SOURCES OF THE INFRARED RADIATION GENERATED BY THE INTERACTION OF FAST O(P-3) WITH H2O IN-SPACE

Recent broad band-pass infrared (2.3-3.6 mu m) observations of the int eraction of the exhaust plumes from space shuttle ram firing dual prim ary reaction control system (PRCS) engines with atmospheric atomic oxy gen, O(P-3), are analyzed. The results from previous laboratory and sp ace-based experiments that observed the IR emissions from the high-vel ocity interaction of O(P-3) and H2O are reexamined. Specifically, emis sion in the 2.7-mu m region is reinterpreted in terms of the reactive process O(P-3) + H2O --> OH(nu) + OH rather than the collisional excit ation mechanism O(P-3) + H2O --> H2O (nu(1) and nu(3)) + O(P-3), which was the focus of the previous analyses. A spectral analysis is presen ted of a previously reported molecular beam experiment that obtained s pectrally resolved emission measurements for a relative collision velo city of 8 km/s between O(P-3) and H2O and that shows that OH(nu) is th e dominant source of emission in the 1 to 5-mu m region. The effect of rotational radiative relaxation is discussed, and it is shown that fo r highly rotationally excited molecules the timescale for this process can be much faster than vibrational radiative decay, thus resulting i n much narrower spectral distributions than might ordinarily be expect ed.