Core-level attosecond transient absorption spectroscopy of laser-dressed solid films of Si and Zr

We investigated experimentally as well as theoretically the ultrafast response of the wave function of the conduction band (CB) of Si and Zr to a near-infrared laser field using extreme ultraviolet (XUV) absorption spectroscopy in the spectral range of 80--220 eV. The measured dynamics of the XUV transmission demonstrates that the wave function of the CB follows the electric field of the dressing laser pulse. In these terms, laser dressing was earlier mainly studied on gases. Measurements with two-femtosecond and 200-attosecond temporal steps were performed in the vicinity of the $\mathrm{Si}\phantom{\rule{0.16em}{0ex}}{L}_2,3$ edge near 100 eV, the $\mathrm{Si}\phantom{\rule{0.16em}{0ex}}{L}₁$ edge near 150 eV, and the $\mathrm{Zr}\phantom{\rule{0.16em}{0ex}}{M}_4,5$ edge near 180 eV. The observed changes were dependent on the core states being excited by the XUV probe pulse. At the $2p$ to CB transitions of Si, the XUV transmission increased via the effect of the dressing laser pulse, while at the $2s$ to CB transition of Si and the $3d$ to CB transition of Zr, the XUV transmission decreased. Furthermore, beats between the transition from $2{p}_1/2$ and $2{p}_3/2$ levels of Si and from $3{d}_3/2$ and $3{d}_5/2$ levels of Zr were observed with 20.7 fs and 3.6 fs periods.