the high frequency dynamics of liquids and supercritical fluids
DESCRIPTION
The high frequency dynamics of liquids and supercritical fluids. by Filippo Bencivenga. OUTLINE. Introduction Experimental description Data analysis Experimental results (Dispersions) Experimental results (Relaxations) Conclusions Outlook. Supercritical. Critical Point. - PowerPoint PPT PresentationTRANSCRIPT
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The high frequency dynamics of liquids and supercritical fluids
by Filippo Bencivenga
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OUTLINEOUTLINE
• Introduction
• Experimental description
• Data analysis
• Experimental results (Dispersions)
• Experimental results (Relaxations)
• Conclusions
• Outlook
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LIQUIDS & SUPERCRITICAL FLUIDS (1)LIQUIDS & SUPERCRITICAL FLUIDS (1)
So
lid
Triple Point
Vapor
Liquid
Critical Point
Supercritical
Temperature
Pre
ssu
re
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0 9 18 270
2
4
L (p
s-1
)
Q (nm-1)
c sQ
LIQUIDS & SUPERCRITICAL FLUIDS (2)LIQUIDS & SUPERCRITICAL FLUIDS (2)
Thermodynamicproperties
Microscopic
structure (nm)
Microscopic dynamics (ps)
SC fluids: a few cases
Systematic studies: none
What is missing?
Qm~ 2/r0
What is Known:
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AIM OF THE THESIS AIM OF THE THESIS
… what is the role of inter- and intra-molecular interactions ?
… what is the difference between a liquid and a SC fluid ?
From a microscopic point of view …
Microscopic dynamics ( ps - nm)
Liquidphase
Supercriticalphase
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0.5 1.0 1.5 2.00.1
1
10
P /
Pc
T / Tc
Supercritical
Liquid
H2O NH3 Ne N2
EXPERIMENTS (1)EXPERIMENTS (1)
Ne N2 NH3 H2O
Pc (bar) 27 34 113 221
Tc (K) 45 126 405 647
/ c
H2O 3.2 1.1
NH3 2.8 1.1
N2 2.7 1.8
Ne 2.6 1.2
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in out
in
out
EXPERIMENTS (2)EXPERIMENTS (2)
Ne N2 NH3 H2O
Pc (bar) 27 34 113 221
Tc (K) 45 126 405 647
Large Volume HP Cells• Low pressures ( Kbar)• “Large” samples ( cm3)• Versatility (High-T & Low-T)
Sample
Cell body
Pressureconnector
sample
10 mm
NutCell body
X-raybeam Scattered
beam
Sealingsystem
X-ray beam
Scattered beam
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Sample
Q,E
Ni Ein, kin
N o E out,
k out
• Q = |kout – kin| 2 kin sin()
• = E / ħ = (Eout– Ein) / ħ
INELASTIC X-RAY SCATTERING (IXS)INELASTIC X-RAY SCATTERING (IXS)
lengths nm
times ps
Q nm-
1
THz
No / Ni S (Q,)
ħ = 1
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IXS SPECTRAIXS SPECTRA T = 87 K
0
700
1400
21005 nm-1
0
1000
2000
30008 nm-1
counts
/ 1
50 s
-16 -8 0 8 160
1000
2000
3000 11 nm-1
(meV)
1.5 meV
N2
Q = 8 nm-1
0
1000
2000
3000107 K
c
ou
nts
/ 1
00
s
0
1500
3000
4500148 K
c
ou
nts
/ 8
5 s
-16 -8 0 8 160
1500
3000
4500
(meV)
191 K
co
un
ts /
55
s
N2
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DATA ANALYSISDATA ANALYSIS
S(Q)
S(Q,)=
1 (cTQ)2 m’(Q,)
2 - (cTQ)2 - m’’(Q,)[ ]
2 m’(Q,)[ ] 2+
Free
