Measurements of absorption lineshapes in the A3Πi← X3Σ-(0, 0) band of NH in the presence of Ar broadening

A rapid-scanning ring-dye laser was used to measure fully-resolved absorption lineshapes in the R1 branch of the A3Πi← X3Σ-(0, 0) band of NH in a shock tube. Measurements were performed in a background gas of Ar over a temperature range of 2000–2600 K, with corresponding pressures of 4.7–3.9 atm. No rotational quantum-number dependence of the collision broadening coefficient 2γ was discernable. The magnitude and temperature dependence of the broadening coefficient are in good agreement with previous measurements of OH in this laboratory, namely, 2γ = 0.0320 (2000/T)0.94 cm-1 atm-1. Using these data, calculated results are presented for the absorption coefficient of the NH Q1 bandhead.