Step-scan Fourier transform infrared absorption spectroscopy of acetylene monomer and solid in a supersonic free jet

The infrared spectra of acetylene monomer and solid generated in a pulsed supersonic jet have been obtained near 3300 cm−1 using step-scan Fourier transform infrared (FTIR) absorption spectroscopy. The rotational temperature of monomer was determined to be as low as 10 K. A broad band was also observed between 3220 and 3260 cm−1 with a dominant peak at 3234 cm−1, which was assigned to the high-temperature cubic phase of solid acetylene.