Thermionic emission from small clusters: direct observation of the kinetic energy distribution of the electrons

Weidele, H.; Kreisle, D.; Recknagel, E.; Icking-Konert, G. Schulze; Handschuh, H.; Ganteför, Gerd; Eberhardt, W.

doi:10.1016/0009-2614(95)00344-4

Cited by 77 publications

(64 citation statements)

References 23 publications

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“…The bond length, vibrational frequency, detachment energy of free N À;þ;0 2 are calculated using the B3LYP and PW91 with the same basis sets in our previous work and agree very well with the experimental data [23][24][25][26]. For W n clusters, the most stable isomers and their optimized geometrical parameter, EA, and dissociation energy (adiabatic and vertical dissociation energies) by using B3LYP functional have been reported in our previous work and are all in good agreement with available experimental data [17,18].…”

Section: Methodsmentioning

confidence: 74%

Theoretical study of molecular nitrogen adsorption on Wn clusters

Zhang¹,

Ding²,

Fu³

et al. 2008

Journal of Molecular Structure: THEOCHEM

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a b s t r a c tThe adsorption properties of N 2 molecules on anionic, cationic, and neutral W n clusters (n = 1 -5) are studied using the density functional theory with the generalized gradient approximation and with the hybrid functional. Adsorption energies accompanying charge population and vibrational analysis are used to characterize the adsorption properties of N 2 on W n clusters with different sizes and charge states. Our calculations show that all the W clusters can adsorb one N 2 molecule with adsorption energy about 0.29-1.72 eV at B3LYP level, and 0.35-2.05 eV at PW91 level, by forming a linear or quasi-linear structure W-N-N.

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Section: Methodsmentioning

confidence: 74%

Theoretical study of molecular nitrogen adsorption on Wn clusters

Zhang¹,

Ding²,

Fu³

et al. 2008

Journal of Molecular Structure: THEOCHEM

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“…Model calculations estimate for n ≤ 21 a dissociation energy above 6 eV [26], higher by far than the experimentally determined electron affinity, which is around 2 eV [27]. Obviously, the inner energy of the cations obtained by collisional activation is not high enough to induce fragmentation.…”

Section: Electron Emission Of Tungsten Cluster Anionsmentioning

confidence: 98%

Decay pathways of stored metal-cluster anions after collisional activation

Weidele

Vogel

Herlert

et al. 1999

The European Physical Journal D

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Size-selected gold clusters, Au − n (n ≤ 21), and tungsten clusters, W + n and W − n (n = 4 − 8 and 12), stored in a Penning trap have been collisionally activated. Neutral monomer and dimer evaporation are observed in the case of gold. While no fragment products have been observed for tungsten clusters, there is evidence of electron emission from the anions.PACS. 36.40.c Atomic and molecular clusters -36.40.Qv Stability and fragmentation of clusters -34.90.+q Other topics in atomic and molecular collision processes and interactions

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“…In negative clusters of refractory elements such as tungsten [1][2][3][4][5][6], niobium [7], or fullerenes [8][9][10][11][12], the energy required to remove an electron is significantly lower than the energy required to remove an atom. For example, in small negative tungsten clusters W 2 n ͑n , 15͒ the electron affinity (EA) is less than 2 eV [4] while the bulk heat of vaporization is about 8.9 eV͞atom. In this paper, we focus on the case where the absorption of a single photon of energy hy is sufficient to remove an electron from a finite size negatively charged system: hy .…”

mentioning

confidence: 98%

“…As model systems, we study the photodetachment of W 2 n clusters ͑n , 12͒ by single-photon excitation. Neutral [1-3] and negative tungsten clusters [4-6] have already been extensively studied and the kinetic-energy distribution of photoelectrons has been measured [4,5]. However, our specific experimental setup allows us to study the photoelectron spectrum near threshold which is extremely different in a finite size system as compared to the bulk matter.…”

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confidence: 99%

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Photoelectron Imaging Spectroscopy of Small Clusters: Evidence for Non-Boltzmannian Kinetic-Energy Distribution in Thermionic Emission

et al. 1998

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The competition between thermionic emission and direct photoelectron emission has been measured in small tungsten clusters using photoelectron imaging spectroscopy. The kinetic energy distribution of electrons corresponding to thermionic emission is found to vary as p͑e͒~e 1͞2 exp͑2e͞kT͒, in agreement with theoretical predictions, and does not follow the bulklike function p͑e͒~e exp͑2e͞kT͒ or the simple exponentially decreasing Boltzmann function p͑e͒~exp͑2e͞kT͒, as usually assumed in photoelectron spectroscopy of clusters. Moreover, the angular distribution of direct photoelectrons is observed and the evolution as a function of the size is discussed. [S0031-9007(98)07082-3] PACS numbers: 33.60.Cv The optical excitation of a molecule, cluster, or solid by absorption of one or several photons results in a decay process that follows different channels (emission of atom, molecule, electron, photon . . .) according to the size of the particle and its internal energy. When the excess energy is sufficient to remove an electron or atom from the system, the emission of a photon is usually negligible. In negative clusters of refractory elements such as tungsten [1-6], niobium [7], or fullerenes [8][9][10][11][12], the energy required to remove an electron is significantly lower than the energy required to remove an atom. For example, in small negative tungsten clusters W 2 n ͑n , 15͒ the electron affinity (EA) is less than 2 eV [4] while the bulk heat of vaporization is about 8.9 eV͞atom. In this paper, we focus on the case where the absorption of a single photon of energy hy is sufficient to remove an electron from a finite size negatively charged system: hy . EA. As model systems, we study the photodetachment of W 2 n clusters ͑n , 12͒ by single-photon excitation. Neutral [1-3] and negative tungsten clusters [4-6] have already been extensively studied and the kinetic-energy distribution of photoelectrons has been measured [4,5]. However, our specific experimental setup allows us to study the photoelectron spectrum near threshold which is extremely different in a finite size system as compared to the bulk matter. These clusters, excited above the detachment threshold and below the dissociation threshold, may decay only by electronic emission. The excited state can lead directly to the emission of a photoelectron. This corresponds to direct photoemission (DPE): The excess energy is converted to photoelectron kinetic energy e hy 2 E f (E f energy of the final state of the target). The corresponding kinetic energy photoelectron spectrum mirrors the target excited state spectrum. Before decay, the excited electron may also transfer part of its energy to the nuclei. In a cluster, owing to the combination of a limited number of degrees of freedom and of a large density of states, this kind of indirect process leads to thermionic emission (TE) [13] while in bulk matter this results in inelastic photoelectron scattering [14]. In bulk matter, TE corresponds to the ejection of electrons from a surface at temperature T with a k...

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Thermionic emission from small clusters: direct observation of the kinetic energy distribution of the electrons

Cited by 77 publications

References 23 publications

Theoretical study of molecular nitrogen adsorption on Wn clusters

Theoretical study of molecular nitrogen adsorption on Wn clusters

Decay pathways of stored metal-cluster anions after collisional activation

Photoelectron Imaging Spectroscopy of Small Clusters: Evidence for Non-Boltzmannian Kinetic-Energy Distribution in Thermionic Emission

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