Electronic absorption spectra of C2nH−, C2n−1N− (n=4–7), and C2n−1N (n=3–7) chains in neon matrices

The Σ+1←XΣ+1 electronic transition of the C2nH− and C2n−1N− (n=4–7) anion chains has been observed following mass selection and codeposition with excess neon at 6 K. Photodetachment of the electron resulted in the detection of a band system due to the neutral C2n−1N radical. The spectra suggest that C7N, like C5N, has a Σ2 ground state. The B 2Π←X 2Π transition is detected for the larger C2n−1N (n=5–7) chains. These appear at slightly higher energies than those of the isoelectronic C2nH radicals and show similar spectral features. Several infrared transitions of the anions have also been observed.