Near Infrared Absorption of Pure n - Heptane between 5000 c m 1 and 6500 em - 1 to High Pressures and Temperatures

The near infrared absorption of pure n-heptane between 5000 c m 1 and 6500 c m 1 was measured up to 250 °C and to pressures of 2000 bar. The procedure for measuring vibrational intensities at high pressures and temperatures with a precision of better than ± 1% is described. The integrated molar absorptivity of the combination mode va + vs of the methylene stretching fundamentals turns out to be independent of temperature and density. This offers important applications for high-pressure high-temperature thermodynamic and kinetic studies via quantitative near infrared spectroscopy.