Understanding NMR Spectroscopy phần 9 pps
Understanding NMR Spectroscopy phần 9 pps
... A 105, 167-183 ( 199 3) ). Here, we note the following
features. (a) The optimum dephasing is obtained when the extra offset induced
9 29
doubles the length of the phase cycle.
9. 5.7 Shifting the ... 1st pulse 2nd pulse 3rd pulse receiver
10000
2 90 90 0 180
3 180 180 0 0
4 270 270 0 180
This is exactly the cycle proposed in section 9. 5.5.4.
9. 5 .9 Further examples
In this section...
Understanding NMR Spectroscopy phần 6 pps
... radians (90 °) is the same thing as
a sine wave. Thus, in the EXSY experiment the effect of changing the phase of
the first pulse by 90 ° can be described as a phase shift of the signal by 90 °.
Suppose ... may just as well write
Mnn
z
=−
()
α
β
[2]
†
Chapter 8 "Relaxation" © James Keeler 199 9 and 2002
α
β
x
y
z
A population difference gives
rise to net magnetization along
the...
Understanding NMR Spectroscopy phần 7 ppsx
... zero.
I
Ω
I
Ω
S
Ω
S
Ω
F
1
F
2
{a}
{b}
{c}
0
9 1
9 Coherence Selection:
Phase Cycling and Gradient Pulses
†
9. 1 Introduction
The pulse sequence used in an NMR experiment is carefully designed to
produce ... then uses coherence transfer pathways to specify the
desired outcome of the experiment.
9. 2 Phase in NMR
In NMR we have control over both the phase of the pulses and the receiv...
Understanding NMR Spectroscopy phần 8 ppsx
... 0
2 90 90 0 0 90 270
3 180 –180 0 0 –180 180
4 270 –270 0 0 –270 90
5 0 0 90 180 180 180
6 90 90 90 180 90 90
7 180 –180 90 180 0 0
8 270 –270 90 180 90 270
9 0 0 180 360 360 0
10 90 90 180 ... 90 90 180 360 270 270
11 180 –180 180 360 180 180
12 270 –270 180 360 90 90
13 0 0 270 540 540 180
14 90 90 270 540 450 90
15 180 –180 270 540 360 0
16 270 –270 270 540 270 270
In...
Muhammad ayub understanding islamic finance phần 9 ppsx
... of time value of money; therefore, they argue that either Islamic
2
See Maududi, 198 2– 199 1, 1, pp. 382, 383 (4: 92 ).
An Appraisal of Common Criticism 443
Preference versus Permissibility of Various ... losses to life and
wealth. While Islamic banking emerged in the 196 0s and early 197 0s, Islamic insurance
started no earlier than 197 9. This reveals that the Takaful system developed in...
Muhammad Ayub Understanding Islamic Finance phần 9 ppsx
... Shaikh Jad al-Haq Ali Jad
al-Haq in 199 5 (al-Iqtisadul Islami, July 199 5)
Against life insurance
Fatwah issued in a judicial conference held in Makkah
in Shaban 1 398 AH
Against the validity of insurance
The ... time value of money; therefore, they argue that either Islamic
2
See Maududi, 198 2– 199 1, 1, pp. 382, 383 (4: 92 ).
422 Understanding Islamic Finance
16.3.1 Main Objective of t...
Understanding NMR Spectroscopy phần 1 ppt
... energy levels”
c
James Keeler, 2002
Understanding NMR
Spectroscopy
James Keeler
University of Cambridge, Department of Chemistry
c
James Keeler, 2002
2–10 NMR and energy levels
ααα
αβα
ββα
βαα
1
23
4
ααβ
αββ
βββ
βαβ
5
67
8
Fig. ... NMR. This model has its limita-
tions, but it is very useful for understanding how pulses excite NMR signals.
We can also use the vector model to...
Understanding NMR Spectroscopy phần 2 potx
... approach.
3 .9 Pulses of different phases 3–13
RF
acq
90 ˚
180˚
ττ
2τ
Fig. 3.20 Pulse sequence for
the
spin echo
experiment. The
180
◦
pulse (indicated by an
open rectangle as opposed to
theclosedonefora90
◦
pulse)
is ... commonly used flip angles are π/2 (90
◦
)andπ
(180
◦
). The motion of the magnetization vector during on-resonance 90
◦
and
180
◦
pulses are shown in Fig. 3.12. The 90...
Understanding NMR Spectroscopy phần 3 potx
... offset .
E 3 9
Consider the spin echo sequence to which a 90
◦
pulse has been added at the
end:
90
◦
(x) − delay τ − 180
◦
(x) − delay τ − 90
◦
(φ).
4.4 Sensitivity enhancement 4 9
“more important” ... ppm.
Estimate the minimum 90
◦
pulse width you would need to excite peaks
in this complete range to within 90 % of the their theoretical maximum for a
spectrometer with a B
0
field s...
Understanding NMR Spectroscopy phần 4 doc
... of carbon-13. Using this trans-
mitter at full power the 90
◦
pulse width is found to be 20µs. What power
would be needed to reduce the 90
◦
pulse width to 7.5 µs? Would you have
any reservations ... →
The first arrow affects only the spin-1 operators; a 90 ° rotation of I
1x
about y
gives – I
1 z
(remembering that
ω
1
t =
π
/2 for a 90 ° pulse)
222
22
12 1 12 1 12
12
2
12
2
11 12...
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