Two-photon resonant NFWM is a Doppler-freespectroscopy by using the narrow bandwidth of incident laser beams.
当用窄带宽的激光时，该技术对里德堡能级的窄光谱结构可以获得消多普勒的分辨率。
2
The Doppler-free saturated spectroscopy of the CO2 and SF6 molecules is investigated experimentally by using optoacoustic detection with a resonant multipass cell.
本文使用共振多程池的光声探测法对CO_2和SF_6分子的无多普勒饱和吸收光谱进行了实验研究。
3
The high resolution spectrum can be obtained through many methods, such as saturated absorption spectroscopy, Dopplerfree methods of two-photon spectroscopy, and etc.