A sodium iodide (NaI) solution in ethanol was introduced into vacuum as a continuous liquid flow (liquid beam) and irradiated with a 220 nm UV laser. Cluster cations containing ethoxide such as Na+(NaOEt), Na+(NaI)(n)(NaOEt) (n=1-4), and Na+(NaI)(n)(NaOEt)(2) (n=1-4) were observed by a time-of-flight (TOF) mass spectrometer. Furthermore, addition of NH4+ or n-BuOH into the NaI ethanol solution resulted in suppressing the intensities of the peaks associated with these cluster ions. It is concluded that the ethoxide is produced by a scavenging reaction of a solvated electron with an ethanol molecule, and the reaction of the ethoxide formation competes with a scavenging reaction by NH4+ or n-BuOH. The rate equations of these competing processes predict the dependence of the ethoxide formation on the concentration of NH4+ Or n-BuOH. Similar reaction products were observed from alcohol solutions of several iodides.