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We investigate the depletion of single-electron states in small molecules under the influence of very short XUV pulses. In N$_2$, for a certain window of XUV energies around 50 eV, we observe a marked occupation inversion, i.e. a situation where depletion of the deepest bound valence electron state is much larger than for any other state. This represents a realistic mechanism which is able to cut, almost instantaneously, a hole into a deep lying state, a situation which is often assumed ad hoc in numerous theoretical studies of energetic ultrafast processes. This occupation inversion furthermore drives a dipole instability, i.e. a spontaneous reappearance of the dipole signal long after the laser pulse is over and the dipole signal has died out. The dipole signal that emerges from this instability can be identified as a particular low-energy structure in photo-electron spectra., Comment: 5 pages, 4 figures

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Collinear laser spectroscopy is performed on the nickel isotopes Ni58-68,70, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii Rc are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLOsat, which allows an assessment of their accuracy. We find agreement with experiment in differential radii δ⟨rc2⟩ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLOsat. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy(Δr,HFB). Collinear laser spectroscopy is performed on the nickel isotopes $^{58-68,70}$Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii $R_c$ are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLO$_{\rm sat}$, which allows an assessment of their accuracy. We find agreement with experiment in differential radii $\delta \left\langle r_\mathrm{c}^2 \right\rangle$ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLO$_{\rm sat}$. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy($\Delta r$,HFB).

We analyze recent data on a long series of high-spin states in $^{208}$Pb with a self-consistent phonon-coupling model for nuclear excitations based on the Skyrme functionals. The model is the renormalized time-blocking approximation (RenTBA) which takes the coherent one-particle-one-hole (1p1h) states of the random-phase approximation (RPA) as starting point and develops from that more complex configurations beyond RPA. To the best of our knowledge, this is the first investigation of high spin states in $^{208}$Pb using self-consistent nuclear models. The interesting point here is that complex configurations are compulsory to describe the upper end of the long spin series at all. The data thus provide an ideal testing ground for phonon-coupling models as they give direct access to complex configurations. We find that standard Skyrme functionals which perform well in ground state properties and giant resonance excitations deliver at once an agreeable description of these high spin states., 7 pages, 2 figures

The paper addresses the problem of the self-interaction correction (SIC) in static calculations of atoms and molecules. Key observable is the electron removal energy, the energy required to remove one electron from the given system and to leave it in a definite hole state whereby we discuss hole states not only in the Highest Occupied Molecular Orbital (HOMO), but also deeper lying holes. To that end, we employ a newly developed technique to compute a stationary state for a configuration with a definite hole in a chosen single-particle state. We also compare two different definitions of removal energies, first, the genuine one taking the difference of the total energy of the original system and the energy of final system sustaining the hole, and second, simply the single-particle energy in the original system. According to Koopman’s theorem, both should be close to each other. Four different systems are considered, one atom and three molecules with different bond types, covalent, metallic, and dipolar. The general result is that any SIC brings considerable improvement as compared to the initial Local-Density Approximation (LDA), the better the closer the hole stays to the HOMO. There are variations between different SIC approximations whereby systems with strong binding (atom and covalent molecule) show least variations. Here, the quality of Koopman’s theorem is very satisfying for the HOMO and degrades slightly toward deeper binding. Systems with metallic or dipolar binding are more reactive and show stronger changes with approximation and hole level.

Algebraic collective model (ACM) calculations for the even-even selenium isotopes $^{86,88}\mathrm{Se}$ have been performed to describe collective properties of these two transitional nuclei with only two and four valence neutrons, respectively. From the perspective of the ACM the nuclei turn out to be only weakly deformed, described by a very $\ensuremath{\gamma}$-soft potential. This is confirmed by Skyrme and Gogny energy density functional calculations. Additionally, the fully microscopic symmetry conserving configuration mixing method with the Gogny interaction has been applied to the study of these isotopes. The results show the transitional character of $^{86}\mathrm{Se}$ and the relevant role of the triaxial degree of freedom in the structure of these nuclei.

The low-energy dipole excitations in ^{24}Mg are investigated within the Skyrme quasiparticle random phase approximation for axial nuclei. The calculations with the force SLy6 reveal a remarkable feature: the lowest I^{π}K=1^{-}1 excitation (E=7.92 MeV) in ^{24}Mg is a vortical toroidal state (TS) representing a specific vortex-antivortex realization of the well-known spherical Hill's vortex in a strongly deformed axial confinement. This is a striking example of an individual TS which can be much more easily discriminated in experiment than the toroidal dipole resonance embracing many states. The TS acquires the lowest energy due to the huge prolate axial deformation in ^{24}Mg. The result persists for different Skyrme parametrizations (SLy6, SVbas, SkM*). We analyze spectroscopic properties of the TS and its relation with the cluster structure of ^{24}Mg. Similar TSs could exist in other highly prolate light nuclei. They could serve as promising tests for various reactions to probe a vortical (toroidal) nuclear flow.

