RAMSEY FRINGES IN LASER-ASSISTED COLLISIONS

It is shown theoretically that Ramsey fringes can be produced when a l aser-assisted reaction of the form A2 + A1 + hOMEGABAR --> A1 + A2 is driven by a pair of ultrafast radiation pulses, each of whose temporal widths is less than the duration tau(c) of a collision between the A and A' atoms. The excitation profile of the laser-assisted collision i s calculated as a function of detuning of the laser field frequency fr om the initial- to final-state transition frequency. For radiation pul ses separated by time T, Ramsey fringes appear separated in frequency by T-1. The modulation depth and shift of the central Ramsey fringe as a function of (T/tau(c)) provide information about the collisional in teraction. Both the weak- and strong-field regions are considered and comparison with laser-assisted collisions using excitation pulses havi ng temporal widths greater than tau(c) is made.