title: Diffusivity of asphaltene molecules by fluorescence correlation spectroscopy.
abstract: Using fluorescence correlation spectroscopy (FCS) we measure the translational diffusion coefficient of asphaltene molecules in toluene at extremely low concentrations (0.03-3.0 mg/L): where aggregation does not occur. We find that the translational diffusion coefficient of asphaltene molecules in toluene is about 0.35 x 10(-5) cm(2)/s at room temperature. This diffusion coefficient corresponds to a hydrodynamic radius of approximately 1 nm. These data confirm previously estimated size from rotational diffusion studied using fluorescence depolarization. The implication of this concurrence is that asphaltene molecular structures are monomeric, not polymeric.
authors.affiliation: Schlumberger-Doll Research, 36 Old Quarry Road, Ridgefield, CT 06877, USA. bandrews@slb.com
authors.forename: A Ballard
authors.initials: AB
authors.lastname: Andrews
authors.forename: Rodrigo E
authors.initials: RE
authors.lastname: Guerra
authors.forename: Oliver C
authors.initials: OC
authors.lastname: Mullins
authors.forename: Pabitra N
authors.initials: PN
authors.lastname: Sen