Ultrafast x-rays trace how azobenzene switches between molecular forms

Chemistry World reports that researchers used time-resolved x-ray liquidography to follow azobenzene changing from trans to cis in solution. After exposing the molecule to ultraviolet light, they fired femtosecond x-ray pulses to track its changing structure. The team found that a twist around a carbon–nitrogen bond starts the change, before the nitrogen–nitrogen bond rotates. The researchers say this is the first use of the method on molecules made only of lighter atoms.