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Liquid scintillators are widely used in particle and nuclear physics. Understanding the scintillation and quenching mechanisms is a fundamental issue in designing a high-light-yield liquid scintillator. In this work, the basic scintillation process for two-component liquid scintillators is discussed, highlighting the processes of excitation, ionization, and anion-cation recombination. A molecule’s polar group, polarization characteristics, and the corresponding material’s dielectric constant are found to be correlated with a liquid scintillator’s scintillation efficiency. Polar groups and high relative dielectric constant (permittivity) can cause quenching and should be avoided. The tellurium loading scheme in the liquid scintillator of the SNO+ experiment, TeBD, is discussed. The hydroxyl groups introduce polar structures in the TeBD, and for the first time, the relative dielectric constant of TeBD is measured to be 16 ± 1. These discussions explain part of the quenching of the TeBD liquid scintillator. A new magnetic dipole-dipole interaction is also proposed as a scintillation quenching mechanism. The interaction rate follows as the electric dipole-dipole interaction in Foster resonance energy transfer theory. The proposed mechanism causes a long-range resonance energy transfer, and the resonance condition is that the spins of donor and acceptor electrons both flip, and the energy level differences are the same. When oxygen or organic molecules including heavy elements are dissolved in a liquid scintillator, these requirements are easier to satisfy. The proposal in the paper adds a new approach for scintillation quenching in liquid scintillators.
| 请选择分会 | 粒子物理实验技术 |
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