T = 1/DTQ2 ps
m(Q,t) = 2LQ2(t) + (-1)(cTQ)2exp{-t/T}
S(Q
,)
Hydrodynamics
Low-(Q,) limit
Rayleigh-Brillouin Spectrum
(c∞2
- cT2)Q2exp{-t/} + 2(t)
m (Q,t) = (-1)(cTQ)2exp{-t/T} + 2(t)
+ (c∞2
- cT2) Q2
exp{-t/}
Free
Free Free
Fix Fix
Thermal relaxation
Structuralrelaxation
Instantaneousrelaxation
EoS
L(Q) max [2 S(Q,)]
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Q
SOUND DISPERSIONS & RELAXATIONS (1)SOUND DISPERSIONS & RELAXATIONS (1)
Visco-Elasticity:
1) Low-Frequency limit:
c0=cs=1/2cT
2) High-Frequency limit: c∞
“High” and “low” frequency
is with respect to -1
-1
L(Q)
c 0Q
Fully relaxed:viscous
Fully unrelaxed:elastic
c ∞Q
L(Q
)
Positive sound dispersion
Structuralrelaxation
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Q
-1
L(Q
)
csQ
SOUND DISPERSIONS & RELAXATIONS (2)SOUND DISPERSIONS & RELAXATIONS (2)
Isothermal transition:
“High” and “low” frequency is
with respect to T-1
1) High-Frequency limit:
c∞=cs=1/2cT
2) Low-Frequency limit: c0=cT
Q
-1
L(Q
)
Relaxed
Unrelaxed
Q
L
(Q)
Unrelaxed:adiabatic
c ∞Q L
(Q) T
Relaxed:isothermal
c 0Q
Negative sound dispersion
c sQ
Structural and thermal relaxations:
competing dispersive effects
Structuralrelaxation
Thermalrelaxation
StructuralrelaxationT
-1 = DTQ2
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RESULTS (DISPERSIONS)RESULTS (DISPERSIONS)
Good agreement with S(Q)
measurements
0 4 8 120
3
6
9
(m
eV)
Q (nm-1)
T(Q) = cT(Q)QMS(Q)
kBTQ2
T2(Q) =
s(Q) = √T(Q)
∞(Q) = c∞(Q)Q
L(Q)
N2 @ 400 barT/Tc = 0.69
L =
0 8 16 240.0
0.3
0.6
0.9
S (
Q)
Q (nm-1)
0 4 8 120.05
0.1
0.5
(Q) = e
-AQ
(Q)
(ps)
Q (nm-1)
L(Q) max [2 S(Q,)]
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0 5 10 15
0
2
4
6T/T
c=1.51
(m
eV)
Q (nm-1)
T
D TQ
2
DISPERSION RELATIONS (NDISPERSION RELATIONS (N22))
L = DTQ2
0 4 8 120
3
6
9T/T
c=0.85
Q (nm -1)
(m
eV)
L =
0
3
6T/T
c=1.17
(m
eV) L ~ s
0
3
6
9 T/Tc=0.76
(meV
) L = L
∞
s
T
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0
4
8
12 0.92
(m
eV)
DISPERSION RELATIONSDISPERSION RELATIONS
0
7
14
21T / T
c = 0.57
(m
eV
)
0
6
12
18 0.85
(m
eV
)
0
5
10
15
(m
eV)
T / Tc = 0.76
0
3
6 T / Tc = 0.72
(m
eV)
0
2
4
(m
eV)
1.37
H2O NH3 Ne
c ∞
L
s
L ~ s
D T
Q2
0 4 8 120
1
2
3
Q (nm-1)
(m
eV)
1.62
0 4 8 120
4
8
12
Q (nm-1)
1.09
(me
V)
L=DTQ2
T
L=DTQ2L=DTQ2
0 4 8 12 160
4
8
12
Q (nm-1)
(m
eV)
0.93
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COMMON PHENOMENOLOGY (1)COMMON PHENOMENOLOGY (1)
0.1 1 10
0.00
0.25
0.50
0.75
1.00
M (Q
)
L(Q)(Q)
M(Q)=0
Viscous
M(Q)=1Elastic
QQQM
s
sL22
22
)(
0.1 1 10
0.00
0.25
0.50
0.75
1.00 H
2O
NH3
N2
Ne
M (
Q)
L(Q)(Q)
QQQM
s
sL22
22
)(
M(Q)=0Viscous
M(Q)=1Elastic
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0.1 1 10
0.00
0.25
0.50
0.75
1.00
MT (Q
)
'L(Q)
T(Q)
MT(Q)=0
Isothermal
MT(Q)=1Adiabatic
COMMON PHENOMENOLOGY (2)COMMON PHENOMENOLOGY (2)
MT(Q)=1
Adiabatic
MT(Q)=0
Isothermal
2/1
22
222'
11
QQQQQ
L
sLL
Dispersive effect of structural relaxation
s(Q) ∞(Q) s(Q) T(Q)
>>2(Q) = ∞
2(Q) -s2
(Q) T2(Q) = s
2(Q) -T2
(Q)
Structural relaxation Thermal relaxation
Vs.
