Ion Mobilities in Supercritical Ethane, Xenon, and Carbon Dioxide

Abstract

The mobility of positive ions was measured in supercritical ethane, xenon, and carbon dioxide as a function of pressure at several temperatures. In supercritical CO2 the mobility of negative ions was also measured. Radii of the moving clusters were calculated with a hydrodynamic compressible continuum model that takes the enhancement in density and viscosity near the ions into account. The results show that positive ions move with a large solvation shell. Changes in size of this shell occur as a function of temperature and pressure. The largest radii at each temperature are found to occur at the pressure corresponding to the maximum in the isothermal compressibility. For positive ions the first solvation shell is totally filled under all conditions.

Behavior of charged species in supercritical heavy rare gas fluids

“…Ion mobility, m i , values on all SCF measured are on the order of 10 -3 cm 2 V À1 s À1 and decrease with increasing pressure (Itoh et al, 2001). In all cases when temperature is near the critical temperature, there is small but sharp minima at the pressure where w T has its peak.…”

Rates and energy of reactions of charged species in supercritical xenon

“…(9). To calculate the polarization energy of O 2 À we used the compressible continuum model (Itoh et al, 2001) and the free energy of solution, DG s (e), was approximated by V 0 . In xenon DG r turns out to be À1.8 eV at 100 bar.…”

“…(10) are those of the clustered ions, as calculated from the ion mobilities using either the hydrodynamic compressible continuum model (Itoh et al, 2001), which takes the distance dependence of the density and viscosity, Z, into account, or the Stokes' Eq. (11) and values of the macroscopic…”

“…The polarization energies for the four anions involved are also given. These were estimated using the compressible continuum model (Itoh et al, 2001). While there are large changes in the polarization energies of the ions, which decrease with increasing pressure by approximately 0.2 eV, the values of DG r are constant with pressure.…”

Electrons in Nonpolar Liquids

“…Solute ions are reported to have a mobility of about 0.002 cm2Ns at this temperature in supercritical CO2. [177] Studies have shown that the electron mobility in aromatic liquids changes upon application of external pressure but becomes constant above 2 kbar. At low pressures the electron is trapped in a cavity as discussed for alkanes in section VI-B.…”