Activation energies of fundamental and higher order states in the functional quantum Hall effect.

We report a systematic study of activation energies for the fundamental states in the fractional quantum Hall effect at Landau level filing factors nu = 1/3, 2/3, 4/3 and 5/3 in magnetic fields up to 28T. We also present activation energies for the higher order states at nu = 2/5 and 3/5.