We show experimentally that spectral phase manipulation of ultrashort extreme-uv light pulses can induce and control coherent transient excitation of the $\mathrm{He}\left(1s3p\right)$ excited state by the nonresonant components of the broadband extreme-ultraviolet light. The spectral phase manipulation of the 15th harmonic of an intense $805\mathrm{nm}$, $80\mathrm{fs}$ pulse is achieved by propagation of the euv light through a variable optical density of He gas. The acquired spectral phase due to the dispersive interaction of the off-resonance components in the euv pulse with the $\mathrm{He}\left(1s3p\right)$ resonance enhances and modifies the transient excitation. The temporal evolution of the coherently prepared transient $\mathrm{He}\left(1s3p\right)$ amplitude is probed by ionization to the continuum with a $400\mathrm{nm}$, $80\mathrm{fs}$ pulse.

• Received 16 July 2005

DOI:https://doi.org/10.1103/PhysRevA.73.021805