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

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