Making ultracold molecules in a two-color pump-dump photoassociation scheme using chirped pulses

Abstract

This theoretical paper investigates the formation of ground state molecules from ultracold cesium atoms in a two-color scheme. Following previous work on photoassociation with chirped picosecond pulses [Luc-Koenig et al., Phys. Rev. A 70, 033414 (2004)], we investigate stabilization by a second (dump) pulse. By appropriately choosing the dump pulse parameters and time delay with respect to the photoassociation pulse, we show that a large number of deeply bound molecules are created in the ground triplet state. We discuss (i) broad-bandwidth dump pulses which maximize the probability to form molecules while creating a broad vibrational distribution as well as (ii) narrow-bandwidth pulses populating a single vibrational ground state level, bound by 113 cm −1 . The use of chirped pulses makes the two-color scheme robust, simple and efficient.

Short-pulse photoassociation in rubidium below theD1line

“…Stabilization is most effective if the dump pulse interacts with the molecular wavepacket when it is located at short internuclear distances. For cesium it was found that up to 20% of the excited state wavepacket can be transferred to molecules in the lowest triplet state [27].…”

“…pulses in the picosecond to nanosecond regime. The efficiency of the stabilization step depends on the topology of the potentials and the time-delay between pump and dump pulses [27]. In PA experiments with CW lasers, the stabilization step is determined only by the potentials and the transition dipole moment, i.e.…”

“…Photoassociation with short laser pulses on cold systems has sparked interest from both experiment [8,16,19,20] and theory [13,14,15,25,26,27]. Specifically, a pump-dump scheme has been suggested with the idea to create a wavepacket on the excited state and make use of its timedependence for efficient stabilization [14,15,27]. In order to obtain an overall high efficiency, both excitation (photoassociation) and deexcitation (stabilization) steps must be efficient.…”

“…[27] for the pump-dump scheme. In previous work on cesium, only excitation of the 0 − g (P 3/2 ) excited state and molecule formation in the lowest triplet state a 3 Σ + u were considered [27]. In order to analyze short pulse PA from the point of view of a prospective experiment, the present study goes beyond the two-state description [13,14,15,16,27].…”

“…[13,14,15,16] for PA with chirped pulses and of Ref. [27] for the pump-dump scheme. In previous work on cesium, only excitation of the 0 − g (P 3/2 ) excited state and molecule formation in the lowest triplet state a 3 Σ + u were considered [27].…”