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The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.

The rapidly rotational motion of C60 molecules will provide us with an ingenious way to test Mashhoon's spin-rotation coupling. Geometric phases arising from the time-dependent spin-rotation coupling of electrons in the rotating C60 molecule is considered in the present Letter. It is shown that geometric phases of electrons in C60 molecules may be measured through the photoelectron spectroscopy of C60. A physically interesting fact that the information about rotation and precession of C60 molecules in the orientational ordered (or disordered) phase may be read off from the photoelectron spectroscopy of C60 is also demonstrated.PACS numbers: 03.65. Vf, 61.48.+c The information on the rotational dynamics of C 60 molecule in condensed phases have been obtained from nuclearmagnetic resonance (NMR) studies [1]. Both NMR spectroscopy and quasielastic neutron scattering experiments [2] indicated the rapid rotation of C 60 molecules whose rotational correlation time may be picoseconds in the orientationally disordered phase. Historically, many researches were in connection with the molecular-dynamics of C 60 rotation [3]. Heiney et al. found from x-ray diffraction and calorimetrical measurements that solid C 60 exhibits a phase transition near 249 K from a simple cubic structure at low temperatures to a face-centered-cubic structure at high temperatures [3][4][5]. These studies suggest that the phase above the transition temperature is characterized by free rotation or rotational diffusion and that the phase below the transition is characterized by jump rotational diffusion between symmetry-equivalent orientations. The correlation time for both phases (orientationally ordered phase below 249 K and orientationally disordered phase above 249 K) were measured to fit with an Arrhenius law, which leads to the fact that in the low-temperature phase, the correlation time τ increases by a factor of ∼ 40. . Kiefl et al. reported the study of the molecular dynamics and electronic structure of µ + -C 60 radical in a highly crystalline sample of pure C 60 and showed a signal at room temperature which is a µ + -C 60 radical in crystalline sample C 60 undergoing a quasi-free rotation [5]. Thus it follows that the molecular-dynamics of C 60 rotation is of great importance, since it is related close to the molecular thermal motion, phase transition and crystal structure of solid C 60 .In this Letter we propose a new approach to the investigation of molecular-dynamics of C 60 . We suggest that both the spin-rotation coupling of electrons and the consequent geometric phases can provide us with an insight into the rotational dynamics, intermolecular interaction and thermal motion of C 60 molecules.Basically speaking, the spin-rotation coupling considered here is one of the gravitational effects since the nature of the inertial force (e.g., the Coriolis force) is the gravitational force according to the principle of equivalence. Mashhoon showed that a particle with an intrinsic spin possesses a gravitomagnetic moment that can be coupled...