Vibrational spectroscopy of matrix-isolated, mass-selected cyanoacetylene cations

Recent infrared spectroscopic results from a new setup for the deposition o f mass-selected ions in neon matrices are presented. The strong infrared si gnal observed for the asymmetric stretch of CNC+ and the appearance of the corresponding band for (CNC+)-C-13 in its natural isotopic abundance, demon strates the sensitivity and usefulness of the apparatus. Evidence of a comb ination band of CNC+ involving the low-frequency bend is also obtained. Usi ng this setup, the infrared spectra of the cyanoacetylenic cations, H(D)C3N +, and C4N2+ are observed for the first time. The assignment of the stretch ing vibrations of these linear cations are well-supported by density-functi onal calculations. (C) 2001 American Institute of Physics.