Abstract
The laser two-photon ionization technique has been applied to several aromatic molecules on the surface of water in ambient air. The third harmonic of a NdYAG laser (355nm) was used for excitation and ionization. The photoionization charge (the area of the signal) was linearly proportional to the solute concentration when the incident angle of the laser beam was 85°. Less soluble molecules exhibited larger signals when the molar absorptivities were
equal. The detection limits of aminoanthracene and methylanthracene were 0.2μg/dm3 (ppb). They are almost identical to those obtained at 337nm, but slightly inferior to those obtained in hexane solution.
