STRUCTURE DETERMINATION OF 2-DIMENSIONAL ADENINE CRYSTALS ON GRAPHITE

Two-dimensional molecular-packing structure and monolayer preparation of adenine adsorbates on the graphite (0001) surface have been studied using scanning tunneling microscopy, low-energy electron diffraction, and thermal-desorption spectroscopy. By combining real-space images a nd diffraction data a close-packed hydrogen-bonded network of adenine dimers is proposed, containing two dimers in a unit eel with the symme try group p2gg. The energy-minimized molecular arrangement could be de termined by force field calculations. Adenine adsorbate layers were pr epared by sublimation in UHV.