Primary Study on the Atmospheric Reactions Involving Ice Particles

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1)A differentially pumped two-chamber apparatus was designed and constructed into which ice particles or water droplets were introduced and made to evaporate in collision with a probe of a hot-film anemometer for the mass-analysis of the vapor. The sizes of the inlet apertures and the pumping velocities were determined so as to optimize the particle- and the vapor-introduction efficiency.2)The performance of the anemometer under the reduced pressure was examined by using ice particles introduced into a pressure of 3 Torr. It was found that the particle sizing was possible only by lowering the hot-film voltage by half. However the size distribution measured under the reduced pressure was different from that observed in the atmospheric pressure. After several test experiments it was concluded that the shape of the particle inlet was critical for obtaining an accurate size distribution.3)In order to discriminate between the mass-signals from the vapor and those from the background gas, a triggering circuit was constructed that started the time-sweep of the mass analyzer synchronously with the collision of the particle with the hotfilm. By means of this device, it was observed that H_2O^+ signal from water droplets came to a peak at 15 ms after the collision with the hot-film. Consequently the basic feasibility of an entirely new method of "Particle Evaporation Mass Spectrometry (PEMS)" was proved.4)Ammonium carbonate and sulfite in solution are non-volatile, but they produce gaseous decomposition products when heated. Taking advantage of this fact, PEMS experiments were tried on the droplets containing those substances, resulting in the observation of weak signals from the decomposition products. PEMS was thus shown to be usable, in principle, for investigating chemical reactions involving droplets or ice particles.