Study of excited states of fluorinated copper phthalocyanine by inner shell excitation

Near edge X-ray absorption fine structure (NEXAFS) spectra of hexadecafluoro copper phthalocyanine (FCuPc) films (thickness of 50Å) on MoS₂ substrates were observed near the carbon (C) and fluorine (F) K-edges. From the analysis of the dependence of C and F K-edge NEXAFS spectra on the photon incidence angle (α), the average molecular tilt angle was determined to be 30°. The lowest and second lowest peaks in the F K-edge NEXAFS were assigned to the transition to σ*. In the ion time-of-flight mass spectra of FCuPc excited by photons near the F K-edge, F⁺, CF⁺, and CF₃⁺ ions were mainly observed. These results indicate that C-C bonds as well as C-F bonds are broken by the photon irradiation. From the analysis of the partial ion yield spectra of F⁺ and CF⁺ near the F K-edge, the lowest and second lowest peaks in the F K-edge NEXAFS spectra could be assigned to transitions to σ(C-F)* and σ(C-C)>*, respectively.