THE HOMOGENEOUS NUCLEATION OF CESIUM VAPOR

The homogeneous nucleation behavior of supersaturated cesium vapor was investigated in a redesigned upward thermal diffusion cloud chamber i n the temperature range between 359 K and 554 K. Critical supersaturat ions as a function of temperature were measured at temperatures betwee n 359 K and 481 K. The critical cluster sizes (calculated using the Ke lvin equation) varied between 12 atoms/cluster at 359 K and 40 atoms/c luster at 554 K. Nucleation rates as a function of supersaturation wer e measured at temperatures between 508 K and 554 K. The results obtain ed were compared to the internally consistent version of classical nuc leation theory (ICCT). The critical supersaturations measured were abo ut 2-fold larger at 554 K and about 10-fold larger at 359 K than theor y predictions. The measured dependence of the nucleation rates on supe rsaturation was fit accurately by a power law and was weaker than theo ry prediction. The temperature dependent multiplicative correction to theory necessary for agreement with experiments was large, however, it s temperature dependence was similar to that observed in measurements with n-alkanes. (C) 1998 Elsevier Science B.V.