Calculations of the A(1) phonon frequency in photoexcited tellurium

Calculations of the Al phonon frequency in photoexcited tellurium are prese nted. The phonon frequency as a function of photoexcited carrier density an d phonon amplitude is determined. Recent pump-probe experiments are interpr eted in light of these calculations. It is proposed that, in conjunction wi th measurements of the phonon period in ultrafast pump-probe reflectivity e xperiments, the calculated frequency shifts can be used to infer the evolut ion of the density of photoexcited carriers on a subpicosecond time scale. [S0031-9007(99)09219-4].