Molecular beam study of alkali metal clusters

The production and characterization of a molecular beam containing clusters (aggregates) of potassium atoms, ranging in size from 2 to approximately 10 to the 5th power atoms is described. Thermal time-of-flight measurements and pulse height spectra are discussed as non-conventional forms of mass spectroscopy suitable for a crude characterization of the size distribution of the cluster beam. Attempts to identify, by virtue of their spin paramagnetism, the lightest of these clusters containing an odd number (N) of atoms with N 9 by Stern-Gerlach deflection was unsuccessful due to noise introduced by beam fluctuations and scattering. A molecular beam magnetic resonance (MBMR) study of the alkali beam at 24 GHz was done in a search for resonant spin transitions in K3. The results of a detailed set of X alpha scattered wave calculations which predict the expected MBMR spectra for K3 for several different structures are reported. We discuss line-broadening interactions, in particular relative atomic motions and spin relaxation mechanisms, which could alter the appearance of the actual MBMR spectrum that predicted by the model calculations.