摘要
Based on the interference between two two-photon processes,we reported a four-level ultrafast modulation spectroscopy in Na vapor,where 3S,3P,5S,and 4D formed a four-level system.We studied the temporal behavior of the four-wave mixing signal intensity and obtained signal modulation with period 25fs,corresponding to the splitting between 5s and 4D.This technique can achieve Doppler-free precision in the measurement of the energy level splitting between two excited states which are dipolar forbidden from the ground state.
基金
Supported by the National Natural Science Foundation of China under Grant No.69578030.
