High Resolution Rovibrational Spectroscopy of the ν6 and ν3 + ν7 Bands of H2CCCH.

Abstract

The molecular ion H₂CCCH⁺ has been further investigated in a 4 K cryogenic ion trap instrument employing the leak-out spectroscopy (LOS) method. Transitions within two perpendicular bands, the fundamental ν₆ (antisymmetric H-C-H stretch) and the combination band ν₃ + ν₇ (C≡C stretch and CH₂ rock), have been measured in high resolution for the first time. The spectral analysis was aided by high level quantum chemical calculations and by our previous study of the parallel ν₁ and ν₃ + ν₅ bands [Silva, W. G. D. P. ; Mol. Phys. 2023, e2296613]. The novel results presented here have allowed for a seventy-fold improvement on the accuracy of the value of the A₀ rotational constant of this near-prolate asymmetric top.