Theory of the rotational Brownian motion of a linear molecule in 3D. I. Relaxation and steady-state regimes
Exact analytical expressions for the dielectric and Kerr functions in both relaxation and steady-state regimes are explicitly calculated by solving the Fokker-Planck-Kramers (FPK) equation for the rotational Brownian motion of a linear rigid rotor in 3D. The response functions thus obtained generalize and extend all the results recently published on the topic. The particular cases of the Debye-Smoluchowski and Rocard diffusion models are straightforwardly recovered.