Photoionization photomultiplier

Fig. 2. Mass spectrometer with photoionization 1—built-in hydrogen lamp 2—vacuum monochromator filled with hydrogen 3—LiF window 4—ionic source container 5—photoionization space with the accelerating grids 6—fluorescent layer for intensity calibration of the incident u.v. light 7—photomultiplier 8—magnetic mass analyzer 9—electron multiplier.

Photoionization studies without mass analysis (similar in principle to the first studies of homonuclear associative ionization) have recently been conducted in argon, krypton, xenon, sodium, potassium, rubidium, and cesium. The apparatus used by Huffman and Katayama is depicted in Fig. 5. The ion current reaching the collector plate and the radiation intensity incident on the photomultiplier are measured as a function of wavelength of incident radiation (from a monochromator) and pressure of gas in the cell. For purpose of reaction identification, this method is of value only in the pure gases, in which there... 

In order to evaluate the photoconductivity energy threshold and the quantum yield the spectral distribution of the light entering the liquid must be known. The relative spectral distribution of VUV-light can be obtained by recording the fluorescence of sodium salicylate deposited on the inside of the entrance window of the conductivity cell. The relative quantum yield of the fluorescence emission spectrum with a peak at 420 nm varies less than 20%, with the incident wavelength between 100 and 160 nm (Samson, 1967). The fluorescence is measured with a photomultiplier. For the determination of the quantum flux, the conductivity cell is filled with a few tens mbar of NO for which the absolute quantum yield for photoionization has been reported (Watanabe et al., 1967). Measurement of the photoelectron emission yield of a gold layer can also be employed (Krolikowski and Spicer, 1970). 

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