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Development of lock-in based overtone modulated MARY spectroscopy for detection of weak magnetic field effects

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Modulated magnetically altered reaction yield (ModMARY) spectroscopy is a derivative variant of fluorescence detected magnetic field effect measurement, where the applied magnetic field has both a constant and a modulated component. As in many derivative spectroscopy techniques, the signal to noise ratio scales with the magnitude of the modulation. High modulation amplitudes, however, distort the signal and can obscure small features of the measured spectrum. In order to detect weak magnetic field effects (including the low field effect) a balance of the two has to be found. In this work we look in depth at the origin of the distortion of the MARY signal by field modulation. We then present an overtone detection scheme, as well as a data analysis method which allows for correct fitting of both harmonic and overtone signals of the modulation broadened MARY data. This allows us to robustly reconstruct the underlying MARY curve at different modulation depths. To illustrate the usefulness of the technique, we show measurements and analysis of a well known magnetosensitive system of pyrene/1,3-dicyanobenzene (Py/DCB). The measurements of first (h1) and second (h2) harmonic spectra are performed at different modulation depths for both natural isotopic abundance (PyH10), and perdeuterated (PyD10) pyrene samples.

Original languageEnglish
JournalPhysical Chemistry Chemical Physics
Pages (from-to)1273-1284
Number of pages12
Publication statusPublished - 14 Jan 2021

Bibliographical note

Funding Information:
First and foremost, the authors would like to thank Prof. Christiane Timmel for supervision of their studies and insightful comments on the manuscript. We would like to thank the EMF Biological Research Trust and Air Force Office of Scientific Research (AFOSR, USAF award number FA9550-14-1-0095) for funding; Electronics Workshop in Physical and Theoretical Chemistry Laboratory (University of Oxford), and especially Neville Baker, Phillip Hurst, John Adams and Timothy Powell for building components of the experiment; Dr Christan Kerpal, Gabriel Moise, Matthew Golesworthy and Victoire Déjean for proofreading; Dr Sabine Richert for helpful discussions and Dr William Myers for paper suggestions. Further, the authors would like to extend their thanks to The On-Line encyclopedia of Integer Sequences,49 and the Matplotlib development team.50

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