Slow ground state molecules from matrix isolation sublimation

Abstract

We describe the generation and properties of a cryogenic beam of 7 Li2 dimers from sublimation of a neon matrix where lithium atoms have been implanted via laser ablation of solid precursors of metallic lithium or lithium hydride (LiH). Different sublimation regimes lead to pulsed molecular beams with different temperatures, densities and forward velocities. With laser absorption spectroscopy these parameters were measured using the molecular 7 Li2 (R) transitions. In a typical regime, sublimating a matrix at 16 K, translational temperatures of 6-8 K with a drift velocity of 130 m s −1 in a free expanding pulsed beam with molecular density of 10 9 cm −3 , averaged along the laser axis, were observed. Rotational temperatures around 5-7 K were obtained. In recent experiments we were able to monitor the atomic Li signal -in the D2 line -concomitantly with the molecular signal in order to compare them as a function of the number of ablation pulses. Based on the data and a simple model, we discuss the possibility that a fraction of these molecules are being formed in the matrix, by mating atoms from different ablation pulses, which would open up the way to formation of other more interesting and difficult molecules to be studied at low temperatures. Such a source of cryogenic molecules have possible applications encompassing fundamental physics tests, quantum information studies, cold collisions, chemistry, and trapping.

A sensitive detection method for high resolution spectroscopy of trapped antihydrogen, hydrogen and other trapped species

“…In our group in Brazil we have developed another technique to generate a cryogenic beam suitable to load a magnetic trap of hydrogen and other species, which we call matrix isolation sublimation (MISu) [24][25][26][27][28][29]. It involves three steps: (i) a solid film of inert gas, such as Ne or H 2 , is grown onto a cold sapphire substrate at ∼4K; (ii) atoms are implanted, typically via laser ablation of some suitable solid precursor, such as LiH for the case of interest in Li and H, thus forming the matrix isolation; and (iii) the matrix is sublimated at cryogenic temperatures with a heat pulse to the sapphire substrate.…”