Experimental and theoretical studies of neutral MgmCnHx and BemCnHx clusters

Neutral MgmCnHx and BemCnHx clusters are investigated both experimentally and theoretically for the first time. Single photon ionization at 193 nm is used to detect neutral cluster distributions through time of flight mass spectrometry. MgmCnHx and BemCnHx clusters are generated through laser ablation of Mg or Be foil into CH4/He expansion gas. A number of members of each cluster series are identified through isotopic substitution experiments employing 13CH4 and CD4 instead of CH4 in the expansion gas. An oscillation of the vertical ionization energies (VIEs) of MgmCnHx clusters is observed in the experiments. The VIEs of MgmCnHx clusters are observed to vary as a function of the number of H atoms in the clusters. Density functional theory (DFT) and ab initio (MP2) calculations are carried out to explore the structures and ionization energies of MgmCnHx clusters. Many BemCnHx clusters are also generated and detected in the experiments. The structures and VIEs of BemCnHx clusters are also studied by theoretical calculations. Calculational results provide a good and consistent explanation for the experimental observations, and are in general agreement with them for both series of clusters.