Phase transformation in laser-induced micro-explosion in olivine (Fe,Mg)₂SiO₄

We show that micro-explosions generated by tightly focused single pulses of a femtosecond laser in olivine have produced change of iron valence state. Chemical and structural changes were investigated using synchrotron X-ray spectroscopy, and Raman scattering. Near edge X-ray absorption fine structure (NEXAFS) spectra from laser-affected zone of olivine crystal indicate a modified chemical bonding and a possible formation of regions containing a new crystalline phases of iron. Raman scattering from the laser-affected zone regions reveals loss of crystalline order and formation of a mixture of nano-crystallites due to melting and re-solidification of olivine. These results indicate that spatial separation between ions of different mass occurs in hot, highly excited olivine. The present study confirms that this mechanism may present a general pathway toward creation of novel crystalline and amorphous nano-materials using fs laser-induced confined micro-explosions. Near edge X-ray absorption fine structure spectra from laser-affected olivine show that micro-explosion generated by a femtosecond pulse produces change of iron valence state. This result indicates that spatial separation between ions of different mass occurs in hot, highly excited olivine. This mechanism presents a pathway toward new nano-materials.