This set of assignments is internally quite consistent. However, it is at odds with the traditional assignment scheme which relied on silicon formal oxidation state to assign the observed photoemission features.

According to the traditional assignment scheme, if our structural assignment is correct, we should only observe the green, yellow and dark blue peaks (allowances have been made for hydrogen on Si). The light blue and pink features should not be present. Alternatively, taking our observed spectrum and attempting to assign the reaction products based upon the formal oxidation state fragments predicted using traditional method, one encounters many difficulties. Not least among them is the fact that the pink peak is midway between the accepted shifts for a "Si+2" and a "Si+3" fragment.

The assignments of the core-level features to specific structural fragments made in these papers has been controversial. Pasquarello, Hybertson, and Car have published a series of calculations which support the assignment model based upon Si formal oxidation state that has generally been used in the literature. These calculations are actually some of the very best evidence for the traditional assignment scheme.

Our lab is currently in the midst of a series of experiments using new classes of precursor compounds to generate model interfaces. We hope to shed additional light on this intriguing problem.