FLASH PHOTOLYSES OF NH3 IN THE VACUUM ULTRAVIOLET,

The decomposition of NH3 in the gas phase was investigated in the vacuum ultraviolet by flash photolysis. Quartz windows were used as filters until 2.000A and 1.600A respectively, CaF2 windows until 1.250A. It could be shown that photochemical primary processes can be examined qualitatively in a windowless device. For this purpose a flash light source with sufficient short-time light impulse is necessary to prevent disturbances from the discharge by a large distance between the discharge and the reaction chamber. Disturbances occurred in the reaction chamber - probably as pressure waves - after more than 20 microsec. In accordance with earlier experiments the NH2 radical was found at wavelengths above 2.000A, whereas below 1.600A in addition to it the NH radical was detected as primary product. Around 10 of the NH radicals were formed in the ground state with one vibration quantum v 1. In windowless illuminations and at relatively low pressures the Balmer series of the H atom was found in absorption. Author