We report the measurement of the photoionization (PI) cross section of the lithium 2P 3/2 state in a magneto-optical trap (MOT) using a UV-light-emitting diode (LED). Losses from the lithium MOT induced by additional radiation ionizing the atoms in the 2P 3/2 state have been measured as a function of the intensity of the LED. The experiments have been conducted using a fiber-coupled LED with a flat-top output intensity distribution after the fiber. This makes it possible for us to reduce influences of spatial misalignment between the photoionizing radiation and the MOT density distribution. The PI cross section of lithium in the 2P 3/2 state at 345.5 nm is determined to be (20.1 ± 0.9) Mb. The applied technique allows us to determine the PI cross section with three times better accuracy in comparison with previous measurements. Our result is in good agreement with previously reported experimental results and it differs from the published theoretical data.

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