Femtosecond laser ablation for simultaneous atomization and ionization (fs-SAI) of large organic molecules

Abstract

By applying the femtosecond laser ablation technique, large organic molecules were simultaneously atomized and ionized on solid substrates, namely, silicon, aluminum and glass. All the atomic species in the sample molecule were observed as being mono-atomic ions while no significant ion signals of larger mass numbers were observed. This observation was in contrast to the photoionization of cyclic aromatic hydrocarbons by femtosecond lasers in the gas phase where ions of the parent molecules were dominantly observed. The physical properties of solid substrates contributed to the efficiency of atomization and ionization. This was also supported by the observation that the efficiency was exactly in accordance with the thermal conductivity of each substrate. The ratio between the signals for two sulfur isotopes was found to agree with their natural abundance. This result would promote the development of single-shot chemical analyses of isotope-labeled large organic molecules.

フェムト秒レーザ・アブレーションの技術を用いて固体基板上の大型有機分子の同時の原子化とイオン化を行った。基板には、シリコン、アルミニウム、ガラスを用いた。試料分子に含まれる全ての原子種は単原子イオンとして観測され、大きな質量数のイオン信号はほとんど見られなかった。環状芳香族炭化水素の気相でのフェムト秒レーザによる光イオン化では元の分子のイオンが主に観測されるのと対照的であった。固体基板の物理特性が原子イオン化の効率化に寄与していた。効率が基板の熱伝導率と正確に同じ傾向を示すこともこれを裏付けた。また、イオウの同位体の信号比は自然存在比と同じであった。この結果は、同位体で標識した大型有機分子の単励起化学分析の発展を促すであろう。