QQQM
Ts
TLT 22
22'
)(
QQQM
Ts
TLT 22
22'
)(
0.1 1 10
0.00
0.25
0.50
0.75
1.00 H
2O
NH3
N2
Ne
MT
(Q)
'L(Q)
T(Q)
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CONCLUSIONS (SOUND DISPERSION)CONCLUSIONS (SOUND DISPERSION)
Common evolution with T:
• Evidence of a systematic disappearance of the positive dispersion, related to the structural relaxation, close to Tc
• First experimental observation of an adiabatic to isothermal transition of sound propagation, associated to the thermal relaxation.
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STRUCTURAL RELAXATION TIMESTRUCTURAL RELAXATION TIME
0.6 1.0 1.4 1.8 2.2
0.1
1
(
0) (p
s)
T c / T
Supercritical Liquid
• H2O• NH3
• N2
• Ne
H2O 12 +/- 0.8
NH39.3 +/- 1.3
N20.55 +/- 0.16
Ne 0.27+/- 0.12
E (KJ/mol)
(0) exp{E/kBT}(Q)= (0)exp{-AQ} A ≈ 0.2 ÷ 0.05 nm
RESULTS (RELAXATIONS)RESULTS (RELAXATIONS)
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cs
c∞=(c )2
sQ∞Q
=[cQ Q]2
COMPLIANCE RELAXATION TIMECOMPLIANCE RELAXATION TIME
0 3 6 90
3
6
9
(m
eV)
Q (nm-1)
∞(Q
) = c ∞
Q
EoS
-4 -2 0 2 4 (meV)
S(Q
,) (a
.u.)
c -1(Q)
Q 00.5 1.0 1.5 2.00.1
1
c (p
s)
T c / T
Supercritical Liquid
• H2O• NH3
• N2
• Ne
0.6 1.0 1.4 1.8 2.2
0.1
1
(
0) (p
s)
T c / T
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< >
√(d4/M)*(2T)< >
1
0.6 1.0 1.4 1.8 2.2
10
100
C /
< >
Tc / T
• H2O• NH3
• N2
• Ne
Supercritical Liquid
o P. Giura et al.;
Unpublished (2006)
COMMON PHENOMENOLOGYCOMMON PHENOMENOLOGY
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0.4 0.7 1.0 1.3 1.6 1.90
2
4
6
T / Tc
2 (
106
m2 /s
2 )
STRUCTURAL RELAXATION STRENGTHSTRUCTURAL RELAXATION STRENGTH
= c∞
2- cs2 =C
• H2O• NH3
• N2
• Ne
< C > a(Pa m6/mole2)
H2O 1.90 +/- 0.02 0.551
NH3 1.71 +/- 0.02 0.423
N2 0.95 +/- 0.02 0.136
Ne 0.16 +/- 0.03 0.021
Lines density
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CONCLUSIONSCONCLUSIONS
Common phenomenology:
• Negative sound dispersion Thermal relaxation
• Positive sound dispersion Structural relaxation
• Activation behavior (≈ bond’s energy) of below Tc
• Collision-like behavior of (c) above Tc
• density(correlation with the parameter “a”?)
