Flip-angle dependence of nonequilibrium states yielding information on connectivity of transitions and energy levels of oriented molecules. A modified Z-COSY experiment

Abstract

Nonlinear measurement of the nonequilibrium state of the spin system of oriented acetone by different flip angles of the measuring pulse leads to dramatically different intensities. While such spectra contain information on the connectivity of transitions, it is shown that the low-flip-angle experiment, in the linear regime, yields information on direct connectivities. It is shown that a totality of information on the direct connectivity is obtained by a two-dimensional experiment, namely 90°-t₁-α_φ-τ_δ-β_ψ-t₂. A systematic analysis of this connectivity information leads to a complete reconstruction of the energy-level system of the various symmetry domains of oriented acetone, a six-spin system characterized by C_3v Θ C_3v symmetry. A computer program has been written to reconstruct the energy-level system from the connectivity information. This leads to, in favorable cases, complete information on the parameters of the spin Hamiltonian.