Spectroscopic investigation of fluoroiodomethane, CH 2 FI: Fourier-transform microwave and millimeter-/submillimeter-wave spectroscopy and quantum-chemical calculations

• Published in: The Journal of chemical physics 2011-05, Vol.134 (17), p.174312-174312-9
• Main Authors: Puzzarini, Cristina, Cazzoli, Gabriele, López, Juan Carlos, Alonso, José Luis, Baldacci, Agostino, Baldan, Alessandro, Stopkowicz, Stella, Cheng, Lan, Gauss, Jürgen
• Format: Article
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.3583498

Guided by theoretical predictions, the rotational spectrum of fluoroiodomethane, CH 2 FI, has been recorded and assigned. Accurate values are reported for the ground-state rotational constants, all quartic, sextic, and two octic centrifugal-distortion constants. The hyperfine structure of the rotational spectrum was thoroughly investigated using a Fourier-transform microwave spectrometer and the Lamb-dip technique in the millimeter-/submillimeter-wave region, thus allowing the accurate determination of the complete iodine quadrupole-coupling tensor and of the diagonal elements of the iodine spin-rotation tensor. Relativistic effects turned out to be essential for the accurate theoretical prediction of the dipole moment and quadrupole-coupling constants and were accounted for by direct perturbation theory and a spin-free four-component treatment based on the Dirac-Coulomb Hamiltonian. The relativistic corrections to the dipole moment amount to up to 34% and to the iodine quadrupole-coupling tensor to about 15-16% of the total values.