Experimental determination of the energy barrier for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">Li</mml:mi></mml:mrow><mml:mrow><mml:mn>26</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math>cluster

Bréchignac, C.; Cahuzac, Ph.; Frutos, M. de; Garnier, Philippe; Kébaı̈li, N.

doi:10.1103/physrevb.53.1091

Cited by 18 publications

(10 citation statements)

References 12 publications

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“…This shows a strongly deformed system in the distance domain of the maximum barrier. A similar result has been obtained for Coulombic fission of doubly charged alkali-atom clusters [15].…”

Section: (Received 27 March 1998)supporting

confidence: 84%

Temperature Effects in the Coulombic Fission of Strontium Clusters

et al. 1998

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Coulombic fission of triply charged strontium atom clusters is studied for previously photoheated clusters by unimolecular dissociation experiments. It is shown that the predominant fission channel Sr 31 n ! Sr 21 n2p 1 Sr 1 p depends on the degree of internal excitation of the triply charged parent. Such a result shows evidence of the role played by the entropy in the dynamics of fission process. [S0031-9007(98)07801-6] PACS numbers: 36.40.Qv, 36.40.WaFragmentation of clusters has been considered as a main tool to probe their intrinsic stability and their binding forces. In most cases neutral and singly charged clusters are intrinsically stable and their dissociation is endothermic. Hence an excess of energy is necessary to promote dissociation. This can be achieved from either a vibrational excitation or an excess of charges. The first one produces the heating of the cluster, making it thermally metastable. The second one introduces the well known repulsive Coulombic force which is a source of instability leading to the so-called "fission process."Up to now the Coulombic fission experiments on metal clusters have been interpreted in terms of competing thermally activated processes involving a transition state and an activation barrier [1,2]. If the system adiabatically follows the potential energy curve, the predominant fission channel should have the lowest energy barrier. However, the predictions based only on energetic consideration fail under two circumstances: (i) at a given temperature T when the cluster size is rather large and (ii) at a given and eventually small cluster size when the temperature is high. A recent experiment on fission of K 31 n clusters deals with the first situation [3]. Results show that in the size range n 54 105 and for T n ϳ 700 K, the motion of individual atoms becomes important and the configurational entropy predominates. The net effect is a decrease of the asymmetrical character of the fission process. The aim of this paper is to report results on the second situation, i.e., on the entropy contribution when the temperature of a given size cluster is raised.We present experimental evidence of the influence of the internal thermal excitation on the binary fission channels of triply charged strontium clusters. The cluster size ranges in the "critical size" region for which the repulsive Coulombic forces can overcome the binding forces [4,5]. For such Sr 31 n clusters an increase of internal energy preferentially promotes Coulombic fission.The experimental setup is similar to that used in our previous work [1]. Strontium clusters are produced in a gas aggregation source. They are ionized and warmed up in an ionizing region by the radiation of a pulsed ArF ex-cimer laser having an energy of hn 6.42 eV. Under our experimental conditions this photon energy enables us to produce warmed singly, doubly, and triply charged clusters which shrink down in size without losing charge until they reach a critical size at which they undergo Coulombic fission. The mass to charge cluster ratios ar...

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“…This shows a strongly deformed system in the distance domain of the maximum barrier. A similar result has been obtained for Coulombic fission of doubly charged alkali-atom clusters [15].…”

Section: (Received 27 March 1998)supporting

confidence: 84%

Temperature Effects in the Coulombic Fission of Strontium Clusters

et al. 1998

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“…For the decay of Li ++ 26 → Li + 23 and Li + 3 a value of V Fus = 1.29 eV is obtained from (4), which agrees well with a recent experiment [16] yielding V Fus = 1.19 ± 0.10 eV. At the potential maximum the distance between the point charge and the surface of the large fragment is 3.5Å, well above the jellium radius of Li + 3 .…”

Section: Discussionsupporting

confidence: 89%

Fission of doubly charged binary metal clusters

Heinebrodt

Malinowski

Tast

et al. 1999

The European Physical Journal D

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The coulombic fission of binary metal clusters composed of lithium and calcium atoms has been studied by time-of-flight mass spectrometry following multi-photon ionization. The determined appearance sizes are compatible with predictions of a simple model which assumes a liquid droplet picture for all but the very small clusters involved. Electronic shell effects on the fission process are discussed. PACS. 36.40.-c Atomic and molecular clusters -36.40.Qv Stability and fragmentation of clusters Note added in proof Recently, Chien et al. [18] have calculated the cohesive energy of Ca + 2 to be 1.264 eV. Using this value in the analysis of Sect. 4 instead of the assumed 1.1 eV does not alter any of the results reported here.

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“…in the case of neutral monomer evaporation the energy required for the separation of a neutral atom and in the case of fission the energy required for the decay into two charged particles (the fission barrier). The only exceptions come from a kinetic energy release study of Li 2+ 26 by C. Bréchignac et al [9] and investigations of doubly and triply charged gold clusters [10]. In the following we present the dissociation energies of doubly charged silver clusters as determined by collision induced dissociation (CID) in a Penning trap.…”

Section: Introductionmentioning

confidence: 97%

Fission barriers of doubly charged silver clusters

Krückeberg

Dietrich

Lützenkirchen

et al. 1999

The European Physical Journal D

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The monomer evaporation energies and fission barriers of doubly charged silver cluster ions in the size range 9 ≤ n ≤ 25 are measured by collision induced dissociation. They are compared to the dissociation energies of singly charged silver clusters. A macroscopic liquid drop model combined with empirical microscopic corrections successfully describes the measured fission barriers.PACS. 36.40.Qv Stability and fragmentation of clusters -36.40.Wa Charged clusters

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Experimental determination of the energy barrier for theLi262+cluster

Cited by 18 publications

References 12 publications

Temperature Effects in the Coulombic Fission of Strontium Clusters

Temperature Effects in the Coulombic Fission of Strontium Clusters

Fission of doubly charged binary metal clusters

Fission barriers of doubly charged silver clusters

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