19 September 2008
Chemical Sciences Division scientist Daniel Murphy has been announced as a recipient of the Benjamin Y.H. Liu Award of the American Association for Aerosol Research. He will share the award with Murray Johnston (University of Delaware) for his contributions to aerosol instrumentation and experimental techniques. Murphy and Johnston were coauthors of a 1991 paper that launched a new technique for determining the chemical composition of individual atmospheric fine particles (aerosols). The technique forms the basis for instrumentation currently used in CSD, called the Particle Analysis by Laser Mass Spectrometry (PALMS). Murphy will be presented with the award during the AAAR 2008 annual conference, October 23, 2008.
Background: As stated on the AAAR website: "The Benjamin Y. H. Liu Award recognizes outstanding contributions to aerosol instrumentation and experimental techniques that have significantly advanced the science and technology of aerosols... The award honors Professor Benjamin Liu for his leadership in the aerosol community and his own seminal contributions to aerosol science through instrumentation and experimental research. Professor Liu is a founding father of the AAAR and of the society's journal, Aerosol Science and Technology, and helped establish the International Aerosol Research Assembly."
The PALMS instrument is a laser ionization mass spectrometer which makes in-situ measurements of the chemical composition of individual aerosol particles. Aerosols are brought into a vacuum system and individual particles are detected by light scattered as they cross the beam of a continuous laser. The scattered light signal gives a rough indication of the size of the particle and a provides a trigger for an excimer laser (193nm), which is pulsed so its beam hits the particle to desorb and ionize molecules and atoms. These ions are analyzed with a time of flight mass spectrometer to provide a complete mass spectrum from each particle. The instrument is capable of measuring particles from 0.2 to 3 microns in diameter. Analysis is complete less then 1 millisecond after the aerosols enter the inlet. Furthermore, artifacts are minimized because particles never touch a surface. The instrument can acquire either positive or negative ion spectra.
Significance: The award recognizes Murphy for significant contributions to the advancement of scientific understanding about atmospheric fine particles, which affect both climate and air quality. The award gives tangible evidence of NOAA's crosscutting priorities related to leadership and state-of-the-art research.