MoleCool 3.7.3

Molecular Laser-Cooling and Spectra Simulation

MoleCool

MoleCool is a Python library for numerical modeling of light–matter interactions,
with a focus on laser cooling of molecules — from simple few-level systems and diatomics
to polyatomics and even radioactive species.

📘 Full Documentation • PyPI • GitHub

For citing this package:

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✨ Overview

MoleCool enables you to simulate, analyze, and visualize the dynamics of laser–molecule interactions
for designing and optimizing experimental setups in state-of-the-art cooling and trapping experiments.

Key Features

• Flexible dynamics solvers — rate equations and Optical Bloch equations (OBEs),
  including effects of external magnetic fields.
  MoleCool reads predefined molecular constants (dipole matrix elements, hyperfine frequencies,
  g-factors, etc.) from JSON files.

• Interactive level-scheme handling — intuitive tools for exploring and visualizing
  electronic, vibrational, and rotational structures.

• Laser cooling force profiles — fast evaluation across high-dimensional parameter spaces
  for optimization of cooling configurations.

• Monte Carlo trajectory simulations — track many particles through laser fields
  using pre-evaluated force profiles for statistical reliability.

• Spectra analysis module — compute, fit, and interpret molecular spectra via
  effective Hamiltonians; extract constants for use in dynamics simulations.

Target Audience

MoleCool is intended for researchers and physicists working in
atomic, molecular, and optical (AMO) physics, particularly in:

• Modeling laser–molecule interactions
• Optimizing cooling and trapping experiments
• Interpreting or predicting spectroscopic measurements

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⚙️ Installation

We recommend installing MoleCool in a dedicated virtual environment
(using either virtualenv or conda) to avoid dependency conflicts. See the Installation Guide for more details.

Requires: Python ≥ 3.8 (Python ≤ 3.10 recommended)

Using pip (stable release)

pip install MoleCool

Using conda (via conda-forge)

conda install -c conda-forge MoleCool

Development version (latest from GitHub)

git clone https://github.com/LangenGroup/MoleCool
cd MoleCool
pip install .

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🧪 Verifying the Installation

You can verify a correct installation by running the built-in example suite:

python -m MoleCool.run_examples

Add the -h flag for a help message and a list of all available example scripts.

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🚀 Quickstart Example

Below is a minimal working example demonstrating MoleCool’s basic workflow:

from MoleCool import System

# Initialize a molecular system (e.g. 138BaF)
system = System(load_constants='138BaF')

# Build level scheme and remove loss channels
system.levels.add_all_levels(v_max=0)
system.levels.X.del_lossstate()

# Define a multi-sideband laser configuration
system.lasers.add_sidebands(
    lamb        = 859.83e-9,
    P           = 20e-3,
    offset_freq = 19e6,
    mod_freq    = 39.33e6,
    sidebands   = [-2, -1, 1, 2],
    ratios      = [0.8, 1, 1, 0.8],
)

# Turn on a magnetic field
system.Bfield.turnon(strength=5e-4, direction=[1, 1, 1])

# Run dynamics simulations
system.calc_OBEs(t_int=8e-6, dt=1e-9, magn_remixing=True)
system.calc_rateeqs(t_int=8e-6, magn_remixing=True, position_dep=True)

# Visualize populations
system.plot_N()

For detailed usage, see the
👉 User Guide
and Examples.

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⚡ Performance and Parallelization

• Dynamics equations are solved using scipy.integrate.solve_ivp and compiled with Numba’s just-in-time (JIT) compiler for near-C speed.
• Independent simulations are automatically parallelized across multiple cores
  using Python’s multiprocessing module — ideal for large parameter sweeps
  and Monte Carlo trajectory studies.

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🤝 Contributing

Contributions are welcome! To develop MoleCool locally:

git clone https://github.com/LangenGroup/MoleCool
cd MoleCool
pip install -e .[dev,doc]

The -e flag enables editable mode, allowing immediate testing of code changes.
See the Installation Guide for more details.

⚠️ Important: Do not import the package from its parent folder if the directory name is also MoleCool, as this can confuse Python’s import system.

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📚 Documentation

Full documentation, tutorials, and API reference are hosted on ReadTheDocs:

👉 https://molecool-py.readthedocs.io/

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🧾 Citation and Further Reading

If you use MoleCool in your research, please cite the corresponding paper:

Further background on molecular level structure, spectroscopy, and laser cooling, as well as the application of MoleCool to achieve isotopologue-selective laser cooling of complex molecules via serrodyne modulation, is presented in the PhD thesis

Felix Kogel – Laser Cooling of Molecules for Precision Measurements of Parity Violation

This work introduces a novel strategy for designing optimized optical spectra to laser cool heavy, low-abundant barium monofluoride (BaF) molecules, whose additional nuclear spin creates an exceptionally intricate level structure.

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🧠 License

© Felix Kogel — released under the MIT License.
See LICENSE for details.

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👩‍🔬 Developed by Felix Kogel

For questions or feedback, open an issue on GitHub.

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MoleCool — A modular Python framework for simulating laser cooling of molecules.