References - Bogoliubov Laboratory of Theoretical Physics - JINR

interaction vanishes and a single Zeeman line is observed. If the NMR spectrometer is
tuned to the Larmor frequency νc = γLiHLi = γDHD=16.38 MHz, then the D, 6 Li and
7 Li isotopes are detected at the resonant fields listed in the Table. Fig. 1a [4] shows
the D and 7 Li spectra taken by frequency scanning across the νc. The spin-isotopic
composition obtained by NMR method was found in good agreement with the data of
the mass-spectrometric analysis. It was shown that for the most polarized dielectrics, the
Material Isotopes Spin γ Field νc Quadr. mom
(Hz/G) (G) MHz 10 −26 (cm 2 )
LiD D 1 653.6 25060 16.38 +0.287
LiD 6Li 1 626.6 26141 16.38 +0.05
LiD 7Li 3/2 1654.8 9898 16.38 -1.2 ?
NH3
1H 1/2 4257.7 25060 106.7 0
NH3
14 N 1 307.8 25060 7.713 +1.56
Potassium 39 K 3/2 198. 9 25060 4.984 +14
Soudium 23 Na 3/2 1126.2 25060 28.22 +11
DNP mechanism ensured the equal spin temperature (EST) for all nuclear species (i.e.
Ti=Tj in Eq.(1)). At these conditions Brillouin functions in Eq.(1) are reduced and the
error of � 2% comes mainly from the accuracy of integration.
The spectrum of nitrogen (Fig. 1b) [5] in irradiated ammonia (NH3) illustrates the
problems of detection of 14 N, 39 K, 23 N and similar quadrupole nuclei in the amorphous
biological structures. 14 N-spin (In = 1) has a small gyromagnetic ratio, a large quadrupole
moment (see Table) and the broadened spectrum due to strong quadrupole interactions
with electric field gradients in the lattice. The ability of the spectrometer to detect NMR
spectrum requires the signal width to be a small fraction of the Larmor frequency. At
the fixed central frequency of the spectrometer this condition is fulfilled only for the two
small pieces of the 14 N spectrum (hashed in Fig. 1b). As a result, the total line shape
(Fig. 1b) needs to be reconstructed from these spectral pieces that actual spectra are
shown in Fig. 1c. It is clear that the direct integration by Eq.(1) becomes doubtful.
D, 7 Li Spectra, Arb. Un.
1000
800
600
400
200
D pos.
D neg.
7Li pos.
7Li neg.
0
400 450 500 550 600
Channels, 100 Hz per Chan.
(a) (b) (c)
Figure 1a. Dand 7 Li line shapes at positive and negative spin temperatures. Spectra of the
negative polarization were inverted and aligned with the positive spectra; PD=±39,2%.
Figure 1b. The reconstructed signal of 14 N at about +10% polarization. The hashed areas
represent the detected regions and the actual spectra are shown in Fig. 1(c).
Fig. 1c. Two signals at +10% polarization detected in the hashed regions in Fig. 1b.
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