## low-pressure mercury lamp (arc)

https://doi.org/10.1351/goldbook.L03637
@R05339@ that contains mercury vapour at pressures of about $$0.1\ \text{Pa}$$ ($$0.75\times 10^{-3}\ \text{Torr}$$; $$1\ \text{Torr} = 133.33\ \text{Pa}$$). At $$25\ ^{\,\unicode{x26ac}}\text{C}$$, such a @L03447@ emits mainly at $$253.7$$ and $$184.9\ \text{nm}$$. They are also called germicidal lamps. There are cold- and hot-@C00905@ as well as cooled electrode-less (excited by microwaves) low-pressure mercury lamps. The @W06682@ is a low-pressure mercury arc with an added fluorescent layer that emits in the UV-A spectral region ($$315$$-$$400\ \text{nm}$$).