Collisional decoherence in the presence of ultrafast optical pulses

An expression for the van der Waals interaction between an active atom and a perturber atom is derived using an irreducible tensor representation. This interaction leads to magnetic state decoherence in an ensemble of active atoms. The magnetic state decoherence can be suppressed by the application of ultrafast optical pulses. It is shown that the depolarization cross section can be suppressed by as much as 40% with only four optical pulses during a single collision and that, for a large number of pulses, the cross section is proportional to n(0)(-2/11) where n(0) is the number of pulses at the Weisskopf radius. This paper generalizes our previous results in which the collisional interaction was modeled as a square pulse.