Logowanie do System sprawozdań KDM

Positron Molecule Scattering

Kierownik projektu: Jan Franz

Politechnika Gdańska

Wydział Fizyki Technicznej i Matematyki Stosowanej

Gdańsk

Streszczenie projektu

The objective of this project is the computation of cross sections for collisions of low-energy positrons with biomolecules. A better understanding of the fundamental interactions of positrons with biomolecules is important for the simulation of positron tracks in biological material. Positrons can be produced by nuclear beta(+)-decay of unstable atomic isotopes. The isotope can be incorporated into a tracer molecule, e.g. a biomolecule or a drug molecule, which can be injected or eaten by the patient or organism under study. In this way the positron is emitted from within the living organism. The positron slows down by various interactions and finally annihilates with an electron. The radiation from the positron-electron annihilation is emitted in the form of two gamma-rays, which can be recorded by detectors. Computer algorithm are working out the location, where the positron annihilated and the gamma rays were produced.

If the positron has traveled only a short distance from its creation to its annihilation, the signal from the annihilation radiation can be used to locate the original tracer molecule. This effect is used in positron emission tomography (PET) to locate cancer cells. Beta(+)-decay can also be induced by impact of heavy ions (e.g. 3He and 12C) during ion-beam cancer therapy. The secondary positrons can be utilized for destroying cancer cells and for monitoring the dose of the ion-beam. In order to estimate the dose in ion-beam therapy and PET scans it is important to be able to simulate the positron tracks in biological environments. Computer codes for simulating the positron tracks are depending on reliable cross section data as input quantity. Experimental cross sections are difficult to obtain and only last year the very first experimental differential cross sections for positron scattering from biomolecules have been published. Positron scattering from tetrahydrofuran, a model compound for the sugar backbone in DNA and RNA (L. Chiari et al. J Chem. Phys. 138 (2013) 074301), and positron scattering from pyrimidine, a model compound for the DNA/RNA bases uracil, thymine and cytosine (P. Palihawadana et al. Phys. Rev. A 88 (2013) 012717). During the last year we have studied these molecules and our results are in good agreement with these experiments (J Chem. Phys. 139 (2013) 204309 and Phys. Rev. A 88 (2013) 042711).

The good agreement with the experiments motivates us to look at a bigger variety of biomolecules, especially those, which are not accessible experimentally, but which are important for positron track simulations, e.g. amino-acids. In addition we want to look at the effect on the cross sections when attaching water molecules to the biomolecules. In general, we expect that the long-range dipole moment of the biomolecules will be compensated partly by the water molecules and hence the total cross sections should decrease. This solvation effect is currently not taken into account in positron track simulations.

Our computational model is based on density functional theory (see A. Jain and F.A. Gianturco, J. Phys. B 24, 2387 (1991). The electron densities of the target molecules are computed with the Quantum Chemistry program package, such as Gaussian, Molpro, Turbomole or Gamess. The interaction potentials and the cross sections are computed with the program packages SCELib (see N. Sanna, I. Baccarelli and G. Morelli, Comput. Phys. Comm. 180, 2544 (2009)) and VOLSCAT (see N. Sanna, I. Baccarelli and G. Morelli, Comput. Phys. Comm. 180, 2550 (2009)).

Publikacje

  1. Jan Franz, Solution of coupled integral equations for quantum scattering in the presence of complex potentialsSolution of coupled integral equations for quantum scattering in the presence of complex potentials, Journal of Mathematical Physics 56, (2015) 012104
  2. Jan Franz, Solution of Coupled Integral Equations for Quantum Scattering in the Presence of Complex Potentials, EU COST action MP1306 EUSpec: Introduction to the application of ab-initio method in spectroscopy 1, (2015) 1
  3. F. Carelli, J. Franz, F. A. Gianturco, Dipole-driven dynamics for near threshold electron/positron interactions with DNA/RNA base, Verhandlungen der Deutschen Physikalischen Gesellschaft 1, (2015) 1
  4. Jan Franz, Positron annihilation in molecular hydrogen, 42nd Polish Seminar on Positron Annihilation 1, (2015) 1
  5. G. P. Karwasz, J. Franz, K. Fedus, Do positrons measure atomic and molecular diameters?, POSMOL 2015 1, (2015) 1
  6. Jan Franz, Positron annihilation in molecular hydrogen, 3rd International Workshop on Antimatter and Gravity 1, (2015) 1
  7. Jan Franz, Solution of Coupled Integral Equations for Quantum Scattering in the Presence of Complex Potentials, EU COST action CM 1202 - PERSPECT-H2O: The second European Symposium on Current Challenges in Supramolecular Artificial Photosynthesis 1, (2015) 1
  8. Jan Franz, Positron annihilation in molecular hydrogen, VIII Workshop on Atomic and Molecular Physics 1, (2015) 1
  9. Jan Franz, Radiative electron attachment to NCO, Report number: COST-STSM-CM1401-34125, Affiliation: COST Action CM1401: Our Astro-Chemical History 1, (2016) 1
  10. Jan Franz, Interactions of positrons with atoms and molecules, Seminar at Nicolaus Copernikus University, Torun, 9 June 2016 1, (2016) 1
  11. Jan Franz, Formation of anions by radiative electron attachment, conference: Evolution of Chemical Complexity: From simple interstellar molecules to terrestrial biopolymers, Liblice Castle, Liblice, Czech Republic, 13-15 September 2016 1, (2016) 1
  12. Jan Franz, Interactions of positrons with atoms and molecules, Seminar at University of Innsbruck, Innsbruck, Austria, 1 September 2016 1, (2016) 1
  13. Jan Franz, Interactions of positrons with atoms and molecules, conference The 2nd Symposium of Theoretical Physics - STeP 2, Szymbark, Poland, 25- 27 November 2016 1, (2016) 1
  14. Jan Franz, Interactions of positrons with atoms and molecules, seminar at Politechnika Gdańska, Gdansk, Poland, 3 June 2016 1, (2016) 1

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