Photoionization and density functional study of clusters of alkali metal atoms solvated with acetonitrile molecules, M(CH₃CN)_n (M=Li and Na)

Photoionization mass spectroscopy of clusters of alkali metal atoms solvated with acetonitrile molecules, M(CH₃CN)_n (M=Li and Na), has shown that their ionization potentials decrease from n=1 to 3, while they increase for n≥4. Calculations based on density functional theory are also made for these clusters and their cations with n=1-3. The nature of the anomalous n dependence of the ionization potential is discussed in relation to the stabilization of neutral clusters due to dipole-dipole interaction between acetonitrile molecules.