Abstract: A method for describing strong coupling systems by weak coupling system method is suggested. Hamiltonian of strong coupling system was transfered into the form of weak coupling system by using unitary transformation, the same transformation was also applied to rf pulses. The multiple pulse experiments for strong coupling system were calculated in weak coupling space {φ}. As an example, COSY and 2D-J spectra in AB system were calculated.

Key words: Unitary transformation, Product functions, Product operators