Caloric curves of small fragmenting clusters.
The kinetic energy release distribution of neutral atoms emitted from photoexcited clusters Sr(+)(n) with n=4-15, has been obtained by time-of-flight velocity dispersion. The deduced temperature is plotted as a function of the excitation energy. For small sizes n<7 a general increase is observed. For cluster sizes larger than n=9, the deduced caloric curves first increase, and then show evidence of a plateau regime as excitation energy increases. This limiting temperature in neutral atom ejection is consistent with a bound cluster-vapor phase transition in a microcanonical system.
Bréchignac
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Laboratoire Aimé Cotton CNRS, Université Paris-Sud, Bâtiment 505, F-91405 Orsay Cedex, France.
Cahuzac
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Concina
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Leygnier
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