About the Authors

Yu Li

Affiliation Applied Ion Beam Physics Laboratory (Key Laboratory of the Ministry of Education), Institute of Modern Physics, Fudan University, Shanghai, People's Republic of China

Bin Zhang

binzhang@fudan.edu.cn

Affiliation Applied Ion Beam Physics Laboratory (Key Laboratory of the Ministry of Education), Institute of Modern Physics, Fudan University, Shanghai, People's Republic of China

Huansheng Cheng

Affiliation Applied Ion Beam Physics Laboratory (Key Laboratory of the Ministry of Education), Institute of Modern Physics, Fudan University, Shanghai, People's Republic of China

Jianming Zheng

Affiliation Zhejiang Provincial Institute of Cultural Relics and Archaeology, Hangzhou, Zhejiang, People's Republic of China

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: BZ HC. Performed the experiments: YL BZ HC. Analyzed the data: YL BZ. Contributed reagents/materials/analysis tools: JZ. Wrote the paper: YL BZ.