AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Measurements of Organic Haze Particles Formed from UV Irradiation of Acetylene by High-Resolution Soot-Particle Aerosol Mass Spectrometry
JONATHAN FRANKLIN, Eleanor Browne, Manjula Canagaratna, Timothy Onasch, Paola Massoli, Douglas Worsnop, Hiroshi Imanaka, Kevin Wilson, Jesse Kroll, Massachusetts Institute of Technology
Abstract Number: 425 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract The atmospheres of some planetary bodies (such as Saturn’s moon Titan) are characterized by the presence of organic haze particles, formed by irradiation of simple organic species in the absence of oxygen. In this study, simple organic haze particles were generated in the laboratory and chemically characterized using an Aerodyne High-Resolution Time-of-Flight Soot-Particle Aerosol Mass Spectrometer (SP-AMS) operated with only the laser vaporizer (CW nd:YAG 1064 nm). Particles were formed by irradiating acetylene diluted in nitrogen with short wavelength UV light. Haze particles were measured by the SP-AMS using both the standard electron impact (70 eV) ionization mode as well as a vacuum ultraviolet light (VUV) photoionization mode which uses tunable VUV light (from the Chemical Dynamics Beamline at the Advanced Light Source of the Lawrence Berkeley National Laboratory). The vaporization and detection of these particles by SP-AMS indicate they can absorb in the infrared (1064 nm). Mass spectra show a range of carbon clusters and hydrocarbon components, including major peaks at m/z 91 (C7H7+) and m/z 78 (C6H6+), as well as clear signals at m/z 720 (C60) and m/z 840 (C70). Elemental analysis of the haze particles showed roughly a 1:1 hydrogen-to-carbon ratio, the same as that of the C2H2 precursor. The degree of nitrogen and oxygen incorporation into the particles, and mass spectrometric signatures as a function of ionization wavelengths is also discussed.