Earth Planets Space, Vol. 62 (No. 1), pp. 81-90, 2010
Midori Saito1, Itsuki Sakon2, Chihiro Kaito3, and Yuki Kimura4
1Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8585, Japan
2Department of Astronomy, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
3Laboratory for Nano-Structure Science, Department of Physics, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu-shi, Shiga 525-8577, Japan
4Department of Earth and Planetary Materials Science, Graduate School of Science, TohokuUniversity, Sendai 980-8578, Japan
(Received July 28, 2008; Revised November 21, 2008; Accepted December 5, 2008; Online published February 12, 2010)
It has been known for some time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but with somewhat wider bands and different relative intensities. Some new features were also observed. The anthracene molecules formed photodimer in their grain and showed different infrared features after UV irradiation. This would be the first report concerning nanometer-sized PAH grains.
Key words: PAH, infrared, dust, laboratory experiment.