Spectroscopic absorptance measurements of OH in high-intensity continuous hydrogen/air and methane/air combustion

Absorptance measurements of selected resolved spectral lines in the $\text{OH}{}^2\text{Σ}{}^{\mathrm{+}}\text{?}{}^2\text{Π (0, 0)}$ band near 3100 Å have been used to compute ground electronic state hydroxyl radical concentrations and rotational temperatures for the high-intensity continuous combustion of hydrogen/air and methane/air mixtures in a jet-stirred reactor. For mass throughput rates between 2 and 3 x 10^?2gm/cm³ sec and fuel/air equivalence ratios, Φ_fuel/air, varying from 0.57 to 1.32, maximum (OH) of 1 to 2 x 10¹⁶cm^?3 occurred near Φ_fuel/air = 0.85 Ground-state rotational temperatures were slightly greater than gas kinetic temperatures determined from thermocouple measurements uncorrected for heat losses. An estimate of the vibrational temperature implied that the ground electronic state vibrational and rotational degrees of freedom were also in equilibrium. Values deduced for the collisional broadening parameter, a, agreed favorably with previous results.