Effect of vibrational excitation and spin-rotation coupling on Stern-Gerlach experiments: A detailed case study on GdSn15 as an asymmetric rotor

Stern-Gerlach experiments allow one to study the magnetism of isolated particles in the gas phase. However, gaining insight into the intrinsic magnetic properties of small metal clusters in beam deflection experiments is usually hampered by rotational and vibrational excitation. Here, we address this issue for the magnetic deflection of the cryogenically cooled GdSn15 cluster (T = 16-100 K). A single-sided deflection towards high field and, in the low-temperature regime, a pronounced tailing are observed. We present a microscopic model considering spin, rotational, and vibrational degrees of freedom of the cluster which explains the experimentally observed features in the beam profiles reasonably well. This model will be a helpful tool for the interpretation of results from Stern-Gerlach experiments in future studies, especially to distinguish effects from intrinsic magnetic properties and rotationally or vibrationally excited states of the investigated cluster species.