PHOTON-STIMULATED ION DESORPTION FROM DCOO SI(100) NEAR THE O K-EDGE/

Photon-stimulated ion desorption from deuterated formic acid chemisorb ed on Si(100) has been studied using pulsed synchrotron radiation in t he energy region of the oxygen Is electron excitation. The O Is electr ons of hydroxyl oxygen and carbonyl oxygen could be selectively excite d in the O K-edge region because the chemical environments are differe nt. It is found that the CDO yield is enhanced at the O Is(C-O)-->sig ma(C-O) resonance and the CD+ yield at the O Is(C=O)-->sigma*(C-O) re sonance. The results indicate that inn desorption is related both to t he antibonding character of excited molecular orbitals and the local c haracter of core hole orbitals. (C) 1997 Elsevier Science B.V.