International audience; Differences in mean-square nuclear charge radii of $^{100–130} \rm{Cd}$ are extracted from high-resolution collinear laser spectroscopy of the $5s^2 S_{1/2} \to 5p^2 P_{3/2}$ transition of the ion and from the $5s5p^3P_2 \to 5s6s^3S_1$ transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete $sdgh$ shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius.

Bunched-beam collinear laser spectroscopy is performed on neutron deficient ^{52,53}Fe prepared through in-flight separation followed by a gas stopping. This novel scheme is a major step to reach nuclides far from the stability line in laser spectroscopy. Differential mean-square charge radii δ⟨r^{2}⟩ of ^{52,53}Fe are determined relative to stable ^{56}Fe as δ⟨r^{2}⟩^{56,52}=-0.034(13) fm^{2} and δ⟨r^{2}⟩^{56,53}=-0.218(13) fm^{2}, respectively, from the isotope shift of atomic hyperfine structures. The multiconfiguration Dirac-Fock method is used to calculate atomic factors to deduce δ⟨r^{2}⟩. The values of δ⟨r^{2}⟩ exhibit a minimum at the N=28 neutron shell closure. The nuclear density functional theory with Fayans and Skyrme energy density functionals is used to interpret the data. The trend of δ⟨r^{2}⟩ along the Fe isotopic chain results from an interplay between single-particle shell structure, pairing, and polarization effects and provides important data for understanding the intricate trend in the δ⟨r^{2}⟩ of closed-shell Ca isotopes.

We report the first use of the effective QMC energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the non-relativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having clear physical basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist however multiple Skyrme paramater sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, as derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter., 9 pages, 1 table, 4 figures; in print in Phys. Rev. Letters. A minor change in the abstract, a few typos corrected and some small technical adjustments made to comply with the journal regulations

We investigate from a theoretical perspective a possible pump and probe scenario for analyzing the rotational motion of free deformed metal clusters considering as test case an ensemble of Na7+ clusters. To that end, we develop a simple classical model for the orientational dynamics and rate equations for the ionizing effect of laser pulses. The model parameters are determined microscopically by time-dependent density functional theory for the cluster electrons and a detailed description of the cluster ions by local pseudo-potentials. We find that pump and probe analysis can very well resolve the rotational motion provided that the laser parameters are properly tuned to the Me surface plasmon of the given sample. Moreover, we see that the laser pulses burn a hole into the distribution of orientations. Stroboscopic repetition of pulses will allow to produce an ensemble clusters oriented in a direction perpendicular to the laser polarization axis.

We discuss the response of the H9+ cluster to an excitation by an intense laser beam. Calculations are done within the framework of TDLDA-MD, an approach which has proven to provide a robust tool for investigations in metal cluster dynamics. We first discuss static and low energy properties of H9+ and make comparisons with other existing ab initio results. We then explore the various excitation/deexcitation scenarios as a function of the laser parameters.

We compare the capabilities of rapid highly charged projectiles and intense femtosecond lasers to ionize simple metal clusters while leaving as little intrinsic excitation as possible in the residue. We show that both excitation mechanisms are able to produce highly charged clusters. The deposited excitation energies increase with ionization but with different trends. Cold ionization, corresponding to moderate deposited excitation energy, is better attained with ionic projectiles for low charge states, and with lasers for high charge states.

International audience; Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small- and medium-sized neutral molecules (N2, CO2, and C2H4), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.

Investigations of exotic cluster-like phenomena in the framework of the Skyrme-Hartree-Fock approach are reported. The occurrence of highly excited isomeric states is discussed in connection with the question of their stability in static and time-dependent Hartree Fock (TDHF) calculations. We find rotational stabilization of a 4α chain structure in 16O occurring for a limited range of angular momenta. A toroidal configuration of 40Ca was also stabilized by rotation and provides a very interesting example of rotation about a symmetry axis with a strictly quantized total angular momentum. Finally we look at the formation of nuclear pasta phases in a time-dependent approach and their classification.

The width of the plasmon resonance in the clusters ${\mathrm{Na}}_{9}^{+}$, ${\mathrm{Na}}_{21}^{+}$, and ${\mathrm{Na}}_{41}^{+}$ is investigated in the framework of the structure-averaged jellium model and compared with recent experimental data. The two leading mechanisms for the line broadening are fragmentation of the resonance into nearby 1ph states and splitting through thermal quadrupole fluctuations. The fragmentation becomes activated mainly through octupole fluctuations and it gives the dominating contribution to the width.

We investigate the possibility of the existence of the exotic torus configuration in the high-spin excited states of (40)Ca. We here consider the spin alignments about the symmetry axis. To this end, we use a three-dimensional cranked Skyrme Hartree-Fock method and search for stable single-particle configurations. We find one stable state with the torus configuration at the total angular momentum J=60 ħ and an excitation energy of about 170 MeV in all calculations using various Skyrme interactions. The total angular momentum J=60 ħ consists of aligned 12 nucleons with the orbital angular momenta Λ=+4, +5, and +6 for spin-up or -down neutrons and protons. The obtained results strongly suggest that a macroscopic amount of circulating current breaking the time-reversal symmetry emerges in the high-spin excited state of (40)Ca.

