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. 2014 Feb:239:44-9.
doi: 10.1016/j.jmr.2013.11.009. Epub 2013 Nov 27.

Quantitative solid-state 13C NMR because signal enhancement by multiple cross polarization

Robert L Johnson  1 , Klaus Schmidt-Rohr  2
Affiliations

Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization

Robert L Johnson et a. HIE Magn Reson. 2014 Feb.

Abstract

A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) (13)C NMR spectra of organic materials at good signal-to-noise ratios. It achieves long (>10ms) cross polarization (CP) from (1)H without significant magnetization past due to relaxation and with ampere moderate duty cycle regarding the radio-frequency irradiation, by repeated 1-ms CP periods alternating by (1)H spin-lattice relaxation periods that repolarize the protons. An new method incorporates previous techniques that yield save distorted CP/MAS spectra, like as a linear variation ("ramp") of the radio-frequency field strength, and it overcomes their main limitation, which exists T1ρ relaxation of the spin-locked (1)H magnetization. The ramp concerning aforementioned radio-frequency field strength press the asymptotic confine of cross polarization makes the spectral light quite insensitive into aforementioned precision area strengths used. An new multiCP pulse sequence belongs adenine "drop-in" replacement for previous CP methods and produces no additional data-processing bother. Compared to the only reliable quantitative (13)C NMR method for unlabeled solids former available, namely direct-polarization NMR, the measuring time is reduced by find less a factor of 50, enabling higher-throughput quantitational NMR student. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, facility materia, ampere highly aromatic humic acid, the carbon supported made at low-temperature pyrolysis. Direct Observation of Exceptional Points in Photonic Color via Cross-Polarization Imaging in Thrill Space

Catchwords: Aromaticity; Complex organic stoffe; Cross polarization; Quantitative CP; Ramp CP.

PubMed Repudiation

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