The yield curves for photoions from Ce@C(82) are measured by using synchrotron radiation in the photon energy range from 90 to 160 eV. Parent Ce@C(82) (z+) and fragment ions C(60) (z+) and C(70) (z+) are observed in a mass spectrum (z=1 and 2). The yield curves for doubly charged ionic species exhibit broad resonance in the photon energy region of from 120 to 140 eV which is ascribed to the 4d-->4f giant dipole resonance of the encapsulated Ce atom. The total photoabsorption cross section of Ce@C(82) was determined from partial photoionization cross sections for formation of the parent and fragment ions to be 5.3(-1.1) (+1.8) and 19.6(-3.9) (+6.5) Mb at photon energies of 110 and 130 eV, respectively.

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Photoion yields from gaseous fullerenes, C(60) and C(70), for production of singly and doubly charged ions are measured by mass spectrometry combined with tunable synchrotron radiation at hnu=25-150 eV. Since the signal of triply or highly charged ions is very weak, the total photoionization yield curve can be estimated from the sum of the yields of the singly and doubly charged ions. A distinct feature appears in the resultant curve of C(60) which is absent in the calculated total photoabsorption cross section previously reported. This difference is attributed to C(60) (2+) ions chiefly produced by spectator Auger ionization of the shape resonance states followed by tunneling of the trapped electron or by cascade Auger ionization. Ratios between the yields of doubly and singly charged ions for C(60) and C(70) are larger than unity at hnu>50 eV. These ratios are quite different from those reported in the experiments using electron impact ionization.