"Environmented" electronic systems Deposited clusters or molecules: on rare gas surface ->...

"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)

IIII

Cluster propertiesOptical responsePhotoelectrons

II

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 !

IIII


II



Cluster ElectronsIons

MatrixCores Shells


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

IIII


II



Cluster ElectronsIons

MatrixCores Shells


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

"Environmented" electronic systems Deposited clusters or molecules: on rare gas surface ->...

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