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Method for the measurement of diffusion coefficients of labile gas‐phase species: The diffusion coefficient of O( 3 P ) in He at 294 K
Author(s) -
Plumb I. C.,
Ryan K. R.,
Barton N. G.
Publication year - 1983
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550151012
Subject(s) - chemistry , helium , diffusion , analytical chemistry (journal) , atomic physics , torr , dispersion (optics) , molecular diffusion , thermodynamics , chromatography , physics , optics , metric (unit) , operations management , organic chemistry , economics
The dispersion of a pulse of O( 3 P ) atoms in flowing helium has been analyzed by a modification of Taylor's method in order to determine the diffusion coefficient. Atoms of O( 3 P ) were produced in a flowing stream of helium by a pulsed microwave discharge of molecular oxygen. After traversing a known length of the flow tube, the arrival time distribution of the O( 3 P ) atoms was obtained using a mass spectrometer. The value obtained for D 0 at 294 K, where D 0 = D [He], is (2.40 ± 0.06) × 10 19 cm −1 ·s −1 , which corresponds to a diffusion coefficient of (731 ± 18) cm 2 /s at 1 torr. In addition to D 0 , analysis of the arrival time distributions gives an estimate of the mean flow velocity for O atoms in helium. There was no significant difference between the value of the velocity found this way and that obtained from the mean bulk gas flow measurement. Thus for this system there is no evidence for a chromatographic effect for O( 3 P ) atoms on the walls of the flow tube.