FTIR spectra of CH2F2 in the 1000-1300 cm−1 region: Rovibrational analysis and modeling of the Coriolis and anharmonic resonances in the ν3, ν5, ν7, ν9 and 2ν4 polyad

- Recording the high resolution infrared spectra of difluoromethane (CH2F2).
- The FTIR spectra are studied in a region of atmospheric interest (1000-1300 cm−1).
- A model with eight type of resonances in the system ν3/ν5/ν7/ν9/2ν4 is considered.
- A set of spectroscopic constants for the excited vibrational states is determined.
- The spectral simulations well reproduce the experimental data.

The FTIR spectra of CH2F2 have been investigated in a region of atmospheric interest (1000-1300 cm−1) where four fundamentals ν3, ν5, ν7 and ν9 occur. These vibrations perturb each other by different Coriolis interactions and the forbidden ν5 borrows intensity from the neighboring levels. Furthermore, the v4=2 state has been found to interact with the v3=1 and v9=1 states by anharmonic and c-type Coriolis resonances, respectively. The spectral analysis resulted in the assignment of about 7500 rovibrational transitions which have been simultaneously fitted, together with microwave data available in literature (Hirota E. J Mol Spectrosc 1978; 69: 409-420) [15] using the Watson׳s A-reduction Hamiltonian in the Ir representation and the relevant perturbation operators. The model employed includes eight types of resonances within the pentad ν3/ν5/ν7/ν9/2ν4. A set of spectroscopic constants for the four fundamentals as well as parameters for the v4=2 state and eighteen coupling terms have been determined. The simulations performed in different spectral regions well reproduce the experimental data.