Miriam A. Freedman

Miriam A. Freedman

Main Content

  • Associate Professor of Chemistry
205 Chemistry Building
University Park, PA 16802
(814) 867-4267


  1. B. A., Swarthmore College, 2000
  2. M. S., University of Minnesota, 2002 (Mathematics)
  3. M. S., University of Chicago, 2003
  4. Ph. D., University of Chicago, 2008

Honors and Awards:

  1. NSF Career Award 2014
  2. NOAA Climate and Global Change Postdoctoral Fellowship 2008-2010
  3. NSF Graduate Fellowship 2003-2006

Selected Publications:

M. A. Freedman, Sites for Ice Nucleation on Aluminosilicate Clay Minerals and Related Materials, Journal of Physical Chemistry Letters, 6: 3850-3858 (2015).

D. P. Veghte, J. E. Moore, L. Jensen, M. A. Freedman, Influence of Shape on the Optical Properties of Hematite Aerosol, Journal of Geophysical Research - Atmospheres, 120: 7025-7039 (2015).

S. K. Sihvonen, G. P. Schill, N. A. Lyktey, M. A. Tolbert, M. A. Freedman, Chemical and Physical Transformations of Aluminosilicate Clay Minerals due to Acid Treatment and Consequences for Heterogeneous Ice Nucleation, Journal of Physical Chemistry A, 118: 8787-8796 (2014).

D. P. Veghte, M. A. Freedman, Facile Method for Determining the Aspect Ratios of Mineral Dust Aerosol by Electron Microscopy, Aerosol Science and Technology, 48: 715-724 (2014).

D. P. Veghte, D. R. Bittner, M. A. Freedman, Cryo-Transmission Electron Microscopy Imaging of the Morphology of Submicron Aerosol Containing Organic Acids and Ammonium Sulfate, Analytical Chemistry, 86: 2436-2442 (2014).

D. P. Veghte, M. B. Altaf, M. A. Freedman, Size Dependence of the Structure of Organic Aerosol, Journal of the American Chemical Society, 135: 16046-16049 (2013).

D. P. Veghte, M. A. Freedman, The Necessity of Microscopy to Characterize the Optical Properties of Size-Selected, Nonspherical Aerosol Particle, Analytical Chemistry, 84: 9101-9108 (2012).


Aerosol particles impact climate through their interactions with light, clouds, as well as heterogeneous chemistry.  The physical and chemical properties of aerosol particles that determine the nature of these interactions depend on particle size, shape, composition, and morphology.  Our goals are two-fold: 1) characterize aerosol structure (shape and morphology) and determine the effects of structure on aerosol physical and chemical properties and 2) develop methods for the study of submicron aerosol particles.

1) Optical Properties of Mineral Dust Aerosol

Cavity ring-down spectroscopy is the most sensitive technique that has been developed for the study of aerosol optical properties.  In particular, this sensitivity allows us to study size-selected aerosol particles. We are currently developing methods to study non-spherical mineral dust particles.  Specifically, the size selection technique is designed for spherical particles, and we have found that incorporation of microscopy characterization of non-spherical particles is needed to model their optical properties accurately.

2) Molecular Scale Studies of Ice Nucleation

Heterogeneous nucleation of ice is important for cloud formation, properties, and lifetime.  Some types of heterogeneous nucleation depend sensitively on the presence and activity of surface active sites.  Yet, the details of what these active sites are on the molecular scale, how they evolve in chemical and physical atmospheric processes, and how ice nucleates are unknown.  We use a variety of surface probes to investigate these questions.

3) Phase Separation in Organic Aerosol

Aerosol particles composed of organic compounds and inorganic salts are ubiquitous in the atmosphere.  Depending on the properties of the organic compounds, these particles can undergo phase separation to form an aqueous phase and an organic-rich phase.  We use cryo-transmission electron microscopy to examine phase separation in submicron particles.  Surprising, we observe a size dependence of the morphology for some systems in which large particles phase separate and small particles remain homogeneous.

Research Interests:


Methods development for atmospheric chemistry


Physics and chemistry of atmospheric aerosol particles


Phase transitions and surface science of atmospheric aerosol particles


Cavity ring-down spectroscopy for optical properties & hygroscopicity of aerosol particles