2028-15 joint ictp/iaea workshop on atomic and molecular data for...

2028-15

Joint ICTP/IAEA Workshop on Atomic and Molecular Data forFusion

Tilman MAERK

20 - 30 April 2009

Universitat Innsbruck, Institut fuer Physik, 81 Technikerstrasse, A-6020Innsbruck

Austria

Molecular Processes in Plasmas

Tilmann MärkUniversität Innsbruck

Tyrol

Vienna

ItalySlowenia

SlowakiaGermany

Czech republicSw

itzer

land

Hungary

Institut für Ionenphysik und Angewandte PhysikEURATOM

ÖAW

Ion Physics / Plasma Physics

Clusterphysics, Biomolecules

Mass Spectrometry

Environmental Physics and Analysis

http://info.uibk.ac.at/ionenphysikhttp://info.uibk.ac.at/ionenphysik

E. Alizadeh, F. Ferreira da Silva, F. Zappa, A. Mauracher, M. Probst, S. Denifl, A. Bacher, T. D. Märk, P. Limao-Vieira, P. Scheier, Dissociativeelectron attachment to nitromethane. Int. J. Mass. Spectrom. 1-3/271 (2008) 15-21 PDF; doi:10.1016/j.ijms.2007.11.004; IF:2.337

A. Mauracher, P. Sulzer, E. Alizadeh, S. Denifl, F. Ferreira da Silva, M. Probst, T. D. Märk, P. Limao-Vieira, P. Scheier, Electron attachment studiesto musk ketone and high mass resolution anionic isobaric fragment detection. Int. J. Mass. Spectrom. 1-3/277 (2008) 123-129 PDF; doi:10.1016/j.ijms.2008.06.006; IF:2.411

S. Ptasinska, E. Alizadeh, P. Sulzer, R. Abouaf, N. J. Mason, T. D. Märk, P. Scheier, Negative ion formation by low energy electron attachment to gas-phase 5-nitrouracil. Int. J. Mass. Spectrom. 1-3/277 (2008) 291-295 PDF; doi:10.1016/j.ijms.2008.06.008; IF:2.411

P. Sulzer, E. Alizadeh, A. Mauracher, T. D. Märk, P. Scheier, Detailed dissociative electron attachment studies on the amino acid proline. Int. J. Mass. Spectrom. 1-3/277 (2008) 274-278 PDF; doi:10.1016/j.ijms.2008.06.001; IF:2.411

Elahe AlizadehPhD student6268 / Lab: [email protected]

Masoomeh Mahmoodi-DarianPhD student6268 / Lab: [email protected]

Data acquisition (processes, properties) Data analysis and assessmentData compilation (ADAS, IAEA)

1. Intrinsic fundamental interest2. Provide data needed for plasma modelling

and diagnosis and other applications3. Radiation damage

Elementary processes considered:Inelastic electron interactions withatoms/molecules/nanoparticles(ionization and attachment)

Institutfür

Ionenphysik

EURATOMÖAW

AB + e → AB+ ionization→ A+ + B dissociative ionization→ AB* excitation→ ……

Inelastic low-energy electroninteraction with molecules

AB + e → AB-# electron capture

Dissociative Electron Attachment

Dissociative electron attachment AB + e- => AB-* => A- + B can be described via the formation of a temporary negative ion AB-*. The electron in this molecular anion state AB- (also called the resonant state) can autodetach with a finite lifetime (related to the width of the resonance), leaving behind a vibrationally excited neutral molecule. On the other hand, if the lifetime of the resonance is long enough, the anion AB- can dissociate into A+B-, leading to the process of dissociative electron attachment.

AB + e → AB-# transient negative ion

Electron attachment to molecules

AB-# → AB + e autodetachmentAB-# → AB- stabilization

AB-# → A + B- DEA

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 150

2

4

6

8

10

ion

yiel

d (a

rb. u

nits

)

electron energy (eV)

Positive ion productioncross sections

DEA

4.Photons

0 2 4 6 80

1

2

3

4

5

Ionization with e- release: H+ impact [17]

Total ionization:

e- impact [8] Direct ionization:

H+ impact (present data) Ionization with e- release:

H+ impact [10]

Cro

ss s

ectio

n (1

0-20

m2 )

Velocity (vBohr)

H2O + p+ → ions + p+ DI

H2O + p+ → ions + H EC

Origin of life (photosynthesis)

