Variation in (Hyper)Polarizability of H₂ Molecule in Bond Dissociation Processes Under Spatial Confinement

Area of Science:

• Quantum chemistry
• Molecular physics
• Nonlinear optics

Background:

• The electronic and optical properties of molecules are significantly influenced by their environment.
• Understanding molecular response under confinement is crucial for predicting behavior in condensed phases or nanoscale systems.
• Hydrogen molecule (H2) serves as a fundamental model system in quantum chemistry.

Purpose of the Study:

• To investigate the effects of spatial confinement on the linear polarizability and second hyperpolarizability of the H2 molecule.
• To analyze how confinement modifies the H2 molecule's response during the bond dissociation process.
• To compare the confinement effects on H2 with those observed in polar molecules like LiH.

Main Methods:

• Ab initio calculations were performed to determine the electronic structure and response properties.
• The spatial confinement was modeled using an external two-dimensional (cylindrical) harmonic oscillator potential.
• Calculations were conducted for various interatomic (H-H) distances, simulating bond dissociation.

Main Results:

• Spatial confinement was found to significantly diminish both the linear polarizability and second hyperpolarizability of the H2 molecule.
• This reduction in optical response was observed across all investigated interatomic distances.
• The impact of confinement on H2 was notably different from that observed in the polar LiH molecule.

Conclusions:

• External spatial confinement, modeled by a cylindrical harmonic oscillator potential, substantially alters the electronic and optical properties of the H2 molecule.
• The H2 molecule's response to electric fields, both linear and nonlinear, is significantly suppressed under confinement.
• These findings underscore the importance of environmental effects in determining molecular properties, particularly for nonpolar molecules like H2.