Transcript Diapositiva 1

Otto Stern (Sohrau 1888 – Berkeley 1969)
Nobel Laureate 1943
Otto Stern, O.R. Frisch, I. Estermann
(Hamburg, 1929-1933)
He
2
4.542
[Å] 

1
k[Å ]
Ei [meV]
k  ( K, k z ) k f  ki
K  G
G
2
(m, n)
a
NaCl(001)
“These experiments are of interest not only because of
their confirmation of the predictions of quantum mechanics,
but also because they introduce the possibility of applying
atom diffraction to investigations of the atomic constitution
of surfaces.”
(T. M. Johnson, Phys. Rev. 37 (1931) 847).
Bound-state resonances
Frisch-Stern (1933)
I00
J. E. Lennard-Jones and A. F. Devonshire, Nature 137 (1936) 1069.
INELASTIC SCATTERING
Gas – Surface Interactions:
INELASTIC RESONANCES
- energy transfer
- sticking (adsorption)
Lattice vibrations (phonons)
J.M. Jackson and N.F. Mott, Proc. Roy. Soc. A 137 (1932) 703: Quantum DWBA
kf
d 2( 1 )

dE f dΩ f
kiz
v
2
F fi  uQv
 n(
V ( z)  Ao exp( z)
Qv
)  ( E f -Ei - Qv )   1  n(Qv ) ( E f -Ei  Qv ) 
pi  πkiz /β,
1/ 2
 sinh 2 p f sinh 2 pi 


F fi 
2
2

sinh p f  sinh pi 
4 p f pi

p 2f  pi2
p f  πk fz /β
e-W (Q,  i )
L.D. Landau, Phys. Z. Sowjet. 8 (1935) 489.
B.L. Bonch-Bruevich, Usp. Fiz. Nauka 40 (1950) 369
Classical
Rarified Gas Dynamics
Supersonic
Molecular Beams
High-resolution diffraction
Supersonic He-atom beam sources
Time-of-flight spectroscopy
J. P. Toennies: HUGO (MPI-SF, Goettingen)
Angular distributions
Diffraction
Bound state
resonances, etc.
Time of Flight (TOF)
Inelastic scattering
Phonons
via the mechanical
action (Pauli repulsion)
on the electron density
Phonon dispersion curves
Forces between atoms
Forces between ions and electrons
(electron-phonon interaction)
& electronic susceptibility
Surface waves
Lord Rayleigh (1887)
Irpinia 1980 (Polo Sismico Alberto Gabriele,
FCCSEM Erice)
Surface phonons 1: from 3D lattice to slab
Surface phonons 2: from
2D monolayer to slab
TOF spectrum
Energy-transfer
spectrum
scan curves for 90°
geometry
HAS versus theory
NaF(001)
LiF(001)
theory: Green Function
surface dynamics + DWBA
scattering theory
Metals: Skin & Bones
HAS  hole-electron pairs!
1D conductor
electron-hole excitations
Peierls instability
The Helium-3 Spin-Echo Spectroscopy
P. Fouquet, A.P. Jardine, S. Dworski, G. Alexandrowicz, W. Allison and J. Ellis
"Thermal energy 3He spin-echo spectrometer for ultrahigh resolution surface dynamics measurements“
Rev. Sci. Inst. 76, 053109 (2005).
The Cavendish He3 SpinEcho Apparatus
Parameter
Value
Total scattering angle
44.4 degrees
3He Angular Resolution
0.1 degree
Nominal beam energy
8 meV
Measured beam intensity
1e14 atoms/second
Beam diameter at target
2 mm
Energy resolution (QE peak width)
20 neV
Scattering chamber base pressure
2e-10 mbar
Sample manipulator
6 axis, titanium
Sample manipulator resolution
0.003 degrees
Sample heating
Radiation / E-beam
Sample cooling
Liquid Nitrogen or Helium
Sample temperature range
55 K - >1200 K
A first test for He3 Spin-Echo:
Bound states of He3 on LiF(001)
back to Frisch &
Stern!
A.P. Jardine, S. Dworski, P. Fouquet, G. Alexandrowicz, G.Y.H. Lee, D.J. Riley,
J. Ellis, W. Allison, "Ultrahigh resolution spin-echo measurement of surface
potential energy landscapes", Science 304, 1790-1793 (2004).
Grenoble - 9
SUPERSONIC CLUSTER BEAM DEPOSITION
at the Department of Physics, University of Milano
SOURCE CHAMBER
DEPOSITION CHAMBER
quartz MB sample manipulator
TOF-MS
CHAMBER
He line
PMCS
cluster beam
substrate
time of flight
mass
spectrometer
to
pulsed
power
supply
target
2000 l/s diff.
pump
cluster
assembled film
700 l/s diff.
pump
500 l/s turbo
pump
something more in:
Giorgio Benedek
J. Peter Toennies
Helium Atom Scattering Spectroscopy
of Surface Phonons
Springer-Verlag
Berlin Heidelberg New York 2007