Tracking azobenzene photoisomerization with sub-20-fs UV pulses

Summary form only given. Azobenzene (AB) is a diazene derivative where both hydrogens are replaced by phenyl groups. Under irradiation with UV light, it undergoes ultrafast trans→cis isomerization; the inverse cis→trans isomerization can be driven by light or occurs thermally in dark. AB photochromic properties enable its application as a light triggered switch in numerous molecular devices and functional materials [1]. Here we use femtosecond pumpprobe and two-dimensional electronic spectroscopy in the UV range (2DUV) with sub-20-fs time resolution, combined with ab initio quantum mechanics simulations, to study the initial dynamics of trans-AB isomerization with unprecedented mechanistic detail.