The Raman spectroscopy of n-pentane was investigated in a Moissanite anvil cell from 0.07 GPa to 4.77 GPa at ambient temperature. The result shows that the CH3 symmetric stretching vibration (2877 cm(-1)) and asymmetric stretching vibration (2964 cm(-1)), the CH2 symmetric stretching vibration (2856 cm(-1)) and asymmetric stretching vibration (2935 cm(-1)), and -(CH2)n- in-phase twist mode (1303 cm(-1)) shifted to higher wavenumbers almost linearly with increasing pressure. Around 2.4 GPa an abrupt visible change took place, indicating a sort of phenomenon of freezing due to over-pressurization. In the pressure range of 2.84 to 4.77 GPa a high-pressure phase transition may occur in the crystallized n-pentane. By determining pressure with the method of solid-liquid coexistence, we concluded that the equilibrium freezing pressure of n-pentane is 1.90 +/- 0.05 GPa at 27 degrees C.

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Using a Diamond Anvil Cell combined with micro Raman spectroscopy, the quantitative relations among Raman shifts, pressure and temperature were obtained for the vibration of OeH in H 2 OeNaCl, CeO in CO 2À 3 , SeO in SO 2À 4 and CeH in n-heptane-cyclohexane. Based on the quantitative relationships obtained, it is possible to determine the inner pressure for single fluid inclusions and to further determine the isochore of the systems. It is not only helpful to obtain the forming temperatures and pressures of the enclosing minerals, but also to be able to provide information concerning the chemical compositions of the fluid inclusions. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

The Raman spectroscopy of n-heptane was investigated in a moissanite anvil cell at ambient temperatures and a diamond anvil cell under pressures of up to ~2000 MPa and at temperature range from 298 to 588 K. The results show that at room temperature the vibration modes, assigned to the symmetric and antisymmetric stretching of CH(3) and CH(2) stretching, shifted to higher frequency according to quasi-linearity with increasing pressure, and a liquid-solid phase transition occurred at near 1150 MPa. The high-temperature solidus line of n-heptane follows a quadratic function of P = 0.00737T(2) + 5.27977T - 1195.76556. Upon phase change, fitting the experimental data obtained in the temperature range of 183∼412 K to the Clausius-Clapeyron equation allows one to define the thermodynamic parameters of n-heptane of dP/dT = 0.01474T + 5.27977.