  Recently, an article by the Barnes group reported on the experimental study
of a photoisomerization reaction inside an optical cavity, claiming to
reproduce previous results by Hutchison et al. and making the point that in
such setups, changes in the absorption of ultraviolet radiation by the
molecules in the cavity can lead to modifications in the photochemical reaction
rate. While Hutchison et al. associated such modifications with the emergence
of strong light-matter coupling, in their attempt to re-examine these
experiments, Barnes et al. did not find any evidence that strong coupling needs
to be invoked to explain the observed effects. In response to this publication,
we herein highlight the main differences between the two experimental studies,
and explain why the results of Barnes et al. are irrelevant to the former study
and have no bearing on its conclusions. Specifically, we show that under the
experimental conditions used by Hutchison et al. such intensity-modification
effects are negligible and can therefore be ruled out.
