14N nuclear quadrupole coupling and methyl internal rotation in 3-methylpyrrole investigated by microwave spectroscopy

Thuy Nguyen (1, 2) , Wolfgang Stahl , Ha Vinh Lam Nguyen (2) , Isabelle Kleiner (2)

1 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques
2 IPSL (FR_636) - Institut Pierre-Simon-Laplace

The molecular structure of 3-methylpyrrole in the gas phase has been determined using a combination of high-resolution spectroscopy and quantum chemical calculations. The rotational spectrum was recorded using a molecular jet Fourier transform microwave spectrometer covering the frequency range from 2.0 to 26.5 GHz. The experimental data were analyzed using the programs XIAM and BELGI-Cs-hyperfine. Because the internal rotor axis accidentally lies along the principal a-axis of inertia, the rho axis system and the principal axis system coincide, enabling a direct comparison of the fits. With the program XIAM, the rotational constants A = 8631.1629(12), B = 3342.19750(43), and C = 2445.73846(42) MHz were obtained. Torsional splittings due to internal rotation of the methyl group were observed, leading to the determination of the V3 potential of 245.92445(31) cm-1. Hyperfine splittings arising from the nuclear quadrupole coupling of the 14 N nucleus could be resolved, and the quadrupole coupling constants vaa = 1.4159(49) and vbbvcc = 4.1622(86) MHz were found.

Domaines: Chimie; Physique [physics]

Thuy Nguyen, Wolfgang Stahl, Ha Vinh Lam Nguyen, Isabelle Kleiner. 14N nuclear quadrupole coupling and methyl internal rotation in 3-methylpyrrole investigated by microwave spectroscopy. Journal of Molecular Spectroscopy, 2020, 372, pp.111351. ⟨10.1016/j.jms.2020.111351⟩. ⟨hal-03017989⟩