MECHANISM OF ION EJECTION FROM A LIQUID BEAM FOLLOWING LASER PHOTOIONIZATION

An anisole-ethanol solution was introduced into vacuum as a continuous liquid flow (liquid beam), and the molecules in the liquid beam were ionized by laser two-photon ionization. Ions ejected from the liquid beam were extracted by applying a pulsed electric field for the measurement of time-of-flight mass spectra of the ions. The intensities and peak profiles of the ions were measured by varying the delay time from the laser ionization to the pulse extraction of the ions at different laser powers. All the ions observed have almost the same velocity (approximate to 700 m s(-1)) and need approximate to 1 mu s to leave the liquid beam after laser irradiation. This finding implies that each photoion forming a solvation structure with almost the same number of solvent molecules is expelled from the liquid surface by Coulomb ejection and is dissociated into a cluster ion outside the influence of the Coulomb potential. The rate constants for ion ejection were determined.