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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 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 ...

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

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.

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.

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.

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.

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.