High resolution rotation–vibration Raman spectra of acetylene. I. The spectrum of C₂H₂

Abstract

The Raman spectrum of gaseous acetylene was excited in a multiple-reflection Raman cell by a single-moded Ar + laser and recorded photographically; the gas pressure was 380 Torr and the spectral slit-width ~0.1 cm −1 . The three Raman-active fundamentals ν 1 , ν 2 , and ν 4 1 of C 2 H 2 were analyzed to give the band origin, ν 0 , and the upper state constants, B 1 and D 1 ; accurate infrared values of the lower state constants, B 0 and D 0 , were assumed in the analysis. The values of the constants for the ν 2 band illustrate the accuracy obtained: ν 0 = 1974.317(2), B 1 = 1.170419(14), D 1 = 1.579(18) × 10 −6 cm −1 . Five difference bands originating in transitions from the low-lying ν 4 = 1 and ν 5 = 1 vibrational states were also measured and analyzed.