Title: Direct frequency-comb spectroscopy of $6S_{1/2}$-$8S_{1/2}$ transitions of atomic cesium,
Abstract: Direct frequency-comb spectroscopy is used to probe the absolute frequencies
of $6S_{1/2}$-$8S_{1/2}$ two-photon transitions of atomic cesium in hot vapor
environment. By utilizing the coherent control method of temporally splitting
the laser spectrum above and below the two-photon resonance frequency,
Doppler-free absorption is built in two spatially distinct locations and imaged
for high-precision spectroscopy. Theoretical analysis finds that these
transition lines are measured with uncertainty below $5\times10^{-10}$, mainly
contributed from laser-induced AC Stark shift.