INVESTIGATION OF OH ABSORPTION CROSS SECTIONS OF ROTATIONAL TRANSITIONS IN THE A(2)SIGMA(+), V'=0 [- X(2)PI, V''=0 BAND UNDER ATMOSPHERIC CONDITIONS - IMPLICATIONS FOR TROPOSPHERIC LONG-PATH ABSORPTION MEASUREMENTS

摘要

The accuracy of tropospheric hydroxyl radical measurements by long-path absorption spectroscopy is ultimately limited by the uncertainty Or the effective OH absorption cross sections. The latter were determined from calculated spectra for the and Q(1)(2), Q(1)(3), and P-1(1) rotational lines of the OH A(2) Sigma(+), (upsilon'=0) <-- X(2)II, (v''=0) transition at 308 nm. The calculations took into account Doppler broadening, measured data of the collisional broadening of OH by air molecules, and instrumental line broadening effects. The calculated spectra were compared with OH absorption spectra measured in a flow-reactor near room temperature at 1013 hPa. Excellent agreement between calculated and measured OH spectra was achieved using the collision-broadening parameters determined recently by Leonard (1990). The effective absorption cross sections at the line center (peak absorption cross sections) calculated for the Voigt line shape at 300 K and 1013 hPa are: sigma(eff)((