RichMol: A general variational approach for rovibrational molecular dynamics in external electric fields

Area of Science:

• Quantum chemistry
• Molecular dynamics
• Computational physics

Background:

• Accurate simulation of molecular behavior in external electric fields is crucial for understanding chemical reactions and material properties.
• Existing methods often face limitations in handling complex molecular systems and arbitrary field configurations.

Purpose of the Study:

• To develop a general and computationally efficient variational approach for calculating the rovibrational dynamics of polyatomic molecules in external electric fields.
• To implement this method in a new software package, RichMol, for versatile simulations.

Main Methods:

• Utilizing highly accurate, full-dimensional variational calculations to establish field-free rovibrational states.
• Incorporating electric field effects via a multipole moment expansion up to the second hyperpolarizability term.
• Solving the time-dependent Schrödinger equation numerically.

Main Results:

• The developed method, implemented in RichMol, can simulate the effects of multiple external fields with arbitrary parameters.
• Illustrative calculations demonstrate the capability to model two-color orientation and rotational excitation of ammonia (NH3) using an optical centrifuge.

Conclusions:

• The new variational approach provides a robust and efficient tool for studying molecular responses to electric fields.
• RichMol facilitates advanced simulations of molecular dynamics, aiding in the design and understanding of molecular systems in external fields.