ABSORPTION OF THE C-H STRETCHING FUNDAMENTALS IN PURE ETHYLENE TO HIGH-PRESSURES AND TEMPERATURES

The infrared absorption of the nu //9 and nu //1//1 stretching fundamentals in pure ethylene was measured at supercritical temperatures between 26 degree C and 200 degree C to a maximum pressure of 2000 bar. The density and temperature dependence of the absorption intensity and of the wave-numbers of maximum absorption are reported. The decrease of the nu //9 molar integrated absorptivity toward the highest densities is interpreted as being due to the importance of repulsive interactions in dense pure ethylene. The position of the nu //1//1 band maximum provides a measure for the extent of rotational freedom in the fluid state.