Configuration interaction studies of the excited states of water

Abstract

We report the results of extensive configuration interaction studies on 16 excited states of water. These states can be accurately described as corresponding to excitation from one of the highest two molecular orbitals (1b1 or 3a1) of the ground state into either the 3s or one of the three 3p Rydberg orbitals. The results provide the most accurate and consistent treatment of these states to date (within 0.1 eV for all known transitions) and form a reliable basis for the assignment of the photon and electron impact spectra of H2O.

Scaled Second-Order Perturbation Corrections to Configuration Interaction Singles: Efficient and Reliable Excitation Energy Methods

“…Accordingly, we have used vertical excitation energies 37,38 for these transitions. In the excitation energy calculations, we have used 6-311(2+,2+)G(d,p) basis together with the auxiliary basis of aug-cc-pVTZ.…”

Cross sections and oscillator strengths for electron-impact excitation of the ÃB11 electronic state of water

“…[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] In particular, the peak positions, profile shapes, and widths used in our deconvolution were gleaned and fixed as much as possible from the earlier work. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] An example of our spectral deconvolution is also given in Fig. 1͑a͒.…”

“…[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] These studies are not simply noted here for completeness, as we shall shortly see they were vital in enabling us to deconvolve the respective electronic-state contributions to the measured energy-loss spectra. A summary of the major results from Refs.…”

Excited states of the water molecule: Analysis of the valence and Rydberg character

“…The present study attempts to throw more light into this aspect of the excited states of water which we consider has been somewhat overlooked. 11,14,[21][22][23] Despite earlier conclusions which emphasized the Rydberg character of the band, [17][18][19] the experimental evidence does suggest some valence character for the lowest-energy band of the gas-phase electronic spectrum of water. 11,14,23 The band is broad ͑6.8-8.2 eV͒, with poorly defined vibrational progressions, and has its maximum absorption around 7.4 eV.…”

“…15,16 The observed bands were interpreted as Rydberg series on the basis of the quantum defect analysis and using available ab initio calculations as a guide for the assignments. [11][12][13][16][17][18][19] A comprehensive ab initio study on the excited states of water performed in 1974 by Goddard and Hunt 17 characterized all the computed states below 11.7 eV as having Rydberg nature, a result supported at the configuration interaction ͑CI͒ level. 18,19 As shall be discussed below, the electronic spectrum of water in the gas phase is currently interpreted as composed either of different Rydberg series or implying excited states with a significant Rydberg character at the ground-state equilibrium geometry ͑see, for instance, Ref.…”