Discriminating the influence of thermal excitation and the presence of structural isomers on the Stark and Zeeman effect of AlSn12 clusters by combined electric and magnetic beam deflection experiments

Abstract

AlSn₁₂ clusters were studied in electric and magnetic beam deflection experiments at nozzle temperatures of T_nozzle = 16–100 K. For 16 K, spatial separation of two fractions of clusters in the molecular beam was achieved by deflection with both an electric and a magnetic field gradient. In the electric deflection experiment, about 76% of the clusters are identified as non-polar and the rest as highly-polar, while the magnetic deflection experiment demonstrates that 37% show an atom-like and 63% a Brillouin-like magnetic response. In order to probe the connection between these fractions in electric and magnetic beam deflection, a combination of these two experiments was performed. This clearly demonstrates that the highly-polar clusters show a Brillouin-like magnetic response and only the non-polar clusters can be deflected atom-like in a magnetic field. This observation suggests that two structural isomers are present in the molecular beam, one of which is highly-symmetric, and demonstrates that spatial isomer separation of metal clusters containing heavy elements is feasible. However, vibrational excitation must also be taken into account to explain the observed magnetic response. A stepwise increase of the cluster temperature shows that suppression of the superatomic response is more sensitive to vibrational excitation than the quenching of the permanent electric dipole moment.