Laser-Induced Fluorescence and Phosphorescence of C₆₀ Isolated in Solid Ne

Abstract

Laser-induced fluorescence spectrum of C60 isolated in solid Ne with resolved vibronic lines was recorded with laser excitation at 355 nm or in the 585−645 nm region. The spectrum consists of progressions with spacings ∼260 cm-1, each separated by varied intervals from the origin at 15 648 cm-1. The intervals 272, 412, 971, 1452, 1587, 2883, 2924, and 3023 cm-1 correspond to various vibrational levels of gu and hu symmetry, or their combination with the ag(1) level, of the ground electronic state; the ∼260 cm-1 progression (with 272 cm-1 as the first spacing) corresponds to the Jahn−Teller active hg(8) mode. When the Ne matrix was doped with Xe (1.2%), phosphorescence of C60 was greatly enhanced. The spectrum exhibits a single progression with origin at 12 773 cm-1 and spacings near 260 cm-1; its lifetime at 5 K was approximately 90 μs. The fluorescence excitation spectrum revealed progressions of spacings either ∼180 or ∼260 cm-1, corresponding to excitation to two different singlet excited states, respectively. The first excited singlet and triplet states observed in this work are proposed to be A 1T2g and a 3T2g, respectively. The second excited singlet state, proposed to be B 1T1g, lies approximately 200 cm-1 above the A 1T2g state.