Life in space

Radiation damage at a molecular level

Improved radiation therapy

In space electrons are released via photon matter interactions (photo effect and photo ionization): origin of life

High-energy projectiles release in matter ~40000 electrons per MeV deposited energy with kinetic energies below 20eV: radiation damage

0 10 20 30 40 50 60

N(E

), σ(

E) (a

rb. u

nits

)

Energy (eV)

Secondaryelectron tail

Electroncross sectioni

oniza

tion

DEA

0 10 20 30 40 50 60

N(E

)× σ

(E) (

arb.

uni

ts)

Energy (eV)

ionization

Low-energy electrons have high damage cross sections

DEA

The genotoxic effects of ionizing radiation(α,β,γ,Χ) in living cells (therapeutic, diagnostic) are not only due to the primaryimpact.

The genotoxic effects of ionizing radiation(α,β,γ,Χ) in living cells (therapeutic, diagnostic) are not only due to the primaryimpact.

Single and double strand breaks may beinduced by secondary species: =secondary electrons with kinetic energiesbelow about 20 eV thermalized and sol-vated by inelastic collisons within

OutlineEURATOM

ÖAW

Part I: FundamentalsA. Ionization processes and Ions producedB. Ionization mechanisms

Part II: Kinetics and energetics for theproduction of cations and anions

Part III: Electron attachment

EURATOMÖAW

Direct Ionization – Indirect ionization

Stable ions – unstable (metastable) ionsSingly-charged ionsMultiply-charged ionsParent ions – fragment ionsCations - anions

Part I: FundamentalsA. Ionization processes and Ions produced

Electron-Particle Interaction

e + cluster : ♦ multiple collisions♦ intra-cluster reactions

e + atom : ♠ electronic excitation

e + molecule : ♠ electronic excitation♠ vibrational excitation♠ rotational excitation♠ dissociation

Electron-Particle Interaction

Primary ionization eventEnergy storage and disposalFinal reaction products

ABC + e → [ABC+]* → A+ + BC + KER

A + e → A + e elastic scatteringA* + e excitationA** + e double excitation (A** → A+ + e)A+ + 2e ionizationA+* + 2e excited ion (A+* → A++ + e)A++ + 3e double ionizationA- + hv attachment

Electron impact ionization processes

AB + e → AB + e elastic scatteringAB* + e excitationAB** + e double excitation (AB** → AB+ + e)AB+ + 2e ionizationAB+* + 2e excited ion (AB+* → AB++ + e)AB++ + 3e double ionizationAB- + hv attachment (AB- → A- + B)

Electron impact ionization processes

AB + e → AB(v,k) + e vibrational, rotational excitationA + B dissociationA+ + B + 2e dissociative ionizationA+ + B + + 3e dissociative double ionizationA+ + B+- + e ion pair formationA++ +B + 3e double dissociative ionization

Direct and indirect ionization processes

200 300 400 500 600 70010-1

100101102103104105106

C605+

C603+ C 60

+C602+

Ion

c urr

ent (

Hz)

Mass per charge (Thomson)

C 4+60

C60 + e → parent & fragment ions (200 eV)

102 1030

10

20

30Io

n sig

nal (

Hz)

Mass per charge (Thomson)

13C212C15

2+

13C

12C

1612C

17

2+

,13

C21

2 C33

4+

13C

12C

334+

,12

C34

4+ ,12

C 516

+

13C

12C

506+

13C

12C

425+

12C

435+

13C212C58

7+

&

13C12C597+

12C607+

C60 + e → multiply charged ions

EURATOMÖAW

Part I: FundamentalsB. Ionization mechanisms

1. Franck Condon principle

2. Unimolecular dissociation

H2 + e → H2+

→ H+

H2+H2+

H2+

→H + H+

Internuclear distance in 10-8 cm

V(r) in eV

d = 0.586

15.4 eV adiabatic ionization energy !!