Structural relaxation related to intermolecuar interactions
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OUTLOOKOUTLOOK
0.6 1.0 1.4 1.8 2.2
10
100
C /
< >
Tc / T
Extend the Tc/T range:• high-T for H2O & NH3
• low-T for Ne & N2
H2O NH3 N2 Ne
Other classes of fluids !
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ACKNOWLEDGEMENTSACKNOWLEDGEMENTS
• M. Krisch, F. Sette, G. Monaco and all the ID28-ID16 staff (ESRF)
• A. Cunsolo, L. Melesi (ILL)
• G. Ruocco (Universitá “La Sapienza”, Roma)
• L. Orsingher (Universitá di Trento)
• A. Vispa (Universitá di Perugia)
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IXS BEAMLINE (ID-28)IXS BEAMLINE (ID-28)
sample
Undulators
MonochromatorSi (n,n,n)
E/E ≈ 10-2
Pre-Monochromator
Si (1,1,1)
≈
E/E ≈ 10-4
75 m
Detecto
r6.5 m
Analyzer
Si (n,n,n)
h Ei(KeV) E (meV) Flux (p/s)
8 15.82 5.5 9 * 1010
9 17.79 3 3 * 1010
11 21.75 1.5 7 * 109
Q
5 Analyzers
Si (n,n,n)
5 Detecto
rs Toroidal mirror
B
E/E ≈ 10 -8
B T-scan ≈ mK
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STATIC STRUCTURE FACTORSSTATIC STRUCTURE FACTORS
0 8 16 240.0
0.2
0.4
0.6
0.8
S (
Q) (
a.u
.)
128 K
Q (nm -1)
0 8 16 240.0
0.2
0.4
0.6
0.8
N2 @ 128.5 K
S(Q
) (a
.u.)
Q (nm-1)
400 bar 130 bar 40 bar
0 8 16 240,0
0,5
1,0
1,5
2,0
S (
Q) (
a.u
.)
447 K293 K
Q (nm -1)
H2O @ 400 bar
0 8 16 240.0
0.2
0.4
0.6
0.8
1.0
Ne @ 200 bar
S(Q
) (a
.u.)
Q (nm-1)
32 K 61 K 82 K
N2 @ 400 bar
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M(∞)M(0)=c
cs
c∞=(c )2
sQ∞Q
=[cQ Q]2
0.01 0.1 1 10 100
16
19
22
25
Re[M
()]
M(0)
M(∞)= -1
0.04
0.05
0.06
Re[M
-1()]
COMPLIANCE RELAXATION TIMECOMPLIANCE RELAXATION TIME
0 3 6 90
3
6
9
(m
eV)
Q (nm-1)
∞(Q
) = c ∞
Q
-4 -2 0 2 4 (meV)
S(Q
,) (
a.u.
)
= c-1
M-1(0)
M-1(∞)
EoS
c -1(Q)
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INSTANTANEOUS RELAXATIONINSTANTANEOUS RELAXATION
H2O 0 7 meV
NH3 0 5 meV
N2 0 1.5 meV
Ne 0 meV
2(Q)(t)
300 500 7000
3
6
9
290 370 4500
2
4
6
T (K)
H2O
5 nm-1 8 nm-1
11 nm-1
T (K)
NH3
8 nm-1
11 nm-1
(Q
) (m
eV)
Lines density
(Q) (Q)(Q)
Intramoleculardegree of freedom?
