In this project laboratory experiments on the OH radical pertinent to three major needs for monitoring particular trace species in the atmosphere will be carried out. The study of polarization of laser-induced fluorescence in the A-X electronic system of OH, and the modeling of state-to-state rotational energy transfer in the A-state, concern detection of OH itself in the troposphere. Transition probabilities for weak vibrational bands of the A-X system impact OH detection as well as studies of OH kinetics for atmospheric purposes. Collisional quenching of high rotational levels in the A-State, and the temperature dependence of this process, govern quantum yields in the measurement of stratospheric H2O with a Lyman-a hygrometer. HNO3 is a molecule difficult to detect at the low levels present in the relatively clean troposphere. SRI scientists study the nascent distribution of OH over vibrational and rotational levels, following the photodissociation of HNO3, and the relaxation of this distribution to a thermal one. These data are necessary for the design of a photoframentation/laser-induced fluorescence method for nitric acid monitoring.
