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X-ray Photon Correlation Spectroscopy
(XPCS) Studies of Liquid Surface Dynamics |
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X-ray photon
correlation spectroscopy (XPCS) is the X-ray analog of
Dynamical
Light Scattering (DLS) and is a relatively new technique which uses
coherent X-ray beams to study the dynamics of liquids on time
scales from seconds down to microseconds and length scales from
microns to nanometers.
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XPCS principles |
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| The method relies on
the fact that a particular arrangement of atoms in a sample
produces a characteristic "speckle" pattern when it scatters a
coherent beam of X-rays. If the arrangement of atoms changes,
the speckle pattern changes, and by studying these changes as a
function of time, one can obtain information at the atomic
dynamics at various wavevector transfer (i.e. at different
length scales). |
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| For example,
let's consider the Brownian motion of 100 particles. The
simulated scattering pattern is calculated through the Fourier
transform of the instantaneous positions of these particles. |
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MOVIE: 2D
Brownian Motion of 100 particles |
MOVIE:
Portion of the scattering pattern |
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| The
intensity at an interested region (red box) in the reciprocal
space varies in a random-like way as the absolute time elapses. |
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FIG:
Random-like intensity variations |
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| However, if
an intensity-intensity auto-correlation is performed as a
function of time delay (frame delay here), the characteristic of
the dynamics, which is basically the diffusion coefficient for
Brownian motion, can be revealed. |
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FIG:
Protocol for auto-correlation
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FIG:
Intensity-intensity auto-correlation function |
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| As an
extension of DLS, XPCS has an ability to study the dynamics on a
much smaller length scale than can be achieved by traditional
DLS and on a slower time scale than the
neutron spin-echo (NSE)
technique can usually reach. It allows a study of samples that
are opaque to visible light, and the broadening problem of the
wave vector due to multiple scattering in DLS can be solved. The
following figure shows the frequency and wave vector ranges
accessible to XPCS compared with other frequently used
techniques for the study of dynamics. |
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FIG:
Frequency-scattering vector space covered by XPCS and
complementary techniques: photon correlation spectroscopy with
visible coherent light (PCS), Raman and Brillouin Scattering,
inelastic neutron (INS) and x-ray scattering (IXS), neutron
spin-echo and nuclear forward scattering (NFS). Reprinted from [Correlation
spectroscopy with coherent x-rays by G.
Grubel and F. Zontone, J. Alloys Compd. 362, 3 (2004).
DOI: 0.1016/S0925-8388(03)00555-3]. |
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| Liquid
surface dynamics by XPCS |
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We have used this
technique to study the dynamics of capillary wave fluctuations
in
liquid films, molten polymer films for
example, as a function of wavelength. The results
have confirmed theoretical calculations for viscous liquid films
and for thick films, but are revealing new information about
entanglement effects and substrate interactions for thinner
films. We have studied the behavior of thin films as the
temperatures are reduced towards the glass transition. We have
also discovered additional (non-capillary wave) scattering from
the interfaces of polymer films and are trying to understand how
it arises. We find a very interesting increase in the rate of
relaxation as Tg is approached, indicating a freezing out of the
much slower long-wavelength reptation modes of the polymer.
We have also
investigated the dynamics of thin wetting films of hexane on
silicon substrates. To our surprise the scattering behaves like
scattering from capillary waves from a highly viscous liquid,
implying that even films of thickness up to 6 nm are glassy in
nature, even at room temperature. |
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| More on XPCS |
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Here are some short
lectures on XPCS: |
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Publications |
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Partially Wetting
Thin Liquid Films: Structure and Dynamics Studied with Coherent
X Rays
C. Gutt, M. Sprung,
R. Fendt, A. Madsen, S. K. Sinha and M. Tolan
Phys. Rev. Lett. 99, 096104 (2007).
DOI: 10.1103/PhysRevLett.99.096104 |
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Evidence for Viscoelastic Effects in Surface Capillary Waves
of Molten Polymer Films
Z. Jiang, H. Kim, X. Jiao, H. Lee, Y.-J. Lee, Y. Byun, S. Song,
D. Eom, C. Li, M. H. Rafailovich, L. B. Lurio and S. K. Sinha
Phys. Rev. Lett. 97,
227801 (2007). DOI: 10.1103/PhysRevLett.98.227801 |
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Structure and dynamics of thin polymer films using
