Coulomb enhancement of above-band-gap pump-continuum probe spectroscopy

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Abstract
The effect of Coulomb attraction between a photoexcited electron-hole pair on femtosecond pump-continuum probe nonlinear absorption for above-band-gap photoexcitation is discussed. It is shown that in pump-continuum probe experiments the enhancement of the optical matrix element resulting from the Coulomb interaction is strongest near the band gap for the split-off transition and explains the experimentally observed large change in absorption at 1.78 eV. The enhancement factor summed over all transitions must be included to correctly match the experimental results.