Pr

1
"Environmented" electronic systems

• Deposited clusters or molecules
• on rare gas surface -gt "soft-landing"
• FeN _at_ Ru via Ar
• Lau et al., Low Temp.
  Phys. (2003)
• thymine _at_ Ar _at_ Pt
• Levesque et al.,
  Nucl. Instr. Meth. Phys. Res. (2003)
• on oxides (MgO,ZnO,Al2O3,) -gt catalysis studies

2
"Environmented" electronic systems

• Embedded clusters
• in rare gas droplets
• -gt control of
• temperature,size
• Bartelt et al., PRL (1996)

Ag3 _at_ Ar

• in rare gas matrices
• -gt "inert" (?) environment
• Lecoultre et al., JCP (2007)
• Bonacic-Koutecky et al.,JCP (1999)

free Ag3
3
Dynamics of extended systems
Dynamics
model-potential (frozen) electrons

Car-Parrinello MD
All classical charge creation
MM / QM(TDDFT)
TDDFT-MD
MM/QM(TDCI)
TDCI
Electrons
Environment
e- quantal but small systems environment
e- excitation ? charge creation ?
e- quantal but in ground state electronic
excitation
How ??
4

• static parameters
• static polarization
• no e- response of MM

Standard QM/MM
QM quantum chemistry MM classical force fields
stretching
folding
twist
electrostatic
d
d-
Van der Waals
5
Generalized MM explicit dynamical dipoles ?e-
response from MM x no e- emission
Generalized QM/MM
NaN

• VdW
• ab initio
• fine-tuning

soft Coulomb
Rion
Ar, Ne, Kr
MgO
DAr
RMg2
RAr
add new terms in Uext
RO2-

• Lennard-Jones
• soft Coulomb
• oscillators

DO2-

• Buckingam
• soft Coulomb
• oscillators

frozen cores
Madelung potential
6
(Time-resolved) observables
During or after cluster deposition,
laser irradiation,
from electrons

• dipole response (-gt spectral analysis)
• ionization
• number of emitted e-
• kinetic E spectrum of emitted e-
• angular distribution of emitted e-

from ions

• potential and kinetic (temperature) E
• global deformation and shape

from matrix

• potential and kinetic (temperature) E
• global deformation and shape
• internal excitation (dipoles)

7
Guided tour
example of deposition
Cluster properties Optical response Photoelectrons
Deposition dynamics Energies Site deposition Role
of charges
Matrix properties Global excitation Internal
excitation
8
Optical response
Na6 on MgO(100)
oblate
Na8 in Ar164
shortrange compression
long range polarization
final blue-shift
broken x-y degeneracy g geometry
Laudau fragmentation g core repulsion
subtle balance core repulsion vs. polarization
attraction
9
Optical response
embedded clusters
Rare gas not that inert
10
Photoelectron angular distributions
w5.44 eV
Na8
IP-4.3 eV
I 109 Wcm-2 FWHM 20 fs
MgO
(or Ar)
no problem of orientation
no state dependence !
11
Photoelectron angular distributions
free orientated Na8 state PAD, w2.6 eV
No orientation problem but complex interactions
with surface !
Na8 _at_ MgO total PAD, 3 w
suppression towards surface
Na8 _at_ Ar total PAD, 2 w
12
Guided tour
example of deposition
Cluster properties Optical response Photoelectrons
Deposition dynamics Energies Site deposition Role
of charges
Matrix properties Global excitation Internal
excitation
13
Na _at_ Ar384 Ekin0 136 meV
Charged atom deposition
Inclusion of Na in a dynamically created Ar
vacancy
Na slight minimum
Na deep minimum
thanks to Ar vacancy
14
Deposition of Na dimers

1. Na _at_ Ar384
2. Na _at_ Na/Ar383

Na2 _at_ Ar384
Na2 _at_ Ar384
more robust attachment when charged
15
Guided tour
example of deposition
Cluster properties Optical response Photoelectrons
Deposition dynamics Energies Site deposition Role
of charges
Matrix properties Global excitation Internal
excitation
16
Dipole d.o.f
Na6 deposition, Ekin0 136 meV/ion
fixed Ar cores
fixed Ar dipoles
full Ar
dynamical dipoles crucial ingredient for
cluster dynamics
17
Ar electronic response
at impact
Ekin0 136 meV/ion
Eexc µ d2
16 meV
9 meV
Na
Na6
charge effect gtgt size effect
0.2 meV
1.2 meV
Na6
Na
18
Time evolution of dipoles
Ekin0 6.8 eV
NaQ _at_Ar Ekin0 136 meV
Q 0, 1, -1
Q 0
Q 1
Q -1

• Important effect of charge
• Q 0 ahigh Ar excitation energy
• Threshold for reflection
• factor 20 between Na and Na

Dipoles ?
19
Dipole localization
Na6_at_Ar384 Ekin0 800 meV/ion
Impact
Radial dipole distribution at different times
Initial

• Localized excitation
• Sizeable dipole "noise"
• Moderate time evolution

Longer time
20
Conclusion and perspectives

• Clusters and molecules _at_ environment
• Hierarchical approach for a generalized QM/MM
• Nan_at_Ar,Ne,Kr done
• Nan_at_MgO done
• dynamical electronic response of substrate
• Nan_at_MgO with defects in progress
• C,N,O,H _at_ H2O in near future
• C,N,O,H _at_ H2O _at_ rare gas in future

M. Farizon L. Sanche
21
(No Transcript)
22
Context and motivations

• Clusters

deposited on surface embedded in matrix
(nano)technologies surface engineering
Exp
Theory
free

• Particular interest rare gas substrates (Ne, Ar,
  Kr)

•  soft-landing 
• AgN _at_ Pt(111) via Ar
• Bromann et al., Science 274, (1996) 956
• FeN _at_ Ru(001) via Ar
• Lau et al., Low Temp. Phys. 29 (2003) 296

23
Context and motivations
AgN codeposited with Ar _at_Au
Harbich et al., PRB 76 (2007) 104306
fluorescence Ag1_at_Ar

• Neutralization ofAgN by
• e- from Au then
• going through Ar
• non trivial electronic effect of Ar matrix

luminescence Ag1_at_Ar_at_Au
24
Na6 deposited on MgO
energy dependence
site dependence
25
Réponse optique
Na8_at_Ar434
Na83_at_Ar434
hw 1.9 eV I 21012 W.cm-2 ?t 50 fs (FWHM)
initial

• élargissement vers le rouge
• en accord avec exp

Seifert et al., Appl. Phys. B 71 (2000) 795