Fluorescence studies of neptunium and plutonium hexafluoride vapors

The first observation of fluorescence from gas phase, electronically excited, transuranic hexafluorides is reported. Fluorescence peaking at 1360 nm was observed from 237NpF6 gas excited at 1064 nm. The measured fluroescence lifetime was 3.53±0.01 ms, independent of NpF6 pressure. Fluourescence peaking at 2300 nm has been observed from 242PuF6 gas excited at 1064 nm. The measured fluorescence lifetime was 204±12 μs, independent of PuF6 pressure. In both cases the emitting state is assigned as a vibronic component of the first excited electronic state of the hexafluoride based on previously reported absorption spectra and energy level calculations. Fluorescence in the 1900 and 4800 nm region was observed from PuF6 gas excited at 532 nm. The lifetime of this fluorescence was 86±4. The emitting state giving rise to this shorter-lived fluorescence was not identified. Estimated fluorescence quantum yields are reported.