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We develop a formalism to calculate electromagnetic (EM) transition rates for rotational-vibrational models of nuclei. The formalism is applied to recently proposed models of ¹²C and ¹⁶O which are inspired by nuclear dynamics in the Skyrme model. We compare the results to experimental data as well as other nuclear models. The results for ¹²C are in good agreement with the data across all models, making it difficult to differentiate the models. More experimental data is needed to do this, and we suggest which transitions would be most interesting to measure. The models of ¹⁶O are less successful in describing the data, and we suggest some possible improvements to our approximations which may help.

We propose a method for enacting the unitary time propagation of two interacting neutrons at leading order of chiral effective-field theory by efficiently encoding the nuclear dynamics into a single multilevel quantum device. The emulated output of the quantum simulation shows that, by applying a single gate that draws on the underlying characteristics of the device, it is possible to observe multiple cycles of the nuclear dynamics before the onset of decoherence. Owing to the signal's longevity, we can then extract spectroscopic properties of the simulated nuclear system. This allows us to validate the encoding of the nuclear Hamiltonian and the robustness of the simulation in the presence of quantum-hardware noise by comparing the extracted spectroscopic information to exact calculations. This work paves the way for transformative calculations of the dynamical properties of nuclei on near-term quantum devices.

Molecular frame angular distributions of electrons released by interatomic Coulombic decay of ${\mathrm{He}}^{+*}(2\ensuremath{\ell})\text{\ensuremath{-}}\mathrm{He}$ states are studied theoretically by means of electronic structure and nonadiabatic nuclear dynamics calculations. In previous experimental work [Phys. Rev. A 82, 063405 (2010)], distinct variations of the angular emission patterns have been observed for different ranges of kinetic-energy release of the fragment ions. Good agreement between the presently computed and these measured angular distributions can be achieved by assuming nonequal populations of ${}^{2}{\mathrm{\ensuremath{\Sigma}}}_{g/u}^{+}$ and ${}^{2}{\mathrm{\ensuremath{\Pi}}}_{g/u}$ decaying electronic states via initial shake-up ionization of the dimers.

We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O $K^{−2}$ threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) states in water. Furthermore, we have identified symmetric and antisymmetric dissociation modes characteristic for particular DCH states. Our results serve as a fundamental reference for state-of-the-art studies of DCH dynamic processes in liquid water both at synchrotron and free-electron-laser facilities.

The predissociation of the ${\mathrm{N}}_{2}{}^{+}$ molecular ion in the $C {}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}{}^{+}$ electronic state through the nonadiabatic coupling with the $B {}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}{}^{+}$ electronic state is studied by solving the Schr\"odinger equation. The predissociation rates are calculated using Fermi's golden rule and compared with experimental results. We characterize the dynamics by calculating the nuclear probability density $\ensuremath{\rho}(R,t)$, the nuclear flux density $j(R,t)$, and the two-electron flux density $\mathbf{j}({\mathbf{r}}_{1},{\mathbf{r}}_{2},t)$. It is found that at the early dynamics, $t\ensuremath{\le}100$ fs, Fermi's golden rule breaks down, while a strong correlation between the electronic and nuclear dynamics is observed. Fourier analyses of the probability and flux densities are also presented and yield insight in their frequency dependency.

We present the basic concepts and recent developments in the time-dependent density functional theory (TDDFT) for describing nuclear dynamics at low energy. The symmetry breaking is inherent in nuclear energy density functionals (EDFs), which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, we treat the quantum fluctuations associated with slow collective motions assuming that time evolution of densities are determined by a few collective coordinates and momenta. The concept of collective submanifold is introduced in the phase space associated with the TDDFT and used to quantize the collective dynamics. Selected applications are presented to demonstrate the usefulness and quality of the new approaches. Finally, conceptual differences between nuclear and electronic TDDFT are discussed, with some recent applications to studies of electron dynamics in the linear response and under a strong laser field., Comment: 57 pages, 15 figures, Review article

We present a detailed experimental-theoretical analysis of O K-edge resonant 1 sigma-2 pi inelastic x-ray scattering (RIXS) from carbon monoxide with unprecedented energy resolution. We employ high ...

