Question

Are there molecules that interconvert between isomers upon irradiation with UV light?

Answer 1

Sometimes. There is one case I know of:

If you hit it with a camera flash (`hv`), you can catalyze the cis-trans isomerization of this azo dye compound, methyl red, into its cis configuration. Then what you could do is monitor it as it goes back to the more stable trans configuration and analyze its kinetics mechanism (it's a first order "half-life" decay).

There may be others, but that's one I could think of.