text: DEPT (Distortionless Enhancement by Polarisation Transfer) is a pulse sequence used to distinguish between the multiplicity of hydrogen bonded to carbon, that is it can separate C, CH, CH and CH groups. It does this by exploiting the heteronuclear carbon-hydrogen -coupling and varying the tip angle of the final pulse in the sequence. The basic pulse sequence is shown below.
  Under the weak coupling assumption, the chemical shift terms commute with the -coupling term in the Hamiltonian. Hence we can ignore the refocussed chemical shift (see ) in the two intervals containing -pulses, namely  and , and additionally refrain from evaluating the chemical shift evolution in the last  period . The pulse separation time  is adjusted to the coupling strength  (with associated Hamiltonian coefficient ) such that it satisfies
  because then the first term in the evolved density operator in Equation  vanishes under the pure coupling evolution between the pulses.