18.1

Ionization mechanism I: The Franck Condon principle

E=100 eV: v=6x108cm/s; t=s/v=10-8/6x108 ~ 2x10-17s « tv~10-14s

The Franck Condon principle

Electron impact ionization: mechanism

Reflection principle

Franck Condon Factors


The Franck Condon Range and different Cases

E=100 eV: v=6x108cm/s; t=s/v=10-8/6x108 ~ 2x10-17s « tv~10-14s


The Franck Condon principle

15.424 (15.47)

18.09 (18.08)

H2 + e → H2+

→ H+

H2+H2+

H2+

→H + H+

Distance in 10-8cm

V(r) in eV

BE (H-H+) = 2.666 eV

av

AE and BE of molecules

HEM data analysis:O3 + e → O3+(O3)2 + e → (O3)2+

Fit function: σ(E) = b + σo ·(E-IE)p

1

10

100

7 8 9 10 11 12 13 14-3

0

3

6

9

O3+/O3

Corrected electron energy (eV)

Ion

sign

al (

arb.

uni

ts)

(O3)2+/(O3)n

ΑΕ: 12.70 ± 0.02 eV

ΑΕ: 10.10 ± 0.2 eV

HEM data analysis:O3 + e → O3+(O3)2 + e → (O3)2+

D(O3- O3): 0.13 eV

D(O3+- O3): 2.70 eV

10.10(22) eVIE((O3)2

+)

O3+ + O3

(O3)2

(O3)2+

O3+

O3

12.70(2) eVIE(O3

+)

Binding energy of ozone dimer ion:

„dimer geometry“

„twisted boat“

„O2 – O4+ “

Photoelectron spectroscopy:Adiabatic & vertical IE

(AB…CD) + e → → parent & fragment ions

(AB…CD)+* → → →→ A+ + BCD* → A+ + B + CD→ AB+* + CD* → A+ + B + CD

A + B+ + CD→ A + BCD+* → A + B+ + CD

A + B + CD+→ AB* + CD+ → A + B + CD+

Ionization mechanism II: Vibrational predissociation

Decay paths for parent ion formed: If the the molecular ion is complexenough so that Lissajous motion on the potential energy hypersurface issufficiently complicated, the existence of metastable ions can berationalized in the framework of QET or RRKM.

Ionization of alkenes:

CnH2n+2 + e →parent & fragment ions


C3H8 + e → parent & fragment ions(decay paths & relative abundance in mass spectrum)


AE = 43.7 eVIE = 7.6 eV

BE + KS

C60 + e →

C60+ C58+

Final result for the C60+ binding energy

Experiment: 17 Measurements - which have been analysed by using the complete today’s knowledge- yield a binding energy(mean value) of

10.0 ± 0.2 eVTheory: A.D.Boese and G.E.Scuseria have carried out very accurate

D(ensity)F(unctional)T(heory) calculations and obtain for the ionicC60+ binding energy

10.2 eV

Binding energy (10 eV) larger than ionization energy (7.6 eV) !!!

Infrared multiphoton excitation, dissociation and ionization of C60 , M.Hippler, M.Quack, R.Schwarz, G.Seyfang, S.Matt, T.D.Märk, Chem.Phys.Lett. 278(1997)111

500 hν ≈ 61 eV

emovie

Unimolecular (metastable) dissociation

3 major mechanisms:

1. Vibrational (statistical) predissociation

2. Electronic predissociation

3. Tunneling through a (rotational) barrier

Electronic predissociation: Transition forbidden by (i) some selection

rule or (ii) hindered by small overlap integral

SH2 + e → [SH2+]*

[SH2+]* → S+ + H2

Tunneling through a barrier

0.5 1.0 1.5 2.0 2.5-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Ene

rgy

(eV

)

RN(1)-H (Å)

(U-H)+Hπ2*

Dipole bound state

(U-H)-+H

σ*(N1-H)

01

0 1 20

1

2

3

Cro

ss s

ectio

n (1

0-20

m2 )

Electron energy (eV)

2

ν=2

3

ν=3

U + e → (U-H)- + H

Schematic potential energy curves for uracilalong the N1-H streching coordinate. DBS: Kaufmann, Bowen, Schermann

ν3: N Feshbach Resonance: H atomtunneling will be rapid (broad width)ν2: NFR: barrier for tunneling large, lifetime longer and narrower width

1

(U-H)-

Tunneling of H from N1 site, throughpotential barrier formed by avoided curvecrossing of the dipole bound state and theantibonding σ*(N1-H) anion state

Stretching coordinate

Tunneling through barrier

Veff effective potential energycombination of V plusrotational energy of diatomic

V potential for L=0

J =K=Lrotational quantum number


Time evolution of the ionization process


Time evolution of the ionization

process

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