title: Combining absorption and dispersion signals to improve signal-to-noise for rapid-scan EPR imaging.
abstract: Direct detection of the rapid-scan EPR signal with quadrature detection and without automatic frequency control provides both the absorption and dispersion components of the signal. The use of a cross-loop resonator results in similar signal-to-noise in the two channels. The dispersion signal can be converted to an equivalent absorption signal by means of Kramers-Kronig relations. The converted signal is added to the directly measured absorption signal. Since the noise in the two channels is not correlated, this procedure increases the signal-to-noise ratio of the resultant absorption signal by up to a factor of square root 2. The utility of this method was demonstrated for 2D spectral-spatial imaging of a phantom containing three tubes of LiPc with different oxygen concentrations and therefore different linewidths.
authors.affiliation: Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Tseitlin
authors.forename: Richard W
authors.initials: RW
authors.lastname: Quine
authors.forename: George A
authors.initials: GA
authors.lastname: Rinard
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Eaton
authors.forename: Gareth R
authors.initials: GR
authors.lastname: Eaton
mesh_terms: D000465:Algorithms; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted