Positron Annihilation Lifetime Spectrometer (PALS)
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Transcript Positron Annihilation Lifetime Spectrometer (PALS)
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+), 22Na
2.Pair formation by high energy γrays
3+
EC 10%
2+
22Na
(t1/2=2.60 y)
.. .... ... ... .... ... ... ....
+ 90%
(t1/2=3 ps)
+ 0.05%
1.2746 MeV
0+
22
Ne
10
(stable)
22Na
22Ne
+ γ + β+ + υe
Fig. 1 Decay scheme of a 22Na nucleus
POSITRON-MATTER INTERACTION
Free positron annihilation
0.5 MeV
e+
e
0.5 MeV
=0.2-0.5 ns
-
Para-positronium (p-Ps) annihilation
....
0.5 MeV
e+
ep-Ps
0.5 MeV
=0.125 ns
Orto-positronium (0-Ps) annihilation
0.5 MeV
e+
eo-Ps
....
e-
exotic atom
0.5 MeV
=142 ns
Source preparation and sandwich type sample prepapation
a
b
Kapton foils
Samples
deposited 22NaCl
Source 22Na in
kapton foil
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
PMT
Base
HV
Start
PMT
SC
22Na
SC
Source and
Sample zone
(liquid or solid)
PMT
PMT
Base
HV
Stop
CFD
CFD
DB
DB
FC
TAC
ADC/MCA
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
-5.00E-09
0
0.00E+00
-0.2
5.00E-09
1.00E-08
Voltage (volt)
-0.4
-0.6
-0.8
-1
-1.2
-1.4
-1.6
-1.8
-2
Time (ns)
1.50E-08
2.00E-08
Energy window
for stop
Detector
(0.51 MeV)
Energy window
for start
Detector
(1.28 MeV)
Fig. 8 Energy spectrum of 22Na detected by a multichannel analyzer of PAL
spectrometer with the plastic detectors scintillator
Fig. 9 Energy spectrum of 22Na detected by a multichannel analyzer of PAL
spectrometer, after lower and upper level adjustment for start signals
300
2ns
250
5ns
8ns
10ns
14ns
Count
200
150
FWHM
100
50
0
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
Channel number
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)
Delay time (ns)
16
14
12
10
8
6
4
2
0
y = 0.052x - 2.115
R2 = 1.000
0
100
200
300
400
Channel number
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
a
Count
Count
b
0
25
50
75
100
Channel number
125
150
0
2
4
6
8
Time (ns)
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
(kGy)
τ1 (ns)
I1 (%)
τ2 (ns)
I2 (%)
τ3 (ns)
I3 (%)
0
0.36±0.01
78.0±0.1
1.05±0.05
10±0.1
3.10±0.10
12.0±0.2
1
0.36±0.01
82.0±0.1
1.03±0.03
7.4±0.1
2.90±0.10
10.6±0.2
52
0.36±0.01
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
3.00±0.20
12.0±0.1
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:
-1
1
R
R
sin
o-Ps =0.5 1- R +
R0
0
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
(kGy)
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
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
Hydroxethylmethacrylate (HEMA)
CH3
CH2=C
COOCH2CH2OH
COOCH2CH2OCH2CH2OOC
CH2CH
COOCH2CH2OCH2CH2OOC
CH2CH
CH2CH
PHEMA
CH3
( CH2C )
n
O=C
OCH2CH2OH
CH2CH
COOCH2CH2OCH2CH2OOC
CH2=CH
CH2=CH
Dietilenglikoldiakrilat (DEGDA)
trietilenglikoldiakrilat (DEGDA)
CCH2
CH3
COOCH2CH2OCH2CH2OCH2CH2OOC
CH3
CCH2
COOCH2CH2OCH2CH2OCH2CH2OOC
CH3
CCH2
CCH2
CH3
CH3
C=CH2
C=CH2
CH3
COOCH2CH2OCH2CH2OCH2CH2OOC
Polypropylenglycoldiakrilat (PPGDA)
CH3
CCH2
CH3
CH3
COOCH2CH(OCH2CH)OCH2CHOOC
n
CH3
CCH2
CH3
CH3
C=CH2
CH3
CH3
CH3
C=CH2
CH3
COOCH2CH(OCH2CH)OCH2CHOOC
n
CH3
CCH2
CH3
CH3
CH3
CCH2
CH3
COOCH2CH(OCH2CH)OCH2CHOOC
n
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
ionization and excitation of atoms
free radicals
e+
molecule dissociation
(200 keV)
defects in crystalline structures
Spur
e- М+
R
e-
М+
e-
e- М+
e- R
t ~ 1 ps
+
М+ e (~ eV)
e- R
М- +
Re
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
Positron
Annihilation
Lifetime
Spectroscopy
Correlation of
- ACAR Annihilation
Radiation
t - PALS
sample
termalization
22Na
e+
e-
diffusion
Aged
MOmentum
Correlation
100 nm
511 keV
~
t , E1-511 - AMOC
Coincidence
Doppler
Broadening
Spectroscopy
E1+E2- CDBS
Doppler
Broadening of
Annihilation
Line
E1-511 - 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
+ SiO2 (+ZrO2)
35
30
25
20
a) S2
3
4
b) S11
Tg
Tc
2
4
c) S13
3
I3
3
2
35
30
25
20
30
50 100 150 200 250 300 350
Temperature (K)
PDMS+Silica – 1 long-lived component
6
25
20
4
4
3
I4
I3 15
10
2
Intensity (%)
3
35
30
25
20
o-Ps intensity (%)
o-Ps lifetime (ns)
2
Lifetime (ns)
4
5
0
50
100 150 200 250 300 350
Temperature (K)
0
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
• TL9
• MELT
• PORE SİZE CALCULATION
• ORIGIN /EXCEL
LT 9 programı kullanılarak elde edilen eğriler
PALS
s (t ) I i i exp t i
i
y(t ) R(t ) Nt s(t ) B
• POSITRONFIT
• PALFIT
• LT v.9
Tao-Eldrup model
o-Ps lifetime (ns)
102
RT
10
Goworek-Gidley model
Tao-Eldrup
Goworek-Gydley
1
10-1
102
1
10
Pore Radius (nm)
100
cylinder r=1.8 nm
90
o-Ps lifetime (ns)
sphere R=2.4 nm
80
70
60
50
40
30
0
100
200
300
Temperature (K)
400
500
Intensity
1
Intensity
2
dev.
Intensity
3
dev.
dev.
Lifetime1
dev.
Lifetime2
dev.
Lifetime3
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
3
31
29
2.5
2
Seri 1
1.5
Seri 2
Seri 3
1
o-Ps (intensity)
27
25
Seri 1
23
Log. (Seri 1)
21
19
17
0.5
15
0
0
0
2
4
6
8
10
12
14
16
2
4
6
8
Time (h)
10
12
14
16
Continuous Distribution
Relative Intensity (%)
• More realistic presentation:
continuous distribution
s(t ) 1 I exp t d
0
y(t ) R(t ) Nt s(t ) B
0.02
CONTIN
MELT
LT v.9
0.01
0
0.1
0.5
1
Lifetime (ns)
5
10
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()
0.14
Ps
100PE0EVA
Normalized Intensity
0.12
o-Ps()
0.10
0.08
0.06
0.04
0.02
0.00
-0.02
0.1
1
Time (ns)