Guided by the survey scans, higher resolution scans were then performed, scanning the laser with a step size of 0.0004 cm -1 yielding more accurate peak centers and intensities. This enabled accurate measurement of the translational and rotational temperatures of the target species. Spectra for individual rotational transitions were collected in a randomized sequence, with each transition measured a minimum of 3 times. The data were baseline subtracted and fit in IgorPro, using a Gaussian function. Because the pressure within the buffergas cell is low, the spectra are Doppler-limited and the full-width at half-maximum (FWHM, in cm -1 ) of the Gaussian lineshape can be used to extract the translational temperature (T trans , in K) according to Eq. 2 (Bernath 1995).