Otto Stern (Sohrau 1888 – Berkeley 1969) Nobel Laureate 1943

Otto Stern, O.R. Frisch, I. Estermann (Hamburg, 1929-1933)

He

NaCl(001)

[meV]542.4

][Å2[Å] 1

iEk

),(2GG K

),K(k

nma

kkk ifz

“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)

J. E. Lennard-Jones and A. F. Devonshire, Nature 137 (1936) 1069.

I00

Gas – Surface Interactions:

- energy transfer

- sticking (adsorption)

INELASTIC SCATTERING

INELASTIC RESONANCES

)()(1)-()( QQQQ

212vifvvifvQvfi

iz

f

ff

)(

-EEn-EEnk

dΩdEd

vk

uF

Lattice vibrations (phonons)

)exp()( zAzV o

),(e4

2 sinh2sinhsinhsinh

2/1

22

22

i-Wpp

pppp

pp

if

if

if

i

f

fi

QF

/βπkp/βπkp fzfizi ,

J.M. Jackson and N.F. Mott, Proc. Roy. Soc. A 137 (1932) 703: Quantum DWBA

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

Supersonic He-atom beam sourcesTime-of-flight spectroscopy

High-resolution diffraction

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

Forces between atoms

Forces between ions and electrons (electron-phonon interaction)

& electronic susceptibility

Phonon dispersion curves

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

theory: Green Function surface dynamics + DWBA

scattering theory

LiF(001)

NaF(001)

Metals: Skin & Bones

1D conductor

Peierls instability

electron-hole excitations

HAS hole-electron pairs!

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).

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

The Cavendish He3 Spin-Echo Apparatus

A first test for He3 Spin-Echo:

Bound states of He3 on LiF(001)

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).

back to Frisch & Stern!

PMCS substratecluster beamtime of flight

mass spectrometer

quartz MB

2000 l/s diff. pump

500 l/s turbo pump

700 l/s diff. pump

He line

sample manipulator

target cluster assembled film

to pulsed power supply

SOURCE CHAMBERDEPOSITION CHAMBER TOF-MS

CHAMBER

SUPERSONIC CLUSTER BEAM DEPOSITION at the Department of Physics, University of Milano

Grenoble - 9 

Giorgio Benedek J. Peter Toennies

Helium Atom Scattering Spectroscopy of Surface Phonons

Springer-VerlagBerlin Heidelberg New York 2007

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