A new, accurate, global, mass-independent, first-principles potential energy surface (PES) is presented for the ground electronic state of the water molecule. The PES is based on 2200 energy points computed at the all-electron aug-cc-pCV6Z IC-MRCI(8,2) level of electronic structure theory and includes the relativistic one-electron mass-velocity and Darwin corrections. For H2 16O, the PES has a dissociation energy of D0 = 41109cm-1 and supports 1150 vibrational energy levels up to 41083cm-1. The deviation between the computed and the experimentally measured energy levels is below 15cm-1 for all the states with energies less than 39000cm-1. Characterization of approximate vibrational quantum numbers is performed using several techniques: energy decomposition, wave function plots, normal mode distribution, expectation values of the squares of internal coordinates, and perturbing the bending part of the PES. Vibrational normal mode labels, though often not physically meaningful, have been assigned to all the states below 26500cm-1 and to many more above it, including some highly excited stretching states all the way to dissociation. Issues to do with calculating vibrational band intensities for the higher-lying states are discussed.
|Number of pages||22|
|Journal||Journal of Quantitative Spectroscopy and Radiative Transfer|
|Publication status||Published - jún. 1 2010|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics