How Do Networks of Water Accommodate How Do Networks of Water Accommodate an Excess Electron?an Excess Electron?

Nathan I. Hammer, Joseph R. Roscioli, and Mark A. Johnson, Joseph R. Roscioli, and Mark A. JohnsonYale UniversityYale University

International Symposium on Molecular SpectroscopyInternational Symposium on Molecular Spectroscopy 6060thth Meeting – June 20-24, 2005 Meeting – June 20-24, 2005

Kit BowenKit Bowen

Mark JohnsonMark Johnson

Jim CoeJim Coe

Dan NeumarkDan Neumark

Photoelectron Spectra Reveal Three Isomer Classes of (HPhotoelectron Spectra Reveal Three Isomer Classes of (H22O)O)nn

J. V. Coe, et al., J. Chem. Phys., 92, 3980 (1990)J. Kim, et al., Chem. Phys. Lett., 297, 91 (1998)

J. –W. Shin, et al., Chem. Phys. Lett., 399, 349 (2004)J. R. R. Verlat, et al., Science, 309, 93 (2005)

0 10 20 30 40 50 60 70 80 90 1000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

Isomer IIIIsomer III

Isomer IIIsomer II

Ele

ctro

n B

indi

ng E

nerg

y (e

V)

Water Cluster Size n

Isomer IIsomer I

N. I. Hammer, et al., J. Phys. Chem. A, accepted (2005)

Water ClusterWater ClusterFD11 – 11:42

Bulk ?

mid - IR(600-4500 cm-1)500 mJ

10 Hz

YAG

1064 nmOPO/OPA

MCP ion detector

MCP neutral detector

reflectronvalve

pulsed

1 keV electron gun

ion beam

drift tube

YAG

PES detector

1064 nm

photo-electrons

L.M. Posey and M.A. Johnson, J. Chem. Phys., 88, 5383 (1988)

Synthesizing and Studying (HSynthesizing and Studying (H22O)O)nn and (H and (H22O)O)nn

·Ar·Armm

1100 1200 1300

Photon Energy (cm-1)

(D2O)6-

(D2O)4-

(D2O)3-

1500 1600 1700

Photon Energy (cm-1)

(H2O)6-

(H2O)5-

(H2O)4-

Isomer I Binds the Electron Primarily by Isomer I Binds the Electron Primarily by One Water MoleculeOne Water Molecule

N. I. Hammer, et al., Science, 306, 675 (2004)

How Do the Weaker Isomer Classes Bind the Excess Electron?How Do the Weaker Isomer Classes Bind the Excess Electron?

2 3 4 5 6 7 8 9 10 110.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Isomer IIIIsomer II

Ele

ctro

n B

indi

ng E

nerg

y (e

V)

Water Cluster Size n

Isomer I

AA Motif?

OH

0.0 0.2 0.4 0.6 0.8 1.0

(H2O)6

Electron Binding Energy (eV)

I

II

OHOD

HOH

DOD

Photoelectron Spectrum

1100 1200 1300

(D2O)6·Ar2

Photon Energy (cm1)

Electron Binding Energy (eV)

0.0 0.2 0.4 0.6 0.8 1.0

I

II

10 Ar

6 Ar

2 Ar

(D2O)6¯

*

1100 1200 1300

(D2O) 6·Ar 2

(D2O) 6·Ar 3

(D2O) 6·Ar 6

(H2O) 6

(D2O) 6·Ar 8

(D2O) 6·Ar10

1500 1600 1700 1800

1500 1600 1700 1800

Photon Energy (cm1)

(H2O)6·Ar4

Isomer I Only!

1100 1200 1300

1100 1200 1300

Photon Energy (cm1)

AD

AAD

AA

AAD

AD

ADD

Isomer IIIsomer I

ADDAD

AA

AAD ADD

AD

AAD

How Does Isomer II Bind the Excess Electron?How Does Isomer II Bind the Excess Electron?

How High Up in Size Do the Electron Binding Motifs Persist?How High Up in Size Do the Electron Binding Motifs Persist?

0 10 20 30 40 50 60 70 80 90 1000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

Isomer IIIIsomer III

Isomer IIIsomer II

Ver

tical

Det

achm

ent E

nerg

y (e

V)

Water Cluster Size n

Isomer IIsomer I

Johnson Lab

Prof. Mark A. JohnsonProf. Gary H. Weddle (Fairfield U.)Dr. Joong-Won ShinEric G. DikenJeffrey M. HeadrickJoseph R. RoscioliJoseph C. BoppKevin C. Jones

AcknowledgementsAcknowledgements

Dan NeumarkKit BowenKen JordanJohn Herbert

“Book” Neutral

“Armchair” Anion

“Book” Anion

“Book”AA Anion

How are the Anions Created?How are the Anions Created?

AA

vs.

Collective

• High dipole moment

• Bound to one side of cluster

• Requires much rearrangement from neutral clusters

• Low dipole moment

• Bound to one side of cluster or can be internally solvated in cage of water molecules

• Requires little rearrangement from neutral clusters

Comparing the Two Electron Binding Motifs Comparing the Two Electron Binding Motifs

AA Collective

Examples of the Two Electron Binding MotifsExamples of the Two Electron Binding Motifs