High-sensitivity CRDS absorption spectroscopy of acetylene between 5851 and 6341 cm⁻¹

Abstract

The absorption spectrum of acetylene has been recorded at room temperature (297 K) using high-sensitivity cavity ring-down spectroscopy (α min ∼ 5 × 10 −11 cm −1 ) in the 5851 and 6341 cm −1 interval corresponding to a region of very weak absorption. A list of about 10,700 absorption features with estimated absolute line intensities was constructed. The smallest intensities are of the order of 5 × 10 −29 cm molecule −1 . The line list includes about 2500 absorption lines of ethylene present at the ppm level in the acetylene sample and identified on the basis of a high-resolution Fourier transform spectrum specifically recorded. A total of more than 2700 lines of 12 C 2 H 2 were rovibrationally assigned in comparison with accurate predictions provided by a global effective operator model. Overall, the present effort adds about 2260 new assignments to the set of about 500 assigned transitions available in the literature. The new assignments correspond to 45 new bands and 17 already-known bands, for which additional J lines were assigned. Spectroscopic parameters were derived for the upper vibrational levels from a band by band fit of the line positions (typical root mean square deviation values are of the order of 0.001 cm −1 ). A few of the analysed bands were found to be affected by rovibrational perturbations, which are discussed. The new data will be valuable to refine the parameters of the global effective Hamiltonian and dipole moments of 12 C 2 H 2 .

Doppler Broadening Thermometry Based on Cavity Ring-Down Spectroscopy

“…The central part of the R(9) line in the V = 3 − 0 band is out of the dynamic range. polyatomic molecule like C 2 H 2 , the density of rovibrational transitions is very high, even for lower vibrational states (see example in a recent study [42]). Insufficient knowledge on the weak transitions will make it difficult to secure a precision of 1 ppm in DBT determination of k B , since one needs to consider all the nearby lines with strengths in a dynamic range of six orders of magnitudes.…”

The 2020 edition of the GEISA spectroscopic database

“…The EDB17 covers the range of the ΔP = 9-14 series excluding the 6341-7000 cm -1 interval roughly corresponding to the ΔP = 10 series. The EDB17 was constructed by gathering results of three studies by Fourier transform spectroscopy [103][104][105] and three studies by cavity ring down spectroscopy (CRDS) [106][107][108]. In the regions of low absorption, the sensitivity of the CRDS technique enabled the detection of weak lines with intensities on the order of 10 -29 cm/molecule.…”

“…For all 12 C2H2 and 12 C 13 CH2 isotopologues, the vibrational assignment has been changed to V1 V2 V3 V4 V5 ℓ4 ℓ5 from V1 V2 V3 V4 V5 ℓ, where ℓ is the sum of ℓ4 and ℓ5. Indeed, the ℓ4 and ℓ5 quantum numbers are necessary to assign the various bands that include strong resonance interactions between ro-vibrational states [100][101][102][103][104][105][106][107][108] used to update the GEISA-2020 database. Based on the new vibrational assignment and the symmetry E/F of the rotational levels, the symmetries +/-have been generated for all transitions of both isotopologues, and symmetry u/g have been generated only for symmetric 12 C2H2 isotopologue.…”

Shock-wave processing of C60 in hydrogen

“…6. Top: experimental CRD spectrum of the sampled gas collected after exposure to a shock wave (initial mixture: C 60 = 139 µmol, Ar = 0.229 mol, H 2 = 0.054 mol) with a reflected shock gas temperature T g of 2996 K. Bottom: simulated spectrum of methane CH 4 and ethylene C 2 H 4 from the WKMC (Campargue et al 2012) and ethylene linelists (Lyulin et al 2014). The presence of residual water vapor is accounted for with the help of the Hitran 2012 database (Rothman et al 2013).…”

“…The cavity ring down spectra displayed on Fig. 6 were analyzed with the help of the Hitran 2012 database (Rothman et al 2013), the WKMC line-list (Campargue et al 2012) and an ethylene line-list (Lyulin et al 2014). They reveal the presence of methane CH 4 , acetylene C 2 H 2 , and ethylene C 2 H 4 in the gas sampled after exposure of 139 µmol of C 60 to a shock wave in an Ar/H 2 (5:1) mixture.…”