Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates

The effects of gas‐phase collisions in mixtures of gases rapidly desorbed from surfaces are studied using direct Monte Carlo techniques. The results are compared with the effects observed in the desorption of pure gases under similar conditions. The translational energy distribution of the desorbed...

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Main Authors:	Ibrahim Ali , Noorbatcha, Lucchese, Robert R., Zelri, Yehuda
Format:	Article
Language:	English
Published:	American Institute of Physics (AIP) 1988
Subjects:	QD Chemistry
Online Access:	http://irep.iium.edu.my/37068/ http://irep.iium.edu.my/37068/ http://irep.iium.edu.my/37068/ http://irep.iium.edu.my/37068/1/JCP1988.pdf

id	iium-37068
recordtype	eprints
spelling	iium-370682014-06-26T05:32:31Z http://irep.iium.edu.my/37068/ Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates Ibrahim Ali , Noorbatcha Lucchese, Robert R. Zelri, Yehuda QD Chemistry The effects of gas‐phase collisions in mixtures of gases rapidly desorbed from surfaces are studied using direct Monte Carlo techniques. The results are compared with the effects observed in the desorption of pure gases under similar conditions. The translational energy distribution of the desorbed particles are found to deviate from the Boltzmann distribution and are found to be well represented by ellipsoidal Boltzmann distributions. In this respect the rapid desorption process is found to have similarities to the expansion of gases in nozzle sources. The influence of mass, internal degrees of freedom, and surface coverage of the adsorbates on the focusing, accelerating, and cooling effects due to gas‐phase collisions are analyzed. The presence of molecules with active internal degrees of freedom is found to increase the average number of collisions experienced by the rapidly desorbed molecules. However, the influence of this increased number of collisions on the focusing effects due to gas‐phase collisions is less pronounced compared to the focusing effects due to collisions between the desorbed atoms. In a gas mixture containing molecules as the minor constituents (10%) and atoms as the major constituents (90%), atoms are found to be more focused towards the surface normal than the molecules and the mean translational energies of the molecules are found to be less than those calculated in the desorption of pure molecules under similar conditions. The presence of atoms in the desorbed gas mixture is found to increase the most probable speed of the desorbing molecules and this accelerating effect increases with decrease in the mass of the coadsorbed atoms. The light atoms are found to be more efficient than heavy atoms in cooling the internal degrees of freedom. American Institute of Physics (AIP) 1988-10-15 Article PeerReviewed application/pdf en http://irep.iium.edu.my/37068/1/JCP1988.pdf Ibrahim Ali , Noorbatcha and Lucchese, Robert R. and Zelri, Yehuda (1988) Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates. Journal of Chemical Physics , 89 (8). pp. 5251-5263. ISSN 0021-9606 http://scitation.aip.org/content/aip/journal/jcp/89/8/10.1063/1.455616 10.1063/1.455616
repository_type	Digital Repository
institution_category	Local University
institution	International Islamic University Malaysia
building	IIUM Repository
collection	Online Access
language	English
topic	QD Chemistry
spellingShingle	QD Chemistry Ibrahim Ali , Noorbatcha Lucchese, Robert R. Zelri, Yehuda Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
description	The effects of gas‐phase collisions in mixtures of gases rapidly desorbed from surfaces are studied using direct Monte Carlo techniques. The results are compared with the effects observed in the desorption of pure gases under similar conditions. The translational energy distribution of the desorbed particles are found to deviate from the Boltzmann distribution and are found to be well represented by ellipsoidal Boltzmann distributions. In this respect the rapid desorption process is found to have similarities to the expansion of gases in nozzle sources. The influence of mass, internal degrees of freedom, and surface coverage of the adsorbates on the focusing, accelerating, and cooling effects due to gas‐phase collisions are analyzed. The presence of molecules with active internal degrees of freedom is found to increase the average number of collisions experienced by the rapidly desorbed molecules. However, the influence of this increased number of collisions on the focusing effects due to gas‐phase collisions is less pronounced compared to the focusing effects due to collisions between the desorbed atoms. In a gas mixture containing molecules as the minor constituents (10%) and atoms as the major constituents (90%), atoms are found to be more focused towards the surface normal than the molecules and the mean translational energies of the molecules are found to be less than those calculated in the desorption of pure molecules under similar conditions. The presence of atoms in the desorbed gas mixture is found to increase the most probable speed of the desorbing molecules and this accelerating effect increases with decrease in the mass of the coadsorbed atoms. The light atoms are found to be more efficient than heavy atoms in cooling the internal degrees of freedom.
format	Article
author	Ibrahim Ali , Noorbatcha Lucchese, Robert R. Zelri, Yehuda
author_facet	Ibrahim Ali , Noorbatcha Lucchese, Robert R. Zelri, Yehuda
author_sort	Ibrahim Ali , Noorbatcha
title	Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
title_short	Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
title_full	Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
title_fullStr	Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
title_full_unstemmed	Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
title_sort	effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates
publisher	American Institute of Physics (AIP)
publishDate	1988
url	http://irep.iium.edu.my/37068/ http://irep.iium.edu.my/37068/ http://irep.iium.edu.my/37068/ http://irep.iium.edu.my/37068/1/JCP1988.pdf
first_indexed	2023-09-18T20:53:10Z
last_indexed	2023-09-18T20:53:10Z
_version_	1777410129377886208

Effects of gas‐phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates

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