Line intensities and temperature-dependent line broadening coefficients of Q-branch transitions in the v2 band of ammonia near 10.4 μm

- Spectroscopy of nine ammonia transitions in the Q-branch of ν2 band.
- High resolution spectroscopy performed with quantum cascade lasers (QCLs).
- Line intensities were measured using pure ammonia at room temperature.
- Collision broadening coefficients measured with Ar, N2, O2, CO2, H2O, and NH3.
- Temperature-dependence of broadening coefficients were measured up to 600 K.

We report measured line intensities and temperature-dependent broadening coefficients of NH3 with Ar, N2, O2, CO2, H2O, and NH3 for nine sQ(J,K) transitions in the ν2 fundamental band in the frequency range 961.5-967.5 cm−1. This spectral region was chosen due to the strong NH3 absorption strength and lack of spectral interference from H2O and CO2 for laser-based sensing applications. Spectroscopic parameters were determined by multi-line fitting using Voigt lineshapes of absorption spectra measured with two quantum cascade lasers in thermodynamically-controlled optical cells. The temperature dependence of broadening was measured over a range of temperatures between 300 and 600 K. These measurements aid the development of mid-infrared NH3 sensors for a broad range of gas mixtures and at elevated temperatures.