Fig. 1. Schematic diagram of three-level model of helium

Fig. 2. Attosecond transient absorption spectroscopy

Fig. 3. The response function S（τ） at specific frequencies and the corresponding wavelet analysis

Fig. 4. Wavelet analysis amplitude vs. delay time for different frequencies

Fig. 5. In the case of $\delta =$-0.01 a.u.， the response function S（τ） at specific frequencies and the corresponding wavelet analysis

Fig. 6. In the case of $\delta =$-0.01 a.u. and ${\varphi }_{\mathrm{C}\mathrm{E}\mathrm{P}}=\mathrm{\pi }/\mathrm{2}$， the response function S（τ） at specific frequencies and the corresponding wavelet analysis