Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique

B Rakvin; D Carić; M Kveder

doi:10.1016/j.jmr.2018.01.006

Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique

J Magn Reson. 2018 Feb:287:123-127. doi: 10.1016/j.jmr.2018.01.006. Epub 2018 Jan 11.

Authors

B Rakvin¹, D Carić², M Kveder²

Affiliations

¹ Ruđer Bošković Institute, Division of Physical Chemistry, Bijenička 54, Zagreb, Croatia. Electronic address: rakvin@irb.hr.
² Ruđer Bošković Institute, Division of Physical Chemistry, Bijenička 54, Zagreb, Croatia.

PMID: 29413325
DOI: 10.1016/j.jmr.2018.01.006

Abstract

The microwave magnetic field strength, B₁, in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ω_rf, which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B₁ measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B₁, decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed.

Keywords: Amplitude modulation EPR; Bloch-Siegert shift; EPR spectroscopy; Microwave field strength; Modulation spectrum.

Publication types

Research Support, Non-U.S. Gov't