Studies of thin films and surfaces with optical harmonic generation and electron spectroscopy

Abstract

Optical second harmonic generation (SHG) and sum frequency generation (SFG) were used to study C{sup 60} thin solid films (low energy ED forbidden electronic excitations), and electron spectroscopy was used to study organic overlayers (xylenes) on Pt(111). Theory of SHG from a thin film is described in terms of surface and bulk contributions as well as local and nonlocal contributions to the optical nonlinearities. (1)In situ SHG data on C{sub 60} films during UHV film growth can be described in terms of only nonlocal contributions to both surface and bulk nonlinear susceptibilities. Microscopic origin of SHG response is discussed in terms of electric quadrupole and ED transitions of C{sub 60}. (2)Adsorption and thermal decomposition of ortho- and para-xylene on Pt(111) is studied using HREELS, LEED, AES, and thermal desorption spectroscopy. We have observed preferential decomposition of the methyl groups which leads to distinct decomposition pathways for ortho- and para-xylene on Pt(111).