Ultrasensitive Detection of Atmospheric Constituents by Supersonic Molecular Beam, Multiphoton Ionization Mass Spectroscopy

摘要

An ultrasensitive detection method for atmospheric monitoring has been developed based on the technique of supersonic molecular beam, resonance enhanced multiphoton ionization, time-of-flight mass spectroscopy (MB/REMPI/TOFMS). Several organophosphonate and organosulfide compounds, representing simulants to a class of toxic compounds, were studied. Detection levels as low as 300 ppt (dimethyl sulfide) were obtained. Single vibronic level REMPI of the cooled molecules in conjunction with TOFMS provided selectivity approx 10,000 against chemically similar compounds in moist air expansions. The fragmentations formed by REMPI excitation are shown for diisopropyl methylphosphonate to depend strongly on the resonant intermediate state of the neutral molecule. Atmospheric monitoring, chemical warfare agent simulants, multiphoton ionization, organophosphonates, organosulfides, pesticides. (mjm)