title: Ab initio rotation-vibration energy levels of triatomics to spectroscopic accuracy.
abstract: The factors that need to be taken into account to achieve spectroscopic accuracy for triatomic molecules are considered focusing on H3+ and water as examples. The magnitude of the adiabatic and non-adiabatic corrections to the Born-Oppenheimer approximation is illustrated for both molecules, and methods of including them ab initio are discussed. Electronic relativistic effects are not important for H3+, but are for water for which the magnitude of the various effects is discussed. For H3+ inclusion of rotational non-adiabatic effects means that levels can be generated to an accuracy approaching 0.01 cm(-1); for water the error is still dominated by the error in the correlation energy in the electronic structure calculation. Prospects for improving this aspect of the calculation are discussed.
authors: Department of Physics and Astronomy, University College London, UK. j.tennyson@ucl.ac.uk
authors: Jonathan
authors: J
authors: Tennyson
authors: Paolo
authors: P
authors: Barletta
authors: Maxim A
authors: MA
authors: Kostin
authors: Oleg L
authors: OL
authors: Polyansky
authors: Nikolai F
authors: NF
authors: Zobov
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D008962:Models, Theoretical; D015203:Reproducibility of Results; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014732:Vibration; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D006859:Hydrogen