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Title: Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling

Abstract

The size distribution of para-H{sub 2} (pH{sub 2}) clusters produced in free jet expansions at a source temperature of T{sub 0} = 29.5 K and pressures of P{sub 0} = 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, N{sub k} = A k{sup a} e{sup −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 (pH{sub 2}){sub k} magic number cluster of k = 13 as has been observed previously by Raman spectroscopy. The predicted linear dependence of b{sup −(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{sub 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 theirmore » size can explain the larger cross sections found for He.« less

Authors:
;  [1]
  1. Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 17, 37077 Göttingen (Germany)
Publication Date:
OSTI Identifier:
22416145
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 142; Journal Issue: 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AGGLOMERATION; COMPARATIVE EVALUATIONS; CROSS SECTIONS; EXPANSION; HELIUM; HYDROGEN; KERNELS; LIQUIDS; PH VALUE; RAMAN SPECTROSCOPY; REACTION KINETICS; RECOMBINATION; THREE-BODY PROBLEM

Citation Formats

Kornilov, Oleg, and Toennies, J. Peter. Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling. United States: N. p., 2015. Web. doi:10.1063/1.4907601.
Kornilov, Oleg, & Toennies, J. Peter. Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling. United States. https://doi.org/10.1063/1.4907601
Kornilov, Oleg, and Toennies, J. Peter. 2015. "Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling". United States. https://doi.org/10.1063/1.4907601.
@article{osti_22416145,
title = {Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling},
author = {Kornilov, Oleg and Toennies, J. Peter},
abstractNote = {The size distribution of para-H{sub 2} (pH{sub 2}) clusters produced in free jet expansions at a source temperature of T{sub 0} = 29.5 K and pressures of P{sub 0} = 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, N{sub k} = A k{sup a} e{sup −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 (pH{sub 2}){sub k} magic number cluster of k = 13 as has been observed previously by Raman spectroscopy. The predicted linear dependence of b{sup −(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{sub 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.},
doi = {10.1063/1.4907601},
url = {https://www.osti.gov/biblio/22416145}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 7,
volume = 142,
place = {United States},
year = {Sat Feb 21 00:00:00 EST 2015},
month = {Sat Feb 21 00:00:00 EST 2015}
}