Ultrafast change in optical properties of gallium: the evidence of a new transient state of matter

Summary form only given. The fundamental reasons behind the rapid reflectivity rise of gallium films deposited on fused silica substrates have been considered in detail. The increase of reflectivity from the value of /spl sim/60%, typical for crystalline /spl alpha/-Ga, to 70-75% in /spl sim/2 ps has been measured by the probe-pump technique using Ti:sapphire laser (150 fs, 800 nm). After the initial 2-ps rise the reflectivity approaches the value characteristic for liquid Ga of /spl sim/85% in more than 100 ps. The developed self-consistent theoretical model considers the laser-gallium interaction process, absorption, and heating of the conduction electrons. The induced transient changes of the optical properties of gallium layer are in qualitative agreement with the experimental data.