Electron density decay measurements using the 447.1 nm line of neutral helium

The 447.1 nm line of neutral helium has been used to measure the time-dependent decay of the electron density in the afterglow of a pulsed, atmospheric pressure helium discharge. The technique involves using a shutter which consists of a Pockels cell combined with crossed polarizers to gate the light pulse, allowing observation of the spectrum during various time windows in the discharge.