Re-evaluation of <i>ortho</i>-<i>para</i>-dependence of self pressure-broadening in the <i><b><i>?</i></b></i>₁ + <i><b><i>?</i></b></i>₃ band of acetylene

Optical frequency comb-referenced measurements of self pressure-broadened line profiles the R(8) to R(13) lines in ?1 + ?3 combination band acetylene near 1.52 µm are reported. The analysis data found no evidence for a previously reported [Iwakuni et al., Phys. Rev. Lett. 117(14), 143902 (2016)] systematic alternation widths with nuclear spin state molecule. present work brought out need use an accurate profile model and careful accounting weak background absorptions due hot lower abundance isotopomer lines. were adequately fit using quadratic speed-dependent Voigt model, neglecting small shift. Parameters describing most probable pressure-broadening, shift, strength determined each line. Detailed modeling results Iwakuni al. showed that their neglect collisional narrowing broadening term combined strongly absorbing recorded analyzed transmission mode reasons results.