High-resolution infrared spectrum of triacetylene: The [formula omitted] state revisited and new vibrational states

Abstract

New data are presented that follow from a high-resolution survey, from 3302 to 3352cm−1, through expanding acetylene plasma, and covering the CH asymmetric (ν5) fundamental band of triacetylene (HC6H). Absorption signals are recorded using continuous wave cavity ring-down spectroscopy (cw-CRDS). A detailed analysis of the resulting spectra allows revisiting the molecular parameters of the ν5 fundamental band in terms of interactions with a perturbing state, which is observed for the first time. Moreover, four fully resolved hot bands (5011011,5011111,5011311, and 1018011110), with band origins at 3328.5829(2), 3328.9994(2), 3328.2137(2) and 3310.8104(2)cm−1, respectively, are reported for the first time. These involve low lying bending vibrations that have been studied previously, which guarantees unambiguous identifications. Combining available data allows to derive accurate molecular parameters, both for the ground state as well as the excited states involved in the bands.