Rotational spectrum of anti- and gauche-4-cyano-1-butyne (C5H5N) – An open-chain isomer of pyridine

• Rotational transitions from 8 to 38 and 130 360 GHz used study anti- gauche- 4-cyano-1-butyne (an isomer of pyridine). Spectroscopic constants for the ground vibrational states determined first time. Hyperfine resolved included determine quadrupole coupling ( χ aa , bb cc ). Experimental energy difference between conformers (Δ E anti – gauche The analysis rotational spectrum 4-cyano-1-butyne, an open-chain pyridine, is presented herein Transitions both conformational isomers, were observed in 8–38 130–360 frequency ranges fit effective sextic distorted-rotor Hamiltonians with low uncertainty (σ < 50 kHz), allowing their potential detection by radioastronomy or harsh reaction environments. microwave region includes hyperfine-split conformers, experimental determination constants. In millimeter-wave region, not every observable ground-state transition could be satisfactorily addressed a single-state Hamiltonian due Coriolis low-energy vibrationally excited states. Thus, fits obtained including only K -series without obviously perturbed levels. Importantly, does include most intense throughout ranges. predicted values (MP2/cc-pVTZ) are close agreement spectroscopic These data provide sufficient foundation identification interstellar medium radioastronomy. conformer estimated lie 1.00 (5) kcal/mol higher than conformer, as using intensities.