FREQUENCY EVOLUTION OF RADIATIVELY ASSISTED COLLISIONS OF K-RYDBERG ATOMS

Ramsey interference fringes are observed in the line shape of resonant Rydberg-atom-Rydberg-atom collisions occurring in the presence of a r adiation field of frequency comparable to the inverse of the collision time. At low frequencies the fringes are phase dependent, but at high frequencies they are not. We present a theoretical interpretation bas ed on a quasistatic field description which connects the low- and high -frequency regimes. In the high-frequency regime, this model gives res ults equivalent to those obtained using a ''dressed-atom'' approach.