High-angular-momentum states in cold Rydberg gases

Cold. dense Rydberg gases produced in a cold-atom trap are investigated usi ng spectroscopic methods and time-resolved electron counting. Optical excit ation on the discrete Rydberg resonances reveals longlasting electron emiss ion from the Rydberg gas (> 20 ms). Our observations are explained by lm-mi xing collisions between Rydberg atoms and slow electrons that lead to the p opulation of long-lived high-angular-momentum Rydberg states. These atoms t hermally ionize slowly and with large probabilities.