A simulation experiment of photochemical reactions in the mesosphere.

An ionospheric simulation experiment has been performed in a large vacuum chamber. The chamber is filled with NO and other gases including N2, O2, CO2, NH3 and H2O in the pressure range of 10-2 Torr. A lamp which produces photons at 1236 and 1165A by means of microwave discharge in krypton is utilized as an ionization source.In addition to 30+ large quantities of the water cluster ions 55+, H3O+·(H2O)2, 73+, H3O+·(H2O)3 and 91+, H3O+·(H2O)4 were observed when nitric oxide and water were present. This closely approximates the condition of the terrestrial D region. After long periods of UV irradiation 74+ and 104+ ions grow in intensity. These ions are tentatively identified as NO+. N2O and NO+·NO·N2O. In addition the series 18+, 36+, 54+ and 72+ is detected which can be labeled NH4+, NH4+·(H2O), NH4+·(H2O)2 and NH4+·(H2O)3. These same species of ions are observed with the introduction of ammonia into the chamber. Presumably both N2O and NH3 are products of the photolysis.