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

2. Positron Annihilation Lifetime Spectrometer (PALS)

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

4. The decay of neutron-deficiency radio isotopes (β+), 22Na
POSITRON SOURCE
The decay of neutron-deficiency radio isotopes (β+), 22Na
Pair formation by high energy γ-rays

5. 22Na 22Ne + γ + β+ + υe Fig. 1 Decay scheme of a 22Na nucleus

6. POSITRON-MATTER INTERACTION

7. Source preparation and sandwich type sample prepapation

8. POSITRON ANNIHILATION IN MATTER

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

10. 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,
22Na; Positron source within the sample.
Fig. 3 Flowchart for PAL spectrometer

14. Energy window
for stop
Detector
(0.51 MeV)
for start
(1.28 MeV)
Fig. 8 Energy spectrum of 22Na detected by a multichannel analyzer of PAL spectrometer with the plastic detectors scintillator

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

16. 2ns
5ns
10ns
8ns
14ns
FWHM
Fig.10 The prompt curve for 60Co γ-rays, under 22Na window settings at the different
delay times (2, 5, 8,10 and 14 ns)

17. 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 ps

18. 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 ns.

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

20. Dose (kGy) τ1 (ns) I1 (%) τ2 (ns) I2 (%) τ3 (ns) I3 (%) 0.36±0.01
Table 1 Positron annihilation lifetime data of the PEf samples
Dose (kGy)
τ1 (ns)
I1 (%)
τ2 (ns)
I2 (%)
τ3 (ns)
I3 (%)
0.36±0.01
78.0±0.1
1.05±0.05
10±0.1
3.10±0.10
12.0±0.2 1
82.0±0.1
1.03±0.03
7.4±0.1
2.90±0.10
10.6±0.2 52
81.0±0.1
1.10±0.10
7.8±0.2
3.00±0.20
11.0±0.2 98
0.35±0.01
79.0±0.1
0.98±0.05
8.8±0.1
12.0±0.1

21. R is the average radius of the free volume holes. Ro is a constant =
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

22. Table 2 Radius of a free volumes and volumes
of PE-Foam polymers as a function of the dose
Dose (kGy)
Radius (Å), (τ3)
Volume
(Å3),(τ3)
Radius (Å), (τ2)
(Å3), (τ2)
3.70
212
1.74
22.1 1
3.57
190
1.71
21.0 52
3.64
202
1.82
25.2 98
1.63
18.1

23. 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

24. 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

25. Dichloromethane Buthylacetate

26. 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

27. Positron annihilation lifetime spectroscopy of molecularly imprinted hydroxyethyl methacrylate based polymers Nikolay Djourelov, Zeliha Ates, Olgun Güven, Marijka Misheva, Takenori Suzuki Polymer 48 (2007)
Free-volume hole radius (R)) for dry samples versus the type of crosslinking agent at different concentrations. Irradiated samples (D = 5 kGy) 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

31. Radiation Physics and Chemistry 76 (2007) 146–149
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

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

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

35. 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 ns, o-Ps – 142 ns.
In Polymers o-Ps lifetime is quenched to some ns because of the pick-off annihilation.

36. Methods of positron annihilation
Angular
Correlation of
Annihilation
Radiation
 - ACAR 
1274 keV
t - PALS 
511 keV
t , E AMOC
Positron
Annihilation
Lifetime
Spectroscopy
Coincidence
Doppler
Broadening
Spectroscopy
22Na
sample
E1+E2- CDBS
termalization e+ e-
diffusion~ 100 nm 
511 keV
Doppler
Broadening of
Annihilation
Line
Aged
MOmentum
Correlation
E DBAL

37. 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)

40. Positron annihilation lifetime study of organic- inorganic hybrid materials prepared by irradiation
+ SiO2 (+ZrO2)
These are some of the results for organic-inorganic hybrid prepared by gamma irradiation.
It is Poly Di Methyl Siloxane with Silica or with Silica and Zirconia.
For the samples without Zirconia we see one long lifetime with polymer like behavior which indicates that the organic inclusion is well dispersed in the PDMS matrix.
For the samples with Zirconia we see two long-lived components with very strange behavior. Explain the figure.
It was a real puzzle for us.
PDMS+Silica+Zirconia – 2 long-lived
components
PDMS+Silica – 1 long-lived component
N.Djourelov, T.Suzuki, M.Misheva, F.M.A.Margaça, I.M.Miranda Salvado, J Non-Crystalline Solids 351 (2005) 340–345

42. TL9 MELT PORE SİZE CALCULATION ORIGIN /EXCEL
POZİTRON YOK OLMA YAŞAM SÜRESİ
SPREKTROMETRESİNDE
KULLANILAN PROGRAMLAR
TL9
MELT
PORE SİZE CALCULATION
ORIGIN /EXCEL

43. LT 9 programı kullanılarak elde edilen eğriler

44. PALS
POSITRONFIT
PALFIT
LT v.9

45. Tao-Eldrup model
Goworek-Gidley model

46. Intensity1
dev.
Intensity2
Intensity3
Lifetime1
Lifetime2
Lifetime3
27.375
55.428

47. Continuous Distribution
More realistic presentation: continuous distribution
CONTIN
MELT
LT v.9
In some cases discrete positron states are not acceptable and you may represent the lifetime as a continuous distribution.
These are the used computer programs for extracting the lifetime information.

48. Ödev Sorusu : p-Ps() Ps o-Ps()
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
p-Ps() Ps
o-Ps()