ROTATIONALLY RESOLVED ROTATIONALLY RESOLVED AA22AA11——X X 22E E

ELECTRONIC SPECTRA OF DEUTERATED ELECTRONIC SPECTRA OF DEUTERATED ISOTOPOMERS OF THE METHOXY RADICALISOTOPOMERS OF THE METHOXY RADICAL

Jinjun LiuJinjun Liu, Ming-Wei Chen, Ming-Wei Chenand Terry A. Millerand Terry A. Miller

Laser Spectroscopy FacilityDepartment of ChemistryThe Ohio State University

6/21/2007

~~ ~~

Outline

Talk II (RF02): CHD2O Introduction: asymmetric deuteration Theory: PES, effective Hamiltonian Experimental setup and spectral

result Global fitting and molecular

constants Discussion: lifting of vibronic

degeneracy Summary and future work

Talk II (RF02): CHD2O Introduction: asymmetric deuteration Theory: PES, effective Hamiltonian Experimental setup and spectral

result Global fitting and molecular

constants Discussion: lifting of vibronic

degeneracy Summary and future work

Talk I (RF01): CH3OTalk I (RF01): CH3O

Asymmetric Deuteration

Introduces asymmetries in the PES Reduces the symmetry of the normal vibrations

without affecting the electronic symmetry properties Helpful in the investigation of systems that are subject

to vibronic coupling (e.g., Jahn-Teller effect ) by “decoupling” the correlation between electronic and nuclear dynamics: lifts the vibronic degeneracy through ZPE effects reveals the geometry distortion in the case of dynamic

Jahn-Teller distortion decouples the Jahn-Teller effect and spin-orbit interaction

Reduces the permutational symmetry Helpful in understanding the properties of molecules

performing large-amplitude motions (tunneling/free rotation)

Introduces asymmetries in the PES Reduces the symmetry of the normal vibrations

without affecting the electronic symmetry properties Helpful in the investigation of systems that are subject

to vibronic coupling (e.g., Jahn-Teller effect ) by “decoupling” the correlation between electronic and nuclear dynamics: lifts the vibronic degeneracy through ZPE effects reveals the geometry distortion in the case of dynamic

Jahn-Teller distortion decouples the Jahn-Teller effect and spin-orbit interaction

Reduces the permutational symmetry Helpful in understanding the properties of molecules

performing large-amplitude motions (tunneling/free rotation)

Asymmetric Deuteration: A Chronicle

1964 : ESR of Jahn-Teller related molecules [1] Benzene anion (C6H5D-): different spectra after single

deuteration Cyclo-octatetraene anion (C8H7D-): no difference

1964-: ESR of matrix-isolated molecules 1982 : Optical spectroscopy of benzene in gas phase [2]

Direct measurement of the splitting of the degenerate states 1993 : Rotationally resolved LIF spectra of asymmetrically

deuterated cyclopentadienyl (C5H4D, C5HD4) [3] Two vibronic bands (ΔE~±9cm-1) showing the lifting of the

vibronic degeneracy Rotational analysis of the split states revealing different

symmetry and geometry of the two split states 2007 : Rotationally resolved PFI-ZEKE spectra of

asymmetrically deuterated methane cation (CH3D+, CHD3+)

[4] Isotopic isomers Tunneling-free pseudorotation structure

1964 : ESR of Jahn-Teller related molecules [1] Benzene anion (C6H5D-): different spectra after single

deuteration Cyclo-octatetraene anion (C8H7D-): no difference

1964-: ESR of matrix-isolated molecules 1982 : Optical spectroscopy of benzene in gas phase [2]

Direct measurement of the splitting of the degenerate states 1993 : Rotationally resolved LIF spectra of asymmetrically

deuterated cyclopentadienyl (C5H4D, C5HD4) [3] Two vibronic bands (ΔE~±9cm-1) showing the lifting of the

vibronic degeneracy Rotational analysis of the split states revealing different

symmetry and geometry of the two split states 2007 : Rotationally resolved PFI-ZEKE spectra of

asymmetrically deuterated methane cation (CH3D+, CHD3+)

