A cold and slow molecular beam

Abstract

Employing a two-stage cryogenic buffer gas cell, we produce a cold, hydrodynamically extracted beam of calcium monohydride molecules with a near effusive velocity distribution. Beam dynamics, thermalization and slowing are studied using laser spectroscopy. The key to this hybrid, effusive-like beam source is a “slowing cell” placed immediately after a hydrodynamic, cryogenic source [Patterson et al., J. Chem. Phys., 2007, 126, 154307]. The resulting CaH beams are created in two regimes. In one regime, a modestly boosted beam has a forward velocity of v_f = 65 m s⁻¹, a narrow velocity spread, and a flux of 10⁹ molecules per pulse. In the other regime, our slowest beam has a forward velocity of v_f = 40 m s⁻¹, a longitudinal temperature of 3.6 K, and a flux of 5 × 10⁸ molecules per pulse.