Theory of photon interference X-ray absorption fine structure.

Area of Science:

• Materials Science
• Solid-State Physics
• X-ray Spectroscopy

Background:

• X-ray absorption fine structure (XAFS) provides insights into atomic environments.
• Photon interference effects in XAFS have been theoretically described but require experimental validation.
• Understanding atomic arrangements is crucial for materials characterization.

Purpose of the Study:

• To describe the theory of photon interference x-ray absorption fine structure (piXAFS).
• To explain the origin of piXAFS signals from coherent x-ray scattering.
• To demonstrate the utility of piXAFS for determining atomic distances in powdered samples.

Main Methods:

• Theoretical description of piXAFS based on coherent x-ray scattering.
• Analysis of spatial intensity variations within a sample.
• Comparison of piXAFS formulas with extended X-ray absorption fine structure (EXAFS) for powders.
• Application of Fourier transform to extract atomic distances.

Main Results:

• piXAFS produces spatial variations in x-ray intensity due to coherent scattering.
• The intensity at absorbing atoms varies with incident energy, generating piXAFS in extended absorption spectra.
• For powders, piXAFS formulas are equivalent to EXAFS, with Fourier transforms yielding neighbor atom distances.
• piXAFS in powders exhibits sharp structures attributed to crystal grain orientation averaging of x-ray standing wave effects.

Conclusions:

• piXAFS is a viable technique for probing local atomic structures.
• The theory explains sharp features in piXAFS spectra of powders.
• piXAFS offers an alternative or complementary method to EXAFS for atomic distance determination.