New Insights into the Chromium Dimer Cr₂'s Rovibrational Spectrum

Recent research has made significant strides in understanding the chromium dimer, Cr₂, particularly in predicting its Born-Oppenheimer rovibrational spectrum. The study, titled "Towards the 'puzzle' of Chromium dimer Cr₂: predicting the Born-Oppenheimer rovibrational spectrum," was authored by Horacio Olivares-Pilón, Daniel Aguilar-Díaz, and Alexander V. Turbiner. It was submitted to arXiv on January 6, 2024, and revised on August 24, 2024.

The chromium dimer presents a complex electronic structure that has posed challenges for theoretical calculations over the past decades. The authors of this study successfully derived an analytic form of the potential energy curve for the ground state X¹Σ⁺ of the Cr₂ dimer across all internuclear distances. This was achieved by integrating perturbation theory at small internuclear distances with multipole expansion at larger distances, along with Rydberg-Klein-Rees (RKR) turning points from previous experimental data.

For the first time, the potential energy curve has been established for the entire range of internuclear distances, providing an accuracy of three to four decimal digits in 29 experimental vibrational energies. The findings indicate that the ground state supports 19,694 rovibrational states, with a maximum vibrational number of 104 at zero angular momentum, and a maximum angular momentum of 312. Additionally, the study identified 218 weakly-bound states near the dissociation limit.

This research not only enhances the understanding of Cr₂ but also has broader implications for the study of molecular interactions and the development of quantum chemistry models. The complete findings can be accessed through the paper available on arXiv: arXiv:2401.03259.