Hess, Maurus, Dr.

Research

Research Field

• Heterogeneous chemistry on sea salt aerosols
• Utilization of Rutherford Backscattering Spectrometry for research in atmospheric chemistry

Motivation

Sea salt particles belong to the major aerosol components globally. They affect many aspects of the troposphere, e.g., atmospheric radiation, cloud physics, meteorology and atmospheric chemistry. Sea salt aerosols are of great importance for atmospheric chemistry. They have a large reservoir of halogens, which are highly reactive and have a substantial impact on the chemistry of hydrocarbons or ozone in the atmosphere. Such halogens can be released to the atmosphere by heterogeneous reactions between the aerosol and gas phase species, such as sulfuric or nitric acid.

Since heterogeneous reactions usually occur in the near surface region (~ the outermost 100 monolayers) of the condensed phase, we are especially interested in physical and chemical processes within this region of liquid or solid salt particles. Such processes include water adsorption, partitioning of ions between different phases, uptake of gas phase components into the condensed phase, chemical reaction and diffusive transport inside the condensed phase.

Method

Using Rutherford Backscattering Spectrometry allows us to measure directly elemental concentration profiles down to a depth of about one micrometer with a typical resolution of 50 nm in salt crystals. This enables us to combine physical and chemical processes on the surface as well as inside the condensed phase to an overall picture. For further information about this technique, please visit http://www.eaglabs.com/training.

Conferences

• ICNAA International Conference on Nucleation & Atmospheric Aerosols, 2007 (Galway, Ireland):
  Poster: Uptake of Nitric Acid on NaCl Single Crystals at Different Relative Humidities and Vapor Pressures Measured by Backscattering Spectrometry
• IAC International Aerosol Conference, 2006 (St. Paul, USA)
  Poster: Uptake of Nitric Acid on NaCl at Different Relative Humidities Measured by Backscattering Spectrometry
• AGU American Geophysical Union Fall Meeting, 2005 (San Francisco, USA)
  Presentation: Bromine Surface Enrichment and Nitric Acid Uptake on NaCl Single Crystals diagnosed by RBS
• IGAC International Global Atmospheric Chemistry Conference, 2004 (Christchurch, New Zealand)
  Poster: The Use of Rutherford Backscattering Spectrometry for studying the Near-Surface Region of Bromine-doped NaCl-crystals: Extent and Kinetics of the Bromine Surface Enrichment

Publications

• M. Hess, U. K. Krieger, C. Marcolli, T. Huthwelker, M. Ammann, W. A. Lanford, and Th. Peter
  Bromine Enrichment in the Near-Surface Region of Br-Doped NaCl Single Crystals Diagnosed by Rutherford Backscattering Spectrometry
  J. Phys. Chem. A, 111, 4312-4321, 2007.
• M. Hess
  Utilizing Backscattering Spectrometry for studying Physical and Chemical Processes on Salt Crystals
  PhD-thesis, ETH Zurich, Diss. No. 16454, 2006.
• L. M. Keller, B. Fügenschuh, M. Hess, B. Schneider, and S. M. Schmid
  Simplon fault zone in the western and central Alps: Mechanism of Neogene faulting and folding revisited
  Geology, 34/4, 317-320, 2006.
• L. M. Keller, B. Fügenschuh, M. Hess, and S. M. Schmid
  Structural and metamorphic evolution of the Camughera - Moncucco, Antrona and Monte Rosa units southwest of the Simplon line,Western Alps
  Eclogae geol. Helv. 98, 19-49, 2005.
• M. Hess
  Strukturgeologie und Spaltspurdatierungen an Apatit und Zirkon an der Simplonlinie im Gebiet um Domodossola (I).
  Diploma thesis, Univ. Basel., 2003.