Time-resolved study of energy-transfer collisions in a sample of cold rubidium atoms

In this work we probe the time dynamics of a collisional process involving energy transfer in a sample of cold Rydberg atoms produced in a rubidium magneto-optical trap. The 31S_1/2 population, produced by collisions between the 29P_3/2 and 29P_1/2,3/2 states, is monitored as a function of time through the pulsed-field ionization technique. The experimental results were compared with a dynamic model based on a two-body interaction using a 1/R⁵ potential. The model can reproduce well the time evolution of this collisional process. We are also able to explain the large electric-field range over which inelastic collisions are possible based on the existence of thresholds where collisional channels open and close.