It is usually asserted that H2O is characterized by an sp3 distorted hybridization with the two lone pairs degenerate. Actually, this is the case of water in liquid or solid state. In the gas phase, when the molecule is isolated, the two O–H bonding orbitals form an angle of about 104.5 and the two lone pairs are not degenerate, being one aligned along the C2v molecular axis (3a1, the sp2 lone pair orbital) and the other one perpendicular to the molecular plane (1b1, the 2pip oxygen non bonding orbital). This is well conﬁrmed by recent measurements from my laboratory in a Penning ionization electron spectroscopy study of water molecules by neon metastable atoms. In our experiment, due to the available energy of Ne*(3P2,0) atoms, the two not degenerate lone pair orbitals of the H2O molecule are selectively involved in the ionization process. The non-degeneracy of the two lone pairs is also well conﬁrmed by the presence of two separated bands in the electron energy spectra of H2O, obtained by photo- or Penning ionization, assigned to the two different approach directions of the Ne* atom to the molecule (both towards the O atom: one along the C2v molecular axis and the other one along the perpendicular direction of the molecular plane).
|Titolo:||Molecular Reaction Dynamics in Gases, Liquids and Interfaces: General Discussion|
|Data di pubblicazione:||2012|
|Parole Chiave:||Penning ionization; water; hydrogen bond|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1039/C2FD90011D|
|Appare nelle tipologie:||1.1 Articolo in rivista|