Using small angle x-ray scattering to measure the homogeneous nucleation rates of n-propanol, n-butanol, and n-pentanol in supersonic nozzle expansions

Abstract

In our earlier publication [M. Gharibeh et al., J. Chem. Phys. 122, 094512 (2005)] we determined the temperatures and partial pressures corresponding to the maximum nucleation rate for a series n-alcohols (C(i)H(2i+l)OH; i=3-5) during condensation in a supersonic nozzle. Although we were able to determine the characteristic time Deltat(Jmax) corresponding to the peak nucleation rate, we were unable to measure the number density of the aerosol and, thus, unable to directly quantify the nucleation rate J. In this paper we report the results of our pioneering small angle x-ray scattering (SAXS) experiments of n-alcohol droplets formed in a supersonic nozzle together with a new series of complementary pressure trace measurements. By combining the SAXS and pressure trace measurement data we determine the nucleation rates as a function of temperature and supersaturation.