FIG. 3.

(a) Colored lines: sequential sulfur K-edge XAS spectra of l-cysteine in air-saturated pH 5 solution showing the progress of X-radiolysis. Inset: the points and fitted trends of (blue line) l-cysteine, (orange line) elemental sulfur, and (red line) R₃S⁺. The ±1σ uncertainty bars are within the points. (b) Sulfur K-edge XAS of (○) the tenth scan and (purple line) the fit. The fit components are (blue line) l-cysteine, (orange line) elemental sulfur, (brown line) cystine, and (red line) (CH₃)₃S⁺. Inset: the second derivative of (○) the tenth scan and (purple line) the fit. Cystine did not emerge until the third scan but exhibited complex behavior (see below).