An optical system is described in which ultraviolet light from a suitable source is dispersed by a grating monochromator and focused on a specimen. Fluorescent light from the specimen passes through a second grating monochromator and is detected by a photomulitplier tube. The specimen is placed in a stand which rests on a kinematic trolley, by means of which the specimen is brought into focus and which allows stands with reference markings, an MgO surface, or a cold cell to be used.
The optical system is calibrated photometrically by means of a standarized tungsten-quartz lamp. The spectral sensitivity characteristics of the detecting photomultiplier, together with its associated monochromator and mirrors, are corrected by means of a cam driven in synchronism with the wavelenght drive drive of the detecting monochromator.
In order to cancel fluctuations in the exciting light source a fraction of the light emerging from the source monochromator is focused on to a second photomultiplier, whose output is used to operate a servo system. The recorded spectrum is thus a measure of the ratio of fluorescent to exciting light. The currents from the photomultipliers are amplified by dc amplifiers with silicon diode modulators, which are described.
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