Department of Nuclear Radiospectroscopy - Overview

Full text: Research at the Department of Nuclear Radiospectroscopy encompasses various aspects of nuclear magnetic resonance (NMR) and its applications to solids and to biosystems. Current research activity covers two areas: investigation of molecular dynamics and structures in solids using NMR spectroscopy, and examination of human organs, small animals and plants using MR imaging and localized spectroscopy. MAGNETIC RESONANCE IMAGING LABORATORY Biomedical applications of magnetic resonance imaging (MRI) and spectroscopy (MRS) together with development and modification of the existing hardware were our main topic of research in the year 2000. The following projects have been carried out: * Investigation of the water diffusion tensor in biological systems in vivo and in vitro; * Study of localized MR spectra in the skeletal muscles of the human limbs; * Structure and physiological processes of the tissue and organs in the normal and pathological state studied by MRI and MRS methods; * Generation of the magnetic field gradients and design of highly specialized RF coils for MR localized spectroscopy and MR Imaging. This work has been done in collaboration with Collegium Medicum of the Jagiellonian University and the Institute for Biodiagnostics in Winnipeg, Canada. As far as the hardware and the methodology side are concerned our, tasks in the year 2000 included: * Development and modifications of home-built MR Microscopy based on 8.4T magnet; * Modifications of the 4.7T magnet console; * Designing and optimizing the ergometer used in skeletal muscle research; * Implementation of the fast imaging methods based on the spin echo sequences. MAGNETIC RESONANCE LABORATORY Deuteron NMR spectroscopy was applied to the study of reorientational dynamics and tunnelling rotation of ammonium ion isotopomers. As particular achievements we point out results concerning structure refinement of structure, establishing the symmetry of the rotational potential, and detection of the order-disorder phase transition. Results from X-ray structural studies are now supplemented by precise determination of deuteron positions, D-O distances and N-D-O angles in ammonium persulphate. These results are based on the quadrupole coupling constants obtained from analysis of the angular dependence of spectra for partially deuterated ammonium persulphate single crystals. Studies of fully and partially deuterated ammonium persulphate provide a picture of the complex rotational dynamics. ND4+ ions perform rotational tunnelling about the C34 axis at the tunnelling frequency vt4 = 1.6 MHz. For NDH3+ ions also a stochastic reorientation of protons about this axis was found. Moreover, an increased abundance of deuterons at this position provides an evidence for the isotope ordering process. A secondary tunnelling rotation was found about C32 axis, characterized by much lower tunneling frequency vt2 = 4 kHz. Protons tunnel about the axis at 200 kHz at respective position of NDH3+ ions. There is no tunnelling about two other C3 axes for ND4+ and protons tunnel in respectively oriented NDH3+ ions at vt= 70 kHz. Measured tunnelling frequencies allow estimation of potentials 5.45 kJ/mol, 15.25 kJ/mol and 17 kJ/mol, respectively. The two components are observed below the order-disorder phase transition at 38.4 K in the spectra of (ND4)2PbCl6. It indicates the existence of two subsystems of ammonium ions characterized by different potential barriers. Those attributed to ordered domains contribute about 70% and tunnel at 270 kHz. Remaining tunnel at 780 kHz which indicates that ions in transition regions are subjected to a significantly lower potential. (author)