|Budget Amount *help
¥7,600,000 (Direct Cost : ¥7,600,000)
Fiscal Year 1996 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1995 : ¥5,300,000 (Direct Cost : ¥5,300,000)
For the surface strcuture analysis, it is generally of great importance to extract information from surfaces by eliminating intense signals from substrates. Surface XAFS spectroscopy and the x-ray standing-wave method require further exploitation concerning this subject. For instance, soft x-ray regions from Si K to Cl K edges by means of the fluorescence yield method are useful for 3d metal surfaces such as Ni and Cu, while it is impossible for heavier elements due to elastically scattered x rays.
In the polarization-dependent XAFS measurements, both experimental setups of s and p polarizations of incident x rays, and the total-reflection conditions for both setups allow us to perform the experiments. In this situation, however, a whole system of an ultrahigh vacuum chamber should be rotated, this being not practical. In the present study, we employed our previous system without much modification and tried to measure polarization dependent XAFS by applying normal-incidence grazing-emssion for s polarization and total-reflection-incidence normal-emission modes. Consequently, S K-edge XAFS spectra of Sadsorbed (less than 0.2 ML) Pd surfaces were successfully obtained. For s polarization, the fluorescence intensity in the total-reflection emission condition was found to be a little too low, and hence the solid angle was required to be enlarged compared to the complete total-reflection mode.
We investigated SO_2 and C_4H_4S on Pd (100) and Pd (111), whose surface structures were found to be noticeably different from those corresponding to the Ni and Cu surfaces studied previously. This successfully demonstrates the usefulness of the present experimental technique.