NEXAFS Sensitivity to Bond Lengths in Complex MolecularMaterials: A Study of Crystalline Saccharides.

Detailedanalysis of the C K near-edge X-ray absorption fine structure(NEXAFS) spectra of a series of saccharides (fructose, xylose, glucose,galactose, maltose monohydrate, α-lactose monohydrate, anhydrousβ-lactose, cellulose) indicates that the precise determinationof IPs and σ* shape resonance energies is sensitive enough todistinguish different crystalline saccharides through the variationsin their average C–OH bond lengths. Experimental data as wellas FEFF8 calculations confirm that bond length variations in the organicsolid state of 10–2Å can be experimentallydetected, opening up the possibility to use NEXAFS for obtaining incisivestructural information for molecular materials, including noncrystallinesystems without long-range order such as dissolved species in solutions,colloids, melts, and similar amorphous phases. The observed bond lengthsensitivity is as good as that originally reported for gas-phase andadsorbed molecular species. NEXAFS-derived molecular structure datafor the condensed phase may therefore be used to guide molecular modelingas well as to validate computationally derived structure models forsuch systems. Some results indicate further analytical value in thatthe σ* shape resonance analysis may distinguish hemiketals fromhemiacetals (i.e., derived from ketoses and aldoses) as well as αfrom β forms of otherwise identical saccharides. [ABSTRACT FROM AUTHOR]