[4] Isotopic isomers Tunneling-free pseudorotation structure

[1] A. Carrington, H. C. Longuet-Higgins, R. E. Moss, P. F. Todd, Mol. Phys. 9, 187 (1965) [2] B. Sharf, R. Vitenberg, B. Katz, Y. Band, J. Chem. Phys. 77, 2226 (1982)[3] L. Yu, D. W. Cullin, J. M. Williamson, T. A. Miller, J. Chem. Phys. 98, 2682 (1993)[4] H. J. Wörner and F. Merkt, J. Chem. Phys. 126, 154304 (2007)

Lifting of Vibronic Degeneracy: a qualitative view

COH

Cs

A’

D

DCO

HCs

A” H

H

C3

v

E

D

D

PES

Normal JT (linear only)

aQ

U

2 20

2 2 1/ 21

1( )

2

( )

a b

a b

U k Q Q

k Q Q

U

aQ

JT w/ SO2

2

20

2 2 1/ 21

1( )

2

[ ]( )2

a b

a be

i

a d

k

U k Q Q

k Q Q

(CH3O, CD3O)

JT w/ SO & asym. deuteration2 2

0

2 2 1/1

0

1

22

1( )

2

[(2

)2

) ](

a b

a be

i

E a d

U k Q Q

kk

Q Qk

aQ

U

(CH2DO, CHD2O)

bQ

CH3O and CD3O:

HEFF = HROT + HCOR + HSO + HSR + HJT + HCD

Effective Hamiltonian: ground state

CH2DO and CHD2O:

Reduction of molecular symmetry (C3vCs):

HROT, sym HROT, asym (B-C)/2

HCOR, sym HCOR, asym θ

HSO, sym HSO, asym θ

HSR, sym HSR, asym εac , (εbb-εcc)/2

Removal of electronic degeneracy of the

vibrationless level: + HQ

(1/ 2)

(1/ 2)

x y

x y

e e i e

e e i e

0 2

02Q

E eH

eE

or

* D. Melnik, J. Liu, R. F. Curl, T. A. Miller, Mol. Phys. 105, 529 (2007)

02

0 2

x

Qy

E eH

E e

ΔE=Ex(A’)-Ey(A”)

with

CH2DO

CHD2O

Principal Axis Sys.Internal Axis Sys.

Experimental Apparatus: LIF & SEP, hi & mod. res.

CH2DONO/CHD2ONO/CD3ONO+1st run Ne

General Valve ControllerDG535 Pulse Generator

XeF Excimer Laser

XeCl Excimer Laser

Ar+ Laser

Nd:YAG Laser Sirah Dye Laser

Pulsed Dye Amplifier

PC #1

PC #2

Nozzle

Ring Laser

T0

PMT

SHG

SHG

Frequency reading

Photolysis

Q-Switch

Flash Lamp

T0 / GPIB

T0

program

0

11 '

S

SS

synchronizing

Lens

Experimental

Simulation

CHD2O, 320 Band

Experimental

Simulation

CHD2O, 320 Band

Accomplishment and Drawback

Global fitting of mw* and LIF (two rotationally resolved vibronic bands: ) spectra for CHD2O and CH2DO with standard deviation consistent with the experimental accuracy (<3MHz for mw and ~50MHz for LIF). Vibronic degeneracy is lifted by the asymmetric

deuteration ΔE at the same order of magnitude as aξed (50-60cm-1)

but different sign for CHD2O (+) and CH2DO (-) Validity of the Hamiltonian

Combined fitting of LIF spectra (two bands) for CD3O.

Global fitting of mw* and LIF (two rotationally resolved vibronic bands: ) spectra for CHD2O and CH2DO with standard deviation consistent with the experimental accuracy (<3MHz for mw and ~50MHz for LIF). Vibronic degeneracy is lifted by the asymmetric

deuteration ΔE at the same order of magnitude as aξed (50-60cm-1)

but different sign for CHD2O (+) and CH2DO (-) Validity of the Hamiltonian

Combined fitting of LIF spectra (two bands) for CD3O. The upper component of the spin-orbit splitting (E1/2) is

accessible to neither of the experiment (mw and LIF, T~3K) ΔE and aξed can not be well-determined for CHD2O and

CH2DO due to the strong correlation between them ( ) and lack of information of the E1/2 state

The upper component of the spin-orbit splitting (E1/2) is accessible to neither of the experiment (mw and LIF, T~3K)

ΔE and aξed can not be well-determined for CHD2O and CH2DO due to the strong correlation between them ( ) and lack of information of the E1/2 state

( , ) 0.999858eCor a d E

* D. Melnik, V. Stakhursky, V. A. Lozovsky, T. A. Miller, C. B. Moore and F. C. De Lucia, WJ09, 59th International Symposium on Molecular Spectroscopy, 2004.

