Fig. 4. Phase-resolved real-time dephasing of a Fano resonance in argon.

a Excitation scheme for preparation and probing of the Ar 3s-6p inner subshell-valence coherence. b Decay of the 3s-6p coherence in the time domain, with real part of the complex signal S = A(τ)e^iϕ(τ) (blue) and its decomposition into amplitude A(τ) (green) and phase ϕ(τ) (dashed-gray). c Linear susceptibility of the process obtained from Fourier transform of the signal: Absorption (blue) and dispersion (red) curve compared to the Fano lineshape from ref. ²⁹ (black) and spectral phase ϕ(ω) (dashed gray), exhibiting a characteristic phase jump at the resonance of ≈π.