QUANTUM JUMPS AND THE SINGLE TRAPPED BARIUM ION - DETERMINATION OF COLLISIONAL QUENCHING RATES FOR THE 5D D-2(5/2) LEVEL

A single Ba+ atom was confined in a radio-frequency ion trap and cooled by near-resonant laser light. Quantum jumps into and out of the metastable 5d D5/22 level were observed that followed the expected exponential distribution in dark periods to good agreement. Measurement of quantum-jump distributions together with careful measurements of the absolute partial pressures of all residual gas species enabled accurate measurements of the quenched 5d D5/22 lifetime as a function of quenching gas pressure. Measurements of quenching were observed at pressures where the mean collision rate was on the order of 1 s-1. The results yielded quenching rate constants for the metastable level for a series of gases that typically make up the residual gas environment of ultra-high-vacuum systems (H2, He, CH4, H2O, CO, N2, Ar, and CO2) together with an improved value of the 52D5/2 radiative lifetime of t0=34.53.5 s. The above quenching rate constants were then compared with classical ion-molecule collision theory. It was found that the quenching rates for molecular gases were comparable to the classical collision rates, while the rates for atomic gases were considerably lower. © 1990 The American Physical Society.