Kosmidis C, Siozos P, Kaziannis S, Robson L, Ledingham K W D, McKenna P, Jaroszynski D A
Department of Physics, University of Ioannina, 45110 Ioannina, Greece.
J Phys Chem A. 2005 Feb 24;109(7):1279-85. doi: 10.1021/jp045500j.
The interaction of 1-iodopropane, 2-iodopropane, 1-iodobutane, 2-iodobutane, and 1-iodopentane with (5 x 10(13-)5 x 10(15) W/cm2) femtosecond laser fields is studied by means of a time-of-flight mass spectrometer. It is found that multiphoton ionization (MPI) and field ionization (FI) processes are involved in the molecular ionization. The contribution of these processes can be distinguished using the peak profile of the ions in the mass spectra. Thus, from the mass spectra of 2-iodoropane and 2-iodobutane, it is concluded that MPI processes are taking place even for Keldysh parameter values gamma approximately 0.3. The field ionization process depends on the characteristics of the molecular binding potential well and leads to an asymmetric charge distribution of the transient multiply charged parent ions. In the case of 1-iodobutane, the MPI processes lead to a stable doubly charged parent ion production with a laser intensity threshold higher than that found for I2+ ions. In addition, the isomers studied exhibit distinct differences in their mass spectra and their origin is discussed in detail.
利用飞行时间质谱仪研究了1-碘丙烷、2-碘丙烷、1-碘丁烷、2-碘丁烷和1-碘戊烷与（5×10¹³ - 5×10¹⁵ W/cm²）飞秒激光场的相互作用。研究发现分子电离过程涉及多光子电离（MPI）和场致电离（FI）。利用质谱中离子的峰形可以区分这些过程的贡献。因此，从2-碘丙烷和2-碘丁烷的质谱可以得出，即使对于凯尔迪什参数值γ约为0.3的情况，也会发生多光子电离过程。场致电离过程取决于分子束缚势阱的特性，并导致瞬态多电荷母离子的电荷分布不对称。在1-碘丁烷的情况下，多光子电离过程导致产生稳定的双电荷母离子，其激光强度阈值高于I₂⁺离子的阈值。此外，所研究的异构体在质谱中表现出明显差异，并对其来源进行了详细讨论。
