Dielectric functions of DNA base films from near-infrared to ultra-violet

This work is reporting the dielectric functions of DNA base films, i.e. guanine, adenine, cytosine, and thymine in the energy range from near-infrared to ultra-violet. Spectroscopic ellipsometry using synchrotron radiation was employed in situ on DNA base films grown on hydrogen terminated Si(I 11) surfaces under ultra-high vacuum conditions. The optical response of adenine and guanine films is described by a uniaxial model while in the case of thymine and cytosine films an isotropic model was employed. The imaginary part of the dielectric functions epsilon(2) of the DNA base films is compared with the electronic transitions of single molecules calculated using time-dependent density functional theory. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.