THE D'-]A' TRANSITION IN IBR - A DEPERTURBATION ANALYSIS

The D'2(P-3(2)) --> A'2(3PI) transition in IBr occurs with maximum int ensity near 3850 angstrom when mixtures of I2 and Br2 in Ar are excite d by a Tesla coil. Spectra are recorded photographically for I79Br and I81Br separately, and 24 upsilon'-upsilon'' bands spanning upsilon' = 0-5 and upsilon'' = 11-17 are rotationally analyzed, yielding approxi mately line assignments. Together with existing high-quality data cove ring the high-upsilon', low-upsilon'' region, these data are analyzed through a deperturbation model which assumes that minor anomalies in t he D'-state rotational constants are the result of weak interactions w ith the nearby beta1(P-3(2) state. This fit pins down the absolute ene rgies of both states for the first time, yielding T(e)' = 39 457(4) cm -1, T(e)'' = 11 437 (4) cm-1. Other primary spectroscopic constants (c m-1) are DELTAT(e) = 28 019.22 omega(e)' = 123.064, omega(e)xi'e = 0.2 812, B'e = 0.02860, omega''e = 147.631, = 1.260, B''e = 0.04290, R'e = 3.4806 angstrom, R''e = 2.842 angstrom. (C) 1994 Academic Press, Inc.