Absolute Far-Infrared Absorption Intensities of α-Nitrogen

The absolute intensities of the translational lattice mode absorptions of α‐N₂ in the far infrared have been measured. The experimental values are smaller by a factor of 5 than the calculated intensities obtained from a quadrupole‐induced mechanism theory. This discrepancy is discussed in terms of the model on which the theory was based. The intensity of the 50‐cm⁻¹ line was found to be temperature dependent and decreased gradually between 15°K and 35°K. No discrete absorption was observed for the $\beta$ phase above 36°K. The 50‐cm⁻¹ line has a width smaller than 0.5 cm⁻¹ and the 70‐cm⁻¹ line has a width of 6 cm⁻¹. Evidence was found for a decrease of the frequency of the 50‐cm⁻¹ line as the phase transition temperature is approached.