The lower-order diamondoid hydrocarbon molecule, cyclohexamantane (C26H30), has been recently isolated from distilled Gulf Coast petroleum. While the structure of C26H30 has been confirmed through X-ray diffraction, mass spectroscopy, and H-1/C-13 NMR spectroscopy, its vibrational Raman spectra has only been identified through an indirect comparison with the experimental Raman spectra for adamantane and diamond. We used density-functional theory (DFT) to calculate a Raman spectra whose frequencies and relative intensities are in excellent agreement with the experimental Raman spectra for C26H30, thus providing direct vibrational proof of its existence. (C) 2004 Elsevier B.V. All rights reserved.