Isotope Effect in D

Area of Science:

• Physical Chemistry
• Chemical Physics
• Atomic and Molecular Collisions

Background:

• Understanding electron transfer processes in molecules is crucial for chemical dynamics.
• Water (H2O) and its isotopologue (D2O) are fundamental molecules in chemistry and physics.
• Investigating ion-molecule reactions provides insights into molecular electronic structures.

Purpose of the Study:

• To investigate electron transfer processes in H2O/D2O collisions with neutral potassium.
• To determine the energy dependence of branching ratios and isotope effects.
• To characterize the electronic states and bond dissociation energies involved.

Main Methods:

• Time-of-flight mass spectrometry of negative ions (OH-/OD-, O-, H-/D-) from H2O/D2O collisions with potassium.
• Potassium cation energy loss spectroscopy at 205 eV impact energy.
• Quantum chemical calculations for unoccupied molecular orbitals in K-H2O/D2O systems.

Main Results:

• Observed OH-/OD-, O-, and H-/D- negative ions, with energy-dependent branching ratios.
• Significant isotope effect observed in D2O collisions.
• Determined the D-O bond dissociation energy of D2O to be 5.41 ± 0.10 eV.
• Supported experimental findings with quantum chemical calculations, identifying electronic states involved.

Conclusions:

• Electron transfer collisions of H2O/D2O with potassium exhibit significant energy dependence and isotope effects.
• The study provides the first experimental determination of the D-O bond dissociation energy in D2O.
• Collision dynamics elucidate the nature of singly and doubly excited molecular orbitals in K-H2O/D2O systems.