光外差速度调制分子离子激光光谱

Optical Heterodyne Velocity Modulation Molecular Ions Laser Absorption Spectrum

通过求解分子离子在电场中速度分布,获得了小调制度近似下,速度调制分子离子光谱信号强度与调制度成正比、线型为Gauss线型的一次微分线型;理论分析了光外差频率调制光谱的线型亦为Gauss线型的一次微分线型,并分析了该两种光谱技术的优缺点.基于此,提出了光外差速度调制分子离子激光光谱技术,理论分析表明该技术测量获得的谱线线型为Gauss线型的二次微分线型,比纯速度调制测量灵敏度提高大约100倍.它不导致复杂的谱线线型,非常适合进行分子离子的振转光谱测量.

By solving the distribution of velocity of molecular ions in the electrical field, it is deduced that the spectral intensity is linear to the velocity modulation depth and the line shape is the 1^(st) deviation of Gaussian profile in the small modulation limit; the line shape of frequency modulation spectroscopy is also the 1^(st) deviation of Gaussian profile, and the features of these two spectroscopy are summarized that velocity modulation spectroscopy is selective to molecular ions while immune to neutrals and optical heterodyne spectroscopy is immune to laser amplitude noise. Therefore, optical heterodyne velocity modulation molecular ions laser absorption spectroscopy is presented in the paper, and theoretical analysis indicates that its spectral line shape is the 2^(nd) deviation of Gaussian profile and it increases the detection sensitivity which is 100 times as high as that of pure velocity modulation spectroscopy. It doesn't complicate the spectral line shape and is most suitable for detecting the ro vibrational spectrum of molecular ions.