Double Electron-electron Resonance Technique Research Articles

Proposal for observing dynamic Jahn–Teller effect by single solid-state defects

The Jahn–Teller effect (JTE) widely exists in polyatomic systems including organic molecules, nano-magnets, and solid-state defects. Detecting the JTE at single-molecule level can provide unique properties about the detected individual object. However, such measurements are challenging because of the weak signals associated with a single quantum object. Here, we propose that the dynamic JTE of single defects in solids can be observed with nearby quantum sensors. With numerical simulations, we demonstrate the real-time monitoring of JT axis jumps between different stable configurations of single substitutional nitrogen defect centers (P1 centers) in diamond. This is achieved by measuring the spin coherence of a single nitrogen-vacancy (NV) center near the P1 center with the double electron-electron resonance technique. Our work extends the ability of NV center as a quantum probe to sense the rich physics in various electron-vibrational coupled systems.

Radical distributions in ammonium tartrate single crystals exposed to photon and neutron beams

The radiation therapy carried out by means of heavy charged particles (such as carbon ions) and neutrons is rapidly becoming widespread worldwide. The success of these radiation therapies relies on the high density of energy released by these particles or by secondary particles produced after primary interaction with matter. The biological damages produced by ionising radiations in tissues and cells depend more properly on the energy released per unit pathlength, which is the linear energy transfer and which determines the radiation quality. To improve the therapy effectiveness, it is necessary to grasp the mechanisms of free radical production and distribution after irradiation with these particles when compared with the photon beams. In this work some preliminary results on the analysis of the spatial distributions of the free radicals produced after exposure of ammonium tartrate crystals to various radiation beams ((60)Co gamma photons and thermal neutrons) were reported. Electron spin resonance analyses were performed by the electron spin echo technique, which allows the determination of local spin concentrations and by double electron-electron resonance technique, which is able to measure the spatial distance distribution (range 1.5-8 nm) among pairs of radicals in solids. The results of these analyses are discussed on the basis of the different distributions of free radicals produced by the two different radiation beams used.