Microwave cavity resonance spectroscopy of ultracold plasmas

Abstract

We present an in situ study of the electron dynamics of an ultracold $^{85}\mathrm{Rb}$ plasma using microwave cavity resonance spectroscopy with submicrosecond temporal resolution and vastly improved sensitivity. We observe a three times faster plasma decay than predicted by a self-similar Gaussian expansion model, which might be attributed to collisional microwave heating and plasma-wall interactions. The demonstrated sensitivity enables nondestructive probing of other (nearly) ionized media of fundamental importance as well, such as cold Rydberg gases and antihydrogen plasmas.