Direct Determination of Hyperfine Coupling Constants from Complex and Poorly Resolved ESR Spectra with Numerical Decoupling Analysis

Abstract

Abstract Numerical decoupling analysis (NDA) has been developed as a useful analytical method for determining accurate hyperfine coupling constants (hfccs) involved in isotropic ESR spectra with constant line-widths. NDA was found to have a number of advantages over other methods developed for the extraction of hfccs from ESR spectra. For example, the nuclear spin (e.g., I=1⁄2 or 1) can easily be distinguished and hfccs as small as a linewidth can be determined. Furthermore, false hfccs which often appear and lead to confusion in obtaining the true values in other methods are largely eliminated. Owing to these advantages NDA has enabled us to interpret not only complex but also poorly resolved ESR spectra. The practical use of NDA could be demonstrated by analyzing the ESR spectra of t-butyl 4-nitrophenyl nitroxide and t-butyl 2-chlorophenyl nitroxide radicals.