Philip Croteau
2nd Year Graduate Student Chemistry philip_croteau-at-berkeley.edu |
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Current Research
In the atmosphere of Titan, the largest moon of Saturn, a hydrocarbon aerosol haze is photochemically produced in an atmosphere that is roughly 95% nitrogen and 5% methane.1 The presence of this haze is thought to have a net cooling effect on the surface because the particles absorb solar radiation while transmitting infrared radiation from the surface. However, the mechanism by which the lower hydrocarbons polymerize to form condensible species is poorly understood.2
In order to better understand this mechanism (and others), an instrument was constructed by Boering group alumnus Máté Ádámkovics. This instrument is capable of measuring, simultaneously, the time evolution the chemical makeup of a VUV irradiated mixture of gases, using an RGA quadrupole mass spectrometer as well as the formation of particles, by the scattering of polarized laser light. Comparing the time evolution of the particles and the mixture composition gives insight into the particle formation mechanism. The instrument also includes a rotating stage for the
collection optics, allowing for angularly resolved scattering measurements, which provide further insight in to the nature of the particles.3 It is also possible to collect the aerosols for "offline" analyses such as field emission scanning electron microscopy to determine particle shape and size and microprobe laser-desorption, laser-ionization mass spectrometry to detect polyaromatic hydrocarbons.
One of the goals of my research is to use this instrument to simulate Titan-like atmospheres to gain insight into the particle formation mechanism as well as the optical properties of the particles.
1Niemann, H.B., et al., Nature, 438, 779 (2005)
2Yung, Y.L., and DeMoore, W.B., Photochemistry of planetary
atmospheres (1999)
3Ádámkovics, M.A., and Boering, K.A., J.
Geophys. Res., 108, 5092 (2003)
