上海科技大学知识管理系统

The isomer 229 mTh is the most promising candidate for clocks based on the nuclear transition because it has the lowest excitation energy of only 8.10 ± 0.17 eV. Various experiments and theories have focused on methods of triggering the transition between the ground state and isomeric state, among which the electronic bridge (EB) is one of the most efficient. In this paper, we propose a new electronic bridge mechanism via two-photon excitation based on quantum optics for a two-level nuclear quantum system. The long-lived 7 s1 / 2 electronic shell state of 229 mTh3 +, with a lifetime of approximately 0.6 s, is chosen as the initial state and the atomic shells (7s–10s) could be achieved as virtual states in a two-photon process. When the virtual states return to the initial state 7 s1 / 2, there is a chance of triggering the nucleus 229Th3 + to its isomeric state 229 mTh3 + via EB. Two lasers at moderate intensity ((1010-1014)W/m2), with photon energies near the optical range, are expected to populate the isomer at a saturated rate of approximately 109s-1, which is much higher than that due to other mechanisms. We believe that this two-photon EB scheme can help in the development of nuclear clocks and deserves verification via a series of experiments with ordinary lasers in laboratories. © 2021, China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society.