Infrared spectroscopic study of C(2)F(6) monolayers and bilayers on graphite

The Journal of Chemical Physics
Todd A HopkinsGeorge B Hess

Abstract

We report an experimental study of adsorbed films of C(2)F(6) on graphite by using infrared reflection absorption spectroscopy supplemented by ellipsometry. The vibrational C-F stretch modes nu(5) (parallel to the molecular axis) and nu(7) (perpendicular) in the film are strongly blueshifted by dynamic dipole coupling, and these shifts are sensitive to lattice spacing and molecular tilt. The relative strength of the absorption peaks mainly depends on the tilt angle relative to the surface normal. We use the strength data to estimate the tilt angle across the known monolayer phases, information that is difficult to obtain by other techniques. Although only the surface-normal component of the induced dipole moment appreciably couples to the external infrared field, surface-parallel components contribute to the intralayer coupling and hence to the frequency shifts for tilted molecules. Comparison to model calculations for a range of herringbone tilt configurations allows us to draw conclusions regarding the pattern of tilt azimuths. On this basis, we offer a revised interpretation of the origin of the Ising-type ordering transition found by Arndt et al. [Phys. Rev. Lett. 80, 1686 (1998)] in heat capacity measurements. Our phase bo...Continue Reading

References

Dec 1, 1986·Physical Review. B, Condensed Matter·Q M ZhangM H Chan

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Citations

Mar 25, 2011·The Journal of Chemical Physics·Petros ThomasGeorge B Hess
Oct 2, 2009·The Journal of Chemical Physics·Petros ThomasGeorge B Hess
May 24, 2014·The Journal of Chemical Physics·Petros Thomas, George B Hess
Sep 24, 2015·The Journal of Chemical Physics·Petros ThomasGeorge B Hess
Sep 10, 2017·The Journal of Chemical Physics·G B Hess, Yu Xia

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Methods Mentioned

BETA
neutron diffraction
x-ray diffraction

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