1994 Volume 10 Issue 6 Pages 849-852
The two-photon ionization spectra (wavelength dependence of the photoionization charge) of the three title molecules have been measured on the water surface in the region of 340-440nm using a Ti-sapphire laser. The signal was quadratic to the laser pulse energy. The peaks in the observed spectra are closely correlated with those in the one-photon absorption spectra in solution. The detection limit depended on the wavelength used and was better at band peaks in the photoionization spectrum.