A Novel Intraline of Conical intersections for Methylamine: A Theoretical Study

C. Levi, G. J. Halasz, A. Vibok, I. Bar, Y. Zeiri, R. Kosloff, M. Baer

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In this article the study of conical intersections (ci) related to the NOHbond in the methylamine, CH3NH2, molecule is extended. In a previous publication(Levi et al., J Chem Phys 2008, 128, 244302) we reported on a novel feature associatedwith the intersection of the two lowest states1A’ and1A of the methylamine. Weestablished the existence of a finite (closed) line of ci located in the HCONHH plane—aline that is formed by moving a single hydrogen on that plane while fixing the (six)other atoms. The validity of this line was proved by studying the singularities of the(angular) nonadiabatic coupling terms (NACT)—a study that was later supported byrevealing the degeneracy points formed by the two interacting adiabatic potentialenergy surfaces (PESs). This situation led to two additional interesting features: (i)Along any (open) contour in the above plane that intersects this line is formed anarrow, spiky NACT for which the area under it is ␲/2; (ii) In case of a closedcontour the corresponding topological (Berry) phase is zero (and not an integer multiple
Original languageEnglish GB
Pages (from-to)2482-2489
JournalInternational Journal of Quantum Chemistry
Issue number11
StatePublished - Sep 2009


  • conical intersection
  • nonadiabatic coupling
  • methylamine
  • topological phase


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