Fast-beam laser lifetime measurements of the cesium6p2P1/2,3/2states

We provide a detailed description of our fast-beam laser lifetime measurements in atomic cesium. Selective excitation of the neutral ${}^{133}\mathrm{Cs}$ $6p{}^2{P}_{1/2}$ and $6p{}^2{P}_{3/2}$ states is accomplished with resonant diode laser light directed transversely to the atomic velocity. The in-flight decay of the excited-state fluorescence is observed with a position-correlated single photon-counting detector. The Doppler-shifted $6p{}^2{P}_{3/2}$ resonance, when probed with longitudinally propagating laser radiation, provides a precise means for determination of the beam velocity, and converts the position scale to a time scale. Our lifetime results are $35.07\pm 0.10\hspace{0.5em}\mathrm{ns}$ for the $6p{}^2{P}_{1/2}$ state and $30.57\pm 0.07\hspace{0.5em}\mathrm{ns}$ for the $6p{}^2{P}_{3/2}$ state. These results represent a data set larger than in our previous work, and include beam divergence corrections which have been evaluated by two different methods. We present comparisons of our results with previous measurements and with relativistic many-body calculations of atomic transition matrix elements in this neutral alkali system.