Murakami Masanao, Tanaka Michinori, Yatsuhashi Tomoyuki, Nakashima Nobuaki
Department of Chemistry, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585, Japan.
J Chem Phys. 2007 Mar 14;126(10):104304. doi: 10.1063/1.2713107.
The authors compared circularly and linearly polarized lights in the ionization and fragmentation of anthracene, using 800 nm femtosecond laser pulses at intensities of 10(13)-10(15) W cm-2. Singly and doubly charged intact molecular ions as well as numerous fragment ions were observed in the mass spectra, which were investigated as a function of laser intensity and polarization. At comparable intensities above the saturation threshold for complete ionization, the fragmentation pathways are enhanced with a circularly polarized field compared to a linearly polarized field. Resonant excitation of the molecular cation through the 2Au<--2Bg transition is proposed to be the initial step to ion fragmentation. The circularly polarized field interacts with a larger fraction of the randomly oriented molecules than the linearly polarized field, and this is considered to be the reason for the enhanced fragmentation brought about by circularly polarized light.
作者使用强度为10(13)-10(15) W cm-2的800 nm飞秒激光脉冲，比较了圆偏振光和线偏振光对蒽的电离和碎片化的影响。在质谱中观察到了单电荷和双电荷的完整分子离子以及大量碎片离子，并研究了它们作为激光强度和偏振的函数。在高于完全电离饱和阈值的可比强度下，与线偏振场相比，圆偏振场增强了碎片化途径。分子阳离子通过2Au<--2Bg跃迁的共振激发被认为是离子碎片化的初始步骤。与线偏振场相比，圆偏振场与更大比例的随机取向分子相互作用，这被认为是圆偏振光导致碎片化增强的原因。
