Heteronuclear molecules from matrix isolation sublimation and atomic diffusion.

Abstract

We demonstrate the production of cryogenic beams of heteronuclear molecules from the matrix isolation sublimation (MISu) technique. A sapphire mirror serves as a substrate whereupon a solid Ne matrix is grown. Atoms of Li, H, Ca, and C are implanted into the matrix via subsequent laser ablation of different solid precursors such as Ca, Li, LiH, and graphite. The matrix is sublimated into vacuum generating a cryogenic beam of Ne carrying the previously isolated neutral atomic and molecular species. A compact and low energy electron source and time-of-flight mass spectrometer was designed to fit this system at low temperature. With electron ionization time-of-flight mass spectrometry, we analyze the species coming from MISu and demonstrate the formation of heteronuclear molecules in the matrix. In this first study, we produced LiCa from the sequential implantation of Li and Ca into the matrix and some clusters of CnLim after Li and C ablation. Also from ablation of a single LiH pellet, we observed clusters of LinHm. This novel technique opens up the opportunity to generate cryogenic beams of different molecules for precision physics and chemistry studies. Laser or microwave high resolution spectroscopy of a molecular beam benefits from low translational and rovibrational temperatures and forward velocities, such as the ones produced in this technique. Toward the prospect of enhancing the molecular formation, we introduce a new method to study the atomic diffusion of Li and Ca in the Ne matrix via laser spectroscopy during sublimation. We estimate a small diffusion coefficient at 7 K, but a surprisingly linear atomic dispersion during sublimation. The method is extensive to other species and matrices.