The orientation of the transition

Determine the nature of the electronic excited state

In high resolution gas phase studies the orientation of the transition dipole moment can be determined. Hence, it is tempting the assign the nature of the electronically excited state, either La or Lb, based on the orientation of this vector. This works out good for a number of modified indoles, like 5-methoxyindole, tryptamine and serotonin. However, for a few molecules like 6-methoxyindole and 6-fluoroindole