Narrow-line absorption at 689 nm in an ultracold strontium gas

Fachao Hu, 2, ∗ Canzhu Tan, 2, ∗ Yuhai Jiang, 2, † Matthias Weidemüller, 2, 4, ‡ and Bing Zhu 1, 2, § Hefei National Laboratory for Physical Sciences at the Microscale and Shanghai Branch, University of Science and Technology of China, Shanghai 201315, China CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany (Dated: January 28, 2021)