NIXSW

It was nevertheless important to verify this unusual structure by independent experimental methods. This was achieved by a normal-incidence x-ray standing wave (NIXSW) [45, 49] study in 1992, a LEED study [17] in 1994, and in an STM study [50] in 1995. Fig. 7 shows a comparison of experimental LEED spectra with spectra calculated for the Al(l 11)—( 3 x, /3)/ 30°—Na structure with Na atoms adsorbed in substitutional sites. 

Milligan PK, Murphy B, Lennon D, Cowie BCC, Kadodwala M (1999) Probing the adsorption structure of a multifunctional organic molecule a NIXSW and NEXAFS study of 3-chlorothiophene in Cu(lll). SurfSci 430 45-54... 

Acronyms XSW X-ray standing wave, NIXSW normal incidence X-ray standing wave. 

XSW was initially restricted to very high quality single crystals such as semiconductors due to its extreme sensitivity to the degree of crystal perfection, although the recent development of NIXSW techniques that have wider angular rocking curves, (and are hence less sensitive to crystal perfection), have now made it applicable to conventional single crystal metallic samples. 

Recently, the method has been combined with an energy-resolved detection of the corresponding photoelectrons, which makes it possible to determine the geometric position of one type of atom in different chemical environments separately. Eor example in the case of PF3 adsorbed on Ni(lll) this so called chemical-shift normal incidence X-ray standing wave (CS-NIXSW) technique makes it possible to determine the position of three different P-species independently [99JAC]. 

A clever extension of the NIXSW method has been introduced by the Fadley group [83] synthetic multilayer films of typically 40 repeat units of [B4C/W] grown... 

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