Figure 4. Soft x-ray irradiation effect on Li₂O₂ revealed by Li K-edge XAS spectra.

(top) The XAS spectrum of Li₂O₂ evolves towards that of the Li₂O upon increasing the radiation exposure. The top spectrum is the first one collected from spot A. From top to bottom, the first ten spectra were collected every ten minutes, with an hour of x-ray exposure at the same spot to maximize the dosage, then the measurements resumed with again ten minute each spectrum. The bottom red spectrum is collected on Li₂O for comparison. (bottom) Li₂O₂ Li K-edge XAS spectrum measured from a new spot B on the same sample stored in the ultra-high vacuum chamber for one week.