SITE-SELECTIVE PHOTOSELECTION STUDY OF INDOLE IN ARGON MATRIX - LOCATION OF THE (1)L(A) ORIGIN

Polarized fluorescence excitation and dispersed fluorescence spectra o f indole in solid Ar at 20 K under site selective conditions have reve aled that nu(28) is Herzberg-Teller (HT) active, both in the excitatio n and the nuorescence spectrum. The two lines 455 and 480 cm(-1) above the (1)L(b) origin are a Fermi doublet involving 28(0)(1) and the our -of-plane combination 39(0)(1)41(0)(1) and derive (1)L(a) optical char acter via the HT coupling by nu(28). The true (1)L(a) origin appears t o be about 1400 cm(-11)L(b) origin in vapor, as discerned by the diffe rential red shift in the Ar matrix.