2 CHEMISORBED SPECIES OF O-2 ON AG(110)

Using electron energy loss spectroscopy and thermal desorption spectro scopy, we show that the adsorption of O-2 on Ag(110) creates two disti nct molecular chemisorbed species. Only one, alpha-O-2, can be accesse d by warming (converting) the physisorbed state and, unlike beta-O-2, does not dissociate to atomic O at higher temperatures. With the aid o f molecular dynamics simulations, we propose that the lateral interact ion between neighboring O-2 molecules in a dense physisorbed layer sta bilizes the appropriate precursor orientation to enable the conversion into alpha-O-2 to occur.