AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA3
Negative Ion Enhancement in Transport of Low Energy F@super -@ Ions Through Rare-Gas (Xe) Films

Tuesday, November 3, 1998, 2:40 pm, Room 314/315

Session: Photon- and Electron-Induced Chemistry
Presenter: Q.B. Lu, Rutgers, The State University of New Jersey
Authors: Q.B. Lu, Rutgers, The State University of New Jersey
T.E. Madey, Rutgers, The State University of New Jersey
Correspondent: Click to Email
As part of a program to understand the energy-transfer and charge-transfer processes that affect ion transport through surface layers, we have studied the transmission of low energy (<10 eV) F@super -@ through ultrathin Xe films (up to several monolayers (ML)). The ions are created by electron-stimulated desorption from CF@sub 2@Cl@sub 2@-covered Ru(0001) at ~25 K, and their yields and angular distributions are measured by a digital detector with time-of-flight (TOF) capability. Our new findings include the following. (i) A strong enhancement is observed as 0.5~1.0 ML Xe is deposited onto a fractional monolayer CF@sub 2@Cl@sub 2@ covered surface, and most strikingly, the magnitude of enhancement depends on the intensity of incident electron current. (ii) The negative ion enhancement decreases with increasing precoverage of CF@sub 2@Cl@sub 2@. (iii) The angular distribution of F@super -@ is centered along the surface normal under all conditions. These results will be discussed in terms of several different mechanisms: dielectric screening of the Xe overlayer, coupling between an anionic exciton (Xe@super *-@) and a [CF@sub 2@Cl@sub 2@]@super *-@ state, and charge transfer between a Xe@super *-@ and a F atom.