Information theory of the lineshape for collision-induced absorption: Nitrogen gas

Abstract

We present a simple theory of the far-infrared collision-induced absorption spectrum of nitrogen gas. Assuming a quadrupolar induction mechanism and neglecting the small anisotropy in the N 2 pair potential, we represent the spectral profile as the convolution of a free-rotation spectrum with a translational component. Information theory is used to estimate the “least biased” form for the latter, based on our knowledge of its spectral moments. Our theory contains no adjustable parameters, yet yields results in excellent agreement with experiment over a wide range of temperatures.