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A N A L Y T I C A L CHEMISTRY, VOL. 51, NO. 3, MARCH 1979
LITERATURE CITED (1) L. A. Vismara, D. T. Mason, and E. A. Amsterdam, Clln. pharmacal. Ther., 16, 330 (1974). (2) A. Karim, R. E. Ranney. and S.Kraychy, J . Pharm. Sci.. 61, 888 (1972). (3) R. E. Ranney, R. R. Dean, A. Karim, and F. M. Radzialowski. Arch. Int. Pharmacodyn., 191, 162 (1971). (4) T. C. Hutsell and S. J. Stachelski, J . Chromatogr., 106, 151 (1975). (5) J. W. Daniel and S. Subramanian, J. Int. Med. Res. Suppl. 1 , 4, 2 (1976). (6) A. Johnston and D. McHaffie, J . Chromatogr., 152, 501 (1978).
(7) A. M. Hayler and R . J. Flanagan, J . Chromatogr., 153, 461 (1978). (8) A. M. J. A. Duchateau, F. W. H. M. Merkus, and E. Schobben, J . Chromatogr., 109, 432 (1975). (9) P. J. Meffin, S. R. Harapat, and D. C. Harrison, J . Chromatogr., 132, 503 (1977). (10) A. C . Moffat and K. W. Smalldon, J . Chromatogr., 90, 9 (1974).
RECEIVED for review September 15,1978. Accepted December 9, 1978.
CORRESPONDENCE Improved Timing Resolution in Time-Correlated Photon Counting Spectrometry with a Static Crossed-Field Photomultiplier Sir: Time-correlated photon counting is a power analytical technique for studying a variety of properties of chemical systems. Recently, reported experimental measurements using gated detection techniques have an overall timing uncertainty (light source plus detection system) of 1 ns or less, limited principally by the transit time dispersion in conventional photomultiplier tubes (1-4). Because many physiochemical processes of interest display a temporal behavior requiring time-correlated measurements for analysis and/or to improve signal-to-noise ratio, even small reductions in timing uncertainty on the subnanosecond time scale can extend significantly the applicability of this analytical method to, inter alia (1) the study of fluorescent molecules with very short lifetimes, (2) the elimination of Raman background-scattering from fluorescence emission spectra, (3) time-resolved emission spectra of transient species, and (4) the enhancement of Raman spectra by rejection of fluorescence background emission. Previously, we reported the use of a synchronously pumped tunable dye laser producing very short light pulses (
