"Environmented" electronic systems
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Transcript of "Environmented" electronic systems
"Environmented" electronic systems
Deposited clusters or molecules:
on rare gas surface -> "soft-landing"• FeN @ Ru via Ar [Lau et al., Low Temp. Phys. (2003)]• thymine @ Ar @ Pt
[Levesque et al., Nucl. Instr. Meth. Phys. Res. (2003)]
on oxides (MgO,ZnO,Al2O3,…) -> catalysis studies
"Environmented" electronic systems
Embedded clusters in rare gas droplets -> control of temperature,size[Bartelt et al., PRL (1996)]
free Ag3+
Ag3+ @ Ar
in rare gas matrices -> "inert" (?) environment[Lecoultre et al., JCP (2007)][Bonacic-Koutecky et al.,JCP (1999)]
Dynamics
ElectronsEnvironment
Dynamics of extended systems
model-potential (frozen) electrons
e- quantal but in ground stateelectronic excitation
All classicalcharge creation
e- quantal but small systemsenvironment
Car-Parrinello MD
TDDFT-MD
TDCI
How ??
MM / QM(TDDFT)
MM/QM(TDCI)
e- excitation charge creation
Standard QM/MM
QM: quantum chemistryMM: classical force fields
stretchingfolding
twist
electrostatic
Van der Waals
static parameters static polarization no e- response of MM
DAr
RRArAr
RRionion
Generalized QM/MM
NaN
DO2-
RRMgMg2+2+
Ar, Ne, Kr MgO
RROO2-2-
frozen cores
Madelung potential
• Lennard-Jones• soft Coulomb• oscillators
• Buckingam• soft Coulomb• oscillators
soft Coulomb
• VdW• ab initio + fine-tuning
Electrons
Generalized MM:explicit dynamical dipolese- response from MMx no e- emission
add new terms
in Uext
(Time-resolved) observables
from electrons: dipole response (-> spectral analysis)ionization
> number of emitted e-
> kinetic E spectrum of emitted e-
> angular distribution of emitted e-
from ions: potential and kinetic (temperature) Eglobal deformation and shape
During or after cluster deposition, laser irradiation, …
from matrix: potential and kinetic (temperature) Eglobal deformation and shapeinternal excitation (dipoles)
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Cluster propertiesOptical responsePhotoelectrons
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Matrix propertiesGlobal excitationInternal excitation
Deposition dynamicsEnergiesSite depositionRole of charges
Guided tour example of deposition
short–range compressionlong –range polarization
Na8 in Ar164
Na6 on MgO(100)
final blue-shiftx y
z
subtle balancecore repulsion vs.
polarization attraction
broken x-y degeneracy geometry
Laudau fragmentation core repulsion
oblate
Optical response
Exp: Rostock
Com
pre
ssio
n
Polarization
Caution: "helium blue-shift"
embedded clusters
Rare gas not that inert…
Optical response
Photoelectron angular distributions
Na8
lase
r pol.
I = 109 Wcm-2
FWHM = 20 fs
=5.44 eV
IP=-4.3 eV
no state dependence !
MgO (or Ar)
no problem of orientation
Photoelectron angular distributions
free orientated Na8
state PAD, =2.6 eV
Na8 @ MgOtotal PAD, 3
suppressiontowards surface
Na8 @ Artotal PAD, 2
No orientation problem but…complex interactions with surface !
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Cluster propertiesOptical responsePhotoelectrons
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Matrix propertiesGlobal excitationInternal excitation
Deposition dynamicsEnergiesSite depositionRole of charges
Cluster ElectronsIons
MatrixCores Shells
Guided tour example of deposition
Charged atom depositionNa+ @ Ar384
Ekin0= 136 meV
Na: slight minimum
Na+: deep minimumthanks to Ar vacancy
fixed layers
Inclusion of Na+ in a
dynamically created
Ar vacancy
Deposition of Na dimers
Na2+ @ Ar384 Na2 @ Ar384
i) Na+ @ Ar384
ii) Na @ Na+/Ar383
more robust attachment when charged
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Cluster propertiesOptical responsePhotoelectrons
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Matrix propertiesGlobal excitationInternal excitation
Deposition dynamicsEnergiesSite depositionRole of charges
Cluster ElectronsIons
MatrixCores Shells
Guided tour example of deposition
Na6 deposition, Ekin0 = 136 meV/ion
fixed Ar cores fixed Ar dipoles full Ar
Dipole d.o.f
dynamical dipoles =
crucial ingredient for cluster dynamics
at impact…
Ar electronic response
Ekin0 = 136 meV/ion Eexc d2
Na+ Na6+
Na6Na
16 meV 9 meV
0.2 meV 1.2 meV
Na+ Na6+
Na6Nacharge effect >> size effect
Ar dipoles
Q= 0
NaQ @Ar Ekin0 = 136 meV
Q= 0, +1, -1
Q= +1Q= -1Important effect of chargeQ = 0 high Ar excitation energyThreshold for reflection: factor 20 between Na+ and Na
NaQ
Ar atoms
Dipoles ?
Ekin0 = 6.8 eVTime evolution of dipoles
Na6+@Ar384
Ekin0 = 800 meV/ionImpact
Longer time
Radial dipole distribution at different times
Localized excitation Sizeable dipole "noise" Moderate time evolution
Dipole localization
Initial
Conclusion and perspectives
Clusters and molecules @ environment
o Hierarchical approach for a generalized QM/MM• Nan@Ar,Ne,Kr done• Nan@MgO done• dynamical electronic response of substrate• Nan@MgO with defects in progress
o C,N,O,H @ H2O in near futureo C,N,O,H @ H2O @ rare gas in future
M. FarizonL. Sanche
Clustersdeposited on surfaceembedded in matrix
free
Exp Theory
(nano)technologiessurface engineering
Particular interest: rare gas substrates (Ne, Ar, Kr)« soft-landing » • AgN @ Pt(111) via Ar
Bromann et al., Science 274, (1996) 956• FeN @ Ru(001) via Ar
Lau et al., Low Temp. Phys. 29 (2003) 296
Context and motivations
Harbich et al., PRB 76 (2007) 104306
AgN+ codeposited with Ar @Au
fluorescence Ag1@Ar
luminescence Ag1+@Ar@Au
Neutralization ofAgN+ by
i.e- from Au thenii.going through Ar non trivial electronic effect of Ar matrix
Context and motivations
Na6 deposited on MgO structuremismatch
energy dependence
site dependence
P.M.Dinh, Séminaire LCPQ/LPT, 19 juin 2008
initial
Seifert et al., Appl. Phys. B 71 (2000) 795
Réponse optique Na8@Ar434 Na83+@Ar434
h = 1.9 eVI = 2×1012 W.cm-2
Δt = 50 fs (FWHM)
élargissement vers le rouge en accord avec exp