Nuclear clustering, alpha decays, and multiparticle correlations are important components of nuclear dynamics. In this work we put forward the cluster-nucleon configuration interaction model. We use the modern configuration interaction approach with advanced realistic shell-model Hamiltonians in order to study clustering phenomena; the study is facilitated by the algebraic properties of many-nucleon configurations in the harmonic oscillator basis. Using a translationally invariant formalism we built cluster channels that satisfy the Pauli exclusion principle as well as orthogonality and normalization conditions. We formally justify the formalism and demonstrate that, within the new method, clustering strengths satisfy sum rules that are consistent with the statistical properties of nuclear reactions with composite particles. Using properly renormalized cluster form factors our approach appears to resolve long-standing problems related to absolute normalization of the alpha clustering spectroscopic factors and their behavior in $sd$-shell nuclei. Our methods are demonstrated in studies of $\ensuremath{\alpha}$ spectroscopic factors in $sd$-shell nuclei and in $^{16}\mathrm{O}$ treated in $p\ensuremath{-}sd$ shells. Comparison with experimental data supports the validity of the approach.

We demonstrate that even for adsorbed molecules, the vibrational fine structure of resonant core hole decay channels after narrow-band excitation can show a dependence on the variation of the primary excitation energy as known from isolated molecules. Despite several adsorption-induced broadening mechanisms, the so-called detuning effect can be observed in the autoionization of a ${\mathrm{N}}_{2}$ monolayer physisorbed on Xe/Ru(001) for the $1{\ensuremath{\pi}}_{u}^{\ensuremath{-}1}$ final state of participant decay, in good agreement with theoretical predictions and observations for isolated ${\mathrm{N}}_{2}.$ However, contrary to the corresponding decay channel of isolated ${\mathrm{N}}_{2}$ and to the theoretical predictions for it, the decay into the $3{\ensuremath{\sigma}}_{g}^{\ensuremath{-}1}$ final state shows clearly different behavior much closer to that of normal Auger decay. This is partly due to final-state broadening.

The electron nuclear dynamics theory is applied to the study of proton collisions with ground-state oxygen atoms at collision energies of 0.5, 1.0, and 1.5 keV. Total electron transfer cross sections are calculated in reasonable agreement with recent expe

Problems of production and study of new neutron-enriched heavy nuclei are discussed. Low-energy multinucleon transfer reactions are shown to be quite appropriate for this purpose. Reactions with actinide beams and targets are of special interest for synthesis of new neutron-enriched transfermium nuclei and not-yet-known nuclei with closed neutron shell $N=126$ having the largest impact on the astrophysical r-process. The estimated cross sections for the production of these nuclei look very promising for planning such experiments at currently available accelerators. These experiments, however, are rather expensive and difficult to perform because of low intensities of the massive projectile beams and problems of separating and detecting the heavy reaction products. Thus, realistic predictions of the corresponding cross sections for different projectile-target combinations are definitely required. Some uncertainty still remains in the values of several parameters used for describing the low-energy nuclear dynamics. This uncertainty does not allow one to perform very accurate predictions for the productions of new heavier-than-target (trans-target) nuclei in multinucleon transfer reactions. Most of these parameters (nucleon transfer rate, nuclear viscosity, and fission barriers) are fundamental characteristics of low-energy nuclear dynamics. Determination of the values of these parameters (as well as their temperature dependence) is of significance in its own right. The available experimental data on the production of heavy nuclei in low-energy multinucleon transfer reactions are still insufficient and fragmentary. Several new experiments are proposed, these include those in which the role of shell effects in reaction dynamics can be better clarified.

The NIMROD-ISiS array was used to study the transverse flow of intermediate mass fragments in 35 MeV/nucleon ${}^{70}\mathrm{Zn}+{}^{70}\mathrm{Zn}$, ${}^{64}\mathrm{Zn}+{}^{64}\mathrm{Zn}$, and ${}^{64}\mathrm{Ni}+{}^{64}\mathrm{Ni}$ reactions. The intermediate mass fragment flow was previously shown to be sensitive to the density dependence of the symmetry energy. To explore the model dependence of the results, the antisymmetrized molecular dynamics, constrained molecular dynamics, and stochastic mean-field models were each compared to the experimental results to extract information on the form of the symmetry energy. The results demonstrate that sensitivity of the models to the nuclear equation of state can vary significantly based on the treatment of the nuclear dynamics. Despite the differences in the sensitivity, improved agreement with the experimental data is observed for each model with a stiff density dependence of the symmetry energy.

