A. T. Wyker and J. N. Demasl University of Virginia Charlottesville,22901
I I
Computer Programs for Evaluating Luminescence Decay Times
Two computer programs LUMEN and DECAY in Hewlett Packard time sharing Basic are available for evaluating luminescence decay times. DECAY can he used whenever the data are exponential and taken at even time intervals. The input is the time interval between data points, At, the number of data points, N, the observed intensity at each point, I(&)(tl = 0). 7 is obtained from a linear least-squares fit to the ln[I(t;)] versus t plot. Output includes the least-squares 7 and I a t t = 0, Io. A goodness of fit parameter G is given by
where G"2 is the standard deviation between the observed and calculated curve, Icalc(tj).If the data are on graph paper and A1 is calculatt:d in advanrr, a 20-point decay curve may he read direct1.v dfof the qaph, entered into the terminal, and the results obtained in under 2 min. LUMEN is used whenever r is so short that the luminescence decay no longer exhibits an exponential region. The observed flash, F(t), and decay, D(t), are deconvoluted by the
656 / Journal of Chemical Education
Phase-Plane method by first transforming into W(t) and Z(t) coordinates (eqn. (11) of the following a r t i ~ l e ) The . ~ Z(t) versus W(t) plot is then fit by a linear least-squares to compute the required K and r. The first 25% of the W(t) - Z(t) points are disregarded in the fit because of their high noise level. From K and 7 the expected decay Dcalc(t)and G'I2 are computed from eqns. (12) and (13) of the preceding article.? The Droeram is versatile in that time consuming. mintout . . mdy he suppressed and any numher d d e c a y s may be used with a rommon flash without having- to reenter the flash data each time. We gratefully acknowledge support of the Petroleum Research Fund, administered hy the American Chemical Society, the Research Corporation, and the' NIH for a biomedical Support Grant administered by the University of Virginia, the National Science Foundation, and the Department of Chemistry.
1
To whom correspondence should be addressed.
2 Demas,
J. N., J. CHEM. EDUC., 53,657(1976).
