High-resolution ion translational energy spectrometry of C60. Excitation of singlet and triplet states in collisions with H+ and H2+

A new ion translational energy spectrometer has been utilised to carry out energy-loss experiments with H+ and H2+ protectiles colliding with C60 vapour at impact energies of 2–4 keV, and an energy resolution of 14–20 meV FWHM. H+-C60 collisions allow access to the singlet manifold of electronically excited states of buckminsterfullerene which lie in the spectral region from the infrared to the vacuum ultraviolet. Corresponding experiments with H2+ projectiles access both the singlet and the triplet states. Agreement was found between present measurements, theoretical predictions and electron energy loss data for H+-C60 collisions, where only excitation to singlets is involved. However, for H2+-C60 the satisfactory interpretation of the spectrum will require further triplet state calculations to higher excitation enegries.