Determining the atomic excited-state fraction in a magneto-optical trap

This talk introduces an empirical method for determining the excited-state fraction of atoms in a magneto-optical trap (MOT). The four-level theoretical model was verified experimentally for atoms in a MOT, and two experimental saturation parameters were extracted from the model to estimate the excited-state fraction as a function of the MOT trap parameters.  This type of measurement is essential for the use of cold atoms as a sensor when they are held in a MOT since their interactions with other particles and fields is quantum state dependent.  We plan to use this method to distinguish the ground and excited state collision cross section of Rb atoms with species in residual gas of the vacuum. This is the first step to establishing atom loss rates from a MOT as an atomic primary pressure standard.