Collisions of slow hydrocarbon ions CD4+, CD5+, C2D4+, and C2H5+ with room temperature and heated tungsten surfaces

The interaction of selected hydrocarbon ions with tungsten surfaces, at room temperature and heated to 600 °C, was investigated at incident energies of 15-45 eV and at incident angles of 60° and 45° to the surface normal. Results were compared with earlier published studies on carbon (highly oriented pyrolytic graphite, HOPG) surfaces. The ion survival probability for both room temperature and heated W surfaces was in general a factor of 2-15 smaller than on carbon (HOPG) surfaces and tended to be smaller for radical cations (CD4+ and C2D4+) than for closed-shell ions (CD5+ and C2H5+). Mass spectra, translational energy distributions and angular distributions of product ions from collisions with W surfaces were very similar to distributions estimated earlier for carbon (HOPG) surfaces. Mass spectra of radical cations on room temperature surfaces indicated fragmentation of projectile ions and reactions (of H-atom transfer and carbon-chain build-up) with hydrocarbons on the surface. Closed-shell ions showed only fragmentation processes. On heated surfaces, only fragmentations of the incident projectile ions were observed. The similarity of results on heated tungsten and HOPG surfaces may be due to substantial coverage of W surfaces with tungsten carbides originating from cracked surface hydrocarbons.