THE HE-I VALENCE PHOTOELECTRON-SPECTRUM OF C-70 IN THE GAS-PHASE

The high-resolution He I photoelectron spectrum of C70 in the gas phase is reported and compared with that of C60 and theoretical calculations. Similar to C60, the C70 spectrum shows two separate valence ionization band envelopes in the low energy region, but there are more separate ion states visible within the two envelopes. The first envelope of overlapping ionizations spans from about 7.3 to 8.8 eV, and the second from about 8.9 to 10.3 eV. The greater complexity of the C70 spectrum compared to that of C60 is expected due to the lower symmetry of C70 and the ten additional pi electrons from the additional carbon atoms. The first vertical ionization energy is 7.47 +/- 0.02 eV, which is destabilized 0.17 eV from that of C60.