We report a pilot study of whether laser-assisted scanning tunneling spectroscopy (STS) can be used to investigate the changes in electronic structure between the ground state and first singlet (S 1) excited states of thin films of organic molecules. STS measurements of 4 ″, 3 ″-dimethylsexithiophene and pentacene, excited into their S 1 states using suitable continuous wave laser excitation, show a narrowing of the electronic gap. These results are consistent with theoretical calculations of the electronic structure of these molecules in their S 1 states.
American Physical Society
9 Aug 2005
Volume: 72 Issue: 8 Pages: 085425
Physical Review B