Stern-Gerlach deflection of cryogenically cold polyatomic molecules in superfluid nanodroplets

TL;DR

This study demonstrates how superfluid helium nanodroplets can be used to precisely measure magnetic moments and spin relaxation dynamics of cryogenically cooled polyatomic molecules, overcoming previous experimental challenges.

Contribution

The paper introduces a method for accurate magnetic and spin relaxation measurements of polyatomic molecules in superfluid helium nanodroplets, revealing new insights into their magnetic ordering and relaxation mechanisms.

Findings

Magnetic moments are precisely determined at low temperatures.

Dimers and trimers exhibit antiferromagnetic order.

Spin relaxation mechanisms within helium droplets are characterized.

Abstract

Beam deflection is capable of providing valuable information about the magnetic moments of molecules and clusters as well as the relaxation dynamics of their spins. However, observations have been hampered by magnetic couplings to excited vibrational and rotational states of polyatomic systems, which are challenging to control, characterize, and systematize. In this work, we carried out deflection measurements on superfluid helium nanodroplets doped with high-spin FeCl2 and CoCl2 molecules and their complexes. This enabled quantitative determination of the magnetic moments of molecules and clusters at extremely low, and fully defined, temperature of all of their degrees of freedom. The spin magnetic moments become thermalized and oriented along the applied field. Dimers and trimers are found to be antiferromagnetically ordered. The issue of rates and mechanisms of molecular spin relaxation within the cryogenic helium matrix is highlighted.