SPECTROSCOPY OF ATOMIC LITHIUM AND SODIUM ATTACHED TO HELIUM AND HYDROGEN CLUSTERS

Abstract

Beams of large helium and hydrogen clusters are produced and subsequently doped with alkali atoms through a pickup technique. The $n^{2}P_{3/2.1/2} \leftarrow n^{2}S_{1/2}$ transitions of lithium and sodium atoms attached to the clusters are observed by laser induced fluorescence detection downstream of the pick-up point. While large shifts are seen for alkali atoms solvated in liquid and solid helium, small spectral shifts from the gas phase lines are observed in the excitation spectra of the atoms on the helium clusters. Atomic spectra of doped hydrogen clusters can be recorded despite the quenching of the fluorescence by the cluster. Both shifted and unshifted peaks in the spectrum of $M(H_{2})_{n}$ are seen and may be due to surface and interior states of the resident alkali atom.