PMID- 12810026
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20040120
LR  - 20191107
IS  - 1090-7807 (Print)
IS  - 1090-7807 (Linking)
VI  - 162
IP  - 2
DP  - 2003 Jun
TI  - SCAM-STMAS: satellite-transition MAS NMR of quadrupolar nuclei with 
      self-compensation for magic-angle misset.
PG  - 402-16
AB  - Several methods are available for the acquisition of high-resolution solid-state 
      NMR spectra of quadrupolar nuclei with half-integer spin quantum number. 
      Satellite-transition MAS (STMAS) offers an approach that employs only 
      conventional MAS hardware and can yield substantial signal enhancements over the 
      widely used multiple-quantum MAS (MQMAS) experiment. However, the presence of the 
      first-order quadrupolar interaction in the satellite transitions imposes the 
      requirement of a high degree of accuracy in the setting of the magic angle on the 
      NMR probehead. The first-order quadrupolar interaction is only fully removed if 
      the sample spinning angle, chi, equals cos(-1)(1/3) exactly and rotor 
      synchronization is performed. The required level of accuracy is difficult to 
      achieve experimentally, particularly when the quadrupolar interaction is large. 
      If the magic angle is not set correctly, the first-order splitting is 
      reintroduced and the spectral resolution is severely compromised. Recently, we 
      have demonstrated a novel STMAS method (SCAM-STMAS) that is self-compensated for 
      angle missets of up to +/-1 degrees via coherence transfer between the two 
      different satellite transitions ST(+)(m(I)=+3/2<-->+1/2) and 
      ST(-)(m(I)=-1/2<-->-3/2) midway through the t(1) period. In this work we describe 
      in more detail the implementation of SCAM-STMAS and demonstrate its wider utility 
      through 23Na (I=3/2), 87 Rb (I=3/2), 27 Al (I=5/2), and 59 Co (I=7/2) NMR. We 
      discuss linewidths in SCAM-STMAS and the limits over which angle-misset 
      compensation is achieved and we demonstrate that SCAM-STMAS is more tolerant of 
      temporary spinning rate fluctuations than STMAS, resulting in less "t(1) noise" 
      in the two-dimensional spectrum. In addition, alternative correlation 
      experiments, for example involving the use of double-quantum coherences, that 
      similarly display self-compensation for angle misset are investigated. The use of 
      SCAM-STMAS is also considered in systems where other high-order interactions, 
      such as third-order quadrupolar effects or second-order quadrupole-CSA 
      cross-terms, are present. Finally, we show that the sensitivity of the experiment 
      can be improved through the use of amplitude-modulated pulses.
FAU - Ashbrook, Sharon E
AU  - Ashbrook SE
AD  - School of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.
FAU - Wimperis, Stephen
AU  - Wimperis S
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Magn Reson
JT  - Journal of magnetic resonance (San Diego, Calif. : 1997)
JID - 9707935
EDAT- 2003/06/18 05:00
MHDA- 2003/06/18 05:01
CRDT- 2003/06/18 05:00
PHST- 2003/06/18 05:00 [pubmed]
PHST- 2003/06/18 05:01 [medline]
PHST- 2003/06/18 05:00 [entrez]
AID - S1090780703000168 [pii]
AID - 10.1016/s1090-7807(03)00016-8 [doi]
PST - ppublish
SO  - J Magn Reson. 2003 Jun;162(2):402-16. doi: 10.1016/s1090-7807(03)00016-8.