Femtosecond Dynamics of Molecular and Cluster Ionization and Fragmentation

Baumert, Thomas; Thalweiser, Rainer; Weiß, Volker; Gerber, G.

doi:10.1007/978-3-642-84910-7_20

Cited by 3 publications

(7 citation statements)

References 6 publications

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“…Compared to the dimer oscillations we find much lower frequencies in the range of 30-50 cm -1. These are in the range of those observed in the pump and probe experiments [8]. Furthermore, these frequencies show no definite size and charge dependence, but rather show fluctuations between 30cm-1 and 50cm-I due to geometrical effects.…”

Section: ~(R) = Tb(ro/r) 2 Exp[(ro/rc) N~ --(R/rc)n~] 2mentioning

confidence: 68%

“…The kinetic energy of the holes is small, since hole hopping is suppressed by Coulomb correlations. We also find c~c > wRSince the motion of the charges and dipoles affects the po-tential acting on the Rydberg electron, and therefore also its wave-function, the ionization probability of the excited cluster must show, in a pump-probe experiment, oscillations as a function of the delay time, given by a superposition of a:R and ozc [8]. We obtain that a:c is charge-dependent, but almost size independent, and very large in comparison to the vibrational frequency (c~vaw) of a van der Waals Hg2 molecule.…”

Section: Discussionmentioning

confidence: 96%

“…Dynamics after ionization: To apply our theory to the experiments by Gerber et al [8], we must determine from E the time dependence of the electronic energy relaxation after ionization of the cluster due to energy transfer into kinetic energy of the atoms. This is done by allowing the inter-atomic distances within the cluster to vary.…”

Section: Qli(qjj) --mentioning

confidence: 99%

“…Recently, pump-probe measurements have been used to study the dynamics of small Hg~ clusters [8,9], In these experiments neutral Hg~ clusters are excited at time t = 0 by the pump pulse through a multi-photon-absorption process. One or two electrons are promoted into a Rydbergstate.…”

Section: Introductionmentioning

confidence: 99%

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Theory for the short-time response of small Hg n clusters after excitation

Klaus

Garcia

1995

Z Phys D - Atoms, Molecules and Clusters

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Abstract. The short-time behavior of small Hg,~ clusters immediately after single or double ionization is studied. We calculate self-consistently the ground state electronic energy E of ionized Hg~ clusters. Upon ionization changes of the potential energy surface (PES) occur, which govern the atomic motion in the cluster. These changes depend on cluster size and charge and are determined by the interplay between the localization of the holes within an ionic core and the polarization energy of the neutral rest of the cluster. In the case of single ionization of the cluster the PES results mainly from hole delocalization. In contrast, in the case of double ionization the PES is governed almost only by strong environment polarization, We use our theory to explain the physical origin of the oscillations in the ionization crosssection of singly and doubly excited Hg~ clusters observed in recent pump-probe experiments.

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Section: ~(R) = Tb(ro/r) 2 Exp[(ro/rc) N~ --(R/rc)n~] 2mentioning

confidence: 68%

Section: Discussionmentioning

confidence: 96%

Section: Qli(qjj) --mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theory for the short-time response of small Hg n clusters after excitation

Klaus

Garcia

1995

Z Phys D - Atoms, Molecules and Clusters

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“…The latter models neglect the core potentials of the ions and their geometric arrangement, assuming instead, that an interacting electron gas is confined by a structureless background. It is computationally and conceptually interesting to see where the two concepts merge.Optical spectra of small, neutral sodium clusters have been reported earlier [10][11][12]. The neutral clusters are not mass selected in these experiments.…”

mentioning

confidence: 94%

Transition of the electronic response from molecular-like to jellium-like in cold, small sodium clusters

Ellert

Schmidt

Reiners

et al. 1997

Z Phys D - Atoms, Molecules and Clusters

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Absolute photoabsorption cross sections for Na + n (2≤n≤21) were measured in the visible energy range. The cluster ions were produced in a gas aggregation source and thus have a canonical distribution of internal energy corresponding to a temperature of ∼ 105 K. The spectra for n≤9 and 11 exhibit between two and six absorption lines, and are in qualitative agreement with ab inito quantum chemical calculations. For n=15 and 21, the position of the resonances can be explained as excitations of a nearly free electron gas in a spheroidal container. An evolution is thus observed from molecular-like transitions to a giant collective resonance of the electron cloud. The integrated oscillator strength is 0.95 per 3s-electron in the energy range covered for n≥4, showing that the main excitations of the valence electrons have been found. 36.40.Cg; 36.40.Gk; 36.40.Mr PACS: I IntroductionAlkali metal clusters have been studied intensively in recent years [1][2][3][4][5][6][7]. Two reviews have appeared summarizing the current theoretical [5] and experimental [6] knowledge. Sodium in particular serves as a prototype case for the free electron model, since its Fermi-surface deviates less than 0.1 % from the spherical shape [7,8]. Therefore, the transition from the atom, via the molecule, the cluster, the small particle, to bulk matter can be well studied in this system.In this paper we address the question up to which cluster size the molecular description is appropriate, and when one can change to the computationally less demanding solid state models. For a small numbers of atoms per cluster, the modern methods of quantum chemistry are effective in describing the electronic excitation of the valence electrons [9]. The quantum chemical methods solve the Schrödinger equation using the Born-Oppenheimer approximation. This is the more accurate method, in principle. But the computer time needed increases dramatically with increasing cluster size, making calculation for n > 21 impractical today. For larger alkali clusters a description in terms of solid state or nuclear physics concepts yields good results for the abundance spectra as well as for the electronic properties [4,5]. The latter models neglect the core potentials of the ions and their geometric arrangement, assuming instead, that an interacting electron gas is confined by a structureless background. It is computationally and conceptually interesting to see where the two concepts merge.Optical spectra of small, neutral sodium clusters have been reported earlier [10][11][12]. The neutral clusters are not mass selected in these experiments. After photo excitation and ensuing fragmentation, the neutral clusters are ionized, thus fragmentation from larger clusters onto the species under investigation has to be considered carefully [11]. In order to avoid this problem, several groups have studied charged clusters, which allow for a mass selection prior to photofragmentation, making the interpretation of the data much easier [13][14][15][16]. The evolution of the plasmon resona...

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Laser-Femtochemistry of Small Clusters

Schreiber¹

1999

Theory of Atomic and Molecular Clusters

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Femtosecond Dynamics of Molecular and Cluster Ionization and Fragmentation

Cited by 3 publications

References 6 publications

Theory for the short-time response of small Hg n clusters after excitation

Theory for the short-time response of small Hg n clusters after excitation

Transition of the electronic response from molecular-like to jellium-like in cold, small sodium clusters

Laser-Femtochemistry of Small Clusters

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