The adsorption and condensation of Hg(CH 3) 2 on Pt(111) at 95 and 310 K: an UPS study

• Published in: Applied surface science Vol. 93; no. 1; pp. 17 - 24
• Main Author: Cassuto, A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 1996; Elsevier Science
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-gas interface; Surface physical chemistry; Gas solid adsorption; Chemisorption; Ultraviolet radiation; Platinum; Organic adsorbate; Gas solid interface; Metallic adsorbent; Photoelectron spectrometry; Transition metal; Experimental study; Condensation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(95)00322-3

We have studied the adsorption and condensation of dimethyl mercury at 95 and 310 K with UPS, using He I and He II excitation. The advantage of these two excitation energies is a distinct dependence of Hg and CH, CHg derived molecular orbitals on photon energy. The agreement between the multilayer and the gas phase spectra is good. In the monolayer range, at both temperatures, the positions of the carbon-induced orbitals are not representative of the intact molecule. At 95 K dissociative adsorption leads to the major formation of adsorbed methyl radicals. At 310 K, only a monolayer is adsorbed. In agreement with literature results, methyl radicals transform into ethylidyne (CCH 3) or CH 2 radicals and other C x H y species. We attribute a faint feature seen at 95 K and a strong one at 310 K, both located at about 4.8–4.9 eV below the Fermi level, to the possible formation of CC bonds. These ethylenic species may be the precursors of the polymeric deposit found previously during the homogeneous decomposition of dimethyl mercury, when wall effects are important.