1. Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
2. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, Sichuan 610065, China.
3. Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM 87131, USA.