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          Institute: MPI für Dynamik und Selbstorganisation     Collection: Molekulare Wechselwirkung     Display Documents

ID: 711944.0, MPI für Dynamik und Selbstorganisation / Molekulare Wechselwirkung
Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling
Authors:Kornilov, Oleg; Toennies, Jan Peter
Date of Publication (YYYY-MM-DD):2015-02-21
Title of Journal:Journal of Chemical Physics
Start Page:074303-1
End Page:074303-11
Sequence Number of Article:074303
Title of Issue:7
Review Status:not specified
Audience:Not Specified
Abstract / Description:The size distribution of para-H2 (pH2) clusters produced in free jet expansions at a source temperature of T0 = 29.5 K and pressures of P0 = 0.9–1.96 bars is reported and analyzed according to a cluster growth model based on the Smoluchowski theory with kernel scaling. Good overall agreement is found between the measured and predicted, Nk = A  ka e−bk , shape of the distribution. The fit yields values for A and b for values of a derived from simple collision models. The small remaining deviations between measured abundances and theory imply a (pH2)k magic number cluster of k = 13 as has been observed previously by Raman spectroscopy. The predicted linear dependence of b −(a+1) on source gas pressure was verified and used to determine the value of the basic effective agglomeration reaction rate constant. A comparison of the corresponding effective growth cross sections σ 11 with results from a similar analysis of He cluster size distributions indicates that the latter are much larger by a factor 6-10. An analysis of the three body recombination rates, the geometric sizes and the fact that the He clusters are liquid independent of their size can explain the larger cross sections found for He.
External Publication Status:published
Document Type:Article
Communicated by:Folkert Müller-Hoissen
Affiliations:MPI für Dynamik und Selbstorganisation/Molekulare Wechselwirkung
External Affiliations:Max Born Inst, Max Born Str 2 A, D-12489 Berlin, Germany.
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