Evidence for dual La and L b emission in 5-methylindole.

The steady-state fluorescence anisotropy of 5-methylindole is shown to depend on both excitation and emission wavelengths, at room temperature in glycerol. A simulation is presented that shows that this emission wavelength dependence of the anisotropy can be explained in terms of dual emission from both the La and the Lb transition moments of the indole ring. For such dual emission to occur, the lowest excited-state energy level of both of these oscillators must be very similar.