129Xe-NMR spectrum

Figure 1. Top Original "tennis ball" monomer 1, its syn- the guests and 129Xe-NMR spectrum of a solution of 1 1 thesis, and analogs 2 and 3. Bottom left X-ray structure of with Xe added. Due to the aromatic centerpieces of the cap-...

Figure 2. Time dependence of 129Xe NMR spectrum (left) and intensity (inset) as HP Xe diffuses into a cylinder of porous Vycor glass (right). The stronger line close to 0 ppm is due to Xe gas.

The distributions of the Xe atoms among the cages of the zeolite are provided by the relative intensities of the Xe1 Xe2, Xe3,. ..Xe8 peaks seen individually in the 129Xe NMR spectrum. Thus, the NMR experiment provides a direct measure of the distribution of Xe atoms among the cavities, e.g., what fraction of the zeolite cages have 5 exactly Xe atoms This is reproduced very well by the grand canonical simulations described above. 

The adsorbed-129Xe NMR spectrum allows us to choose between these interpretations. The chemical shifts extrapolated to N = 0, (0), are 59.6 and 58.0 0.5 ppm for NaY zeolite and NaY zeolite-V205 (.R = 0.05), respectively. Although the difference between these values is small, it may be associated with a difference in the Na+ concentration (19). However, according to the relationship between 6S and the pore free space (79), this result proves that the size of cavities where xenon is adsorbed remains unchanged. On the other hand, the variation of 6 with N (6 = f[N]) is rectilinear, with good correlation coefficients (0.9998 6) for NaY zeolite and the sample with R = 0.05 (Figure 4). 

Figure 12.1 A typical 129Xe NMR spectrum of a polymer at a temperature above the glass transition temperature (T ) (here ethylene-propylene diene terpolymer (EPDM)) in a ca. 1,000,000 Pa Xe atmosphere. The signal of the free gas is used as an internal...

Figure 12.22 The room temperature 129Xe NMR spectrum of the iPP/EP blend investigated by Xe diffusion NMR...

The addition of OMCTS to a BEA zeolite does not modify its 5xe(BEA) = 113 ppm, nor its line width, AH= 4.3 ppm for an equilibrium xenon pressure of 600 T, whatever the interval between the moment at which the OMCTS is added and the 129xe NMR spectrum recorded, up to 6 months later (Figure not shown). This observation indicates ... 

Fig.2 129xe-NMR spectrum under 400 Torr of Xe at RT a) mixture of NaY and CaY b) Diffusion-blocked (OMTS) mixture of NaY and CaY.

Fig. 5.3.2 (A) NMR spectrum of hyperpolar- abundance of approximately 25% of the, 29Xe ized 129Xe from a sample that contains bulk gas isotope. (B) 2D slice of 3D chemical shift phase (0.3 ppm) and xenon occluded within selective MRI of the bulk gas phase. (C-E) 2D aerogel fragments (25 ppm). The gas mixture slices of 3D chemical shift selective MRI of the used for the experiment contained 100 kPa of 25 ppm region for various recycle times T.

Fig. 5.3.3 (A) NMR spectrum of hyperpolarized 129Xe in NaX zeolites. (B) 2D slice in the flow direction of a 3D chemical shift selective MRI of gas in the zeolite pellets. (C) 2D slice perpendicular to the flow direction of the same 3D chemical shift selective MRI as in (A). Adapted from Ref. [14].

One of the resulting 129Xe NMR spectra is shown in Figure 5.3.8 (solid line 2) in comparison with the spectrum of the same initial mixture without combustion (dashed line 1). Referenced with 0 ppm is the gas phase peak at room temperature. 

Fig. 5.3.8 Photograph of the detection region of the NMR probe with radiofrequency coil. A methane—air mixture was ignited above the zeolite pellets. The mixture also contained xenon for NMR detection. Hp-129Xe NMR spectra with 30% xenon (from high-density xenon optical pumping) in 70% methane is depicted. (1) The spectrum in the absence of combustion and (2) the spectrum during combustion. Adapted from Ref. [2],...

Figure 4. Variable temperature flowing HP 129Xe NMR MAS spectra of xenon adsorbed in montmorillonite pillared with pyridinium ions. The Xe/N2/He mixture flow rate was 300 cc/min. The sequence of temperature steps progresses from bottom to top. The spectrum at 373K was after drying in a stream of flowing helium for 3 hrs at 373K.

Figure 5. HP 129Xe Chemical Shift Imaging (left and centre) of a phantom consisting of a 7 mm porous Vycor tube filled with NaY zeolite and placed inside an open 9 mm ID glass tube (right). Images from Xe in the three different chemical shift environments can be clearly separated. The NMR spectrum is shown bottom left.

Fig. 69. 129Xe NMR spectra at 24.9 MHz of xenon adsorbed on zeolite Na-Y containing finely dispersed metal particles with and without preadsorbed ethylene (341). Spectrum 1, Pt4-Na-Y 2, Pt4-Na-Y + C2H4 at 25°C 3, Pt4-Na-Y + C2H4 at 60°C. Chemical shifts are in ppm from xenon gas at zero pressure.

Figure 12.8 Two-dimensional 129Xe NMR exchange spectrum of the blend of Figure 12.7 with an exchange time of 5 seconds. The clear cross-peaks between the peaks due to absorbed Xe shows that within the exchange time the Xe atoms change location very often. During 5 seconds no exchange with the gas surrounding the...

Xe NMR spectra were recorded with a Bruker WM-250 NMR spectrometer at 69.19 M Hz. Each spectrum is the accumulation of 500 transients with a relaxation delay of 0.5 seconds. The chemical shifts are reported with respect to bulk xenon gas extrapolated to P=0, using a secondary standard of xenon adsorbed in Na-Y zeolite at 590 Torr(3). Positive chemical shifts are to higher frequency than the reference. 

Finally the zeolite catalyst samples were equilibrated to a known pressure of xenon (Air Liquide, 99.995%) at RT. The NMR tube was flame-sealed after transferring the liquid OMCTS onto the sample. 129xe-NMR spectra were obtained at RT on a Bruker AC 250L spectrometer operating at a frequency of 69.19 MHz for 129xe. Typically, 2000 signal acquisitions were accumulated for each spectrum with a recycle delay of 1 s between %H pulses. Chemical shift measurements are precise to within 1 ppm and are expressed relative to xenon gas at zero pressure [15]. Downfield (high frequency) chemical shifts are considered to be positive. 

Fig. 5.3.9 Hp-129Xe 2D EXSY NMR spectra frequency discrimination (states) with 64 scans recorded during combustion for various ex- per spectrum. The average experimental time change times. Adapted from Ref. [2], The per EXSY with 0.5-s recycle delay was 40—50...

FIGURE 64. 13C MAS NMR spectra of Cgo acquired at 150 K (a) Spectrum obtained when the gas stream is not laser-polarized (laser off), (b) Difference between the spectrum obtained when the gas stream is laser-polarized (laser on) and spectmm (A). This spectrum quantitatively represents the observed SPINOE intensity, (c) Difference between two successively recorded spectra obtained when the 129Xe flowing into the rotor is not laser-polarized. This demonstrates that the difference spectrum is free of artifacts. Reproduced by permission of Elsevier Science B. V. from Reference 70... 

Figure 7.43 (top) 129Xe CP-MAS NMR solid-state spectra for a the xenon clathrate of Dianin s compound obtained at 1 atmosphere pressure (bottom) the DQ filtered spectrum showing only the resonance due to the doubly occupied cavity. (Reproduced by permission of The Royal Society of Chemistry). 

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