The rovibrational Hamiltonian for ammonia-like molecules

Vibrational energy levels for symmetric and asymmetric isotopomers of ammonia with an exact kinetic energy operator and new potential energy surfaces

“…We encountered no problems with coupled integration limits 46 or with configurations with one bond angle larger than 180°in the planar configuration. 23 This is supported by the observation that energies in both E symmetry blocks are identical for all calculated eigenvalues up to 20 000 cm Ϫ1 at least within 0.1 cm Ϫ1 .…”

“…Problems caused by coupled integration limits for the three symmetrized bond angle coordinates 46 can also be circumvented using the three-step contraction scheme. In the contracted one-and two-dimensional bases, all eigenfunctions corresponding to converged eigenvalues disappear before these coupled integration limits are reached.…”

A simple method for derivation of the rovibrational Hamiltonian: application to orthogonal radau coordinate systems as special cases

“…Radau coordinates are suitable for describing the vibrational motions of molecules with a heavy central atom [21][22][23]. Radau coordinates for triatomic molecules are defined as shown in Fig.…”

A new proof of the molecular Hamiltonian in Radau coordinates for triatomic molecules based on tensor form

“…Although H 2 O has been studied extensively in Radau coordinates [29,30,32], this coordinates system can be used for other triatomic molecules such as H 2 S, N 2 O, SO 2 , OBrO [5,[33][34][35][36]. In addition, Radau coordinates have commonly been considered for molecules having central heavy atom AB n such as NH 3 , CH 4 [37][38][39][40]. Triatomic molecules are simple and useful models for finding optimal coordinates and appropriate Hamiltonian, because it is easy to evaluate the vibration-rotation terms in the Hamiltonian.…”