Calculation of the infrared and raman spectra of short linear carbon chains

Summary form only given. Beside fullerenes, linear carbon clusters also attracted much interest in the last years, both experimentally and theoretically. In a recent work Raman spectroscopy of electrochemically prepared carbyne was reported. The Raman spectra can be explained - as usual for conjugated polyenes - by the effective conjugation length model, taking into account the distribution of the conjugation lengths. We carried out vibrational analysis for short linear chains: H - C/sub 2n/ - H (n = 1, 2, 3, 4, 5) and H/sub 2/ - C/sub 2n/ - H/sub 2/ (n = 1, 2, 3, 4, 5), modelling the alternating carbyne, and the cumulene type carbon chains, respectively. Geometries were optimized by using ab initio Hartree-Fock theory with Dunning´s double-/spl zeta/ basis set. IR- and Raman-intensities were obtained by calculating dipole- and polarizability derivatives, respectively. No resonance Raman effect was taken into account.