2025ApJS..280...41H

Propargylamine (HC≡C-CH₂-NH₂), with a triple bond and an amine group, is a nitrogen-bearing organic molecule of astrochemical interest due to its potential role as a precursor to aminoacetonitrile and other complex organic molecules in the interstellar medium (ISM). Despite the detection of the structurally related molecules propargylimine (HC≡C-CH=NH) and aminoacetonitrile (NH₂-CH₂-CN) in the ISM, it remains undetected. This work presents the first high-resolution far-infrared spectroscopic study of propargylamine, conducted using a synchrotron-based Fourier transform infrared spectrometer at the Canadian Light Source. The rotationally resolved vibrational spectra were measured in the range of 50-480 cm^–1, targeting its three lowest vibrational modes. The rovibrational analysis led to the assignment of two bands centered at 338.8342332(25) and 228.5012023(26) cm^–1, corresponding to the out-of-plane HC≡C-C linear bending (ν₂₀) and -NH₂ torsion (ν₂₁) modes, respectively. Also, a band origin of 199.10535(19) cm^–1 was determined for the in-plane HC≡C-C linear bending (ν₁₃) mode through a Coriolis-type resonance with the ν₂₁ mode. The accurate assignment clears up a discrepancy over these vibrational energy levels between previous millimeter-wave and low-resolution infrared studies and made possible the determination of an updated rovibrational partition function. These data provide spectroscopic parameters for future astronomical searches in the ISM.