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References - Bogoliubov Laboratory of Theoretical Physics - JINR

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SPIN-ISOTOPIC ANALYSIS AT SUPERLOW TEMPERATURES<br />

Yu.F. Kiselev and S.I. Tiutiunnikov<br />

Joint Institute for Nuclear Research, LPHE, 141980 Dubna, Moscow Reg., Russia<br />

E-mail: Yury.Kiselev@cern.ch<br />

Abstract<br />

Free electrons produced by beam irradiation <strong>of</strong> any dielectrics, are able to provide<br />

studying its nuclear surroundings. At superlow temperatures, the nuclear signals<br />

can be enhanced due to electron-nuclear dipolar interactions by the Dynamic Nuclear<br />

Polarization method. Electron spins induce the Fermi indirect interactions<br />

between nuclear spins in surrounding molecules. This allows one to obtain the<br />

”squeezed” image <strong>of</strong> quadrupole nuclei in the proton spectra. Herein we discuss the<br />

application <strong>of</strong> this method for early cancer detection using the irradiated samples <strong>of</strong><br />

the human blood. The method is demonstrated on the simplest irradiated LiD and<br />

NH3 materials [1] investigated by SMC and COMPASS collaborations at CERN.<br />

1. Introduction.<br />

The spin-isotopic analysis <strong>of</strong> biological structures is a new endeavour for early cancer<br />

detection applying the technique <strong>of</strong> strong magnetic fields, superlow temperatures, and<br />

the dynamic nuclear polarization (DNP). Unlike the ”warm” nuclear magnetic resonance<br />

(NMR) at room temperatures, the proposed method operates with hundreds-fold DNPenlarged<br />

signals. DNP requires the presence <strong>of</strong> paramagnetic dopant (F-centres) that can<br />

be induced by a human blood sample exposure to the x-ray, electron, or other ionizing<br />

radiation [2]. As compared with the chemical analysis, the method distinguishes isotopes,<br />

allows one to detect the routine NMR spectra and the quadrupole spectra called by us<br />

”squeezed”. In the case considered, we use the data taken after completing DNP-process<br />

and cooling the samples below 0.1 K. It is difficult to judge and compare the results<br />

because there are no experiments having applied this advanced tool in biological studies.<br />

2. Isotopic analysis at superlow temperatures.<br />

The isotope density (Ni) is proportional to the integral <strong>of</strong> the NMR-signal absorption<br />

part vi(ω). The relative densities <strong>of</strong> two spin species (Ni/Nj) are as follows [3]:<br />

� ∞<br />

Ni B(γjhH0/kBTj) 0<br />

B(γihH0/kBTi)<br />

vi(ω)dω<br />

, (1)<br />

vj(ω)dω<br />

Nj<br />

= Ijγ 2 j<br />

Iiγ 2 i<br />

where h is the Plank constant, indices i and j stand for the two species, B(i, j) ,Ii,j, γi,j<br />

are the Brillouin function, the spins, the gyromagnetic ratios, respectively.<br />

At superlow temperatures, the nuclear spin lattice relaxation times reach days and for<br />

precise measurements it is convenient to keep the fixed tuning <strong>of</strong> the spectrometer varying<br />

the magnetic field to any isotope resonances. Typical measurements are illustrated with<br />

LiD material having the cubic crystalline lattice. In a perfect cubic crystal the quadrupole<br />

401<br />

� ∞<br />

0

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