Bruker BioSpin Solid State NMR - Table 14.1. Recommended Probe;Spin Rates for Different Experiments and Magnetic Field

182 (327) BRUKER BIOSPIN User Manual Version 002
Symmetry Based Recoupling
Running the experiment on enriched
15
N samples is of course possible, but one
should consider that most samples will not have nitrogen atoms directly attached
to each other, so small couplings will prevail, requiring long DQ-excitation and -re
-
conversion times, with a nucleus that requires high RF power levels to achieve a
certain RF-field. On the other side, the shift range is not large, allowing relatively
slow spinning. Considering a nucleus like
31
P, there is no need for enrichment, but
cases with directly bonded
31
P-atoms are rare. Phosphates are usually easy,
since the shift range is small (couplings are also rather small). If however a large
shift range (possible with
31
P) needs to be covered, there may be a substantial
problem.
1. C7 is not recommended due to restricted excitation bandwidth.
2. SPC5 can be recommended as a standard sequence for 4mm probes and not
too high fields.
3. SC14 or sequences with similar RF-field requirements are recommended for
small spinners/high fields
4. Maximum speed results from max. possible RF-field
5. Maximum
13
C RF fields taken from
13
C RF field specification, or
1
H RF field
specification, considering the requirement of an off HH condition.
6. Maximum RF field for decoupling
7. +LG means cw decoupling with optimized LG-offset frequency at the given RF
field in order to avoid HH contact.
Table 14.1. Recommended Probe/Spin Rates for Different Experiments and Magnetic Field Strengths
Sequence
n=
(ν
RF
/
masr)
rotor
diameter/
masr max.
masr max.
rec.
4
(Hz)
ν
RF
(
13
C) max.
(kHz/μs)
5
ν
RF
(H) max.
(kHz/μs)
6
B
o
max.
(MHz)
8
POST-C7
1
7 7/6000 5000 35 / 7.15 70 / 3.5 +LG 300
4/15000 9000 63 / 4 100 / 2.5 +LG
7
500
3.2/24000 12000 84 / 3 110 / 2.27 +LG
7
600
2.5/35000 14000 100 / 2.5 130 / 1.95 +LG
7
800
SPC5
2
5 7/6000 5000 25 / 10 70 / 3.5 300
4/15000 13000 65 / 3.85 100 / 2.5 +LG
7
500
3.2/24000 17000 85 / 3 none 700
2.5/35000 20000 100 / 2.5 none 900
SC14
3
3.5 7/6000 6000 21 / 12 70 / 3.5 200
4/15000 15000 52.5 / 4.75 100 / 2.5 +LG
7
500
3.2/24000 22000 77 / 3.25 none 700
2.5/35000 28000 100 / 2.5 none 950