Irreversible isomerization of the azobenzene derivate Methyl Orange on Au(1Â 1Â 1)

Isolated molecules of 4-dimethylaminoazobenzene-4-sulfonic acid, an azobenzene derivate called Methyl Orange, adsorbed on the Au(1 1 1) surface are investigated with scanning tunneling microscopy at 5 K. Inelastic tunneling electrons induce the trans-cis isomerization.