Charge-Transfer Energy in the Water−Hydrogen Molecular Aggregate Revealed by Molecular-Beam Scattering Experiments, Charge Displacement Analysis, and ab Initio Calculations

Abstract

Integral cross-section measurements for the system water-H(2) in molecular-beam scattering experiments are reported. Their analysis demonstrates that the average attractive component of the water-H(2) intermolecular potential in the well region is about 30% stronger than dispersion and induction forces would imply. An extensive and detailed theoretical analysis of the electron charge displacement accompanying the interaction, over several crucial sections of the potential energy surface (PES), shows that water-H(2) interaction is accompanied by charge transfer (CT) and that the observed stabilization energy correlates quantitatively with CT magnitude at all distances. Based on the experimentally determined potential and the calculated CT, a general theoretical model is devised which reproduces very accurately PES sections obtained at the CCSD(T) level with large basis sets. The energy stabilization associated with CT is calculated to be 2.5 eV per electron transferred. Thus, CT is shown to be a significant, strongly stereospecific component of the interaction, with water functioning as electron donor or acceptor in different orientations. The general relevance of these findings for water's chemistry is discussed.

Overtone vibrational spectroscopy in H2-H2O complexes: A combined high level theoretical ab initio, dynamical and experimental study

“…Several 5D "rigidrotor" surfaces have been obtained, either by averaging the 9D potential over vibrational wavefunctions of H 2 29 with the VGS and VAP potentials shown to provide very similar cross sections even at collision energies below 1 cm −1 . The high accuracy of these H 2 -H 2 O PES's has also been confirmed recently by a number of comparisons between theory and experiment including inelastic differential cross sections, 26 pressure broadening cross sections, 30,37 elastic integral cross sections, 18 and IR spectra of the complex. 15,17,21 In the present work, we use two different vibrationally averaged 5D PES's, with (i) both H 2 and H 2 O monomers in their ground vibrational state (as discussed in Valiron et al 1 ) and (ii) ground state H 2 (v = 0) and H 2 O in its doubly excited |02 − ) state, utilizing the wavefunction of Lodi and Tennyson.…”

“…The current work focuses on spectroscopy, dynamics, and interaction potentials for H 2 + H 2 O, 1,13,[15][16][17][18][19][20][21] which proves to be relevant in a wide range of terrestrial and extraterrestrial venues. 2,[22][23][24][25][26] In high temperature H 2 /O 2 combustion, for example, collisions of the highly energized product H 2 O molecules with H 2 reactant provide an important mechanism for heat flow as well as establishing local thermodynamic equilibrium in the flames.…”

State-to-state differential and relative integral cross sections for rotationally inelastic scattering of H2O by hydrogen

“…Brudermann et al 3 presented measurements of differential cross sections for H2O+He elastic scattering and reported partially state--resolved inelastic angular dependent energy loss spectra, at two different collision energies. Capelletti et al 12,14 reported determination of the potential parameters for the isotropic component of the D2O--He and D2O-D2 interaction by elastic scattering studies. They compared their fitted parameters with those of previous studies using different potential models and with the predictions of ab initio calculated potential surfaces.…”

A SAPT Study of the H2O X2 Complexes; X = H, N and F

“…In a recent work, Belpassi et al [8] [38], for systems in which induction is predicted to be the leading term, or being the same order as dispersion, the hybrid approach should be the best choice. The need of δE…”

“…[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. Theoretical works were mainly focused on the development of potential energy surface (PES) or relate to accurate calculations of interaction energy using the supermolecular approach.…”