飞行时间质谱法研究Si(CH_3)_4分子的多光子解离和电离过程

Study on multiphoton dissociation and lonization process of tetramethylsilane using TOF mass spectroscopic method

采用超声分子束技术 ,以飞行时间 (TOF)质谱仪 ,于 410～ 371nm内 ,在不同能量的激光作用下 ,着重检测了气相Si(CH3 ) 4分子在 15个波长点处的多光子电离 (MPI)TOF质谱分布。根据实验结果 ,讨论了Si(CH3 ) 4可能的MPI机理。得到了Si+ 主要来自于母体分子及中性碎片的多光子解离—硅原子的共振电离、Si(CH3 ) + n(n=1,2 ,3)主要来自于中性碎片Si(CH3 ) n(n =1,2 ,3)的自电离、而Si(CH3 ) + 4则来自于母体分子的 (3+1)电离的结论。

Time-of-Flight (TOF) mass spectra distribution of the multiphoton dissociation and ionization of Si(CH 3) 4 in a supersonic molecular beam is investigated with a XeCl excimer laser(308nm) and a tunable dye laser(410-371nm) by a TOF mass spectrometer at the different laser energy irradiation.According to the experimental results,the possible multiphoton ionization (MPI) mechanisms of tetramethylsilane are discussed.We can conclude that the Si + ions might be mainly produced via a sequential photodissociation of parent molecules and neutral molecular fragments to form Si atoms first and followed by a nonresonant or resonant enhanced multiphoton ionization of Si atoms,Si(CH 3) + n(n=1,2,3) ions might be mainly produced via the photodissociation of Si(CH 3) 4 to from neutral molecular fragments Si(CH 3) n(n=1,2,3) first and followed by auto-ionization,whereas Si(CH 3) + 4 ions might be mainly produced from(3+1) ionization of parent molecules.