Lecture 3 Part 1 Positron Annihilation Lifetime Spectroscopy

Lecture 3 Part 1 Positron Annihilation Lifetime Spectroscopy (PALS) Principles and applications for nano science

Positron Annihilation Lifetime Spectrometer (PALS)

• POSITRON SOURCES • POSITRON-MATTER INTERACTION • POSITRON ANNIHILATION LIFETIME SPECTROMETER (PALS) • PALS APPLICATIONS on POLYMERS

POSITRON SOURCE 1. The decay of neutron-deficiency radio isotopes (β+), 22 Na 2. Pair formation by high energy γrays

22 Na 22 Ne + γ + β + + υe Fig. 1 Decay scheme of a 22 Na nucleus

POSITRON-MATTER INTERACTION

Source preparation and sandwich type sample prepapation

POSITRON ANNIHILATION IN MATTER

Defect Type Size Materials Atomic Vacancies 0. 1 nm Metals Dislocations 1 nm - 10 mm Metals Voids 0. 1 nm - 1 mm Metals Holes 0. 1 nm - 10 mm Polymers

HV; High Voltage power supply, SC; Plastic scintillator, PMT Base; Photomultiplier main base, PMT; Photomultiplier tube, CFD; Constant fraction discriminator, FC; Fast coincidence, DB; Delay box, TAC; Time to amplitude converter, ADC/MCA; Analogical to digital converter/Multi cannel analyzer, 22 Na; Positron source within the sample. Fig. 3 Flowchart for PAL spectrometer

Energy window for stop Detector (0. 51 Me. V) Energy window for start Detector (1. 28 Me. V) Fig. 8 Energy spectrum of 22 Na detected by a multichannel analyzer of PAL spectrometer with the plastic detectors scintillator

Fig. 9 Energy spectrum of 22 Na detected by a multichannel analyzer of PAL spectrometer, after lower and upper level adjustment for start signals

2 ns 5 ns 8 ns 10 ns 14 ns FWHM Fig. 10 The prompt curve for 60 Co γ-rays, under 22 Na window settings at the different delay times (2, 5, 8, 10 and 14 ns)

Fig. 11 The plot of delay time versus channel number The resolution of the instrument =ns/channel x FWHM Resolution of PALS spectrometers are in the range of 190 -250 ps

PAL spectra of polymers Fig. 13 Positron lifetime spectra of non-irradiated-PE-foam; (a) Count versus channel number (b) Count versus time. One channel corresponds to 0. 052 ns.

Lifetime distribution of silicon sample τ1 = 120 ps, τ2 = 320 ps, and τ3 = 520 ps. (Math. lab. program, melt)

Table 1 Positron annihilation lifetime data of the PEf samples Dose (k. Gy ) τ1 (ns) I 1 (%) τ2 (ns) τ3 (ns) I 3 (%) 0 0. 36 ± 0. 0 1 78. 0 ± 0. 1 1. 05 3. 10 10± 0. 0 ± 0. 1 1 5 0 12. 0 ± 0. 2 1 0. 36 ± 0. 0 1 82. 0 ± 0. 1 1. 03 ± 0. 0 3 7. 4± 0. 1 2. 90 ± 0. 1 0 10. 6 ± 0. 2 52 0. 36 ± 0. 0 1 81. 0 ± 0. 1 1. 10 ± 0. 1 0 7. 8± 0. 2 3. 00 ± 0. 2 0 11. 0 ± 0. 2 98 0. 35 ± 0. 0 1 79. 0 ± 0. 1 0. 98 ± 0. 0 5 8. 8± 0. 1 3. 00 ± 0. 2 0 12. 0 ± 0. 1 I 2 (%)

The o-Ps lifetime, τo-Ps directly correlates with the radius of free volume holes and its intensity (Io -Ps) contains information about the free volume concentration (Jean, 1990). The average radius (R) of free volume holes on a quantum mechanical model developed by Tao (1972) and Eldrup et al. (1981) were proposed as follows: R is the average radius of the free volume holes. Ro is a constant = = (1. 66 Ro-R

Table 2 Radius of a free volumes and volumes of PE-Foam polymers as a function of the dose Dose (k. Gy) Radius Volume Radius (Å), (τ3) (Å3), (τ3) (Å), (τ2) Volume (Å3), (τ2) 0 3. 70 212 1. 74 22. 1 1 3. 57 190 1. 71 21. 0 52 3. 64 202 1. 82 25. 2 98 3. 64 202 1. 63 18. 1

The correlation between free volume and gas separation properties in high molecular weight poly(methyl methacrylate) membranes, Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959– 967

The correlation between free volume and gas separation properties in high molecular weight poly(methyl methacrylate) membranes, Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959– 967

Dichloromethane Buthylacetate

The correlation between free volume and gas separation properties in high molecular weight poly(methyl methacrylate) membranes, Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959– 967 Butil asetat 996000 26

Positron annihilation lifetime spectroscopy of molecularly imprinted hydroxyethyl methacrylate based polymers Nikolay Djourelov, Zeliha Ates, Olgun Güven, Marijka Misheva, Takenori Suzuki Polymer 48 (2007) 2692 -2699 Free-volume hole radius (R)) for dry samples versus the type of crosslinking agent at different concentrations. Irradiated samples (D = 5 k. Gy) with 3: 1 HEMA: glucose mole ratio; symbols : ▲, □, ◊, ♦ and ■ indicate 70, 30, 20, 10% and no crosslinking agent containing samples, respectively. NA indicates sample prepared without crosslinking agent. 27

Study on the microstructure and mechanical properties for epoxy resin/montmorillonite nanocomposites by positron B. Wang and et al. Radiation Physics and Chemistry 76 (2007) 146– 149 31

Lecture 3 Part 2 Positron Annihilation Lifetime Spectroscopy (PALS) Principles and applications for nano science.

