替国外留学同学问作业：
The surface of an aluminium sample was thoroughly cleaned by abrasion and immediately put into the sample chamber of an XPS spectrometer. Two prominent peaks in the spectrum occurred at binding energies of 72.3 and 75.0 eV, with relative intensities of 15.2 and 5.1 units, respectively. The sample was removed from the chamber, placed on a bench top, and then rerun a week later. The two peaks were again observed at 72.2 and 74.5 eV, but the intensities were 6.2 and 12.3 units, respectively. Sketch the XPS peaks (use different colour pens for before and after) and explain the phenomenon.
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