highly excited states; simple parametrizations for the resonance energy and width in terms of the scattering length are established. Decreasing the attraction, the resonances rise not much above the threshold but broaden rapidly and become physically unobservable, evolving into subthreshold resonances. Finite-range effects are studied and related to those in the bound-state regime.

Background: Several collective low-lying states are observed in ${}^{96}\mathrm{Zr}$ whose properties, which include excitation energies and $E2, E0$, and $M1$ transition probabilities, indicate that some of them belong to the spherical state and the other to deformed states. A consideration of these data in the full framework of the geometrical collective Model with both intrinsic shape variables, $\beta$ and $\gamma$, and rotational degrees of freedom is necessary for ${}^{96}\mathrm{Zr}$.

Purpose: We investigate the properties of the low-lying collective states of ${}^{96}\mathrm{Zr}$ based on the five-dimensional geometrical collective model including triaxiality as an active degree of freedom.

Method: The quadrupole-collective Bohr Hamiltonian, depending on both $\beta$ and $\gamma$ shape variables with a potential having spherical and deformed minima, is applied. The relative depth of two minima, height and width of the barrier, and rigidity of the potential near both minima are determined so as to achieve a satisfactory description of the observed properties of the low-lying collective quadrupole states of ${}^{96}\mathrm{Zr}$.

Results: It is shown that the low-energy structure of ${}^{96}\mathrm{Zr}$ can be described in a satisfactory way within the geometrical collective model with a potential function supporting shape coexistence without other restrictions on its shape. It is shown that a correct determination of the $\beta$ dependence of the collective potential from the experimental data requires a consideration in the framework of the full Bohr collective Hamiltonian. It is shown also that the excitation energy of the $2_2^{+}$ state can be reproduced only if the rotation inertia coefficient is taken to be four times smaller than the vibrational one in the region of the deformed well. It is shown also that shell effects are important for the description of the $B(M1;2_2^{+}\to 2_1^{+})$ and $B(M1;3_1^{+}\to 2_1^{+})$ transition probabilities. An indication of the influence of the pairing vibrational mode on the $0_2^{+}\to 0_1^{+}$ transition is confirmed, in agreement with the previous result.

Conclusion: Qualitative agreement with the experimental data on the excitation energies and $B\left(E2\right)$ and $B(M1;2_2^{+}\to 2_1^{+})$ reduced transition probabilities is obtained.