Interaction of 25 keV Electrons with the Nucleic Acid Bases, Adenine, Thymine, and Uracil. I. Outer Shell Excitation

摘要

The energy loss functions mdash; Im(1sol;egr;) of thin films of the nucleic acid bases, adenine (C5N5H5), thymine (C5N2O2H6), and uracil (C4N2O2H4) have been determined in the range 2ndash;50 eV from energy loss experiments with 25 keV electrons at room temperature. An analysis of the electronic structure of these materials in the region of outer shell excitation has been obtained in the form of determination of the dielectric constants egr;1and egr;2from a Kramersmdash;Kronig analysis of the energy loss function. In the spectral region where ultraviolet absorption data exists (10 eV), the calculated optical absorption coefficient mgr; is shown to be in good agreement with the optical measurements.