Knowledge about the hydrogen bond network of water is essential for understanding its anomalies as well as its special role for biochemical systems. Different types of x-ray spectroscopy allow prob ...

We discuss the strong-field dynamics of HeH${}^{+}$, the simplest stable heteronuclear molecule, focusing on identifying a laser regime for which there is a sufficient dissociation signal for experimental measurement. We numerically solve the time-dependent Schr\"odinger equation to obtain total dissociation probabilities, kinetic-energy release spectra, and momentum distributions for wavelengths from 800 to 2400 nm. The suitability of this simple system as a prototype for understanding the strong-field nuclear dynamics of heteronuclear dissociation is discussed.

The branching classical trajectory method for inelastic atomic collision processes is proposed. The approach is based on two features: (i) branching of a classical trajectory in a nonadiabatic region and (ii) the nonadiabatic transition probability formulas particularly adapted for a classical trajectory treatment. In addition to transition probabilities and inelastic cross sections, the proposed approach allows one to calculate incoming and outgoing currents. The method is applied to inelastic Na + H collisions providing the results in reasonable agreement with full quantum calculations.

In this article we present a semi-classical approximation to the Kramers-Heisenberg formula for calculating x-ray emission (XES) spectra, including vibrational effects. We compare the method to the ...

We report calculations on high-order harmonic generation in water molecules. Spectra are determined for various initial vibrational states of ${\mathrm{H}}_{2}\mathrm{O}$ and its isotope ${\mathrm{D}}_{2}\mathrm{O}$. It is demonstrated that the ratio of the spectra for ${\mathrm{D}}_{2}\mathrm{O}$ and ${\mathrm{H}}_{2}\mathrm{O}$ is close to unity when the initial state is the vibronic ground state, indicating that nuclear dynamics is of minor importance. For vibrationally excited initial states, the high-harmonic intensities show a clear dependence on both the initial-state quantum number and the isotopic species.

Element distributions and fragment multiplicity distributions have been measured for E/A=50 MeV $^{129}\mathrm{Xe}$${+}^{12}$C, $^{27}\mathrm{Al}$, $^{51}\mathrm{V}$, $^{\mathrm{nat}}\mathrm{Cu}$, $^{89}\mathrm{Y}$, and $^{197}\mathrm{Au}$ reactions using a low threshold 4\ensuremath{\pi} detector. Both distributions show a strong correlation with the detected charged particle multiplicity and a large degree of target independence. The measured distributions are compared with hybrid model calculations which incorporate important dynamical aspects in both the preequilibrium and statistical emission phases. Results of these calculations are in reasonable agreement with the data. However, uncertainties with regard to the compressibility of nuclear matter remain due to uncertainties in the coupling of the two models.

We performed nuclear dynamics calculations on ${\text{C}}_{2}{\text{H}}_{2}$ and ${\text{C}}_{2}{\text{D}}_{2}$ to study the isotope effect in dissociative electron attachment (DEA). Our previous calculations at 0 K led to a ratio ${\ensuremath{\sigma}}_{0\ensuremath{\rightarrow}\text{DEA}}^{({\text{C}}_{2}{\text{H}}^{\ensuremath{-}})}/{\ensuremath{\sigma}}_{0\ensuremath{\rightarrow}\text{DEA}}^{({\text{C}}_{2}{\text{D}}^{\ensuremath{-}})}$ of about 28.9 which is about a factor of 2 higher than recent experimental results. This discrepancy was attributed to the contribution of higher vibrational modes in the yield of the anion fragments. We included the four lowest bending vibrational states presenting nonvanishing populations at the experiment temperature of $T=333\text{ }\text{K}$. The resulting ratio is found to be 17.9 which is in closer agreement with the measured value.

