355nm激光作用下Si(CH3)4分子的MPI质谱研究

在 35 5nm的激光作用下 ,利用扩散分子束技术和四极质谱装置相结合研究了气相Si(CH3 ) 4分子多光子电离 (MPI)质谱分布。测量了Si(CH3 ) + 4,Si(CH3 ) + 3 ,Si(CH3 ) + 2 ,Si(CH3 ) + 及Si+ 离子的激光光强指数 ,检测了这 5种碎片离子的信号强度占总信号强度的分支比随光强的变化关系。据此 ,讨论了该分子MPI过程可能经历的通道 ,得到了Si+ 主要来自于母体分子的多光子解离—硅原子的电离 ,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 ,Si(CH3 ) + 4来自于母体分子的 (3+1)电离的结论

Multiphoton Ionization Mass Spectra Study of Tetramethylsilane at 355 nm Laser Radiation

Multiphoton ionization (MPI) mass spectra distributions of tetramethylsilane in gaseous phase are investigated using a quadrupole mass spectrometer and a pulsed molecular beam at 355 nm laser radiation. The dependence of the signal intensity of the ions Si(CH 3) + n (n=1,2,3,4) and Si + on laser power is measured. The fractions of signal Si(CH 3) + n(n=1,2,3,4) and Si + vs. laser intensity are obtained. According to these, the possible MPI channels and the chemical kinetics mechanisms of this molecule are discussed. The conclusion is gained that Si + ions might be mainly produced via a sequential photo-dissociation to form Si atoms first and followed by a multiphoton ionization of Si atoms, Si(CH 3) + n(n=1,2,3) ions might be mainly produced from self-ionization of neutral fragments Si(CH 3) n, and the Si(CH 3) + 4 ions might be produced from (3+1) ionization of parent molecules.