The operators have physical interpretations; for example,
E¼I^ S^ þI^ S^ þI^ S^ þI^ S^ ½ 2 : 219
denotes equal populations of all energy levels, and
Iz¼^12 I^ S^ þI^ S^ I^ S^ I^ S^
½ 2 : 220
denotes equal polarization across the two single-quantum transitions of
theIspin.
IaSa
IbSa
I
a IbSb
IbS–
IaS+
IaS–
b IbS+
I–Sa
I+Sa
I–Sb
I+Sb
c
I–S+
e
I–S– I+S+
d
I+S–
aSb
FIGURE 2.4 Single-transition-basis operators for IS spin system.
(a) Populations, (b) S-spin and (c) I-spin single-quantum coherences,
(d) double-quantum coherences, and (e) zero-quantum coherences.
2.7 PRODUCTOPERATORFORMALISM 83