The 4 d–4 f dipole resonance of the Pr atom in an endohedral metallofullerene, Pr@C 82

Abstract

The photoion yield spectra of an endohedral metallofullerene Pr@C 82 were measured in the photon energy range of 100–150 eV by using time-of-flight mass spectrometry. Parent ions Pr@C 82 +, Pr@C 82 2+ and Pr@C 82 3+ were observed in the mass spectra. The photoion yield spectra of Pr@C 82 2+ showed a broad peak at 120–140 eV that was assigned to the 4 d–4 f giant dipole resonance of the encapsulated Pr atoms. Absolute photoabsorption cross sections of Pr@C 82 were evaluated from the photoion yield spectra to be 37±12 Mb at 110 eV (off-resonance) and 52±13 Mb at 130 eV (on-resonance). These cross sections of Pr@C 82 were compared with the results of Ce@C 82, the only metallofullerene whose photoionization properties have ever been studied near the 4 d edge of the encapsulated metal atom. The enhancement of photoabsorption due to the giant resonance was found to be similar in Pr@C 82 and Ce@C 82, but there are marked differences in the peak shapes, which can be explained as due to interference effects between the fullerene cage and the encapsulated metal atoms.