Control of Resonance Transitions of Substances Encapsulated in Fullerenes by Using Synchrotron Radiation

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(1) The photoion yield spectra of an endohedral metallofullerene M@C_<82> (M=Ce, Pr) were measured in the photon energy range of 100-150 eV by using time-of-flight mass spectrometry. Parent ions, M@C_<82>+, M@C_<82>+ and M@C_<82>^<3+> were observed in the mass spectra. The photoion yield spectra of M@C_<82>^<2+> showed a broad peak at 120-140 eV that was assigned to the 4d-4f giant dipole resonance of the encapsulated metal atoms. Absolute photoabsorption cross sections of M@C_<82> were evaluated from the photoion yield spectra at off- and on-resonance positions.(2) A new technique has been developed for observing the velocity distribution of a fast molecular beam by making use of a velocity map imaging method. The photoion images of fullerene C_<60> molecular beams were observed with this technique. At the center of the image there is a narrow and intense pattern which stems mainly from C_<60>^<2+>. The temperature of the neutral beam evaluated from the images agrees well with that of the hot oven containing C. sample powder.(3) Absolute photoabsorption cross sections of C_<60> thin films are determined in the hv range from 1.3 to 42 eV by using photon attenuation method. The spectrum shows a prominent peak of 1180 Mb at 22.1 eV with several fine structures due to single-electron excitation similarly to the case of C_<60> in the gas phase. The complex refractive index and complex dielectric function are calculated up to 42 eV through the Kramers-Kronig analyses. From the present data of C60 thin films the cross section curve of a molecular C_<60> is calculated with an assumption that the polarization effect of surrounding C_<60> molecules can be expressed by the Clausius-Mossotti relation. The spectrum thus obtained shows an excellent agreement with that of C_<60> in the gas phase.