Secondary ion emission from ethanol microdroplets induced by fast heavy ions

We have developed a new experimental setup that allowed us to study collision interactions between fast ions and liquid microdroplets under a high vacuum condition. Microdroplets of ethanol are irradiated with 1.0-MeV H⁺ and 2.0-MeV C²⁺ ions. The size distribution of the droplets is evaluated from energy-loss measurements of projectile ions penetrating through the microdroplets. We obtain time-of-flight mass spectra of secondary ions from ethanol droplets. It is demonstrated that coincidence measurements with secondary electrons can distinguish specific ions produced in collisions with the droplets. Production mechanisms of H₃O⁺, C₄H₉O⁺, (C₂H₅)₂OH⁺ in the liquid ethanol are discussed. (paper)