Cooling effects in the Stark deceleration of Rydberg atoms/molecules with time-dependent electric fields

This paper presents calculations for realizing the deceleration of H₂ Rydberg molecules with n = 16, where n is the principal quantum number. A double-dipole decelerator (Softley T P, Procter S R, Yamakita Y, Maguire G and Merkt F 2005 J. Elec. Spectrosc. Relat. Phenom. 144–147 113) operated with an optimum time-dependent electric field allows, in principle, complete deceleration of the Rydberg molecules to zero mean velocity. A bunch of molecules in a supersonic beam is decelerated from the initial velocity centered at ∼900 ms⁻¹ and translational temperature 1 K to the final velocity 0 ms⁻¹ and temperature 13 mK. The calculations are performed using the 4th-order symplectic integrator based on representations in phase space {q, p}, and show that an ensemble with narrow δq₀ and broad δp₀ distribution is converted to one at standstill with broad δq and narrow δp. Cooling effects are reinforced by field ionization in which the fast components that move to regions of high electric field are effectively filtered out.