Experimental determination of air-broadening parameters of pure rotational transitions of HNO3: intercomparison of measurements by using different techniques

We report on the air-broadening of the 44d, 25 ← 44d, 26, 43d, 25 ← 43d, 26, 25d, 25 ← 24d, 24, 27d, 25 ← 27d, 26, 261, 25 ← 260, 26, 1513, 3 ← 1413, 2, and 27d, 27 ← 26d, 26 transitions of HNO3 at room temperature, which are useful for measurements of nitric acid in the Earth's atmosphere by microwave limb sounders. In fact, the lines selection was essentially made on the basis of the spectral range requirements of MASTER, a limb sounding instrument managed by ESA. It is well established that the collisional-broadening parameters have a crucial influence on reduction of remote sensing data, but it is also well known that systematic errors make the evaluation of pressure-broadening parameters accuracy difficult. To this purpose, the investigation has been carried out in two different laboratories employing different techniques: the intercomparison allowed us to check the accuracy of the retrieved parameters as well as to estimate the extent of systematic errors affecting them.