A six-dimensional H(2)-H(2) potential energy surface for bound state spectroscopy.

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Understanding intermolecular forces in van der Waals complexes like (H2)2 is crucial for molecular physics.
• Accurate potential energy surfaces (PES) are essential for predicting spectroscopic properties and dynamics of molecular dimers.

Purpose of the Study:

• To construct a highly accurate six-dimensional potential energy surface for the (H2)2 dimer.
• To accurately describe the bound and quasibound states of (H2)2, (D2)2, and H2-D2 dimers.
• To predict infrared and Raman transition energies for these dimers.

Main Methods:

• Coupled-cluster electronic structure calculations with large basis sets and midbond functions.
• Close-coupled approach to compute dimer state energies.
• Empirical adjustments to the ab initio PES using experimental transition energies.

Main Results:

• The adjusted PES accurately reproduces 56 experimentally observed infrared and Raman transitions within 0.036 cm(-1).
• For 26 transitions, the agreement falls within experimental uncertainty.
• Predicted energies for 34 unobserved transitions are provided.

Conclusions:

• The developed PES provides a highly accurate description of the (H2)2, (D2)2, and H2-D2 systems.
• The surface is suitable for studying rovibrational states and predicting spectroscopic transitions.
• This work advances the understanding of van der Waals interactions in simple molecular systems.