Direct Observation of Charge-Exchange Collisions between Mass-selected<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Na</mml:mi></mml:mrow><mml:mrow><mml:mi>n</mml:mi></mml:mrow><mml:mrow/><mml:mrow/><mml:mrow><mml:mo>+</mml:mo></mml:mrow><mml:mprescripts/></mml:mmultiscripts></mml:mrow></mml:math>Clusters and Cs Atoms

Bréchignac, C.; Cahuzac, Ph.; Leygnier, J.; Pflaum, Ronald T.; Weiner, J.

doi:10.1103/physrevlett.61.314

Cited by 55 publications

(31 citation statements)

References 12 publications

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“…There is also a lasting interest to study non-adiabatic cluster collisions where electronic transitions occur. Experiments in this field concern the measurements of the charge transfer [8][9][10], ionization and electronic excitation [11], as well as the selective observation of vibrational and electronic excitations [12].Theoretically, adiabatic cluster collisions can be well described by quantum molecular dynamics (QMD) or molecular dynamics (MD) [13][14][15][16][17]. Also, isomeric [18] and solid-liquid phase transitions [19,20] [25,26] approaches where the atomic structure, and thus the vibrational degrees of freedom, are not taken into account.…”

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Excitation and Relaxation in Atom-Cluster Collisions

Saalmann

Schmidt

1998

Phys. Rev. Lett.

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Electronic and vibrational degrees of freedom in atom-cluster collisions are treated simultaneously and self-consistently by combining time-dependent density functional theory with classical molecular dynamics. The gradual change of the excitation mechanisms (electronic and vibrational) as well as the related relaxation phenomena (phase transitions and fragmentation) are studied in a common framework as a function of the impact energy (eV. . . MeV). Cluster "transparency" characterized by practically undisturbed atom-cluster penetration is predicted to be an important reaction mechanism within a particular window of impact energies.PACS numbers: 31.70. Hq, 31.15.Ew, 34.50.Bw, 36.40.Ei Collisions with atomic clusters represent a relatively new branch of collision physics as compared to the well established fields of ion-atom collisions [1] and ion-solid interaction [2]. The study of cluster collisions is of particular interest and importance because it offers the possibility to tackle bridge-building questions (like the continuous transition from individual excitations in the elementary ion-atom collision to the macroscopic stopping power in solids) as well as fundamental problems (like phase transitions in finite systems). It is also an extremely challenging and complicated field as the comprehensive understanding of these collisions still requires the development of basically new techniques for both, large-scale (multi-parametric) experiment and manybody (quantum-mechanical) theory. In this request, the present situation resembles very much that of nuclear physics at the beginning of the 80's [3].Experimentally, large progress has been made, meanwhile, in the investigation of adiabatic cluster collisions where the reaction mechanism is determined by vibrational excitations only. Typical examples are the study of the vibrational energy transfer [4], the fusion between clusters [5], the formation of endohedral complexes [6], and the collision induced dissociation (CID) [7]. There is also a lasting interest to study non-adiabatic cluster collisions where electronic transitions occur. Experiments in this field concern the measurements of the charge transfer [8][9][10], ionization and electronic excitation [11], as well as the selective observation of vibrational and electronic excitations [12].Theoretically, adiabatic cluster collisions can be well described by quantum molecular dynamics (QMD) or molecular dynamics (MD) [13][14][15][16][17]. Also, isomeric [18] and solid-liquid phase transitions [19,20] [25,26] approaches where the atomic structure, and thus the vibrational degrees of freedom, are not taken into account. Recently, a general theory has been developed [27] which is able to describe simultaneously adiabatic and non-adiabatic collisions and, in particular, also the still completely unknown transition regime where both -electronic and vibrational -excitations occur. This so-called non-adiabatic quantum molecular dynamics (NA-QMD) [27] can also be used to study, for the first time, phase transitions i...

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Excitation and Relaxation in Atom-Cluster Collisions

Saalmann

Schmidt

1998

Phys. Rev. Lett.

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“…8 Neutralization of size-selected ionic clusters produces a narrow size distribution of clusters, but the vibrational energy of the neutralized clusters exceeds that of thermalized clusters at the temperature of the incoming cluster beam. 9 Deflection of a neutral cluster beam with an atomic beam has been used to separate a cluster beam with atomic resolution for small clusters ͑less than 10 rare gas atoms 10 or up to 13 molecules 11 ͒. Many applications require knowledge of the properties of larger clusters.…”

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Thermodynamic properties and homogeneous nucleation rates for surface-melted physical clusters

McClurg

Flagan

Goddard

1996

The Journal of Chemical Physics

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We predict the free energy of van der Waals clusters (F n ) in the surface-melted temperature regime. These free energies are used to predict the bulk chemical potential, surface tension, Tolman length, and vapor pressure of noble gas crystals. Together, these estimates allow us to make definitive tests of the capillarity approximation in classical homogeneous nucleation theory. We find that the capillarity approximation underestimates the nucleation rate by thirty orders of magnitude for argon. The best available experiments are consistent with our calculation of nucleation rate as a function of temperature and pressure. We suggest experimental conditions appropriate for determining quantitative nucleation rates which would be invaluable in guiding further development of the theory. To make the predictions of F n , we develop the Shellwise Lattice Search ͑SLS͒ algorithm to identify isomer fragments and the Linear Group Contribution ͑LGC͒ method to estimate the energy of isomers composed of those fragments. Together, SLS/LGC approximates the distribution of isomers which contribute to the configurational partition function ͑for up to 147-atom clusters͒. Estimates of the remaining free energy contributions come from a previous paper in this series.

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“…He However, these factors should not play a role in systems where a geometri cal change does not occur, since the electrons are largely delocalised, as is the case for metal clusters. Very recent experiments for Nan clusters which are produced by charge exchange from Nan + + Cs show indeed this behaviour [6], By carefully choosing the photon energy for ionisation, the fragmentation is found to be very small with the exception of Nag and Na21 for which the evaporation of one atom is mainly found. This result is attributed to the internal excitation of the size selected neutrals produced by the charge transfer and the relative stability of the products Na8 and Na20 because of the closed electron shells.…”

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confidence: 81%