Measuring the Effect of Ion-Induced Drift-Gas Polarization on the Electrical Mobilities of Multiply-Charged Ionic Liquid Nanodrops in Air

摘要: The electrical mobilities of multiply-charged nanodrops the ionic liquid 1-ethyl, 3-methylimidazolium dicyanamide (EMI-N[CN]2) were accurately measured in air at 20 °C for mass-selected clusters composition [EMI-N[CN]2] n [EMI+] z , with 2 ≤ n 369 and 1 z 10. We confirm prior reports that mobility Z a globular ion mass m is given approximately by modified Stokes–Millikan law spheres, Z  =  Z SM,mod (d m +  d g , z, m), where d  (6m/πρ)1/3 nanodrop mass-diameter based on density ρ (corrected capillary compression electrostatic deformation nanodrop), an effective molecule diameter. There however measurable (up to 7 %) systematic z-dependent departure from Z . As theoretically expected small e * this effect described simple correction factor form Z/Z  δ(1  −  βe *), kTe * potential energy due ion–induced dipole (polarization) attraction between perfectly-conducting charged polarized neutral gas-molecule distance )/2 its center. An excellent fit model hundreds data points found ≈ 0.26 nm, β 0.36, δ 0.954. Accounting polarization decreases considerably respect values inferred earlier measurements ignored effect. In addition, spite ambiguities calibration scale, constant smaller than unity increases Millikan’s drag enhancement accepted value ξ 1.36 new ξ /δ 1.42  ± 0.03.