photoisomerization

In photoisomerization no chemical bonds are broken, but the molecule changes shape. For example, absorption of optical radiation by a stilbene molecule converts the central double bond from trans to cis. As in photodissociation, this is caused by the electron distribution in the excited…

…process is called one of photoisomerization, the absorption of light energy causing the molecule to twist into a new shape. Having suffered this alteration in shape, the retinal presumably causes some instability in the opsin, making it, too, change its shape, and thereby exposing to the medium in which it…