QMGreensite_merged

refocused INEPT experiment ( 18 ) can now be written as

Ispin: 90x
t
 180 x
t
 90 y

 180 x

decouple,

Sspin: 180 x 90 x 180 x acquire:

½ 2 : 289 Š

By setting¼1/(4JIS), the final echo component of the sequence yields

KI 2 IzSy )


ðÞ
IxþSx 

KISx: ½ 2 : 290 Š

This is an in-phase doublet and can now be decoupled to give enhanced
sensitivity in the spectrum. As will be discussed in Chapter 7
(Section 7.1.1.3), the value of required for optimal sensitivity in a
refocused INEPT sequence depends upon the nature of the spin system
and must be adjusted appropriately for spin systems other than the two-
spin system considered in this example.
TheSxoperator obtained following the refocused INEPT sequence
can be converted to anSzoperator by application of a 90ypulse to the
Sspin:

KISx )



2 S
yK

ISz: ½^2 :^291 Š

The equilibrium magnetization for theSspin is proportional toKSSz;
therefore, the remarkable result is obtained that the Boltzmann
population difference for theIspin has been transferred to theSspin
by the refocused INEPT pulse sequence.

2.7.7.4 Spin-State Selective Polarization Transfer Numerous
modern NMR experiments, including Transverse Relaxation
Optimized Spectroscopy (TROSY; Chapter 7) and measurements of
scalar and residual dipolar coupling constants (Chapter 7), utilize pulse
sequence elements that transfer polarization between operators in the
single-element basis, corresponding to transfer of coherence between
individual transitions or between spin states. Although useful in their
own right, these methods also provide additional insights into the
behavior of spin systems that continue to lead to new applications. For
example, the pulse sequence element

Ispin: 180 x 180 x,

Sspin: 90x
t
 180 x
t
 90 y,

½ 2 : 292 Š

2.7 PRODUCTOPERATORFORMALISM 99