We present lifetime measurements of the $5D_{3∕2}$ and $5D_{5∕2}$ states of rubidium using the time-correlated single-photon-counting method. We perform the experiment in a magneto-optical trap of ${}^{87}\mathrm{Rb}$ atoms using a two-step excitation with the trap laser at $780\mathrm{nm}$ as the first step. We record the $761.9\mathrm{nm}$ fluorescence from the decay of the $5D_{3∕2}$ state to the $5P_{1∕2}$ state, and measure the lifetime of the $5D_{3∕2}$ state $\tau =246.3\left(1.6\right)\mathrm{ns}$. We record the $420.2\mathrm{nm}$ fluorescence from the cascade decay of the $5D_{5∕2}$ state to the $5S_{1∕2}$ state through the $6P_{3∕2}$ state, and extract the lifetime of the $5D_{5∕2}$ state $\tau =238.5\left(2.3\right)\mathrm{ns}$.

• Received 4 September 2008

DOI:https://doi.org/10.1103/PhysRevA.78.062506