Spectrum deuterium lamp

Continuous sources The sources of choice for measurements in the ultraviolet spectral region are hydrogen or deuterium lamps [1]. When the gas pressure is 30 to 60 X10 Pa they yield a continuous emission spectrum. The maxima of their radiation emission occur at different wavelengths (Hi A = 280 nm Di 2 = 220 nm). This means that the deuterium lamp is superior for measurements in the lower UV region (Fig. 15). 

These lamps show moderately good color rendering properties, the very broad spectrum being one of their main utilities. For instance, high-pressure Xe lamps or deuterium lamps are commonly used in optical spectroscopy techniques. 

Figure 14.12 —Schematic of an instrument showing deuterium lamp background correction. Perkin Elmer, model 3300 with a Littrow-type monochromator. This double beam assembly includes a deuterium lamp whose continuum spectrum is superimposed, with the aid of semitransparent mirrors, on the lines emitted by the hollow cathode lamp. One beam path goes through the flame while the other is a reference path. The instrument measures the ratio of transmitted intensities from both beams. The correction domain is limited to the spectral range of the deuterium lamp, which is from 200-350 nm. (Reproduced by permission of Perkin Elmer.)...

A tungsten light source does not supply sufficient radiant energy for measurements below 320 nm. In the UV region of the spectrum, a low-pressure mercury-vapor lamp that emits a discontinuous or line spectrum is useful for calibration purposes but is not very practical for absorbance measurements, because it can be used only at certain wavelengths. Hydrogen and deuterium lamps provide sources of continuous spectra in the UV region with some sharp emission... 

Figure 25-5 (a) A deuterium lamp of the type used in spectrophotometers and (b) its spectrum. Note that the maximum intensity occurs at —225 nm. Typically, instalments switch from deuterium to tungsten at —350 nm. 

Why does a deuterium lamp produce a continuum rather than a line spectrum in the ultraviolet range ... 

Deuterium lamp A source that provides a spectral continuum in the ultraviolet region of the spectrum radiation results from application of about 40 V to a pair of electrodes housed in a deuterium atmosphere. 

Quartz windows must be employed in deuterium and hydrogen lamps because glass absorbs strongly at wavelengths less than about 3s()nm. Although the deuterium lamp continuum spectrum extends to wavelengths as short as IbOnm.the useful lower limit is about 190 nm because of absorption by the quartz windows. 

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