English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

The formation of dimers and trimers in free jet 4He cryogenic expansions

MPS-Authors
/persons/resource/persons173647

Schöllkopf,  W.
Emeritus Group Molecular Interactions, Max Planck Institute for Dynamics and Self-Organization, Max Planck Society;

/persons/resource/persons173691

Toennies,  J. P.
Emeritus Group Molecular Interactions, Max Planck Institute for Dynamics and Self-Organization, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)
There are no public fulltexts stored in PuRe
Supplementary Material (public)
There is no public supplementary material available
Citation

Bruch, L. W., Schöllkopf, W., & Toennies, J. P. (2002). The formation of dimers and trimers in free jet 4He cryogenic expansions. Journal of Chemical Physics, 117(4), 1544-1566.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0029-176B-9
Abstract
The formation of dimers, trimers, and tetramers in a free jet cryogenic expansion of 4He atoms has been studied by diffraction from a nanostructure transmission grating. The final average velocities, speed ratios and ambient temperatures of the expansions for source temperatures of 30, 12, and 6 K and source pressures between 0.1 and 80 bar were determined from time-of-flight measurements of the He atoms. The final mole fractions of the He2, He3, and He4 clusters in the beam were determined from the intensities of the corresponding first-order diffraction peaks for the same range of source conditions. For each source temperature, the final mole fractions of these small clusters first rise, pass through a maximum and then decrease with increasing source pressure. The processes leading to the formation of these clusters are simulated with a kinetic model that allows for density and temperature changes in the expanding beam. The best-fit three- body recombination rate constant for dimer formation increases by over three orders of magnitude as the thermal energy decreases from 1 K to 1 mK, in qualitative agreement with recent theories. (C) 2002 American Institute of Physics.