Precision Measurement of the 6$P_{3/2}$ State of Cesium

We have refined our atomic lifetime measurement technique$^{1}$ and report a precision value for the 6$P_{3/2}$ state of cesium. A single pulse ($\sim $nJ) from a mode-locked Ti:Sapphire laser excites atoms in counter-propagating thermal beams to the 6$P_{3/2}$ state. A subsequent laser pulse is amplified using a regenerative amplifier to a few $\mu $J and is frequency-doubled, and ionizes atoms in the excited state. The ions are collected using a channel electron multiplier and counted. The measurement is repeated using excitation and detection pulses that are increasingly separated in time, allowing the decay from the excited state to be determined. Our preliminary results indicate a lifetime of 30.44~ns with a statistical uncertainty of 0.02~ns. The dominant systematic effects will be addressed. These include (1) the effects of imperfect extinction ratios of the electro-optic modulators used for laser pulse selection; (2) the effects of atoms moving through spatially non-uniform laser beams; and (3) the effects of misalignment of the excitation and ionization laser beams. $^{1}$B.M. Patterson, C.D. Lindstrom, T. Takekoshi, J.R. Lowell, C. Villarreal, and R.J. Knize, Opt. Lett. \textbf{28} (19), 1814 (2003).