Positronium Chemistry in Liquids - First investigations at the GiPS setup

Transcription

1 Positronium Chemistry in Liquids - First investigations at the GiPS setup Maik Butterling Seite PPC-11 Goa Maik Butterling Prof. Institute Peter Mustermann of Radiation Institut Physics xxxxx

2 Positronium Chemistry in Liquids First investigations at the GiPS setup M. Butterling 1,2, D. Zvezhinskiy 3,4, S.V. Stepanov 3,4, A.Wagner 1, W. Anwand 1, R. Krause-Rehberg 2 and T.E. Cowan 1 1 Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, POB , Dresden, Germany 2 Martin-Luther-Universität Halle-Wittenberg, Institute of Physics, Von-Danckelmann-Platz 3, Halle(Saale), Germany 3 Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, Moscow, Russia 4 National Research Nuclear University MEPhI, Kashirskoye shosse 31, , Moscow, Russia page 2 / 22

3 Positronium Chemistry in Liquids First investigations at the GiPS setup Motivation PAS results in liquids Application of the blob model The Setup GiPS setup Investigating liquids Results Purified water Aqueous solutions of KNO 3 Glycerol page 3 / 22

4 Motivation Temperature dependence of PAS parameters in liquids Stepanov Mater. Sci. Forum, Vol. 666, (2010) deviation from ortho-to-para Ps ratio 3:1 change in intensities with temperature page 4 / 22

5 Motivation The blob model for positrons in liquids Stepanov et al. - Principals and Applications of Positron and Positronium Chemistry, Ed.: Y.C. Yean (2003) positrons thermalize via molecular ionization formation of radicals and oxidizers: H, OH - reaction of positron/ps with one of the track products in the terminal part of the positron track (positron blob) page 5 / 22

6 Motivation Radiolysis induced by high-energy positrons e - /e + scavenging e + AB A + B e + + AB ABe + 2γ I Ps Ps oxidation Ps + M k Ox e + + M I Ps, t ops pick-off annihilation Ps + M e + (M ) 2γ t ops ortho-to-para conversion t ops, ops 3 pps 1 pps/ops + M k OPC 1 pps + 3 ops + M 4 4 n ops = k ep n e n p V ep + k hpn h n p V hp Θ(t > t th ) n ops τ ops n OH n OH k Ox n ops + n k Ox n ops + n H3O+ + n Ac V V PsOH V PsH3O+ V PsH3O+ V PsAc k OPC n ops 3n pps n OH V PsOH + n h V Psh + n H V PsH Stepanov et al. Mater. Sci. Forum, Vol. 607, (2009) Stepanov et al. High Energ. Chem.+, Vol. 39, (2005) page 6 / 22

7 Motivation Blob model fit - Rate equations for positrons N t t = N 0 n pps τ pps + n p τ p + n ops τ ops + BG R(t) Stepanov et al. Radiat. Phys. Chem 76(2), 90-95, 2007 page 7 / 22

8 Positronium Chemistry in Liquids First investigations at the GiPS setup Motivation PAS results in liquids Application of the blob model The Setup GiPS setup Investigating liquids Results Purified water Aqueous solutions of KNO 3 Glycerol page 8 / 22

9 Setup Gamma-induced PAS (GiPS) start positron lifetime stop Age- Momentum Correlation (AMOC) correlated measurement of photon energy (Momentum) and positron lifetime (Age) Barium Fluoride High-Purity Germanium Doppler broadening for one annihilation event page 9 / 22

10 Setup Gamma-induced PAS (GiPS) - Additional information Lauff et al. - Acta Phys. Pol. A 83(3), , 1993 page 10 / 22

11 Setup Sample holder for liquids Heat circuit (20 C < T < 95 C) page 11 / 22

12 Setup Sample holder for liquids Cooling by thermoelectric coolers (7 C < T < 20 C) page 12 / 22

13 Positronium Chemistry in Liquids First investigations at the GiPS setup Motivation PAS results in liquids Application of the blob model The Setup GiPS setup Investigating liquids Results Purified water Aqueous solutions of KNO 3 Glycerol page 13 / 22

14 Results Purified water at different T - check the model Open cirlces: no Ps reactions Closed circles: Ps reactions Ps reactions have to be included in the blob model fit visualization of individual Ps reactions possible Stepanov et al. Mater. Sci. Forum, Vol. 666, (2010) page 14 / 22

15 Results Purified water at different T - blob model fit parameters Ps oxidation radius R Ox,Ps, Ps radius R Ps, contact density h c Ps formation / oxidation rate constant k ep / k Ox, initial blob concentration c bl (t = 0) Stepanov et al. Mater. Sci. Forum, Vol. 666, (2010) page 15 / 22

16 Results Aqueous solutions of KNO 3 only weak Ps quencher oxidation effect confirmed page 16 / 22

17 Results Aqueous solutions of KNO 3 - blob model fit additional fitting parameter successful implementation up to 1 mol/l k Ox n ops n OH V PsOH + n H3O+ V PsH3O+ + n NO3/n blob V PsKNO3 page 17 / 22

18 Results Aqueous solutions of KNO 3 - Additional information from AMOC Ps oxidation confirmed page 18 / 22

19 Results Glycerol Viscosity very high at low temperatures Contribution of competing Ps reactions decreases with decreasing temperature Allows separately studying the viscosity effect and influence of temperature on Ps reactions Ps bubble formation time in glycerol much longer Mikhin et al. - High Energ Chem+ 39(1), (2005) page 19 / 22

20 Results Glycerol strong influence on Ps lifetimes only small influence on intensity (no Ps inhibition or oxidation) page 20 / 22

21 Conclusions Liquids can be easily investigated using Gamma-induced PAS (GiPS) Purified water Blob model successfully applied Reproduction of published results KNO 3 in water Oxidation effect confirmed Adjusted Blob model can explain behaviour AMOC data confirms Ps oxidation page 21 / 22

22 Thanks to my colleagues Martin-Luther-University Halle-Wittenberg R. Krause-Rehberg C. Keßler P. Fobe Institute for Theoretical and Experimental Physics, Moscow S.V. Stepanov D. Zvezhinsy V.M. Byakov Helmholtz-Zentrum Dresden-Rossendorf A. Wagner W. Anwand A. Hartmann ELBE crew and to you for your attention page 22 / 22