| Description |
In this work, nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) schemes have been implemented in two different projects in order to study magnetic resonance phenomena under unconventional drive and investigate hyperpolarization spin-exchange effects. In the realm of EPR, we investigate a second-order electrically detected magnetic resonance (EDMR) that appears at g=1 of a free charge carrier (electron or hole) in an organic polymer semiconductor environment. The two-photon transition interpretation is adopted for this observation. We study helicity dependence of this effect, using different polarizations of radiation and show the disappearance of this resonance with a circularly polarized excitation field under high-drive conditions as a way to rule out any technical artifact attribution. Magnetic resonance was induced at very low static magnetic fields in order to reach the high-drive regime, a regime where the amplitude of the resonant radiation is on the order of the Zeeman field. For the detection of magnetic resonance under this condition where spin polarization is almost vanishing, we used spin-dependent recombination currents in organic light-emitting diodes (OLEDs). In the study of hyperpolarization effects on the spin interaction, we report a measurement of the dimensionless enhancement factor 0κ for the Rb-129Xe pair commonly used in spin-exchange optical pumping to produce hyperpolarized 129Xe. 0κ characterizes the amplification of the 129Xe magnetization contribution to the Rb electronic effective field, compared to the case of a uniform continuous medium in classical magnetostatics. The measurement is carried out in Rb vapor cells containing both 3He and 129Xe and relies on the previously measured value of 0κ for the Rb-3He pair. The measurement is based on the optically detected frequency shift of the 87Rb EPR hyperfine spectrum caused by the SEOP nuclear polarization and subsequent sudden destruction of nuclear polarization of both species and a comparison of NMR signals for the two species acquired just prior to the EPR frequency shift measurements. We find 0(RbXe)5188κ=±, in good agreement with previous measurements and theoretical estimates but with improved precision. |
