1887
banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Sideband separation experiments in NMR with phase incremented echo train acquisition
Rent:
Rent this article for
USD
10.1063/1.4803142
/content/aip/journal/jcp/138/17/10.1063/1.4803142
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/17/10.1063/1.4803142

Figures

Image of FIG. 1.
FIG. 1.

(a) A generic five π pulse sequence when = 2 for both the PASS and MAT experiments along with symmetry pathway. The θ represent the rotor position θ = ω where is the time from the initial excitation pulse. Instead of traditional phase cycling, the signal is acquired with a constant receiver phase while the phase of all π pulses with the ϕ subscript are incremented together into a single phase dimension. (b) The π pulse timings for the PASS experiment along with symmetry pathways and the lines in the ε- coordinates where the unmodulated and modulated evolutions refocus into echoes. (c) The π pulse timings for the MAT experiment along with symmetry pathways and the lines in the ε coordinates where the unmodulated and modulated evolutions refocus into echoes. In both (b) and (c) the direction of constant time relative to the initial excitation pulse is indicated.

Image of FIG. 2.
FIG. 2.

Transformation of acquired signals, shown as grayscale-filled rectangle, into a 2D signal that correlates rotor-modulated evolution to unmodulated evolution. The gray scale gradient represents the signal envelope decay due to processes. The symbol ε labels the line along which pure unmodulated evolution occurs (green), while the symbol ε labels the line along which pure rotor-modulated evolution occurs (red). Along the direct acquisition dimension, , both rotor-modulated and unmodulated evolution occur. The direction of lines of constant time from the initial excitation pulse of the sequence are also indicated. (a) Acquired PASS signal: In the first step, copies of acquired signal are translated according to Eq. (8) . Moving from left to right above is the conventional PASS transformation consisting of a single shear parallel to the ε axis and sheared towards negative values of ε followed by a negative scaling along the ε dimension. Moving from left to right below is the TOP-PASS transformation consisting of a first shear that is parallel to the dimension and sheared towards negative values of . This shear is followed by a second shear parallel to the dimension and sheared towards positive values of . At the end of the conventional and TOP processing paths the desired digital signal is obtained by cropping out a 2D signal from one or more rotor periods of evolution along the dimension. The advantage of applying the TOP transformation to a PASS signal is that it can significantly reduce the number of samples required in the indirect dimension. (b) Acquired MAT signal: The affine transformation begins with a negative shear, , parallel to , to create a 2D signal with unmodulated frequencies refocused along the vertical axis and the modulated frequencies refocused along ′ + = 0. At this stage, the signal is “PASS”-like and copies of the signal can be translated according to Eq. (8) . Then a positive shear, , parallel to the vertical axis, . At the end of the processing paths the desired digital signal is obtained by cropping out a 2D signal from one or more rotor periods of evolution along the dimension.

Image of FIG. 3.
FIG. 3.

Two-dimensional MAT spectrum of L-Histidine along with one-dimensional projections. The 2D spectrum was obtained using double shear (TOP) processing. Isotropic frequencies are referenced to Tetramethylsilane (TMS). Contour levels are plotted from 5% to 100% in increments of 5% of the maximum intensity.

Image of FIG. 4.
FIG. 4.

Rotor modulated cross sections of the -Histidine TOP-MAT spectrum shown in Fig. 3 along with best-fit simulations for each site. Experimental sideband amplitudes are shown as gray bars while best fit simulations are shown as black bars.

Image of FIG. 5.
FIG. 5.

(a) Five π pulse sequence for TOP-PASS or TOP-MAT with PIETA along with symmetry pathways. Instead of traditional phase cycling, the signal is acquired with a constant receiver phase while the phase of all π pulses with the ϕ subscript are incremented together into a PIETA phase dimension. The θ values represent the rotor position θ = ω where is the time from the initial excitation pulse. The PIETA π pulses, shown as unfilled rectangles, must be shifted forward by ε. In PASS, the values of ε depend on the timings of the initial five π pulses as illustrated in Fig. 1 . In TOP-MAT the value of ε = 0 for all timings of the initial five π pulses, that is, all echo train acquisition pulses remain at a fixed time from the initial excitation pulse. (b) The lines where the unmodulated and modulated interactions refocus in the ε- coordinates for even and odd echoes in the PASS experiment. (c) The lines where the unmodulated and modulated interactions refocus in the ε coordinates for even and odd echoes in the MAT experiment.

Image of FIG. 6.
FIG. 6.

Experimental 2D PIETA cross sections taken through the time origin of a Si TOP-MAT-PIETA experiment on a Cu(II)-doped mixed potassium/magnesium tetrasilicate glass. The Δ range from −64 to +64 was obtained using Δϕ = 2π/128. Sixty PIETA echoes were acquired.

Image of FIG. 7.
FIG. 7.

Comparison of the TOP-MAT spectra of a Cu(II)-doped mixed potassium/magnesium tetrasilicate glass in which (a) a single shifted echo was acquired and (b) TOP-MAT-PIETA was used to acquire sixty echoes. All echoes were individually matched and coadded to produce the result. This procedure yields a MAT spectrum with a signal-to-noise ratio that is a factor 2.70 higher than the shifted echo experiment, with only a 1.5% increase of experiment time due to acquisition of multiple echoes.

Image of FIG. 8.
FIG. 8.

Comparison of (a) shifted-echo TOP-QMAT and (b) TOP-QMAT-PIETA spectra of RbSO. PIETA was used to acquire 22 echoes, which were individually matched and coadded to produce the result. This procedure yields a QMAT spectrum with a signal-to-noise ratio that is a factor of 1.74 greater than that of the shifted echo experiment, with a 15.7% increase in experiment time.

Tables

Generic image for table
Table I.

Best fit values of the isotropic shift and principal components of the chemical shift tensor for L-Histidine. All uncertainties are one standard deviation. Also shown, for comparison, are the values obtained by Strohmeier

Loading

Article metrics loading...

/content/aip/journal/jcp/138/17/10.1063/1.4803142
2013-05-07
2014-04-18
Loading

Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Sideband separation experiments in NMR with phase incremented echo train acquisition
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/17/10.1063/1.4803142
10.1063/1.4803142
SEARCH_EXPAND_ITEM