Nucleation onsets of argon and nitrogen with low amounts of carrier gas

Laura Maria Feldmar, 2011:

The homogeneous nucleation of nitrogen and argon with helium as carrier gas was investigated in a cryogenic nucleation pulse chamber. For argon, the data are measured in a temperature range from 59.8 to 64.8 K and for vapour pressures from 9.36 to 21.86 kPa, resulting in supersaturations between 5.5 and 17.2. For nitrogen, the temperature and pressure range is 51.71 ? T/K ? 63.83 K and 14.11 ? p/kPa ? 50.51, with supersaturations between 3.6 and 18.2. The results extend the former measurements by Iland et al. to a higher temperature and pressures range. While the new nitrogen onset data are described well by the analytical fit function by Iland et al, for argon a new fit function must be provided for fitting both the new and the old dataset. Assuming a nucleation rate of J=107±102 cm-3 s-1 for the experiments a comparison with classical nucleation theory is performed. For argon 14-17 orders of magnitude and for nitrogen 2-10 orders of magnitude lower rates are predicted by theory than experimentally found. In addition the empirical fit functions for the quantitative calculation of nucleation rates of argon and nitrogen given by Iland et al had to be modified slightly to also match the results of this work. A comparison of the onset results of both substances using a scaling law shows consistency of the datasets.