The Vibration‐Rotation Energy Levels of Polyatomic Molecules II. Perturbations Due to Nearby Vibrational States

1936 ◽  
Vol 4 (5) ◽  
pp. 313-316 ◽  
Author(s):  
E. Bright Wilson
Keyword(s):  
Energy Levels ◽  
Polyatomic Molecules ◽  
Vibrational States ◽  
Vibration Rotation ◽  
Rotation Energy

Determinable parameters of the effective rotational Hamiltonians for excited vibrational states of semirigid symmetric top molecules of C4v, D4, D2h, andD2d symmetry

1989 ◽  
Vol 54 (12) ◽  
pp. 3107-3116
Author(s):  
Kamil Sarka ◽  
Dušan Papoušek
Keyword(s):  
Symmetry Axis ◽  
Energy Levels ◽  
Contact Transformation ◽  
Centrifugal Distortion ◽  
Vibrational States ◽  
Fourfold Symmetry ◽  
Vibration Rotation ◽  
Symmetric Top Molecules ◽  
Rotation Energy ◽  
General Method

A general method is described for obtaining the S functions which in the contact transformation of the vibration-rotation Hamiltonian of semirigid molecules with the fourfold symmetry axis eliminate the rotational and vibrational l-type operators and the Δk = ±4 centrifugal distortion operators from the λH1 terms of the expanded Hamiltonian. Explicit expressions are given for the vibration-rotation energy levels with independent effective spectroscopic parameters. Expressions are also given for the splittings of energy levels with essential resonances.

CALCULATION OF SELECTED HIGHLY EXCITED VIBRATIONAL STATES OF POLYATOMIC MOLECULES BY THE DAVIDSON ALGORITHM

2003 ◽  
Vol 02 (04) ◽  
pp. 609-620 ◽  
Author(s):  
FABIENNE RIBEIRO ◽  
CHRISTOPHE IUNG ◽  
CLAUDE LEFORESTIER
Keyword(s):  
Energy Levels ◽  
Normal Modes ◽  
Chem Phys ◽  
Polyatomic Molecules ◽  
Zero Order ◽  
Basis Set ◽  
Vibrational States ◽  
Diagonalization Method ◽  
Davidson Algorithm ◽  
High Overtone

We described an improved version of a modified Davidson scheme previously introduced (F. Ribeiro, C. Iung and C. Leforestier, Chem. Phys. Lett.362, 199 (2002)), aimed at computing highly excited energy levels of polyatomic molecules. The key ingredient is a prediagonalization-perturbation step performed on a subspace of a curvilinear normal modes basis set (including diagonal anharmonicities). The efficiency of the method is demonstrated by computing the lowest 350 vibrational states of A′ symmetry of the HFCO molecule. Also shown is the possibility to restrict the calculation to selected energy levels, based on their zero-order description. This State Filtered Diagonalization method is illustrated on a high overtone (7ν5) of the OCF bend, and on the few energy levels (20) which have been experimentally assigned up to 5000 cm -1 of excitation energy.

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