Abstract View
The Effect of Rotation and Preferred Orientation on Particle Mobility in the Free Molecular Regime
CARLOS LARRIBA-ANDALUZ, Viraj Gandhi, IUPUI
Abstract Number: 451
Working Group: Aerosol Physics
Abstract
A recently developed MonteCarlo algorithm, IMoS 2, explores the drift-diffusion of an ion which is subject to an arbitrary field in a modeled real gas. See Figure 1 where the ion is in a buffer gas and subject to an electric field. The electric field accelerates the ion producing gas-ion collisions.
The ion can freely rotate and its orientation, angular velocity and drift velocity are a function of the gas-ion collisions, the reduced mass, the strength of the field over concentration(E/N), and the position of the charges within the ion. The position of the charges may provide a dipole moment that will be taken into account. It is the effect of the collisions and the particle orientation together with the electric field which now establishes the equilibrium drift velocity, preferred orientation, if any, and angular velocity. This equilibrium drift velocity, together with non-linearized theory, establishes the relation between field and mobility which in turn yields the true mobility of the ion.
The mobility calculator has been tested with different sets of isotopomers, (Iodo-TMT molecules) and isotopologues (arginine molecule). The mobility of Iodo-TMT and arginine ions was measured in Nitrogen and Helium using the Structure for Lossless Ion Manipulations (SLIM) platform which allows resolutions of 200-500. Small deviations were observed for both arginine and TMT ions suggesting that the effect of angular momentum and moments of inertia is sufficient to separate two entities in the gas phase. The results of IMoS 2 prove, for the first time, that an ion with identical structure and mass may be separable using electrical/ion mobility through shifts in angular momentum and moments of inertia alone.