Precision Measurements of Acetylene Spectra at 1.4–1.7 μm Recorded with 352.5-m Pathlength

The spectrum of acetylene (C2H2) in the 1.5 μm region has been recorded at room temperature with Doppler-broadening-limited resolution at pathlengths up to 352.5 m. The spectra were obtained by using an all vacuum Fourier transform infrared (FTIR) spectrometer with a multipass cell of 4 m base length attached to it. The calibration of the data is discussed in detail. Thirty-three subbands have been detected in this study for C2H2and five for12C13CH2. These include ten new bands and nine new states in the parent species, and two new bands and two new states in the12C13CH2species. Updated energy level diagrams for HCCH and H13CCH are shown. The spectroscopic constants obtained from the HCCH spectrum are reported.