Sources for UV Region:

For measurements in the UV region, electric discharge sources such as hydrogen or a deuterium lamp are used. Within these, the excitation of the gaseous molecules is brought about through the passage of electrons by the gas at low pressures. A hydrogen lamp is generally used in the spectrophotometers and provides light in the wavelength region of 160-375 nm.  The radiant power of the hydrogen lamp is low and these are replaced through deuterium lamps but it raises the cost of the instrument.

Figure: Radiation sources: a) deuterium lamp for UV range b) tungsten lamp for visible range