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

Abstract

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) ← X12Π1/2 (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 (3Σu-)0u+ (υ′ = 10) ← X1 (3Σg-)0g+ (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.