Ultraviolet femtosecond laser ionization mass spectrometry.

For this study, multiphoton ionization/mass spectrometry using an ultraviolet (UV) femtosecond laser was employed for the trace analysis of organic compounds. Some of the molecules, such as dioxins, contain several chlorine atoms and have short excited-state lifetimes due to a "heavy atom" effect. A UV femtosecond laser is, then, useful for efficient resonance excitation and subsequent ionization. A technique of multiphoton ionization using an extremely short laser pulse (e.g., <10 fs), referred to as "impulsive ionization," may have a potential for use in fragmentation-free ionization, thus providing information on molecular weight in mass spectrometry.