Full-dimensional theoretical description of vibrationally resolved valence-shell photoionization of H2O

Abstract

We have performed a full-dimensional theoretical study of vibrationally resolved photoelectron emission from the valence shell of the water molecule by using an extension of the static-exchange density functional theory that accounts for ionization as well as for vibrational motion in the symmetric stretching, antisymmetric stretching, and bending modes. At variance with previous studies performed in centrosymmetric molecules, where vibrationally resolved spectra are mostly dominated by the symmetric stretching mode, in the present case, all three modes contribute to the calculated spectra, including intermode couplings. We have found that diffraction of the ejected electron by the various atomic centers is barely visible in the ratios between vibrationally resolved photoelectron spectra corresponding to different vibrational states of the remaining H2O+ cation (the so-called v-ratios), in contrast to the prominent oscillations observed in K-shell ionization of centrosymmetric molecules, including those that only contain hydrogen atoms around the central atoms, e.g., CH4. To validate the conclusions of our work, we have carried out synchrotron radiation experiments at the SOLEIL synchrotron and determined photoelectron spectra and v-ratios for H2O in a wide range of photon energies, from threshold up to 150 eV. The agreement with the theoretical predictions is good.

Perturbative and nonperturbative photoionization of H2 and H2O using the molecular R<

“…For the photoionization into the ground state of H 2 O + , Fig. 5 includes the results of Engin et al [70] obtained from a fixed-nuclei density-functional-theory calculation that shows slightly poorer agreement with the experiment. However, very recent B-spline density-functional-theory calculations [71] show similarly good agreement to ours, whereas earlier Rmatrix results [61] show poorer agreement particularly for higher photon energies (their calculations go up to 40 eV only).…”

“…Tan et al [72] Brion and Carnovale [69] Banna et al [68] Truesdale et al [73] Novikovskiy et al [60] Modak and Antony [61] Engin et al [70] FIG. 5.…”

“…The transitions to the three lowest states of H 2 O + are shown. Experimental data are from Tan et al [72], Truesdale et al [73], Brion and Carnovale [69], and Banna et al [68] and calculations are from Engin et al [70], Novikovskiy et al [60], and Modak and Antony [61]. The UKRmol+ results for energies smaller than 20 eV are heavily influenced by smoothing.…”

The quantum chemistry of attosecond molecular science

“…These methods have provided accurate descriptions of attosecond XUV‐pump/IR‐probe and XUV‐pump/XUV‐probe multicoincidence experiments performed in diatomic molecules such as N 2 , O 2 , CO, etc., and are currently being used to describe similar experiments in H 2 O, NO 2 , etc. Preliminary attempts to include quantum nuclear dynamics in full dimensionality in triatomic molecules are currently in progress …”

“…Preliminary attempts to include quantum nuclear dynamics in full dimensionality in triatomic molecules are currently in progress. 220,221 For large and very large molecules, DFT-based methods, like the static exchange DFT method implemented with B-spline functions, are the only sensible alternative to describe the electronic continuum. This method has provided an accurate description of the charge dynamics induced by an XUV attosecond pulse in several amino acids.…”