title: Transient molecular electro-optics Cartesian rotation vector versus Eulerian angles.
abstract: Comparing the Euler angles, the classical choice of generalized coordinates describing the three rotational degrees of freedom of a rigid body, and the Cartesian rotation vector, we show that they both have their advantages and disadvantages in kinetic theory and Brownian dynamics analysis of molecular electro-optics. The Eulerian angles often yield relatively simple, yet singular, equations of motion, while their counterparts expressed in terms of Cartesian rotation vector are non-singular but more complex. In a special case, we show that the generalized force associated with the Cartesian rotation vector equals the torque. In addition, we introduce a new graphical approach to qualitatively track how changes in the Eulerian angles affect the Cartesian rotation vector.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway.
authors.forename: Tom Richard
authors.initials: TR
authors.lastname: Evensen
authors.forename: Arnljot
authors.initials: A
authors.lastname: Elgsaeter
authors.forename: Stine Nalum
authors.initials: SN
authors.lastname: Naess
mesh_terms: D000465:Algorithms; D004058:Diffusion; D004563:Electrochemistry / Q000379:methods*; D007700:Kinetics; D012399:Rotation