Cyanopolyyne molecules, HC 9 N and HC 11 N, were isolated in solutions and UV, IR, and resonance Raman spectra were measured for the study of their electronic and vibrational properties. Strong signals were observed both in the IR and resonance Raman spectra for the stretching vibrational mode of the sp-hybridized linear carbon chain in the electronic ground state, i.e., σ 4 at 2141 cm -1 for HC 9 N and σ 6 at 2105 cm -1 for HC 11 N.Trapped in cryogenic solid acetonitrile matrix hosts at 20 K, transitions in phosphorescence, 3 Σ + → 1 Σ + , were observed for HC 9 N at 582.3 nm (0-0) and longer wavelengths and for HC 11 N at 643.7 nm (0-0) and longer wavelengths. Electronic transitions in the UV, 1 Σ + ← 1 Σ + , were elucidated by phosphorescence excitation mapping to observe asymmetric patterns with sharp emission-absorption features explainable by Shpolsky effects. For HC 9 N, three distinct trapping sites were discernible in solid acetonitrile, while the phosphorescence spectra were blurred in solid n-hexane. The observed phosphorescence lifetime of HC 9 N was longer than that of HighlightsPhosphorescence of cyanopolyyne molecules of HC 9 N and HC 11 N at 20 K Resonance Raman spectroscopy and IR spectra of HC 9 N and HC 11 N Solid acetonitrile or n-hexane matrix hosts provides multiple trapping sites

Laser-ablated polyyne molecules, H(C≡C)nH, were separated by size in solutions and co-condensed with excess hexane molecules at a cryogenic temperature of 20 K in a vacuum system. The solid matrix samples containing C8H2, C10H2, and C12H2 molecules were irradiated with UV laser pulses and the phosphorescence 0–0 band was observed at 532, 605, and 659 nm, respectively. Vibrational progression was observed for the symmetric stretching mode of the carbon chain in the ground state with increments of ~2190 cm−1 for C8H2, ~2120 cm−1 for C10H2, and ~2090 cm−1 for C12H2. Temporal decay analysis of the phosphorescence intensity revealed the lifetimes of the triplet state as ~30 ms for C8H2, ~8 ms for C10H2, and ~4 ms for C12H2. The phosphorescence excitation spectrum reproduces UV absorption spectra in the hexane solution and in the gas phase at ambient temperature, although the excitation energy was redshifted. The symmetry-forbidden vibronic transitions were observed for C10H2 by lower excitation energies of 25,500–31,000 cm−1 (320–390 nm). Detailed phosphorescence excitation patterns are discussed along the interaction of the polyyne molecule and solvent molecules of hexane.