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Fixed periods Free 1H-evolution (homonuclear systems) Homonuclear spin-echo Free X-evolution (heteronuclear systems) 1H-decoupled X-evolution (heteronuclear systems) X-decoupled 1H-evolution (heteronuclear systems) Heteronuclear spin-echo (heteronuclear systems)

Variable t1 periods Free t1 evolution (homonuclear systems)    Free t1 X-evolution (heteronuclear systems)    Homonuclear t1 spin-echo    1H-decoupled X-evolution t1 (heteronuclear systems)    1H,Y-decoupled X-evolution t1 (heteronuclear systems)    X-decoupled 1H-evolution t1 (heteronuclear systems)    Heteronuclear t1 spin-echo (heteronuclear systems)   Simultaneous 1H-decoupled t1 X,Y-evolution   Gradients during t1 (minimizing radiation damping effects)

Concatenated periods 1H-X refocused INEPT followed by a X-S INEPT block. X-decoupled 1H chemical shift evolution t1 period followed by a 1H-X INEPT block. 1H-decoupled X chemical shift evolution t1 period followed by a X-X' INEPT block.

Constant-time t1 periods Constant-time. General scheme   Constant-time for a two-spin IX system   Constant-time for a three-spin IXY system: Case A: No J coupling evolution Case B: Evolution of single coupling Case C: Evolution of single coupling Case D: Evolution ob both couplings

Tutorial: Concatenated evolution periods in HSQC experiments