Improved laser absorption spectroscopy measurements of flame temperature via a collisional line-mixing model for CO2 spectra near 4.17 µm

Temperature-dependent CO2 line mixing models using dual frequency comb absorption and phase spectroscopy up to 25 bar and 1000 K

“…As the name suggests, these scaling laws parameterize collisional population transfer according to the energy difference between the involved states. This approach has been used to model line mixing in CO2 in a number of previous studies [10,19,24,35,36,50]. Using the energygap approach, the real part of the off-diagonal relaxation matrix elements are proportional to the thermally averaged collisional population transfer rates (𝐾), such that [6,7] 𝑅𝑒⟨⟨𝓀‖𝑾(𝑇)‖ℓ⟩⟩ ∝ 𝐾 (9) where 𝑗 and 𝑗 are the lower levels of transitions ℓ and 𝓀, respectively.…”

“…The MEG model differs from the ECS model (Equation 6) in several important ways. It is considerably simpler to implement, which has promoted adoption in applied settings [33][34][35][36] or in cases where more advanced models are not available. However, the MEG model requires significant ad hoc modifications to address effects such as mixing between lines in different branches (inter-vs. intra-branch mixing) as well as mixing between levels with different parities [6,7].…”

“…While there are some notable exceptions (e.g. [10,11,17,19,[30][31][32][33][34][35][36]), the vast majority of the past experimental and theoretical line mixing studies have considered only lower temperature conditions, presumably due to the experimental challenges associated with measuring accurate, high-pressure, hightemperature reference spectra needed to develop and validate absorption models for these conditions. A consequence is that existing models must be significantly extrapolated in order to calculate spectra for high temperature applications in combustion and planetary science.…”

Temperature‐Dependent Line‐Broadening Effects in CO2 Caused by Ar

“…Understanding the role of CO 2 in the radiative balance motivated several experimental, theoretical, and computational studies, with investigations over a wide range of pressure and temperature values. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] It is worth reiterating some of the most important results.…”

“…Furthermore, these collisions have an impact on the radiative balance of the Earth's atmosphere. Understanding the role of CO 2 in the radiative balance motivated several experimental, theoretical, and computational studies, with investigations over a wide range of pressure and temperature values [4–20] . It is worth reiterating some of the most important results.…”