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Egor O. Dobrolyubov, Vladimir M. Manuylov, Sergey V. Krasnoshchekov
A prediction of the
vibration-rotation absorption spectra of the D216O molecule
ν2 band by solving the operator perturbation theory direct
problem and a refinement of the effective rotational hamiltonians
Abstract
Abstract. By means of solving the direct vibration-rotation
problem with the Watson Hamiltonian by the operator Van Vleck perturbation
theory and using the quantum chemical (CCSD(T)/aug-cc-pVQZ) geometrical
molecular structure, sextic force field and cubic dipole moment surface of the D216O molecule, the absorption spectra and
spectroscopic constants of effective rotational Hamiltonians in A-reduction
were predicted for the ground state and ν2 band. The theoretic sixth order
perturbative approach in vibrational variables (fourth for the dipole moment
operator) and third order in rotational variables is based on the systematic
procedure of calculating rotational commutators by means of normal ordering of
cylindrical angular momentum operators. The obtained reduced spectroscopic
constants were refined and augmented using fitting to experimental energy
levels. It is shown that new effective Hamiltonians significantly better
reproduce experimental data for J ≤ 30, while calculated
intensities reproduce experimental counterparts with the high accuracy.
Key words: Vibration-rotation spectroscopy, operator
perturbation theory, effective rotational Hamiltonian, normal ordering, heavy
water
Copyright (C) Chemistry Dept., Moscow State University, 2002
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