Strongly dipolar alkali-metal–silver molecules: electronic structure and spectroscopic properties

We present a relativistic ab initio investigation of the ground and excited electronic states of highly polar alkali-metal–silver molecules (LiAg, NaAg, KAg, RbAg, CsAg, FrAg). Potential energy curves (PECs) are computed for all states dissociating to the lowest ²S_1/2+²S_1/2 and first excited ²S_1/2+²P_1/2 and ²S_1/2+²P_3/2 asymptotes using the Fock-space coupled-cluster method with single and double excitations (FSCCSD). Scalar and spin–orbit relativistic effects are included using small-core energy-consistent pseudopotentials and a two-component relativistic Hamiltonian, resulting in PECs in the Hund’s case (c) representation. We confirm large permanent electric dipole moments for the ground X¹Σ⁺ states [1] and determine spin-spin coupling constants for the a³Σ⁺ states. Franck–Condon factors between ground and excited electronic states are evaluated, revealing favorable optical pathways for molecular stabilization via the A¹Σ⁺ states and for imaging or laser cooling via the b³Π states. In addition, we predict the presence of low-lying heavy Rydberg states. Our results provide essential guidance for the optical formation, detection, and control of strongly polar alkali-metal–silver molecules, highlighting their potential for applications in quantum many-body physics and quantum information science.

[1] M. Śmiałkowski, M. Tomza, Phys. Rev. A 103, 022802 (2021)