The measured R(5) line intensity for HC 3 N was used to calibrate the full spectrum simulated at 20 K in PGO-PHER to obtain the line intensities for all other peaks measured in this work (listed in Table ). The line intensities for the scaled PGOPHER spectrum were summed from 6544.0 cm -1 to 6559.5 cm -1 to obtain the total vibrational band strength for the 2ν 1 transition of HC 3 N, yielding a value of 2.6 × 10 -19 cm -1 /( molecule • cm -2 ) for the full vibrational band. To the best of our knowledge, this is the first report of an estimated band strength for HC 3 N near 1.5 µm.