Energy Levels and Transition Rates for Laser Cooling Os-and a General Approach to Produce Cold Atoms and Molecules

High-resolution photoelectron energy spectra of osmium anions are obtained using the slow-electron velocitymap imaging method.The energy levels of excited states^(4)F_(7/2),^(4)F_(5/2)and^(4)F_(3/2)of Os-are determined to be 148.730(13),155.69(15),and 176.76(13)THz[or 4961.09(41),5193.4(49),and 5896.1(42)cm-1],respectively.The lifetime of the opposite-parity excited state^(6)D^(o)_(9/2)is determined to be 201(10)μs using a cold ion trap,about 15 times shorter than the previous result 3(1)ms.Our high-level multi-configuration Dirac–Hartree–Fock calculations yield a theoretical lifetime 527μs.Our work shows that the laser cooling rate of Os-is as fast as that of Th-.The advantages of Os-are its near-IR range cooling transition and simple electronic structure,which make Os-a promising candidate for laser cooling of negative ions.We propose a general approach to produce cold atoms and molecules based on the sympathetic cooling of negative ions in combination with a threshold photodetachment.