Selective excitation of homogeneous spectral lines.

It is possible, by selective excitation of homogeneously broadened lines, to produce response signals, which are orders of magnitude narrower than the original lines. The new type of echo, which allows detecting such signals, and the formalism, useful for understanding the phenomenon, as well as the experimental examples from NMR spectroscopy are presented. Long-lived partial NMR echo in solids can be excited by a simple two-pulse Hahn sequence.