FORMATION AND EJECTION OF CLUSTER IONS FROM A LIQUID BEAM OF ANILINE ETHANOL SOLUTION BY LASER PHOTOIONIZATION

A simple technique for making a continuous liquid flow in a vacuum (liquid beam) was developed and combined with multiphoton ionization and time-of-flight mass spectrometry. This technique was applied to the resonance two-photon ionization of aniline in ethanol (0.2-3 M). Binary cluster ions of aniline and ethanol together with a trace amount of aniline cluster ions were ejected from a liquid beam of an aniline-ethanol solution when the liquid beam was irradiated by a 270 nm laser exceeding a certain threshold power. The dependence of the threshold power on the aniline concentration reveals that Coulomb explosion of the ions produced in the liquid beam causes ion ejection from the beam. The critical ion density for the Coulomb explosion was found to be independent of the aniline concentration in the range of 0.2-3 M. The finding suggests that clusters of aniline molecules are formed in the ethanol solution.