Funded by: DoE.

Anh T. Le and Timothy C. SteimleDepartment of Chemistry and BiochemistryArizona State University, Tempe,AZ 85287 *

Varun Gupta, Corey A. Rice and John P. MaierDept. of Chem. Univ. of Basel, Basel, Switzerland ‡

Sheng H. Lin and Chih-Kai LinDepartment of Applied Chemistry

National Chiao Tung UniversityHsinchu, Taiwan

Visible spectrum of ZrO2

The 66th International Symposium

on Molecular Spectroscopy, June 2011

‡ Swiss National Science Foundation

Motivation• Bonding in transition metal triatomic molecules.

Structure: a) inserted b) T-shape c) superoxide ; M-OO

•Properties of excited states photochemical precesses a) R and b) vibrational frequencies c) electric dipole moments

TiO2 Publications: PCCP 11, 2649 (2009) ; PCCP 12 15018 (2010)

Previous studies (Exp.)

Structure determination of the X1A1 state. = =108.1 R=1.7710 Å

Pure Rot

X1A1 1 = 887 40 cm-1PES anion

Electrostatic deflection Bent

Matrix isolation IR 1 = 884 cm-1 3 = 818 cm-1

Previous studies (Theory)

X1A1 state properties at RCCSD(T)

X1A1 state properties at CASSCF-CCSD(T)

X1A1 & a3B2 state properties at TD-DFT & EOM-CCSD

No predictions for the A1B1 state.

Experimental method-ASU

Well collimatedmolecular beamRot.Temp.<20 K

Pulsed dye laser

PMT

Box-car integrator

Metal target

Pulse valve

•skimmer

Ablation laser

Reagent&

Carrier

•Zr

Optimized for ZrO2

•Long box-car gate width •Low ablation power

Resolution 0.2 cm-1

Monochromator

PMT

Experimental method-Basel

Pulsed OPO laser

Metal target

Pulse valve

•skimmer

Ablation laser

Reagent&

Carrier

•Zr

Resolution 3 cm-1

F2 (157 nm) laser

MCPIon Detector

Mass-Selected REMPI

Observation REMPI spectra a

LIF low resolution

a.Department of Chemistry, University of Basel, Basel, Switzerland

ZrO2 Dispersed Fluorescence

Position of laser

Progression on

Progression on

Progression of

on top of 1Progressi

on on on top

of 3

DLIF

sig

nal

Wavelength (Å)

17041 cm-1

17562 cm-1

17870 cm-1

ZrO2-Dispersed Fluorescence Analysis

• 268 shifts from 13 bands fluorescence down to ground states

))(()(),,( 21

21

31 3121

31321

ki

i kiki

iiE vvvTvvvG

1

2

3

33

22

Experiment Calculation

Here

898(1)

287(2)

808(2)

9.86(52)

3.52(48)a) Zheng & Bowen J.Phys. A (2005) 109, 11521.

Matrixa

884.3

818

B3LYPb

b) Chertihin & Andrews , J. Phys. Chem. (1995) 99, 6356.

CCSD(T)/Lb

887

281

835

906

295

854

RCCSD(T)c

c) Mok, Chau, Dyke & Lee, Chem. Phys. (2008) 458, 11.

909

278

841

TiO2

968(7)

321(4)

frr=Stretch-stretch force constant

Note: 1 3 frr(X1A1)0

X1A1 Parameters:

Excitation Spectra Assignment

(0,0

,0)

Analogy to TiO2 : X1A1(0,0,0) A1B2(v1,v2,v3)

TiO2 A1B2 state: 1= 876(3), 2 = 184(1), 3 = 316(2)

(0,1

,0)

(0,2

,0)

(0,3

,0)

(0,4

,0)

(0,0

,1)

(0,0

,2)

(0,0

,3)

(1,0

,0)

(2,0

,0)

ZrO2-Excited State Analysis • 40 spectral features in excitation spectra were assigned to 45 transitions

))(()(),,( 21

21

31 3121

31321

ki

i kiki

iiE vvvTvvvG

817(4)

149(4)

519(3)

3(2)

4.43(75)

-

8.50(78)

16307(8

)

854.5

181.3

419.7

16753

794.1

181.8

349.6i

13733

867(3)

184(1)

316(2)

17593

Very Poor agreement

1

2

3

12

23

Exp Calculationa TiO2

33

e

LanL2DZ CASSCF

a) Part of the current study S.H Lin & C-K. Lin Nat. Chaio Tung Univ.

Note: 1 >> 3

frr(A1B2) is significant.

ZrO2 A1B2 Parameters:

Spectral Simulation

Exp. iR, (X1A1) and

Exp. i (A1B2) and

Guess R, (A1B2)

GF MatrixMethods

Assume frr(X1A1)=0fr(A1B2)=0

Duschinskytransformation

Transitionwavenumbe

r and FCF calculation

Predicted SpectrumObserved SpectrumVisual comparison

ImprovedR, (A1B2)

Goal: use only experimental info to predict X1A1(0,0,0) A1B2(v1,v2,v3) spectrum

2

3

2

21 00,0 FCF

X1A1(0,0,0)

A1B2(1,2,3)

Two dimensional (2D) overlap integral for the a1 modes.

One dimensional (1D) overlap integral for the b2 mode. Assuming displaced & distorted harmonic

oscillators Analytical expressions: “2D”: Chang. JCP 128, 174111 (2008)

“1D”: Chang. JMolSpec 1232, 1021 (2005)

Normal coordinates of lower state

Normal coordinates of upper state

Coordinate of lower state

Coordinate of upper state

Spectral Simulation (cont.)

DJQQ )~

()~

( 2

1

1

1 BAAX

Need to relate Q(X1A1) to Q(A1B2). Duschinsky transformation:

Essential :

Also, displacement of nuclei:

Wilson’ “B” matrix: “G” “B”“B”T “L” symmetry coor., S Normal coor., Q, transform

Peter Chen’s review article (“Unimol Rxn Dyn” 1994):

Spectral Simulation (cont.)

0.997100

00.93500.3546-

00.35460.9350

J

0

0.5535

0.5185

D

Intensity Transition Moment Squared

Need A1B2/ B1A1vibronic coupling:

Wavefunction:

A1B2 (1, 2 ,odd ) X1A1(0,0,0) =0 (i.e. odd-3 forbidden)

Even-3 transitions

Odd-3 transitions

Adjustable parameter

Vibronic coupling term

Spectral Simulation (cont.)

(cm-1)

PredictedNo vibronic coupling

Predicted with vibronic coupling

Spectral Simulation (cont.)

ObservedGood!

The best structure and coupling for A1B2 state:

•Vibronic coupling term

1.1

•Bond length Re =1.828 Å bond angle =99º

6900 cm-121 10000 cm-1

Too Big !

Spectral Simulation (cont.)

Consistent with TiO2

X1A1

A1B2

B1A1

C1A2

D1B2

E1B1

Summary

•Large reduction in vibrational frequencies upon excitation (like TiO2).

•Odd-3 quanta transition observed (unlike TiO2).

•First recording and analysis of electronic transitions

for ZrO2. •Vibrational parameters benchmarks for future ab initio

•Simulation of excitation spectra in reasonable agreement with observation.

Anh Le

Fang WangDr. Xiujuan

Zhuang

Sarah Frey Thank you !

A1B2(0,2,0)

A1B2(0,2,1)

A1B2(1,2,0)

Also a manifestation of vibronic coupling.

Trends in lifetimes