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Microstructural evolution of an as-quenched amorphous Se sample during ball milling was investigated by use of x-ray diffraction, a differential scanning calorimeter, infrared and Raman spectroscopy, as well as x-ray photoemission spectroscopy. It was found that the as-quenched amorphous Se is crystallized completely into a nanocrystalline trigonal Se phase after milling for 30 min. Further milling of the as-milled nanocrystalline trigonal Se resulted in a transformation into another amorphous Se phase, which exhibits a lower crystallization temperature and a smaller crystallization enthalpy compared to those for the as-quenched amorphous Se according to thermal analysis. Infrared and Raman spectroscopy measurements revealed that the as-milled amorphous Se is mainly composed of Se-n polymeric chains that are fundamentally different from the as-quenched amorphous Se in which the Se-8 ring structure is predominant. However, despite the phase evolution and changes in molecular structure in Se, x-ray photoemission measurements indicated that no detectable changes in electronic properties (e.g. the density of valence states, the binding energies of core levels, and the characteristic energy loss functions) were observed among different states of Se samples. [S0163-1829(98)00417-2].