We show that illumination by continuous white radiation saturates the population of levels so that some of the transitions are not observed. This reduces the number of observable transitions so that the resolution of transitions is improved. In the case of \nu = 11/2 the improved resolution leads to clear observation of zero in the transverse resistivity which appears as a finite resistivity in absence of saturating radiation.
Cite
@article{arxiv.cond-mat/0109407,
title = {Illumination of quantum Hall effect},
author = {Keshav N. Shrivastava},
journal= {arXiv preprint arXiv:cond-mat/0109407},
year = {2007}
}