Rotational_clusters

Nuclear spin-symmetry breaking in rotational cluster states

This repository contains supplementary code for the manuscript:

Andrey Yachmenev and Guang Yang, Nuclear spin symmetry-breaking and spin polarization in rotational energy level clusters, (2025) submitted.

The package performs variational calculations of the rovibrational energies of the triatomic molecule $\text{H}_2\text{S}$ up to high rotational excitations ($J \leq 60$). At high $J$-values, some rotational states of $\text{H}_2\text{S}$ cluster into groups of four, an effect associated with spontaneous symmetry breaking caused by centrifugal and Coriolis couplings. Additionally, the package performs computations of nuclear hyperfine effects (e.g., spin-rotation interaction) and the Stark effect.

Repository structure

• h2s_rovib.ipynb: Computes the rovibrational energies and wavefunctions of $\text{H}_2\text{S}$, storing the results in files within the rovib_wf_pmax24 folder.

• h2s_clusters.ipynb: Identifies cluster states in both the ground and excited vibrational states by analyzing rotational density distributions. The resulting cluster state indices for different $J$ values and symmetries are stored in files, such as h2s_cluster_states_id_pmax24.txt.

• h2s_cart_me.py: Computes rovibrational matrix elements for various operators, including dipole moment and spin-rotation coupling tensors, for selected rovibrational states. The results are stored in files within the rovib_me_pmax24 folder.

• h2s_hyperfine.ipynb: Computes hyperfine spin-rotation interactions, plots rotational and spin-density distributions, and evaluates the Stark effect for rotational cluster states.

Citation

If you use this code in your research, please cite:

A. Yachmenev and G. Yang, "Nuclear spin symmetry-breaking and spin polarization in rotational energy level clusters," (2025) submitted.

@article{Yachmenev2025,
  author  = {A. Yachmenev and G. Yang},
  title   = {Nuclear spin symmetry-breaking and spin polarization in rotational energy level clusters},
  year    = {2025},
  journal = {Submitted}
}

Contact

For questions or feedback, feel free to open an issue or reach out to the authors directly via [email protected]