High-order harmonic generation in molecular gases is accompanied by short-time evolution of the nuclear vibrational wave function. Using normal coordinate representation, I derive a simple analytical theory of short-time autocorrelation functions and apply it to a test set of 15 small molecules. The results explain large isotope effects observed in CH 4 . At the harmonic cutoff in 800 nm driving field, nuclear dynamics reduces the emission intensity from NO and NO 2 molecules by more than 50%. Autocorrelation functions are sensitive to the initial vibrational state, with the nodal structure of the initial vibrational wave packet reflected in the frequency spectrum of the harmonics.

Neutron total cross-section measurements on {sup 54}Cr up to a neutron energy of 2 MeV have been analyzed to deduce resonance parameters as well as spins and parities. Neutron strength functions have been deduced, based on data in the energy range 20-1000 keV, for s-, p-, and d-wave interactions and, in units of (10{sup -4}), are 2.8{+-}0.9, 0.23{+-}0.06, and 4.4{+-}0.7, respectively. Corresponding level densities in units of keV{sup -1}are 0.025{+-}0.003, 0.032{+-}0.003, and 0.107{+-}0.006, respectively. The distribution of nearest-neighbor spacings for s waves has been compared to Poisson and Wigner predictions for both {sup 54}Cr and {sup 52}Cr. Hints are seen of greater chaotic behavior in the case of the closed-neutron-shell {sup 52}Cr and of regular dynamics for {sup 54}Cr, suggestive of changes in chaoticity of nuclear dynamics with shell closure.

Severe deviations from uniform Coulomb explosion can be manifested for extremely ionized molecular heteroclusters, due to kinematic effects. We established unique features of the spatial distribution, energetics, and time-resolved dynamics in Coulomb explosion of multicharged light-heavy heteroclusters, consisting of light, low-charge and heavy, high-charge, ions, e.g., hydroiodic acid ${({H}^{+}{I}^{{q}_{I}+})}_{n}$ and its isotopic substituents ${({D}^{+}{I}^{{q}_{I}+})}_{n}$ and ${({T}^{+}{I}^{{q}_{I}+})}_{n}$, where extreme multielectron ionization in ultraintense laser fields (peak intensity $I={10}^{17}--{10}^{20}\phantom{\rule{0.3em}{0ex}}\mathrm{W}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$) results in ${q}_{I}=25$ at $I={10}^{19}$ and ${q}_{I}=35$ at $I={10}^{20}\phantom{\rule{0.3em}{0ex}}\mathrm{W}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$. Electrostatic models and simulations, based on the cluster vertical ionization (CVI) initial conditions for Coulomb explosion of ${({D}^{+}{I}^{{q}_{I}+})}_{2171}$ and ${({H}^{+}{I}^{{q}_{I}+})}_{2171}$ ions with ${q}_{I}=25$ (corresponding to $I={10}^{19}\phantom{\rule{0.3em}{0ex}}\mathrm{W}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$), reveal expanding, thin, two-dimensional spherical shells of the light ${D}^{+}$ or ${H}^{+}$ ions, with the monolayer expansion occurring on the femtosecond time scale. Under initial CVI conditions the model and the simulation results for the formation of femtosecond expanding nanoshells of light ions were confirmed by complete simulations involving both electron and nuclear dynamics in ${(HI)}_{2171}$ and ${(\mathrm{DI})}_{2171}$ clusters subjected to a Gaussian laser pulse with $I={10}^{19}\phantom{\rule{0.3em}{0ex}}\mathrm{W}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$. The energetic data for the light ions reveal high energies with a narrow energy distribution, e.g., average energy ${E}_{\mathit{av}}=23\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ at width $\ensuremath{\Delta}E∕{E}_{\mathit{av}}=0.16$ for Coulomb explosion of ${({D}^{+}{I}^{{q}_{I}+})}_{2171}$ clusters. These dynamic, structural and energetic data for light--heavy ${({A}^{+}{I}^{{q}_{I}+})}_{n}$ heteroclusters ($A=H$, $D$, and $T$) arise from kinematic overrun effects of the ${A}^{+}$ ions. Finally, we address the implications of these Coulomb explosion results of ${({D}^{+}{I}^{{q}_{I}+})}_{n}$ heteroclusters for $dd$ nuclear fusion driven by heterocluster Coulomb explosion, where the extremely charged ${I}^{{q}_{I}+}$ ions serve as most effective energetic and kinematic triggers for driving the expanding ${D}^{+}$ ions.

