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 ν1, ν2, and ν41 of C2H2 were analyzed to give the band origin, ν0, and the upper state constants, B1 and D1; accurate infrared values of the lower state constants, B0 and D0, were assumed in the analysis. The values of the constants for the ν2 band illustrate the accuracy obtained: ν0 = 1974.317(2), B1 = 1.170419(14), D1 = 1.579(18) × 10−6 cm−1. Five difference bands originating in transitions from the low-lying ν4 = 1 and ν5 = 1 vibrational states were also measured and analyzed.