Laser produced vaporization of materials for use in mass spectroscopic analysis
The focused output of certain solid state lasers can be used to produce rapid surface heating and consequent vaporization in absorbing materials. For ordinary lasers it appears that the heating process can be adequately explained on the basis of a relatively simple classical thermodynamic treatment; however, for Q-switched lasers it is much more complicated. John F. Ready has presented a theoretical treatment for both cases, and the experimental results with metals agree well with theory. The use of time of flight mass spectrometer to study vaporized material results in a useful analytical tool for study of sample composition and provides information about laser beam-surface interaction as well. Employing a mass spectrometer, a complete spectrum of almost any material, including complex organic substances, can be obtained from a selected surface area, and small chemical concentrations can be detected. In what follows the vaporization process appropriate to ordinary lasers of moderate power output is discussed, and experimental results in the form of mass spectrograms of several substances obtained with a Bendix time-of-flight instrument are presented. Also, the equipment employed is described in detail with particular emphasis on the laser system and experimental difficulties which were encountered.
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