From molecular data, multi parameter

Advanced EMR methods may be used to conduct quantitative measurements of nuclear hyperfine interaction energies, and these data, in turn, may be used as a tool in molecular design because of their direct relation to the frontier orbitals. The Zeeman field dependence of hyperfine spectra enables one to greatly improve the quantitative analysis of hyperfine interaction and assign numeric values to the parametric terms of the spin Hamiltonian. Graphical methods of analysis have been demonstrated that reduce the associated error that comes from a multi-parameter fit of simulations based on an assumed model. The narrow lines inherent to ENDOR and ESEEM enable precise measures of peak position and high-resolution hyperfine analyses on even powder sample materials. In particular, ESEEM can be used to obtain very narrow lines that are distributed at very nearly the zero-field NQI transition frequencies because of a quantum beating process that is associated with... 

In order to correlate the solid state and solution phase structures, molecular modelling using the exciton matrix method was used to predict the CD spectrum of 1 from its crystal structure and was compared to the CD spectrum obtained in CHC13 solutions [23]. The matrix parameters for NDI were created using the Franck-Condon data derived from complete-active space self-consistent fields (CASSCF) calculations, combined with multi-configurational second-order perturbation theory (CASPT2). 

The assumption implicit throughout this book is that the parameters used to fit or represent molecular transition frequencies and intensities contain insights into molecular structure. These insights can be more useful than the multi-digit fit parameters themselves, especially when simplifying assumptions axe made and tested. Comparisons of observable or effective parameters to those obtained from an exact calculation (true parameters) or a simplified electronic structure model (one-electron orbital parameters) are seldom trivial or unique. The purpose of this book is to help experimentalists and theorists to go beyond molecular fit parameters to terms in the exact microscopic Hamiltonian on the one hand and to approximate electronic structure models on the other. Physical insight, not tables of spectral data and molecular constants, is the ultimate purpose of fundamental experimental and theoretical research. 

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