Ionization Energies and Ground-State Structures of Neutral Lan (n = 2–14) Clusters: A Combined Experimental and Theoretical Investigation

Abstract

Neutral lanthanum clusters are studied by photoionization time-of-flight mass spectroscopy, laser threshold photoionization spectroscopy, and density functional theory (DFT). Mass abundance spectra (MS) registered at multiple photoionization wavelengths in the range of 195–230 nm by single photon ionization reveal the production of all sizes, Lan (n ≥ 50), in good abundance, nullifying previously predicted low abundances for certain sizes in the 3–14 size range. Also, the MS do not reveal the extraordinary stability of any specific size, as one would expect, from previous theoretical predictions of 7- and 13-atom clusters as magic. Ionization energies (IEs) are measured for Lan (n = 2–14) clusters. DFT has been used to determine the stable geometric isomers for 2- to 10-atom clusters and to calculate their IEs. The theoretical IEs of 2–7 atom clusters are in decent agreement with their experimental values; however, the theoretical IEs are somewhat lower by ∼0.4 eV for n ≥ 8 than their experimental IEs.