Another way to avoid phase corrections in is to introduce a 180s pulse at the end of the t period, followed by a delay 8,to refocus chemical shift precession during t(0) 1st order(Ip1)=zero order (rp1)=0 if t1(0)~0.0 1st order (Ip1)=-180,zero order(rp1)=90 if t1(0)=1/(2sw1) 1H decoupled HSQC 2xpw 02 1/2 t/2 δ=2×pw+t(0) the off-resonance effects of the two 90S pulses are refocused by the 180S pulse, so they do not have to be included in the phase constant calculation. The Jis coupling evolves for the period 8,but since 8~us,the effect is negligible