Optical constants of liquid isooctane at 3.39 microm

An experimental measurement of the complex refractive index of liquid isooctane at 3.39 microm was made using a two angle reflectance technique. A fused quartz prism was used to suppress liquid evaporation and to prevent index gradients above the liquid surface so that a liquid temperature range from 23 to 80 degrees C could be studied. Results indicate that the real part of the refractive index remains relatively constant over the temperature range decreasing from 1.440 to 1.406. The extinction coefficient, however, increased from 0.0654 to 0.0808 over this temperature range due to the redistribution of molecular states. The errors on the real and imaginary parts of the refractive index are estimated to be 0.05% and 3.0%, respectively.