Journal of Physical Chemistry B, Vol.107, No.31, 7768-7775, 2003
Photoemission from azobenzene alkanethiol self-assembled monolayers
Photoelectron spectra were measured for films of self-assembled azobenzene-terminated alkanethiol monolayers on gold using synchrotron radiation. The azobenzene was substituted either by CF3 or CH3 in the para position. As a result of the orientational order of the molecules within the films, as indicated by the pronounced angle dependence of the photoemission spectra, it is possible to identify laser-induced optical switching of the molecules using combined laser and synchrotron pulses. Molecular switching, i.e., photoisomerization, is recognized by relative intensity changes of the photoemission peaks and also by spectral shifts to higher binding energies. The latter result from a change of the molecular dipole moment associated with the transcis laser-induced photoisomerization of the azobenzene-CF3 group.