Using collisional cooling within a buffer-gas cell coupled with cavity-ringdown spectroscopy, we have identified and assigned previously unpublished ro-vibrational transitions for the 2ν 1 transition of HC 3 N in the 1.5 µm region, refined the excited-state rotational B and D constants, and reported line intensity estimates that motivate the use of this molecular signature in exoplanetary observations. Our technique translationally and rotationally cools our target molecules-which was confirmed using Doppler thermometry-enabling us to extract important spectroscopic properties essential to astrophysical detection. We estimate the total band strength of the 2ν 1 vibrational band of HC 3 N to be ∼ 10 -19 cm -1 /( molecule • cm -2 ), making it a viable candidate for exoplanet transmission spectroscopy in this spectral region. Future efforts include the measurement of collisional cross sections that, when coupled with robust theoretical investigations, will yield information that is essential to a detailed understanding of planetary and interstellar chemistry.