Precision Lifetime Measurement of the Cesium 6P$_{3/2}$ State

We will report the final results from our precision measurement of the cesium 6P$_{3/2}$ atomic state lifetime. The measurement technique consists of an initial pulse ($\sim$ nJ) selected from a mode-locked Ti:Sapphire laser which excites cesium atoms in counter-propagating thermal beams to the cesium 6P$_{3/2}$ state. A subsequent laser pulse is amplified in a regenerative amplifier ($\sim$ $\mu$J) and also frequency doubled, resulting in pulses which nonresonantly ionize the cesium atoms in the 6P$_{3/2}$ state. The ions are collected and counted while varying the delay between the excitation and ionization pulses allowing us to measure the excited state lifetime. Dominant systematic errors in the measurement include: effects from the misalignment of the excitation and ionization laser beams, quantum beats in the photoionization detection, and radiation trapping affecting the observed lifetime. These systematic errors along with others are examined which lead to a total systematic error of 0.04$\%$. Currently our statistical error of 0.1$\%$ results in a total measurement uncertainty of 0.11$\%$, making these among the most precise direct measurements of an atomic lifetime.