Paramagnetic Properties of Neutral Sodium Doped Solvent Clusters
Since the discovery of concentration-dependent colors of alkali metal-ammonia solutions in the early 19th century [1], excess electrons in alkali metal solutions have been found to be important in different areas. They are ubiquitous in liquid-phase chemistry [2] and play an essential role in chemical reactions [3], and biology [4]. Extensive experimental and theoretical work has been done on solvated electrons in alkali metal solutions [2]. However, the underlying correlation effects of the solvated electrons are still not well understood. While magnetic measurements have probed such effects on alkali metal solutions [5],[6], the diamagnetic and paramagnetic species have not yet been identified in such bulk phase experiments [2].
We present a study of the magnetic properties of sodium-doped ammonia, water, dimethyl ether, and methanol clusters (Na(Solv)n, n=1-4) [7]. Using a pulsed Stern-Gerlach deflector, we measure the magnetic deflection of a neutral cluster beam. The experimental deflection is compared with molecular dynamics simulations based on the Zeeman interaction of a free spin ½ system.
The comparison reveals unperturbed magnetic properties of a spin ½ system for the smallest clusters NaNH3 and NaH2O. Larger clusters Na(NH3)n (n=2-4), Na(H2O)n (n=2-4), Na(DME)n (n=1-3) and Na(MeOH)n (n=1-4), by contrast show reduced deflection compared with a spin ½ system. These deviations from a spin ½ behavior are attributed to intracluster spin-relaxation effects -occurring on time scales similar to or faster than the experiment. The determination of spin relaxation times for these systems allows us to identify experimental trends regarding their magnetic behavior. The observed trends are discussed in terms of spin and rotational angular momentum interactions of thermally accessible rovibrational eigenstates.