M. Joyeux, D. A. Sadovskii, and J. Tennyson

  Using the potential surface of Essers, Tennyson, and Wormer in
  [Chem. Phys. Lett. 89 (1982) 223] we show that the system of bending
  vibrational states of the isomerizing molecule LiNC/NCLi has monodromy.  On
  the basis of a deformed spherical pendulum model we explain dynamical and
  geometric reasons of this phenomenon and of its absence in the similar system
  HCN/CNH.

PACS: 33.20.Vq; 45.50.-j; 03.65.Sq; 33.15.Mt
Keywords: Floppy triatomic molecules; Global quantum numbers; Monodromy; 
          Energy-momentum map

submitted to Chem. Phys. Lett. 9/2003