(Q)(t)
(Q) << ps
(Q)exp{-t/(Q)}
(Q) = g(Q)
0 4 8 120
2
4
6
0 4 8 120
3
6
9 H2O
Q (nm-1)
NH3
Q (nm-1)
g(Q
) (m
eV*c
m3 /g
)
g(Q) = <(Q)/>
(Q) Q
(Q)
(Q)
(Q) const
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VISCOSITY (Q-dependence)VISCOSITY (Q-dependence)
0 4 8 12
50
100
500
0 4 8 1210
100
1000
0 4 8 12
100
1000
0 4 8 120.1
1
10
Ne
32 K 42 K 81 K
L (
Q)
(Pa*s
) L (Q
) (Pa*s
)N2
96 K 148 K 190 K
L (
Q)
(Pa*s
)
NH3
Q (nm-1)
293 K 373 K 414 K
L (Q
) (Pa*s
)H2O
Q (nm-1)
293 K 367 K 549 K
L(Q) = Lexp{-BQ}L(Q) = [(Q) (Q) + (Q) / Q2]
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VISCOSITY (T-dependence)VISCOSITY (T-dependence)
30 50 70 900
150
300
450
30 50 70 900
2
4
90 120 150 1800
250
500
750
90 120 150 180
1
3
5
290 340 390 4400
400
800
1200
300 340 380 420
2
4
6
300 400 500 600 7000
2
4
6
300 400 500 600
2
4
6
Ne
(
Pa*s
)
L/
S
T (K)
(P
a*s
)
N2
L/
S
T (K)
(
Pa*s
)
NH3
T (K)
L/
S
T (K)
(P
a*s
)
H2O
T (K)
T (K)
L/
S
L / S constant
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OUTLOOKOUTLOOK
Disappearance of the positive dispersion?
Study high T/Tc and P/Pc region of the
SC plane
Supercritical
Liquid
0.1
1
10
100
1000
0.4 31
P /
Pc
T / Tc
Vapor
O2
F. Gorelli et al.;
Unpublished (2005)
H2O NH3 N2 Ne
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i +i + …
S(Q)
S(Q,)= i +
i +[
-1Im1 [
m2(Q,)
F(Q,t-t’)m3(Q,t-t’)m2(Q,t-t’)m1(Q,t-t’)m2(Q,t’)m3(Q,t’)m4(Q,t’)m1(Q,t’)dm1(Q,t)dm2(Q,t)dm3(Q,t)dF(Q,t)
THEORETICAL FORMALISMTHEORETICAL FORMALISM
MEMORY FUNCTION
S (Q,)Time FourierTransform
F(Q,t)=<(Q,0)(Q,t)>
(Q,t)=jeiQRj(t)
dt= ∫
0
t
MEMORYEQUATION
dt’
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0 5 10 150.2
0.4
0.6
0.8
1.0
2 (Q
) /
[ T
2 (Q)+
2 (Q)]
293 K 373 K 414 K 444 K
Q (nm-1)
0 5 10 150.5
0.6
0.7
0.8
2 (Q
) /
[ T
2 (Q)+
2 (Q)]
32 K 41 K 71 K 81 K
Q (nm-1)
0 5 10 15
0.6
0.8
1.0
87 K 107 K 148 K 190 K
2 (Q)
/ [ T
2 (Q)+
2 (Q)]
Q (nm-1)
0 4 8 12 16
0.2
0.4
0.6
0.8
1.0
293 K 423 K 600 K 660 K 706 K
2 (Q
) /
[ T
2 (Q)+
2 (Q)]
Q (nm-1)
RELATIVE RELAXATION STRENGTHRELATIVE RELAXATION STRENGTH
H2O
N2
NH3
Ne
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0 5 10 15
0.4
0.6
0.8
1.0
87 K 107 K 148 K 190 K
Q (nm-1)
2
/ [
T
2 T+
2 ]
0 5 10 15
0.2
0.4
0.6
0.8
1.0
2
/ [
T
2 T+
2 ]
293 K 373 K 414 K 444 K
Q (nm-1)
0 5 10 15
0.6
0.8
1.0 32 K 41 K 71 K 81 K
2
/ [
T
2 T+
2 ]
Q (nm-1)
0 4 8 12 160.0
0.2
0.4
0.6
0.8
1.0
