Infrared diode laser spectroscopy of the ν3 fundamental and ν3+ν2−ν2 sequence bands of 13C3 and of the ν3 fundamental band of 12C 12C 13C

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Abstract
Gas‐phase infrared spectra of 13C‐substituted C3 molecules have been studied in the region of the ν3 vibration around 5 μm, using a tunable diode laser spectrometer and a hollow‐cathode discharge in a flowing mixture of acetylene and helium. Three bands were observed and assigned: the ν3 fundamentals of 13C3 and of 12C 12C 13C, and the ν3+ν2−ν2 sequence band of 13C3 . The observed band origins are consistent with previous matrix‐isolation spectroscopy of substituted C3 . The rotational and centrifugal distortion parameters are consistent with previous gas‐phase work on 12C3 , and they also reflect the highly anharmonic nature of the bending vibration in this molecule. The ν3 band of 12C 12C 13C, measured here for the first time, provides a sensitive means to measure 13C abundances in astrophysical sources containing C3 .