AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
IMoS: An Efficient Algorithm to Calculate Ion Mobilities from All Atom Models
CARLOS LARRIBA-ANDALUZ, University of Minnesota
Abstract Number: 141 Working Group: Aerosol Physics
Abstract The application of Ion Mobility Spectrometry-Mass Spectrometry to analyze the structures of large gas phase organic ions continues to be of great interest. From a numerical perspective, ion mobility measurements are linked to model ion structures through the collision cross section (CCS). This CCS is strongly dependent mainly on two major constituents: 1)the Physical Cross Section and 2)the manner in which gas molecules effectively interact with ion surfaces through potential interactions. The Physical Cross Section is a property based on the ion structure while potential interactions are exchanges between vibrational, rotational and translational degrees of freedom of ion and gas molecules. In order to make numerical algorithms efficient, structural atoms must be kept fixed and therefore gas molecule impingement-reemission rules need to be established to make up for potential exchanges. These rules are rarely known a priori and hence introduce a degree of ambiguity in ion mobility based analyses. A set of momentum transfer algorithms are then employed on structures to explore the validity of specular vs. diffusive scattering laws in contrast to purely potential interaction laws. Simultaneously, a description of various very efficiently parallelized algorithms (thousands of times faster than existing methods) that make up IMoS suite of algorithms will be given. These include 1)Projection Approximation, 2)Elastic/Diffuse Hard Sphere Scattering, 3)Trajectory Methods that include ion induced dipole and/or Lennard-Jones potentials, 4)Diatomic gas molecules simulations that make up for rotational degrees of freedom in diatomic molecules and 5)Momentum Transfer studies for larger macromolecules, such as large viruses/bacteria or nanoparticles, where the simple scenario in which the ion does not perturb the gas flow is relaxed and the probability of gas molecule-gas molecule collision rarefaction and compression starts to become significant. In such scenario, the Mason-Schamp approximation is not valid and the system starts to deviate from the free molecular regime.