Metastable decomposition of {ROH}n{NH₃}_mH⁺ heterocluster ions

We report the results of our multiphoton ionization studies of mixed ammonia-alcohol cluster ions of the form {ROH}_n{NH₃}_mH⁺ where R = CH₃, C₂H₅, and C₃H₇. By employing a reflectron time-of-flight mass spectrometer, we have investigated the competitive metastable decomposition of these cluster ions by measuring intensity ratio distributions. Our experimental results show that the proton in these mixed cluster ions is bound to an ammonia molecule, forming an NH₄⁺ core ion. The interpretation of the preferential solvation of the core ion is in terms of a combination of factors: electrostatic interactions, proton transfer reactions, and strength of charge enhanced hydrogen bonds.