THE OH MEINEL BAND EMISSIONS ORIGINATING FROM VIBRATIONALLY EXCITED HYDROXYL RADICALS OH(V) REPRESENT SOME OF THE MOST IMPORTANT AIRGLOW FEATURES IN THE EARTH'S UPPER ATMOSPHERE. SUCH EMISSIONS WERE ALSO OBSERVED IN THE NIGHT SIDE OF VENUS DURING THE VENUS EXPRESS MISSION [PICCIONI ET AL. A&A 483 L29-L33 (2008)]. DATA OBTAINED BY CRISM (COMPACT RECONNAISSANCE IMAGING SPECTROMETER FOR MARS) ABOARD THE MRO (MARS RECONNAISSANCE ORBITER) REVEALED OH(V) EMISSIONS IN THE NIGHTGLOW OF MARS [CLANCY ET AL. ICARUS 226 272-281 (2013)]. MODELING STUDIES HAVE SHOWN THAT THE PREDICTED OH(V) EMISSION INTENSITIES CAN VARY DRAMATICALLY DEPENDING ON THE NATURE OF THE VIBRATIONAL RELAXATION MECHANISM ASSUMED [E.G. GARCIA MUNOZ ET AL. ICARUS 176 75-95 (2005)]. DESPITE SEVERAL INVESTIGATIONS THE DETAILS OF THE RELEVANT OH(V) RELAXATION KINETICS AND PATHWAYS IN CO2 ARE NOT WELL UNDERSTOOD. THIS IS THE IMPORTANT PROBLEM THAT THE PROPOSED RESEARCH WILL ADDRESS WITH A COMBINATION OF LABORATORY EXPERIMENTS AND ATMOSPHERIC MODEL CALCULATIONS. OUR RECENT STUDIES DEMONSTRATED A PREVIOUSLY UNKNOWN EFFICIENT PATHWAY FOR VIBRATIONAL RELAXATION OF OH(V) BY O ATOMS THAT COUPLES THE MESOSPHERIC OH(V) EMISSIONS WITH THE CO2 4.3-MICRON EMISSION AND RESOLVES A LONG-STANDING PROBLEM OF SEVERE DISCREPANCIES BETWEEN MODEL PREDICTIONS AND OBSERVATIONS OF THE 4.3-MICRON EMISSION IN THE EARTH'S ATMOSPHERE [PANKA ET AL. ACP 17 9751-9760 (2017); KALOGERAKIS ET AL. GRL 43 8835-8843 (2016)]. THIS RECENT BREAKTHROUGH DEVELOPMENT HIGHLIGHTS THE IMPORTANCE OF INVESTIGATING THE MECHANISTIC DETAILS OF OH(V) COLLISIONAL ENERGY TRANSFER VIA SYNERGISTIC LABORATORY AND MODELING EFFORTS. THE MAIN OBJECTIVE OF THIS PROPOSAL IS TO INVESTIGATE OH(V) VIBRATIONAL RELAXATION RELEVANT TO THE ATMOSPHERES OF MARS AND VENUS. IMPORTANT AREAS OF INTEREST ARE DETERMINING KEY OH(V) + CO2 RATE CONSTANTS AT TEMPERATURES RELEVANT TO THE ALTITUDE OF THE EMISSION LAYER AND ELUCIDATING THE PATHWAYS OF OH(V) VIBRATIONAL ENERGY RELAXATION. THE MEINEL OH(V) EMISSIONS CAN BE USED AS AN INDICATOR OF ATMOSPHERIC COMPOSITION VARIABILITY CIRCULATION GRAVITY WAVES AND AS A PROBE OF LOCAL TEMPERATURE. A DETAILED UNDERSTANDING OF THE SOURCES AND SINKS OF THESE EMISSIONS IS A PREREQUISITE BEFORE THEY CAN BE RELIABLY USED AS A PROXY FOR THE AFOREMENTIONED PROCESSES. AN IMPORTANT COMPONENT OF THE PROPOSED WORK WILL BE TO APPLY THE LABORATORY RESULTS INTO DETAILED REPRESENTATIVE MODELS OF THE NONLOCAL- THERMODYNAMIC-EQUILIBRIUM (NON-LTE) OH AND CO2 VIBRATIONAL LEVEL POPULATIONS AT THE OH EMISSION LAYERS OF MARS AND VENUS AND EVALUATE THE IMPORTANCE OF THE COUPLING BETWEEN THE OH MEINEL AND CO2 4.3-MICRON EMISSIONS. THE LABORATORY INVESTIGATIONS WILL EMPLOY LASER SPECTROSCOPIC TECHNIQUES DEVELOPED AND USED AT SRI INTERNATIONAL. A PULSED ULTRAVIOLET LASER PHOTODISSOCIATES OZONE IN A GAS MIXTURE THAT ALSO CONTAINS ARGON CARBON DIOXIDE AND A SUITABLE H-ATOM-CONTAINING MOLECULE. THE INITIAL PHOTODISSOCIATION STEP GENERATES THE OH(V) VIBRATIONAL LEVEL OF INTEREST. AN ADDITIONAL NEAR-INFRARED PULSE CAN BE USED TO CREATE EVEN HIGHER OH(V) LEVELS. FINALLY A DELAYED LASER PULSE FROM A TUNABLE DYE LASER MONITORS THE TEMPORAL EVOLUTION OF OH(V). THE MODELING STUDIES WILL EMPLOY STATE-OF-THE-ART NON-LTE MODELS APPROPRIATE FOR THE ATMOSPHERES OF MARS AND VENUS. UNDERSTANDING THE DETAILS OF PHOTOCHEMICAL PROCESSES OCCURRING IN PLANETARY ATMOSPHERES IS A MAJOR OBJECTIVE OF THE NASA SOLAR SYSTEM WORKINGS PROGRAM. THE PROPOSED LABORATORY MEASUREMENTS AND MODELING CALCULATIONS WILL INVESTIGATE THE KEY VIBRATIONAL RELAXATION KINETICS AND MECHANISMS INVOLVING OH(V) + CO2 UNDER CONDITIONS APPLICABLE TO THE ATMOSPHERES OF MARS AND VENUS. THE RESULTS OF THIS RESEARCH ARE ESSENTIAL FOR AN ACCURATE AND RELIABLE UNDERSTANDING OF OH(V) AND CO2 EMISSIONS IN PLANETARY ATMOSPHERES.