Fingerprints of level depletion in the photoelectron spectra of small Na clusters in the ultraviolet domain

Dinh, Phuong Mai; Vidal, Sylvain; Reinhard, P.‐G.; Suraud, E.

doi:10.1088/1367-2630/14/6/063015

Cited by 6 publications

(5 citation statements)

References 24 publications

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“…At the lower frequencies, electron depletion occurs predominantly from the HOMO orbital, as expected. At the upper end, depletion approaches an equi-distrbiution similar to what we observed for Na clusters and C 60 [22][23][24]. But in between, we find an occupation inversion over a wide range of frequencies with, by far, the dominant depletion coming from the deepest level α = 1.…”

supporting

confidence: 83%

Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

Reinhard¹,

Dundas²,

Dinh³

et al. 2022

Preprint

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We investigate the depletion of single-electron states in small molecules under the influence of very short XUV pulses. In N2, 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.

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supporting

confidence: 83%

Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

Reinhard¹,

Dundas²,

Dinh³

et al. 2022

Preprint

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show abstract

“…At the lower frequencies, electron depletion occurs predominantly from the HOMO orbital, as expected. At the upper end, depletion approaches an equi-distribution similar to obser- vations in Na clusters and C 60 [22][23][24]. But in between, we find an occupation inversion over a wide range of frequencies with, by far, the dominant depletion coming from the deepest level 2Σ g .…”

supporting

confidence: 77%

“…Indeed low-frequency pulses skim electrons from the Fermi surface while deeper lying electrons come increasingly into play with increasing pulse frequency [22][23][24]. One might expect an equi-distribution of depletion over all valence states, as observed in Na clusters [22,23] and C 60 [24]. However, when considering ultrafast pulses in the few femtosecond regime, we observe in covalent molecules an ionization mechanism very close to the creation of an instantaneous deep-hole.…”

mentioning

confidence: 56%

“…Thanks to a pseudopotential with frozen cores [21], we only consider valence electrons and focus on the depletion of the lowest occupied valence state, easily attainable with an XUV laser. Indeed low-frequency pulses skim electrons from the Fermi surface while deeper lying electrons come increasingly into play with increasing pulse frequency [22][23][24]. One might expect an equi-distribution of depletion over all valence states, as observed in Na clusters [22,23] and C 60 [24].…”

mentioning

confidence: 92%

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Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

Reinhard

Dundas²,

Dinh³

et al. 2023

Phys. Rev. A

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We investigate the depletion of deep-lying single-electron states in the N2 dimer under the influence of very short XUV pulses. We find, first, a marked occupation inversion for a certain window of XUV energies around 50 eV where depletion of the deepest bound valence electron state is much larger than for any other state, and second, that this occupation inversion drives a dipole instability, i.e. a spontaneous reappearance of the dipole signal long after the laser pulse is over and the initial dipole oscillations died out. As a tool for this study, we use time-dependent density functional theory with a self-interaction correction solved on a coordinate-space grid with absorbing boundary conditions. Key observables are state-specific electron emission (depletion) and photoelectron spectra (PES). The dipole instability generates additional electron emission leading to a specific low-energy structure in PES, a signal which could be used to identify the dipole instability experimentally. The here reported dedicated depletion of a deep lying electron state by a well tuned XUV pulse has been found also in other atoms and molecules. It provides a practicable realization of an instantaneously produced deep hole state, a situation which is often assumed ad hoc in numerous theoretical studies of energetic ultrafast processes. Moreover, the identification of the subsequent dipole instability by PES will allow one to study basic decay channels of hole states in detail.

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“…As expected, the theoretical PES resembles the s.p. depletion pattern very much [192]. We now turn to the multi-photon case (right panels of Fig.…”

Section: Impact Of Laser Frequencymentioning

confidence: 97%

Electrons as probes of dynamics in molecules and clusters: A contribution from Time Dependent Density Functional Theory

et al. 2015

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a b s t r a c tThere are various ways to analyze the dynamical response of clusters and molecules to electromagnetic perturbations. Particularly rich information can be obtained from measuring the properties of electrons emitted in the course of the excitation dynamics. Such an analysis of electron signals covers observables such as total ionization, PhotoElectron Spectra (PES), Photoelectron Angular Distributions (PAD), and ideally combined PES/PAD. It has a long history in molecular physics and was increasingly used in cluster physics as well. Recent progress in the design of new light sources (high intensity, high frequency, ultra short pulses) opens new possibilities for measurements and thus has renewed the interest on these observables, especially for the analysis of various dynamical scenarios, well beyond a simple access to electronic density of states. This, in turn, has motivated many theoretical investigations of the dynamics of electronic emission for molecules and clusters up to such a complex and interesting system as C 60 . A theoretical tool of choice is here Time-Dependent Density Functional Theory (TDDFT) propagated in real time and on a spatial grid, and augmented by a Self-Interaction Correction (SIC). This provides a pertinent, robust, and efficient description of electronic emission including the detailed pattern of PES and PAD. A direct comparison between experiments and well founded elaborate microscopic theories is thus readily possible, at variance with more demanding observables such as for example fragmentation or dissociation cross sections.The purpose of this paper is to describe the theoretical tools developed on the basis of real-time and real-space TDDFT and to address in a realistic manner the analysis of electronic emission following irradiation of clusters and molecules by various laser pulses. After a general introduction, we shall present in a second part the available experimental results motivating such studies, starting from the simplest total ionization signals to the more elaborate PES and PAD, possibly combining them and/or resolving them in time. This experimental discussion will be complemented in a third part by a presentation of available theoretical tools focusing on TDDFT and detailing the methods used to address ionization observables. We shall also discuss the shortcomings of standard versions of TDDFT, especially what concerns the SIC problem, and show how to improve formally and practically the theory on that aspect. A long fourth part will be devoted to representative * P. Wopperer et al. / Physics Reports ( ) -results. We shall illustrate the use of total ionization in pump and probe scenarios with fs lasers for tracking ionic dynamics in clusters. More challenging from the experimental point of view is pump and probe setups using attosecond pulses. The effort there is more on the capability to define proper signals to be measured/computed at such a short time scale. TDDFT analysis provides here a valuable tool in the search for the most efficient observab...

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Fingerprints of level depletion in the photoelectron spectra of small Na clusters in the ultraviolet domain

Cited by 6 publications

References 24 publications

Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

Electrons as probes of dynamics in molecules and clusters: A contribution from Time Dependent Density Functional Theory

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