NEW CLASSES OF DIFFRACTION SPECTRA OF ONE-DIMENSIONAL SYSTEMS

New types of diffraction spectra, called (i) infinite-periodic, (ii) i nfinite-quasiperiodic, of 1D two-letter substitutional superlattices w ere found, with delta-peak positions determined by rational multiples of the type m/n(l), l = 0,..., infinity, of (i) a single number, (ii) two incommensurate spatial frequencies. Finite number of l's in (i) ab ove gives periodiclike spectra. The question of experimental distingui shability of some of these new spectra from the spectra of periodic sy stems arises.