Simulation Methods for Looping Transitions

• Published in: Journal of magnetic resonance (1997) Vol. 134; no. 1; pp. 57 - 66
• Main Authors: Gaffney, Betty J., Silverstone, Harris J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.1998
• Subjects: chromium ion; Computer Simulation; Electromagnetic Fields; Electron Spin Resonance Spectroscopy - methods; iron ion; looping transition; Models, Theoretical; Probability; simulation ofS> 1; Software; transferrin; transferrin; simulation ofS> 1; iron ion; looping transition; chromium ion
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1006/jmre.1998.1526

Looping transitions occur in field-swept electron magnetic resonance spectra near avoided crossings and involve a single pair of energy levels that are in resonance at two magnetic field strengths, before and after the avoided crossing. When the distance between the two resonances approaches a linewidth, the usual simulation of the spectra, which results from a linear approximation of the dependence of the transition frequency on magnetic field, breaks down. A cubic approximation to the transition frequency, which can be obtained from the two resonance fields and the field-derivatives of the transition frequencies, along with linear (or better) interpolation of the transition-probability factor, restores accurate simulation. The difference is crucial for accurate line shapes at fixed angles, as in an oriented single crystal, but the difference turns out to be a smaller change in relative intensity for a powder spectrum. Spin-32Cr3+in ruby and spin-52Fe3+in transferrin oxalate are treated as examples.