First far-infrared high-resolution analysis of the ν<SUB>2</SUB> and ν<SUB>4</SUB> bands of phosgene <SUP>35</SUP>Cl<SUB>2</SUB>CO and <SUP>35</SUP>Cl<SUP>37</SUP>ClCO

International audienceA Fourier transform spectrum of phosgene (Cl2CO) has been recorded in the 17.3-μm spectral region at a temperature of 180 K and at a resolution of 0.00102 cm-1 using a Bruker IFS125HR spectrometer coupled to synchrotron radiation, leading to the observation of the ν2 and ν4 vibrational bands of the two isotopologues 35Cl2CO and 35Cl37ClCO. The corresponding upper-state ro-vibrational levels were fit using a Hamiltonian model accounting for the A-type Coriolis interaction linking the rotational levels of the 21 and 41 vibrational states. In this way, it was possible to reproduce the upper-state ro-vibrational levels to within the experimental uncertainty, i.e. ∼0.30 × 10-3 cm-1. Very accurate rotational and centrifugal distortion and interaction constants were derived from the fit, together with the following band centres: ν0(ν2, 35Cl2CO) = 572.526299(30) cm-1, ν0(ν4, 35Cl2CO) = 582.089026(30) cm-1, ν0(ν2, 35Cl37ClCO) = 568.951791(35) cm-1 and ν0(ν4, 35Cl37ClCO) = 581.758279(35) cm-1