Electronic Transitions of CsC2,CsC_2~-,and CsC_4 in Neon Matrixes

摘要

The anions of CsC2 and CsC4 produced by sputtering a graphite surface with Cs~+ were mass-selected and trapped in neon matrixes at 6 K.The electronic absorption spectra of CsC2 and CsC4,obtained by photodetachment of electrons from the anions,were measured subsequently and reveal strong absorptions in the visible range,which resemble the known band systems of C_2~_ and C_4~-,respectively.The origin band of CsC2(500.4 nm)and CsC4(442.6 nm)is shifted by ~1100 or by ~700 cm~(-1)to the blue from the position of the 0_0~0 band of C_2~-or C_4~-.The observed system of CsC2 is assigned to the ~2B_2-X ~2A_1 electronic transition of the T-shaped form.The CsC4 spectrum is consistent with a C_4~-chain slightly perturbed by the Cs atom.The oscillator strength of the observed electronic transition of CsC2 and CsC4 is an order of magnitude larger than for the respective carbon anions.CsC2~ has a weak electronic transition,assigned to ~2B_2-X ~1A_1 in the C_(2v)form,with origin band at 516.5 nm.