A contribution to the theory of OD EPR of spin-correlated radical pairs

Autobiography

On the occasion of my 85th birthday, I share insights about my life and science. This autobiography has been written in an interesting period of my life. Two years ago I formulated a new paradigm in a particular scientific discipline: spin exchange. This work has helped me to see that the paradigm formulation is an effective practical tool for increasing the effectiveness of scientific research. Today I am full of plans to use this tool to continue scientific research.

Simple rules for resolved level-crossing spectra in magnetic field effects on reaction yields

In this work we derive conditions under which a level-crossing line in a magnetic field effect curve for a recombining radical pair will be equivalent to the electron spin resonance (ESR) spectrum and discuss three simple rules for qualitative prediction of the level-crossing spectra.

Estimation of the Fraction of Spin-Correlated Radical Ion Pairs in Irradiated Alkanes using Magnetosensitive Recombination Luminescence from Exciplexes Generated upon Recombination of a Probe Pair

We suggest a convenient probe exciplex system for studies in radiation spin chemistry based on a novel acceptor-substituted diphenylacetylene, 1-(phenylethynyl)-4-(trifluoromethyl)benzene that has a very short fluorescence lifetime (<200 ps) and low quantum yield (0.01) of intrinsic emission, provides efficient electron capture in alkanes and efficient exciplex formation upon recombination in pair with DMA radical cation, while exhibiting a shifted to red exciplex emission band as compared to the parent system DMA – diphenylacetylene. After chemical, luminescent, radiation and spin-chemical characterization of the new system we used the magnitude of magnetic field effect in its exciplex emission band for experimental estimation of the fraction of spin-correlated radical ion pairs under X-irradiation with upper energy cutoff 40 keV in a set of 11 alkanes. For linear and branched alkanes magnetic field effects and the corresponding fractions are approximately 19–20% and 0.28, while for cyclic alkanes they are lower at 16–17% and 0.22, respectively.

Measuring spin relaxation with standard pulse sequences in the singlet-triplet basis

Pulsed electrically and optically-detected magnetic resonance are extremely sensitive to changes in the permutation symmetry of weakly-coupled spin pairs, and are well-suited for investigating devices with a small number of spins. However, the change in observable from conventional electron spin resonance modifies the results of standard inductively-detected pulse sequences which are routinely used to obtain phase coherence and lifetimes. Whilst these effects have been discussed for single-pulse experiments, their role in multi-pulse sequences is less clear. Here, we investigate this effect in Hahn echo and inversion-recovery sequences, and show a second set of narrower echoes are produced that distort measurement outcomes. We demonstrate that phase cycling is able to deconvolve the additional echo signals, allowing spin relaxation times to be reliably extracted.