[scotty79]

I don't think it needs to be monochromatic. If the longest wavelength is 222nm, other penetrate skin even less.

[jefftk]

The longest wavelength isn't 222, that's the peak wavelength.

KrCl excimer lamps produce a relatively narrow spectrum as is: https://pubs.acs.org/doi/10.1021/acsphotonics.2c00041

If it turns out we need it to be even narrower, we could put filters on them.