title: Geometric phase for collinear conical intersections. I. Geometric phase angle and vector potentials.
abstract: We present a method for properly treating collinear conical intersections in triatomic systems. The general vector potential (gauge theory) approach for including the geometric phase effects associated with collinear conical intersections in hyperspherical coordinates is presented. The current study develops an introductory method in the treatment of collinear conical intersections by using the phase angle method. The geometric phase angle, η, in terms of purely internal coordinates is derived using the example of a spin-aligned quartet lithium triatomic system. A numerical fit and thus an analytical form for the associated vector potentials are explicitly derived for this triatomic A(3) system. The application of this methodology to AB(2) and ABC systems is also discussed.
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019, USA. li@nhn.ou.edu
authors.forename: Xuan
authors.initials: X
authors.lastname: Li
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Brue
authors.forename: Brian K
authors.initials: BK
authors.lastname: Kendrick
authors.forename: Juan D
authors.initials: JD
authors.lastname: Blandon
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Parker