Mid-infrared high-resolution dual-comb spectroscopy: Intensity, broadening, and beyond-Voigt parameters of 12C2H2 and 13C12CH2 lines

Abstract

Using a high-resolution mid-infrared dual-comb spectrometer operating in the 1300 cm⁻¹ spectral region, spectra of acetylene were recorded at room temperature. Spectroscopic parameters were measured in 3 vibrational bands of both ${}^{12}{\text{C}}_2{\text{H}}_2$ and ${}^{13}{\text{C}}^{12}{\text{CH}}_2$. Absolute line intensities ($S_0$) and self-broadening coefficients (${\gamma }_0^{self}$) were determined in the ${\nu }_4+{\nu }_5$, $2{\nu }_4^2+{\nu }_5^{-1}\stackrel{}{⟵}{\nu }_4^1$ and ${\nu }_4^1+2{\nu }_5^0\stackrel{}{⟵}{\nu }_5^1$ bands. For the main isotopologue, the collisional narrowing coefficients (${\nu }_0^{VC}$) as well as the speed-dependence of the broadening (${\gamma }_2$) and shifting (${\delta }_2$) coefficients were measured in the ${\nu }_4+{\nu }_5$ band of the main isotopologue of acetylene. Theoretical line-shape models were fitted on experimental profiles using a homemade multi-spectrum fitting procedure to determine spectroscopic parameters. Excellent agreement with the literature was found for self-broadening coefficients and absolute line intensities in the ${\nu }_4+{\nu }_5$ band of ${}^{12}{\text{C}}_2{\text{H}}_2$. For the hot bands, good agreement with the literature is found within experimental uncertainties, while ${\gamma }_0^{self}$ of those hot bands are also reported for the first time. Similarly, the rotational dependence of ${\nu }_0^{VC}$ is found to be close to previous works. ${\gamma }_2$ and ${\delta }_2$ of ${}^{12}{\text{C}}_2{\text{H}}_2$, as well as $S_0$ and ${\gamma }_0^{self}$ of ${}^{13}{\text{C}}^{12}{\text{CH}}_2$ are also reported for the first time in this band.