Theoretical studies of prospective $2p$ emitters are performed in a three-body $\text{core}+p+p$ model. Lifetime dependencies on the decay energy are calculated for $^{45}\mathrm{Fe}$, $^{48}\mathrm{Ni}$, $^{54}\mathrm{Zn}$, $^{58}\mathrm{Ge}$, $^{62}\mathrm{Se}$, $^{66}\mathrm{Kr}$, and compared to the quasiclassical estimates. The observation of products from the in-flight decays is discussed as an important technique supplementing a standard implantation method for a broad range of lifetimes of prospective two-proton emitters. The sensitivity of the model to various aspects of nuclear dynamics is demonstrated on the $^{45}\mathrm{Fe}$ example. Possible momentum correlations for emitted protons are discussed with the emphasis on $^{19}\mathrm{Mg}$ and $^{45}\mathrm{Fe}$. We study convergence and stability of theoretical momentum distributions with respect to different physical and numerical aspects of the model. Opportunities to extract valuable information on $2p$ emission from incomplete kinematics decay data are discussed.

Differential direct and charge-transfer scattering cross sections are calculated for collisions of H + with N 2 using the electron nuclear dynamics formalism. The calculated cross sections are compared to direct scattering measurements which are also reported here and to the experimental charge transfer data of Gao et al. [R. S. Gao, L. K. Johnson, C. L. Hakes. K. A. Smith, and R. F. Stehhings. Phys. Rev. A 41, 5929 (1990)]. Cross sections are presented for projectile energies of 0.5, 1.5, and 5.0 keV and scattering angles of 0.01 ° to 10°. The differential cross section reveals considerable structure over this angular range which is a consequence of small angle quantum interference and the glory and rainbow effects. For the case of charge transfer, we find that at least 90% of charge transfer events result in the hydrogen atom leaving the system in the H( 1s) state.

Collisions between free electrons and the molecular anion ${\mathrm{F}}_{2}^{\ensuremath{-}}$ have been studied in a merged beams experiment at the heavy ion storage ring ASTRID. Absolute cross sections for detachment ${(e}^{\ensuremath{-}}+{\mathrm{F}}_{2}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{F}}_{2}^{0}{+2e}^{\ensuremath{-}}$ or ${\mathrm{F}}^{0}+{\mathrm{F}}^{0}{+2e}^{\ensuremath{-}})$ and dissociation ${(e}^{\ensuremath{-}}+{\mathrm{F}}_{2}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{F}}^{0}+{\mathrm{F}}^{\ensuremath{-}}{+2e}^{\ensuremath{-}})$ are reported in the energy range 0--27 eV. Branching ratios between the two detachment channels are also given. Dissociation is found to be the dominating reaction and the dissociation cross section is about an order of magnitude larger than the detachment cross section in the investigated energy range. The threshold for detachment is as high as 10 eV, and the branching into the channel with a molecular fragment amounts to less than 20% over most of the energy range. The results are compared to previously measured cross sections for other anions and the importance of nuclear dynamics in the processes is discussed.

We present results of calculations of the longitudinal and transverse response function for inelastic electron scattering from $^{56}\mathrm{Fe}$ and $^{12}\mathrm{C}$. In the impulse approximation it is found that the calculated longitudinal response is approximately forty percent too large for $^{56}\mathrm{Fe}$. We discuss those aspects of nuclear dynamics which could account for this discrepancy and suggest that the depletion of the shell model orbitals through various (short-range) correlation effects may play an important role. It is suggested that a significant longitudinal response may exist at energies above the quasi-elastic domain; this response would involve the excitation of 2p-2h states. In our model there is a significant disagreement between theory and experiment for the transverse response. We ascribe this disagreement to meson-exchange-current effects; however, we present no calculations of such effects in this work. Quantitative studies of these effects in finite nuclei are required. If our model for the quenching of the longitudinal response in the quasi-elastic domain proves to be correct, we can infer that quasi-elastic electron scattering studies may provide a measurement of the average probability of the occupation of a shell model orbital.