AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA1
Hot Ethene Desorption by Dissociative Electron Attachment of Adsorbed Halocarbons

Tuesday, November 3, 1998, 2:00 pm, Room 309

Session: Morton M. Traum Student Award Session
Presenter: A.S.Y. Chan, University of Nottingham, United Kingdom
Authors: A.S.Y. Chan, University of Nottingham, United Kingdom
R.G. Jones, University of Nottingham, United Kingdom
Correspondent: Click to Email
The electron stimulated reactions of adsorbed 1,2-dihalocarbons have been studied by measuring the time-of-flight (TOF) velocity distributions of the ethene product ejected from the surface. Both 1,2-dichloroethane (DCE) and 1-bromo-2-chloroethane (BCE) have been found to undergo dissociative electron attachment from secondary electrons generated by a pulsed 2 keV electron beam impinging on the Cu(111) surface, leaving chemisorbed halogens and ethene desorbing in the gas phase. The TOF distributions of the ethene product from both adsorbate molecules are quite similar; both exhibit a bimodal distribution with a hyperthermal channel of ~ 1200 K and a slow channel of ~ 200 K. When the distributions obtained from identical coverages of DCE and BCE are compared, a consistently smaller intensity of the slow channel is observed from the latter molecule. This slow component appears to grow with increasing number of adsorbed layers, indicating that it is most likely due to ethene molecules that have thermalised by interactions with the adsorbate. By comparing the possible dissociation dynamics of the two molecules, we discuss the possibility that a direct dissociation of the adsorbed molecule after electron capture, rather that a surface-mediated energy transfer mechanism, may be responsible for the high translational energy of the hyperthermal ethene.