relative peak heights can be established easily within a few per cent. Figure 3 is an expanded portion of the mass spectrum from flash-heated CdS showing the Cd isot'opes. I n so far as is discernible, the resolution of the mass spectrometer is not affected by the abrupt heating of the sample within the ion source. Flash heating for mass spectrometry is, of course, not 1imit.ed to flashtube thermal sources or to the particular ionsource configuration outlined here. Other possible radiant thermal sources include shuttered carbon arcs and highintensity incandescent lamps, but the most promising extension of this work lies with pulsed lasers for flash heating. The coherent beam from a laser can be focused to concentrat,e the energy on a small area; therefore, the sample need not be prepared to a particular size, shape, or color to reach even higher temperat'ure in a small spot and readily vaporize enough material to produce a spectrum. Thus, a unique method is practicable for performing analysis on minute areas of comparatively large pieces of materials. This concept has been carried out by Honig and Woolstron (3) who have incorporated a laser with the ion source of a mass spectrograph to produce spectra recorded on photographic plates and by Berkowitz and Chupka (I) who have used a laser with the same type of instrument except for an electron multiplier out'put which permits them to record one mass peak
detecting thermally-produced shortlived products of solid materials. The subject of time-resolved mass spectrometry (wherein the time sequence in which the various m a b b peaks occur is manifested) and the methods for achieving it have been delineated previously ( 7 , f 2 ) . LITERATURE CITED
Figure 3. Portion of mass spectrum of flash-heated CdS displaying relative intensities of cadmium isotopes
(1) Berkowitz, J., Chupka, W. A, J . Chem. Phys. 40, 2735--6 (1964).
U. 9. Dept. bf Commerce, 1'346. ( 3 ) Honig, It. E., IVoolstron, J. I
