The bending energy levels of C 2H 2

Abstract

Absorption spectra of C 2H 2 have been recorded between 50 and 1450 cm −1, with a resolution always better than 0.005 cm −1, using two different Fourier transform spectrometers. Analysis of the data provided two sets of results. First, the bending levels with Σ t V t ( t = 4, 5) ≤ 2 were characterized by a coherent set of 34 parameters derived from the simultaneous analysis of 15 bands, performed using a matrix Hamiltonian. The following main parameters were obtained (in cm −1): ω 4 0 = 608.985196(14), ω 5 0 = 729.157564(10); B 0 = 1.17664632(18), α 4 = −1.353535(86) × 10 −3, α 5 = −2.232075(40) × 10 −3; q 4 0 = 5.24858(12) × 10 −3, and q 5 0 = 4.66044(12) × 10 −3, with the errors (1σ) on the last quoted digit. Second, a more complete set of bending levels with Σ t V t ≤ 4, some of which have never previously been reported, and also including V 2 = 1 have been fitted to 80 parameters. This simultaneous fit involved 43 bands and used the same full Hamiltonian matrix. Some perturbations which affect the higher excited levels are discussed.