First-Principles Rovibrational Spectroscopy
Attila G. Császár
Laboratory of Molecular Spectroscopy, Institute of Chemistry,
Eötvös University, P.O. Box 32, H-1518 Budapest 112, Hungary
e-mail: csaszar@chem.elte.hu
For the accurate first-principles computation of preferentially complete rovibrational
spectra one needs to solve both the quantum mechanical electronic structure and nuclear motion problems with exceedingly high accuracy. State-of-the-art ab initio electronic structure
computations can result in highly accurate potential energy (PES) and dipole moment (DMS)
surfaces. Our recent results1-5 are reviewed, highlighting the hierarchy of physical effects to
be considered and the computational procedures to be employed. The emphasis is placed on
the prototypical triatomic molecule H2O. Variational strategies for solving the nuclear motion
problem6-10 are discussed next. Emphasis is put on the simplicity of the approach, the utility of
the solution strategies in handling singularities present in most rovibrational Hamiltonians,
the generality of the protocol and the resulting code, and the efficiency of the numerical solution. Representative results and chemical applications are presented for selected 35-atomic
systems. Comparison of the computed results with the best experimental ones, obtained
through our Hamiltonian-free MARVEL protocol,11-13 standing for measured active rotational-vibrational energy levels, is given at the end.
References
[1] O. L. Polyansky, A. G. Császár, S. V. Shirin, N. F. Zobov, P. Barletta, J. Tennyson, D. W. Schwenke, and P. J.
Knowles, High-Accuracy Ab Initio Rotation-Vibration Transitions of Water, Science 2003, 299, 539-542.
[2] A. G. Császár, G. Czakó, T. Furtenbacher, J. Tennyson, V. Szalay, S. V. Shirin, N. F. Zobov, and O. L. Polyansky, On Equilibrium Structures of the Water Molecule, J. Chem. Phys. 2005, 122, 214305.
[3] S. V. Shirin, O. L. Polyansky, N. F. Zobov, R. I. Ovsyannikov, A. G. Császár, and J. Tennyson, Spectroscopically Determined Potential Energy Surfaces of the H216O, H217O, and H218O Isotopologues of Water, J. Mol. Spectry. 2006, 236, 216-223.
[4] P. Barletta, S. V. Shirin, N. F. Zobov, O. L. Polyansky, J. Tennyson, and A. G. Császár, The CVRQD Ab Initio
Ground-State Potential Energy Surfaces for the Water Molecule, J. Chem. Phys. 2006, 125, 204307.
[5] L. Lodi, R. N. Tolchenov, J. Tennyson, A. E. Lynas-Gray, S. V. Shirin, N. F. Zobov, O. L. Polyansky, A. G.
Császár, J. N. P. Stralen, and L. Visscher, A New Ab Initio Ground State Dipole Moment Surface for the Water
Molecule, J. Chem. Phys. 2008, 128, 044304.
[6] G. Czakó, T. Furtenbacher, A. G. Császár, and V. Szalay, Variational Vibrational Calculations Using HighOrder Anharmonic Force Fields, Mol. Phys. (Nicholas C. Handy Special Issue) 2004, 102, 2411-2423.
[7] G. Czakó, V. Szalay, A. G. Császár, and T. Furtenbacher, Treating Singularities Present in the SutcliffeTennyson Vibrational Hamiltonian in Orthogonal Internal Coordinates, J. Chem. Phys. 2005, 122, 024101.
[8] T. Furtenbacher, G. Czakó, B. T. Sutcliffe, A. G. Császár, and V. Szalay, The Methylene Saga Continues:
Stretching Fundamentals and Zero-Point Energy of X3B1 CH2, J. Mol. Struct. (J. Demaison Special Issue) 2006,
780-781, 283-294.
[9] G. Czakó, V. Szalay, and A. G. Császár, Finite Basis Representations with Nondirect Product Basis Functions
Having Structure Similar to that of Spherical Harmonics, J. Chem. Phys. 2006, 124, 014110.
[10] E. Mátyus, G. Czakó, B. T Sutcliffe, and A. G. Császár, Variational Vibrational Calculations with Arbitrary
Potentials Using the Eckart-Watson Hamiltonians and the Discrete Variable Representation, J. Chem. Phys. 2007,
127, 084102.
[11] A. G. Császár, G. Czakó, T. Furtenbacher, and E. Mátyus, An Active Database Approach to Complete Spectra
of Small Molecules, Annu. Rep. Comp. Chem. 2007, 3, 155-176.
[12] T. Furtenbacher, A. G. Császár, and J. Tennyson, MARVEL: Measured Active Rotational-Vibrational Energy
Levels, J. Mol. Spectrosc. 2007, 245, 115-125.
[13] T. Furtenbacher and A. G. Császár, On Employing H 216O, H217O, H218O, and D216O Lines as Frequency
Standards in the 15-170 cm1 Window, J. Quant. Spectrosc. Rad. Tarnsfer 2008, 109, 1234-1251.