Thermalization ü ionization and excitation of atoms ü free radicals ü molecule dissociation e+ (200 ke. V) ü defects in crystalline structures Spur e - М+ R e- М+ e- e - М+ e- R t ~ 1 ps + М+ e (~ e. V) e- R R М- + e Terminal Spur (Blob)

What is Positronium? e++ e- =Ps • Hydrogen-like bound state of an electron and a positron. • Exists in two states: p-Ps( ) and o-Ps( ) (1: 3) • In vacuum: p-Ps lives 0. 125 ns, o-Ps – 142 ns. • In Polymers o-Ps lifetime is quenched to some ns because of the pick-off annihilation.

Methods of positron annihilation Angular 22 Na sample termalization 511 k e. V Positron Annihilation Lifetime Spectroscopy t - PALS ke. V 4 7 2 1 Correlation of - ACAR Annihilation Radiation e+ e- diffusion Aged MOmentum Correlation 100 nm 511 ke. V ~ t , E 1 -511 - AMOC Coincidence Doppler Broadening Spectroscopy E 1+E 2 - CDBS Doppler Broadening of Annihilation Line E 1 -511 - DBAL

Crosslinking in molecularly imprinted polymers poly(2 -hydroxyethyl methacrylate) (HEMA) crosslinking agents: diethylene glycol diacrylate (DEGDA) polypropylene glycol dimethacrylate (PPGDMA, Mn=560) triethylene glycol dimethacrylate (TEGDMA) N. Djourelov, Z. Ateş, O. Güven, M. Misheva, T. Suzuki, Polymer 48 (2007) 2692 -2699

Positron annihilation lifetime study of organicinorganic hybrid materials prepared by irradiation + Si. O 2 (+Zr. O 2) PDMS+Silica – 1 long-lived component PDMS+Silica+Zirconia – 2 long-lived components N. Djourelov, T. Suzuki, M. Misheva, F. M. A. Margaça, I. M. Miranda Salvado, J Non-Crystalline Solids 351 (2005) 340– 345

POZİTRON YOK OLMA YAŞAM SÜRESİ SPREKTROMETRESİNDE KULLANILAN PROGRAMLAR • TL 9 • MELT • PORE SİZE CALCULATION • ORIGIN /EXCEL

LT 9 programı kullanılarak elde edilen eğriler

PALS • POSITRONFIT • PALFIT • LT v. 9

Tao-Eldrup model Goworek-Gidley model

Intensity 1 dev. Intensity 2 dev. Intensity 3 dev. Lifetime 1 dev. Lifetime 2 dev. Lifetime 3 dev. 14. 9702 3. 042595 57. 6548 2. 472971 27. 375 1. 353191 0. 161957 0. 021891 0. 357935 0. 011249 2. 250871 0. 044658 28. 24608 2. 601578 47. 25761 2. 339542 24. 49631 1. 16315 0. 20049 0. 012991 0. 408704 0. 012448 2. 336901 0. 026631 20. 44259 2. 968188 55. 428 2. 544507 24. 12941 1. 222445 0. 183635 0. 018246 0. 380441 0. 010313 2. 291097 0. 017953 21. 66071 3. 02308 54. 07186 2. 612321 24. 26743 1. 270545 0. 19089 0. 017817 0. 379961 0. 010109 2. 249073 0. 024455 50. 24761 3. 188596 27. 90365 3. 444353 21. 84874 1. 405512 0. 263348 0. 009611 0. 496206 0. 029946 2. 366192 0. 017751 25. 95949 4. 599909 50. 84789 4. 077827 23. 19262 1. 907417 0. 210001 0. 018328 0. 389669 0. 017368 2. 271507 0. 041216 33. 72033 7. 369201 43. 43174 6. 955217 22. 84793 3. 190774 0. 236578 0. 023091 0. 405418 0. 032832 2. 258872 0. 051926 25. 3593 5. 615712 52. 50502 4. 970788 22. 13568 2. 214348 0. 211958 0. 022577 0. 388893 0. 020336 2. 283818 0. 045165

Continuous Distribution • More realistic presentation: continuous distribution n CONTIN n MELT n LT v. 9

Ödev Sorusu : Nano boşlukları olan bir malzemenin pozitron yok olma yaşam süresi spektrometresi (PALS) ile incelenmesi sonucunda aşağıdaki spektrum elde edilmiştir. Bu malzemede bulunan (a) en büyük (b) en küçük boşluğun ve (c) sayısal olarak en fazla oranda bulunan boşluğun büyüklüğü kaç nm dir. NOT : Grafik verilerine ulaşmak için buraya tıklayınız : “PALS ödev verileri” (verileri sayfayı slayt gösterisi şekline dönüştürdükten sonra alabilirsiniz) p-Ps( ) Ps o-Ps( )