We investigate the excitation spectra of closed-shell 3 He droplets using a flexible formulation of the RPA which has been presented in preceeding papers. The calculations are based on an energy functional which thorougly employs finite-range interactions. We compare the results for different stages in a hierarchy of approximations to the full RPA. We furthermore discuss the consequences of taking the zero-range limit of the present energy functional, i.e. of using Skyrme-type interactions

Liquid3He droplets and their shell structure are investigated in the framework of mean-field calculations using a recently developed effective energy functional which employs realistic finite range interactions throughout. The samples range fromN=20 up toN=1360. The shell closures found agree with the harmonic oscillator scheme up toN=168. Above that, magic droplets appear atN=198, 274, 300, 368, 398, 482, 516... The first and second differences of the free energy are computed as signals for the shell structure in future experiments. Shell closures are found to be still visible in these signals at comparatively high temperatures. The finite range character of the effective interaction generates oscillations in the density profile which are suppressed in comparable calculations with zero range interactions.

Outgoing from a time-dependent theory of correlations, we present a stochastic differential equation for the propagation of ensemble of Slater determinants, called stochastic time-dependent Hartree-Fock (stochastic TDHF). These ensembles are allowed large fluctuations to develop in the Hartree-Fock mean fields. An alternative stochastic differential equation, the Boltzmann-Langevin equation, can be derived from stochastic TDHF by averaging over subensembles with small fluctuations.

The density‐constrained time‐dependent Hartree‐Fock (DC‐TDHF) theory is a fully microscopic approach for calculating heavy‐ion interaction potentials and fusion cross sections below and above the fusion barrier. We discuss applications of DC‐TDHF method to fusion, the effects of neutron transfer, and potential application to fission barrier calculations.

A new semi-microscopic energy functional for Hartree-Fock calculations in liquid 3He is presented, which employs finite range forces throughout. It contains the polarization potentials and the Skyrme force as limiting cases. The parameters of the functional are uniquely fixed to these limiting cases. In addition to the reproduction of the ground state of liquid 3He and its Landau parameters, a good simultaneous description of zero sound at finite momentum transfer and of the surface tension of semi-infinite 3He is obtained.

We present a recently introduced hierarchical model for the description of clusters in contact with an environment (embedded or deposited cluster). We briefly outline the ingredients of the model and show the relevance of a proper treatment of the degrees of freedom of the environment, taking as example the optical response of a small embedded metal cluster. We finally discuss the technical and formal difficulties raised by a proper treatment of the Self Interaction Correction problem in a true dynamical situation.

We present a short progress report of the microscopic theoretical description of the irradiation dynamics of small molecules. We discuss separately the short time response of the system to an electromagnetic perturbation and the impact of the environment on irradiation dynamics in the case of embedded metal clusters. We finally discuss some formal theoretical questions raised by the use of density functional theory in this context.

We present the first realization of Stochastic TDHF, a theory which goes beyond pure mean-field dynamics, embracing dissipation as well as fluctuations. Applications to heavy-ion collisions in the Fermi energy domain are given and analyzed in terms of dissipative features and Intermediate Mass Fragment production.

The self-consistent separable RPA (random phase approximation) method is formulated for Skyrme forces with pairing. The method is based on a general self-consistent procedure for factorization of the two-body interaction. It is relevant for various density- and current-dependent functionals. The contributions of the time-even and time-odd Skyrme terms as well as of the Coulomb and pairing terms to the residual interaction are taken self-consistently into account. Most of the expression have a transparent analytical form, which makes the method convenient for the treatment and analysis. The separable character of the residual interaction allows to avoid diagonalization of high-rank RPA matrices and thus to minimize the calculation effort. The previous studies have demonstrated high numerical accuracy and efficiency of the method for spherical nuclei. In this contribution, the method is specified for axial nuclei. We provide systematic and detailed presentation of formalism and discuss different aspects of the model.

We discuss the response of metal clusters subject strong electromagnetic fields in the framework of density functional theory. This allows a fully nonadiabatic treatment of both electronic and ionic degrees of freedom. We give a few general properties of metal clusters which can be accessed with this kind of nonadiabatic approaches and we present an example of application of a metal cluster subject to an intense laser field.

We concentrate on the two most widely used mean-field models, Skyrme-Hartree-Fock and relativistic mean field. We discuss their performance in view of the extended range of experimental information in terms of a guided tour through selected examples of success, failures and subsequent improvement of the models drawn from comparison with key observables as isotopic shifts, trends of binding energies or single-particle spectra. Particular attention is paid to the extrapolative power with respect to superheavy elements (SHE). It turns out that the most important aspect is here the actual level sequence as implied by the given mean-field models. We will compare the performance of available parametrisations and discuss briefly possible improvements.