Homogeneous nucleation of supersaturated cesium vapor

The homogeneous nucleation of supersaturated cesium vapor was investigated in a thermal diffusion cloud chamber operating in both the upward and the d ownward mode. In the upward operating mode, critical supersaturations were measured in the temperature range, 446-492 K. By operating the chamber in t he downward mode, it was possible to circumvent experimental difficulties w hich arise at low pressures (due to phoretic effects) for the measurements made in the upward mode. Our previously published measurements on cesium we re obtained in the upward mode in the temperature range, 421-554 K. These e arlier measurements agree perfectly (to within their scatter) with the meas urements presented here in the temperature range where they overlap, i.e., 421-492 K. The use of the downward mode enabled the extension of the temper ature range of the measurements by 132 K towards lower temperatures. This m akes cesium the substance whose homogeneous nucleation has been measured, i n a thermal diffusion cloud chamber, over the largest range of temperatures , i.e., 289-554 K. The measured critical supersaturations were compared to the predictions of the Internally Consistent version of Classical Nucleatio n Theory and to the predictions of the Classical Theory. (C) 1999 American Institute of Physics. [S0021-9606(99)50723-X].