Modification of quasi two-dimensional surface electron system on Au(111) with adsorption of long-chain n-alkane molecule n-CH(3)(CH(2))(42)CH(3) (tetFatetracontane: TTC) was investigated by angle-resolved photoemission spectroscopy. Significant modification of the energy band structure of the Shockley Surface state was induced by the adsorption of TTC monolayer with "flat-on" structure. The energy shift of the Shockley surface state toward the Fermi level reaches about 160 meV at Gamma point (k=0 angstrom(-1)). The possible origin of the tabilization of the surface electron system with TTC monolayer is discussed. (C) 2009 Elsevier B.V. All rights reserved.