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 b eam were extracted by applying a pulsed electric field for the measure ment of time-of-flight mass spectra of the ions. The intensities and p eak 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 (app roximate to 700 m s(-1)) and need approximate to 1 mu s to leave the l iquid beam after laser irradiation. This finding implies that each pho toion forming a solvation structure with almost the same number of sol vent molecules is expelled from the liquid surface by Coulomb ejection and is dissociated into a cluster ion outside the influence of the Co ulomb potential. The rate constants for ion ejection were determined.