Magnetic dipole-dipole transition for scintillation quenching

Abstract

A magnetic dipole-dipole interaction is proposed as a scintillation quenching mechanism. The interaction rate follows $R^{-6}$ as the electric dipole-dipole interaction in F$\mathrm{\ddot{o}}$ster 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. The new mechanism is distinct to the known spin-orbit coupling induced intersystem crossing, and it can enhance the overall intersystem crossing rate. When oxygen or organic molecules including heavy elements are dissolved in a liquid scintillator, these requirements are possible to be satisfied. The proposal in the paper adds a new approach for scintillation quenching in liquid scintillators.

Figures (3)

• Figure 1: Illustration of the electric dipole-dipole interaction from a donor to a fluor for fluorescence ($\mathrm{D} \to \mathrm{F}$) and the proposed magnetic dipole-dipole interaction from a donor to an acceptor for quenching ($\mathrm{D} \to \mathrm{A}$).
• Figure 2: Demonstration of magnetic dipole-dipole interaction with two magnets. In the first row, the magnetic fields of the donor and acceptor electrons are aligned to have the lowest energy. S and N are the magnetic south and north poles. In the second row, when the spin of the donor electron flipped as well as its magnetic field, the acceptor electron's spin and magnetic field flipped too.
• Figure 3: Interaction of donor and acceptor. The spins of both donor and acceptor electrons are modeled by circular current. The distance vector of the two electrons is $\mathbf{R}$.