synchrotron X-ray scattering
Z. Jiang, H. Kim, H. Lee, Y. J. Lee, X. Jiao, C. Li, L. B. Lurio,
X. Hu, J. Lal, S. Narayanan, A. Sandy, M. Rafailovich and S. K.
Sinha
J. Appl. Cryst. 40, s18 (2007).
DOI: 10.1107/S0021889807007996 |
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Surface and interfacial dynamics
of polymeric bilayer films
Z. Jiang, H. Kim, S. G. J. Mochrie, L. B. Lurio and S. K. Sinha
Phys. Rev. E 74,
011603 (2006). DOI: 10.1103/PhysRevE.74.011603 |
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Observation of a low-viscosity
interface between immiscible polymer layers
X. Hu, Z. Jiang, S. Narayanan, X. Jiao, S. K. Sinha, L. B. Lurio
and J. Lal
Phys. Rev. E 74,
010602 (2006). DOI: 10.1103/PhysRevE.74.010602 |
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Deviations from liquidlike
behavior in Molten Polymer films at interfaces
Y. S. Seo, T. Koga, J. Sokolov, M. Rafailovich, M. Tolan and S.
K. Sinha
Phys. Rev. Lett 94,
157802 (2005). DOI:
10.1103/PhysRevLett.94.157802 |
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Real-time evolution of the
distribution of nanoparticles in an ultrathin-polymer-film-based
waveguide
S. Narayanan, D. R. Lee, R. S. Guico, S. K. Sinha and J.
Wang
Phys. Rev. Lett 94,
145504 (2005). DOI: 10.1103/PhysRevLett.94.145504 |
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Resonantly enhanced off-specular
X-ray scattering from polymer/polymer interfaces
X. Hu,
X. Jiao, S. Narayanan, Z. Jiang, S. K. Sinha, L. B. Lurio
and J. Lal
Eur. Phys. J. B 17,
353 (2005). DOI: 10.1140/epje/i2004-10147-4 |
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Viscosity Measurements of Very
Thin Polymer Films
C. Li, T. Koga, J. Jiang, S. Sharma, S. Narayanan, L. B. Lurio,
X. Hu, X. Jiao, S. K. Sinha, S. Billet, D. Sosnowik, J. C.
Sokolov, and M. H. Rafailovich
Macromolecules 38,
5144 (2005). DOI: 10.1021/ma050440g |
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Synchrotron radiation studies of
the dynamics of polymer films
H. Kim, A. Ruhm, L. B. Lurio, J. K. Basu, J. Lal, S. G. J.
Mochrie and S. K. Sinha
J. Phys.: Condens. Matter 16,
S3491 (2004). DOI:
10.1088/0953-8984/16/33/010 |
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Polymer film dynamics using x-ray
photon correlation spectroscopy
H. Kim, A. Ruhm, J. K. Basu, L. B. Lurio, J. Lal, S. G. J.
Mochrie, and S. K. Sinha
Materials Science and Engineering C:
Biomimetic and Supramolecular Systems 24, 11
(2004). DOI: 10.1016/j.msec.2003.09.038 |
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X-ray photon correlation
spectroscopy on polymer films with molecular weight dependence
H. Kim, A. Ruhm, L. B. Lurio, J. K. Basu, J. Lal, S. G. J.
Mochrie and S. K. Sinha
Physica B 336, 211
(2003). DOI: 10.1016/S0921-4526(03)00291-6 |
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X-ray photon correlation
spectroscopy studies of colloidal diffusion and the capillary
modes of polymer films
S. G. J. Mochrie, L. B. Lurio, A. Rühm, D. Lumma, M. Borthwick,
P. Falus, H. J. Kim, J. K. Basu, J. Lal and S. K. Sinha
Physica B 336, 173
(2003). DOI: 10.1016/S0921-4526(03)00287-4 |
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Observation of heterodyne mixing
in surface x-ray photon correlation spectroscopy experiments
C. Gutt , T. Ghaderi, V. Chamard, A. Madsen, T. Seydel , M.
Tolan, M. Sprung , G. Grubell, and S. K. Sinha
Phys. Rev. Lett. 91,
076104 (2003). DOI: 10.1103/PhysRevLett.91.076104 |
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Surface tension and surface
roughness of supported polystyrene films
L. Lurio, H. J. Kim, A. Ruhm , J. K. Basu , J. Lal, S. K. Sinha,
and S. G. J. Mochrie
Macromolecules 36,
5704 (2003). DOI: 10.1021/ma034189l |
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X-ray scattering from
freestanding polymer films with geometrically curved surfaces
D. R. Lee, K. Shin, O. H. Seeck, H. Kim, Y. S. Seo, M. Tolan, M.
H. Rafailovich, J. Sokolov, S. K. Sinha
Phys. Rev. Lett. 90,
185503 (2003). DOI: 10.1103/PhysRevLett.90.185503 |
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Surface Dynamics of Polymer Films
H. J. Kim, A. Ruhm, L. B. Lurio, J. K. Basu, J. Lal, D. Lumma,
S. G. J. Mochrie and S. K. Sinha
Phys. Rev. Lett. 90,
068302 (2003). DOI: 10.1103/PhysRevLett.90.068302 |
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