Transient Dielectric Function of Fs-Laser Excited Bismuth.

We present time-resolved dual-angle single-wavelength pump-probe study of the reflectivity of femtosecond laser excited bismuth crystal. The recovered real and imaginary parts of the dielectric function show complex a transition to a new quasi-stable excited state at about 20 ps. This state lasts for about 4 ns after the excitation and is not an intermediate state between the solid and the liquid phase. The results suggest that the photo-excited state does not correspond to neither a warm nor a liquid phase, and open general questions on photoexcited phase transition. [ABSTRACT FROM AUTHOR]