获得了在超声分子束条件下,305.0～325.0 nm波长范围内三氯乙烯及四氯乙烯的(2+1)共振增强多光子电离/飞行时间质谱(REMPI-TOFMS)。在此波段,三氯乙烯分子通过双光子跃迁至3d里德堡态再吸收一个光子电离而后解离成CCl+等碎片离子,四氯乙烯分子则经历了π到3p德堡态的(2+1)多光子过程。实验分别获得两种氯代乙烯分子电离解离后产生的碎片离子CCl+的分质量光谱及光强指数。研究表明,该波长范围内三氯乙烯的最佳检测波长为310.8 nm,四氯乙烯的最佳检测波长为322.5 nm。根据CCl+信号强度与样品浓度的线性关系,实现了这两种环境污染物的低浓度探测,探测限可达到μg/L量级。

The (2+1) resonance-enhanced multiphoton ionization/time of flight mass spectra (REMPI-TOFMS) of trichloroethylene and tetrachloroethylene are obtained in the range 305.0～325.0 nm. In this wavelength range, trichloroethylene molecules firstly absorb two-photons to their 3d Redberg state and tetrachloroethylene molecules firstly absorb two-photons to their 3p Redberg state, then the excited molecules further absorb additional photon energy and get ionized. The mass-resolved excited spectra and laser power index of fragment ions CCl+ are obtained. The measurement shows that 310.8 nm is the suitable wavelength for detection of trichloroethylene and 322.5 nm is the suitable wavelength for detection of tetrachloroethylene in this wavelength range. The detection limits of chloroethylenes at μg/L concentration range are presented.