Orientation averaged angular distributions of photo-electrons from free Na clusters

Wopperer, Philipp; Faber, B. J.; Dinh, Phuong Mai; Reinhard, P.‐G.; Suraud, E.

doi:10.1016/j.physleta.2010.10.031

Cited by 20 publications

(24 citation statements)

References 31 publications

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“…The angular distribution of emitted electrons is obtained from recording the absorbed electrons as in TDLDA [48,49]. The angular distribution is characterized by the anisotropy parameter β 2 , the leading parameter in the photo-electron angular cross section dσ/dΩ ∝ (1 + β 2 P 2 (cos(θ) + ....) [50,51] where P 2 is the second order Legendre polynomial and θ the direction with respect to laser polarization axis (here z-axis in 2D cylindrical geometry). A specific quantity to track relaxation processes is the one-body entropy which is computed in diagonal representation (3) by the standard expression [52] …”

Section: Numerical Representation and Computation Of Relevant Obsementioning

confidence: 99%

A quantum relaxation-time approximation for finite fermion systems

Reinhard

Suraud

2015

Annals of Physics

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We propose a relaxation time approximation for the description of the dynamics of strongly excited fermion systems. Our approach is based on time-dependent density functional theory at the level of the local density approximation. This mean-field picture is augmented by collisional correlations handled in relaxation time approximation which is inspired from the corresponding semi-classical picture. The method involves the estimate of microscopic relaxation rates/times which is presently taken from the well established semi-classical experience. The relaxation time approximation implies evaluation of the instantaneous equilibrium state towards which the dynamical state is progressively driven at the pace of the microscopic relaxation time. As test case, we consider Na clusters of various sizes excited either by a swift ion projectile or by a short and intense laser pulse, driven in various dynamical regimes ranging from linear to strongly non-linear reactions. We observe a strong effect of dissipation on sensitive observables such as net ionization and angular distributions of emitted electrons. The effect is especially large for moderate excitations where typical relaxation/dissipation time scales efficiently compete with ionization for dissipating the available excitation energy. Technical details on the actual procedure to implement a working recipe of such a quantum relaxation approximation are given in appendices for completeness.

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Section: Numerical Representation and Computation Of Relevant Obsementioning

confidence: 99%

A quantum relaxation-time approximation for finite fermion systems

Reinhard

Suraud

2015

Annals of Physics

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“…Moreover, one realizes that each ring has its own intensity (not necessarily isotropic) which means that different s.p. states can have different angular distributions [35].…”

Section: Orientation Averaging Schemementioning

confidence: 99%

“…The aim of this paper is thus to present in detail a model providing a fully fledged microscopic theoretical description of C 60 using methods of Time-Dependent DFT (TDDFT) in real time and real space, extensively applied and tested previously in metal cluster dynamics [35,37,38,39]. We will mainly address electronic emission from one-photon processes induced by VUV pulses, but we will also have a look at strong infrared pulses and subsequent multi-photon processes.…”

Section: Introductionmentioning

confidence: 99%

On the dynamics of photo-electrons in C₆₀

Gao¹,

Wopperer²,

Dinh³

et al. 2015

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. We explore photo-electron spectra (PES) and photo-electron angular distributions (PAD) of C 60 with time-dependent density functional theory (TDDFT) in real time. To simulate experiments in gas phase, we consider isotropic ensembles of cluster orientations and perform orientation averaging of the TDDFT calculations. First, we investigate ionization properties of C 60 by one-photon processes in the range of VUV energies. The PES map the energies of the occupied single-particle states, while the weights of the peaks in PES are given by the depletion of the corresponding level. The different influences can be disentangled by looking at PES from slightly different photon frequencies. PAD in the one-photon regime can be characterized by one parameter, the anisotropy. This single parameter unfolds worthwhile information when investigating the frequency and state dependences. We also discuss the case of multi-photon ionization induced by strong infrared laser pulses in C 60 . In agreement with measurements, we find that the PES show a regular comb of peaks separated by the photon energy. Our calculations reveal that this happens because only very few occupied states of C 60 near the ionization threshold contribute to emission and that these few states happen to cooperate filling the same peaks. The PAD show a steady increase of anisotropy with increasing photon order.

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“…Recently, the emphasis has moved more into describing the dynamical processes (e.g. [14]). The most common way of interpreting photoelectron spectra of clusters is to use density of states (DOS) approach applying directly the quantum chemistry codes [15].…”

Section: Introductionmentioning

confidence: 99%

Valence photoionization of free, neutral, and size-varied alkali metal clusters

Jänkälä

Mikkelä

Huttula

2011

J. Phys. B: At. Mol. Opt. Phys.

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.Valence photoionization of free, neutral, and size-varied alkali metal clustersTo cite this version: Abstract. Valence photoelectron spectra of free, neutral, and size varied K and Rb alkali metal clusters are studied. The experimental spectra are simulated with jellium model based calculations with and without inclusion of dipole matrix elements and continuum wave functions. The simple jellium model used is found to provide good qualitative correspondence with the experimental results. It is shown that the dipole matrix elements provide a remarkable improvement to the standard density of states approach in understanding the photoelectron spectra of small to medium size metal clusters.

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Orientation averaged angular distributions of photo-electrons from free Na clusters

Cited by 20 publications

References 31 publications

A quantum relaxation-time approximation for finite fermion systems

A quantum relaxation-time approximation for finite fermion systems

On the dynamics of photo-electrons in C₆₀

Valence photoionization of free, neutral, and size-varied alkali metal clusters

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Orientation averaged angular distributions of photo-electrons from free Na clusters

Cited by 20 publications

References 31 publications

A quantum relaxation-time approximation for finite fermion systems

A quantum relaxation-time approximation for finite fermion systems

On the dynamics of photo-electrons in C60

Valence photoionization of free, neutral, and size-varied alkali metal clusters

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On the dynamics of photo-electrons in C₆₀