Optical spectral features and electric field inversion method for Rydberg atoms under ultra-low frequency electric fieldDongping Xiao, Sheng Yan, Ling Chen and Huaiqing ZhangEPJ Quantum Technol., 12 1 (2025) 86DOI: https://doi.org/10.1140/epjqt/s40507-025-00389-4