293 K 423 K 600 K 660 K 706 K
2
/ [
T
2 T+
2 ]
Q (nm-1)
RELATIVE RELAXATION AMPLITUDERELATIVE RELAXATION AMPLITUDE
H2O
N2
NH3
Ne
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0 5 10 15
-1.5
-1.0
-0.5
0.0
87 K 107 K 148 K 190 K
Q (nm-1)
L(Q
) -
s(Q)
- F
( L )
(m
eV
)
0 5 10 15
-4
-2
0
293 K 373 K 414 K 444 K
L(Q
) -
s(Q
) -
F( L )
(m
eV
)
Q (nm-1)
0 5 10 15
-1.5
-1.0
-0.5
0.0
L(Q
) -
s(Q
) -
F( L )
(m
eV
)
32 K 41 K 71 K 81 K
Q (nm-1)
0 4 8 12 16
-6
-4
-2
0
293 K 494 K 549 K 600 K 660 K 706 K
L(Q
) -
s(Q
) -
F( L )
(m
eV
)
Q (nm-1)
NEGATIVE DEVIATIONSNEGATIVE DEVIATIONS
H2O
N2
NH3
Ne
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0 9 18 270
2
4
L (p
s-1
)
Q (nm-1)
Liquid Indium
S(Q)
0 8 16 240.0
0.3
0.6
0.9
128 K
S (Q
)
87 K
Q (nm -1)
Nitrogen
S(0) T
Qm -1/3
<r2>
-1
cQ
LIQUIDS & SUPERCRITICAL FLUIDSLIQUIDS & SUPERCRITICAL FLUIDS
Microscopic structure (nm)
Microscopic dynamics (ps)
Thermodynamics
Qm~2/r0
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VISCOELASTICITYVISCOELASTICITY
A (t)
t
P (t)
t
A (t)
t
viscouselastic
relaxation time
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RELAXATION TIME (Q-dependence)RELAXATION TIME (Q-dependence)
(Q) = (0)exp{-AQ}
0 4 8 120.1
0.2
0.4
0 4 8 12
0.05
0.1
0.5
0 4 8 120.01
0.1
0 4 8 120.01
0.1
1
Ne
41 K 61 K
(Q
) (p
s)
N2
(Q) (p
s)
96 K 148 K
NH3
(
Q) (p
s)
293 K 373 K
Q (nm-1)
H2O
(Q) (p
s)
293 K 367 K 549 K
Q (nm-1)
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RELAXATION TIME (T-dependence)RELAXATION TIME (T-dependence)
11 21 31
0.2
0.3
0.4
0.5
4 8 12
0.3
0.4
0.5
2.3 2.8 3.3
0.05
0.1
0.5
1.7 2.5 3.3
0.1
1
30 50 70 900.03
0.07
0.11
0.15
90 125 160 1950.06
0.11
0.16
0.21
290 340 390 4400.01
0.06
0.11
0.16
320 440 560 6800.01
0.08
0.15
0.22
Ne
(
0) (p
s)
(0) (p
s)
N2
(0) (p
s)
NH3
1000 / T (K-1)
(0) (p
s)
H2O
1000 / T (K-1)
A (nm
)
T (K) T (K)
A (nm
)
T (K)
A (nm
)
T (K)
A (nm
)
(0) = 0exp{Ea/kBT}
Tc
Tc Tc
Tc
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30 50 70 900.0
0.2
0.4
0.6
90 120 150 1800.0
0.4
0.8
1.2
290 340 390 4400.0
1.5
3.0
4.5
270 420 570 7200
2
4
6
2 (
m2 /s
2 )
Ne
2 (
m2 /s
2 )
2 (m
2/s2)
N2
2 (m
2/s2)
NH3
T (K)
H
2O
T (K)
30 50 70 900.0
0.2
0.4
0.6
90 120 150 1800.0
0.4
0.8
1.2
290 340 390 4400.0
1.5
3.0
4.5
270 420 570 7200
2
4
6
2 (
m2 /s
2 )
2 (m
2 /s2 )
2 (m
2/s2)
2 (m
2/s2)
T (K) T (K)
RELAXATION STRENGTHSRELAXATION STRENGTHS
= c∞
2- cs2
Tc
Tc Tc
Tc