Theoretical And Experimental Research Of Spectra Of Iodine Molecule By Degenerate Four-Wave Mixing

Degenerate four-wave mixing(DFWM) spectroscopy has the advantages of high detection sensitivity,high spectral resolution,good time and space resolution,can be detected for distance,without suffering of severe quenching problems at high pressure,which has been widely used to detect trace of atoms, molecular and radical,received a great deal of attention in combustion diagnosis.This paper we summarized some basic theory of the degenerate four-wave mixing, selected the theoretical model of DFWM, calculated line shape of DFWM spectra versus laser saturation, and DFWM signal intensity versus laser intensity with Matlab. Finally calculated laser intensity when it had maximum DFWM signal.We also compared two kinds of DFWM geometry , and determined which DFWM geometry we use in our experiment.In our experiment,554-555nm DFWM spectrum of iodine has been measured by forward geometry of DFWM.And then we choice two resonance wavelengths of iodine,measured signal intensity of I₂ DFWM versus total input intensity,and line shape of I₂ DFWM spectra versus total input intensity under normal temperature and pure iodine,then analysis the experiment results with theorys. Studied the effect of gas on I₂ DFWM spectrum, Measured I₂ DFWM signal intensity versus total input laser energy for various buffer gas pressures. The results show that the buffer gas pressure could increase I₂ DFWM signal saturation energy. I₂ DFWM signal intensity versus the buffer gas pressure for various total input laser energy spectrum, shown in the lower total input laser energy spectrum, buffer gas had a quenching effect on the DFWM. When the pump higher energy spectrum, the buffer gas I₂ has enhanced on the DFWM. Also studied line shape of I₂ DFWM spectra versus total input intensity under normal temperature and Air as buffer gas. According to theorys we gave a reasonable explanation of the additional air impact with I₂ DFWM spectra.