Homogeneous Nucleation of H₂O and D₂O in Comparison:  The Isotope Effect

Abstract

In the past century, the homogeneous nucleation of light water (H2O) has repeatedly been studied using various experimental techniques. Generally, the onset of nucleation was recorded, while less frequently, the actual nucleation rates were determined. In contrast, the nucleation of heavy water (D2O) has been examined only in a single instance with no nucleation rates measured. Here, we report the first nucleation rate study of D2O along with nucleation rate measurements for H2O, which we repeated for comparison under identical conditions. We find that the nucleation rates for H2O and D2O differ by a factor of 2500, if compared at the same respective vapor pressure p v and temperature T, whereas the comparison at the same supersaturation S shows an agreement within experimental scatter. Also, the numbers of molecules in the critical clusters, which are determined from the slopes of the ln J versus ln S curves, are nearly the same for both isotopic waters. A satisfactory agreement with previous nucleation rate measurements of H2O made by Viisanen et al. (Viisanen, Y.; Strey, R.; Reiss, H. J. Chem. Phys. 1993, 99, 4680; 2000, 112, 8205) is observed, if the onset supersaturations S 0 at nucleation rates of J 0 = 107 cm-3 s-1 are compared. Using the most recent expressions for temperature-dependent vapor pressures, we calculated surface tensions and densities predictions by the classical Becker−Döring nucleation theory. Around T = 240 K, the predictions quantitatively agree with the experimental data. However, as in the case of other systems (e.g., alcohols and alkanes), classical theory shows a stronger temperature dependence than experimentally observed. A temperature-dependent correction of the classical theory is developed which permits analytical calculation of nucleation rates as function of supersaturation and temperature over extended ranges.

The nucleation behavior of supercooled water vapor in helium

“…7 our data are shown together with the data by Wölk and Strey. 2 At each temperature, the data by Wölk and Strey show a range of scaled nucleation rates. The lower values of the scaled ͑isothermal͒ nucleation rates correspond to a higher supersaturation.…”

“…11,15 Nucleation rates of water in argon have recently been measured by Wölk and Strey. 2 They used a pulse expansion cloud chamber, with which they can measure nucleation rates between 10 11 and 10 15 m Ϫ3 s Ϫ1 . So their upper range of nucleation rates corresponds to our lower range.…”

“…The nucleation behavior of water vapor ͑in an inert carrier gas͒ has been studied before, and a recent and extensive study was presented in a paper by Wölk and Strey. 2 They measured nucleation rates in the temperature range of 219-260 K. In their paper only vapor/ liquid nucleation is considered, and no indications for other nucleation processes are given. Another extensive study was performed by Peters and Paikert.…”

High-Resolution Terahertz Spectrometer

“…These H20 molecules interchange with the inserted D20 due to similar partial vapor pressures. Also, the two water species interchange Hand D atoms very rapidly, and the third water species hydrogen deuterium oxide (HDO) is formed [31].…”

Investigation of droplet nucleation in CCS relevant systems – Design and testing of a CO2 branch of the mixture preparation device

“…In the new experimental apparatus, the nucleation of droplets in CO2-rich systems is measured with the help of a rapid pressure drop inside a stainless steel expansion chamber [2][3][4]. The apparatus allows measurement under wide operating conditions at temperatures from -20 °C to +150 °C and pressures up to 130 bar.…”