Knowledge Bank

Pressure broadening coefficients for nitric acid $(HNO3)$, nitrogen dioxide $(NO2),freon-12(CF2Cl2)$, partially deuterated water (HDO), and hydrogen peroxide (HOOH) interacting with $O2$ and $N2$ have been measured. The data were recorded using a broadband mm wave spectrometer with pressures in the range of 0.1-1 torr. The sixteen nitric acid transitions represent a good selection of strong lines in the rotational spectrum from 230-460 GHz and make possible a systematic comparison with earlier theoretical calculations. Comparison shows larger pressure broadening coefficients than predicted by theory, in addition to a larger state to state variation. Two transitions from each of $NO2,CF2Cl2,HDO$, and HOOH near 230 GHz were studied. Comparison among the results for all five molecules shows the expected qualitative relationship between broadening parameters, molecule sizes, and dipole moments.