Lifetime measurements of the 5d states of rubidium

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