HIGH-RESOLUTION ION TRANSLATIONAL ENERGY SPECTROMETRY OF C-60 - EXCITATION OF SINGLET AND TRIPLET-STATES IN COLLISIONS WITH H-2(+)( AND H)

A new ion translational energy spectrometer has been utilised to carry out energy-loss experiments with H+ and H-2(+) projectiles colliding with C-60 vapour at impact energies of 2-4 keV, and an energy resoluti on of 14-20 meV FWHM. H+-C-60 collisions allow access to the singlet m anifold of electronically excited states of buckminsterfullerene which lie in the spectral region from the infrared to the vacuum ultraviole t. Corresponding experiments with H-2(+) projectiles access both the s inglet and the triplet states. Agreement was found between present mea surements, theoretical predictions and electron energy loss data for H +-C-60 collisions, where only excitation to singlets is involved. Howe ver, for H+-C-60 the satisfactory interpretation of the spectrum will require further triplet state calculations to higher excitation energi es. (C) 1997 Elsevier Science B.V.