The electronic spectrum of cyanoacetylene: Part II. Analysis of the 2300-Å system

Abstract

The diffuse banded absorption spectrum of cyanoacetylene in the gas phase between 2300 Å and 2000 Å has been measured and analyzed. The spectrum results from a forbidden electronic transition from the linear ground state with 1Σ + symmetry to a linear excited state with either 1Σ − or 1Δ symmetry, made allowed by π-type vibrations. The values of these for the excited state of HCCCN DCCCN are: ν 5′, 290 235 cm −1 ; ν 6′, 414 407 cm −1 ; ν 7′, 226 (215) cm −1 . Other excited state vibrations that have been identified are: ν 2′ ( σ +), 2120 2090 cm −1 ; ν 4′ ( σ +), 953 930 cm −1 . The electronic origin of the transition is at 44 221 44 248 cm −1 . The diffuseness of the bands precluded rotational analysis.