Interaction induced localization in a gas of pyramidal molecules

Area of Science:

• Chemical Physics
• Molecular Spectroscopy
• Quantum Mechanics

Background:

• Molecules with pyramidal structures exhibit tunneling between equilibrium configurations.
• Dipole-dipole interactions are significant in molecular gases, influencing their bulk properties.
• Pressure-induced changes in molecular behavior, such as inversion line shifts, are experimentally observed but require theoretical explanation.

Purpose of the Study:

• To develop a theoretical model describing the behavior of pyramidal molecules interacting via dipole-dipole forces.
• To explain the pressure-dependent shift of the inversion line in molecular gases like ammonia.
• To investigate the potential emergence of chirality-based selection rules in substituted derivatives at high pressures.

Main Methods:

• A theoretical model was developed to account for dipole-dipole interactions between pyramidal molecules.
• The model analyzes modifications to tunneling properties and molecular localization under pressure.
• Quantitative predictions were made and compared with experimental data for ammonia and deuterated ammonia.

Main Results:

• The model quantitatively explains the observed shift to zero frequency of the inversion line with increasing pressure in ammonia and deuterated ammonia gases.
• It demonstrates that dipole-dipole interactions lead to molecular localization in classical configurations at high pressures.
• The study suggests a super-selection rule for chirality in substituted derivatives at high pressures.

Conclusions:

• Dipole-dipole interactions play a crucial role in the pressure-dependent behavior of pyramidal molecules.
• The proposed model provides a parameter-free explanation for inversion line shifts in ammonia-like gases.
• High-pressure conditions may induce chirality-dependent phenomena in certain molecular systems.