DIODE-LASER SPECTROSCOPY OF THE NU-3 BAND OF C-13(5)

The gas-phase infrared spectrum of the linear molecule C-13(5) has been studied in the region of the nu-3 vibration around 2086 cm-1. The results were obtained using a tunable diode laser spectrometer and a hollow cathode discharge in a flowing mixture of acetylene and helium. Two bands were observed and assigned: the nu-3 fundamental and the associated nu-3 + nu-7-nu-7 hot band. The study of nu-3 in isotopically substituted C5 provides more experimental data for this species, which may be difficult to obtain otherwise because of the predicted weakness of its other infrared transitions. The band origins and rotational constants for C-13(5) are consistent with those from a matrix-isolation study of C5 isotopes and gas-phase studies of C-12(5). By combining the C-13(5) and C-12(5) results it is possible to determine an experimental B(e) = 2548.7 MHz for C-12(5). The nu-3 fundamental band origin of C-13(5) was determined to be 2085.769 cm-1.