Identifying Charge States of Molecules with Spin-flip Spectroscopy

The charge states of single magnetic CoPc chains on Pb(111) film were manipulated with a scanning tunneling microscope and identified by spin-flip inelastic tunneling spectroscopy. We show that the tunneling spectra of the charged and neutral states of the molecular chain exhibit different features associated with the spin-flip processes. Therefore we are able to identify the charge states by the spin-flip spectroscopy. This approach does not rely on the indirect information induced by the additional charges on molecules. The experiment demonstrates a general method for detecting the charge states at the nanometer scale in a more straightforward manner.