High resolution spectroscopic measurement of ¹³⁰Te₂: Reference lines near 444.4 nm for eEDM experiment using PbF molecules

Molecular tellurium (Te₂) offers a wide range of potential applications, including frequency reference. Spectroscopic results about the ¹³⁰Te₂ spectrum were previously reported, but few lines lie around the PbF transition of A (²Σ⁺) (υ′ = 0) ← X₁²Π_1/2 (υ = 0) (∼444.4 nm) which is regarded as an eEDM (electron's Electric Dipole Moment) sensitive transition. Here electronic transition lines for ¹³⁰Te₂ were determined using the Saturated Absorption Spectroscopy method, where the origin of the transition band was investigated for the B₁ (³Σ_u^-)0_u⁺ (υ′ = 10) ← X₁ (³Σ_g^-)0_g⁺ (υ = 5) transition. The Dunham model with high orders was utilized to assign these transition lines, while Dunham parameters of the excited state B₁ (υ′ = 10) were updated to a new level. The Toptica TA-SHG Pro laser was then locked to a single absorption line using a P-I servo. Our results here not only provide the assigned atlas of Te₂ spectrum near 444.4 nm, but also contribute to a stable and sensitive spectroscopic detection of PbF molecules toward the eEDM measurement, which is significant in understanding the fundamental physics beyond the Standard Model.