Refractive index measurement of compressed nitrogen using an infrared frequency-domain interferometer

Frequency-domain interferometry is used to obtain the refractive index of compressed nitrogen in the vicinity of 1550 nm as the pressure of nitrogen increases from 0 to 40 MPa at room temperature. By referring to the equation of state of nitrogen, the relation between the refractive index and the nitrogen density is obtained and the electric polarizability of a nitrogen molecule is thereby determined to be (1.82 ± 0.15) × 10−30 m−3 according to the Lorentz-Lorentz relation.