2 1 2 20 0 1 3/23 and (6') of A EA X

32915 32920 32925 32930 32935 32940

Pa

inte

nsity

(a.

u.)

frequency / cm-1

LIF of CHD2O,

32

0 band of A2A

1-X 2E

3/2

high-res moderate-res

Pb

32915 32920 32925 32930 32935 32940

Pa

inte

nsity

(a.

u.)

frequency / cm-1

LIF of CHD2O,

32

0 band of A2A

1-X 2E

3/2

high-res moderate-res

Pb

SEP experiment of CHD2O: pump transitions

~2

3/2EX

~2

1AA

~2

1/2EX

LIF

32845.4 32845.6 32845.8 32846.00.58

0.60

0.62

0.64

0.66

0.68

0.70

0.72

0.74

0.76

0.78

norm

aliz

ed L

IF

frequency / cm-1

Depletion: ~15%

Linewidth (FWHM): ~200MHz

Freq. Accuracy (1): <100MHz

*

SEP dip by Pa

* LIF excited by dump laser32845.4 32845.6 32845.8 32846.0

0.58

0.60

0.62

0.64

0.66

0.68

0.70

0.72

0.74

0.76

0.78

norm

aliz

ed L

IF

frequency / cm-1

Depletion: ~15%

Linewidth (FWHM): ~200MHz

Freq. Accuracy (1): <100MHz

*

SEP dip by Pa

* LIF excited by dump laser

SEP experiment of CHD2O: dump transitions

~2

3/2EX

~2

1AA

~2

1/2EX

LIF

SEP

SEP experiment of CHD2O: List of transitions

*Too weak to be observed in the high-resolution SEP experiment.

Pump transition Pump freq.

Dump transition Dump freq.

Obs. Cal. Cal.–Obs.

|J’,N’,K’,p’> - |J”,K",Σ”,p”> (cm-1) |J’,N’, K, p’> - |J , K, Σ, p> (cm-1) (cm-1) (cm-1)

Pa

|1/2, 1, 1, -1> - |1/2, 0, 1/2, 1> |3/2, 1, 1, -1> - |1/2, 0, 1/2, 1>

32929.48

|3/2, 1, 1, -1> - |5/2, 2, -1/2, 1> 32842.2258 32842.2251 0.0007

|1/2, 1, 1, -1> - |3/2, 2, -1/2, 1> 32845.4907 32845.4900 0.0007

|3/2, 1, 1, -1> - |3/2, 2, -1/2, 1> * 　 　

|1/2, 1, 1, -1> - |3/2, 0, -1/2, 1> * 　 　

|3/2, 1, 1, -1> - |3/2, 0, -1/2, 1> 32855.5429 32855.5472 -0.0043

|1/2, 1, 1, -1> - |1/2, 0, -1/2, 1> 32856.4708 32856.4690 0.0018

|3/2, 1, 1, -1> - |1/2, 0, -1/2, 1> 32856.4806 32856.4778 0.0028

Pb

|1/2, 0, -1, 1> - |1/2, 0, 1/2, -1>32928.47

|1/2, 0, -1, 1> - |3/2, 2, -1/2, -1> 32845.4461 32845.4474 -0.0013

|1/2, 0, -1, 1> - |3/2, 0, -1/2, -1> * 　 　

|1/2, 0, -1, 1> - |1/2, 0, -1/2, -1> * 　 　

14

320 Band 74

(6')10 Band 96

6190

Weight 5000:2:10.84276

Summary of Global Fitting

# Assigned transitions

microwave

LIF

Total

CHD2O

SEP

microwave:LIF:SEP

Standard Deviation (MHz)microwave

SEPLIF

14

320 Band 74

(6')10 Band 96

6190

Weight 5000:2:10.84276

Summary of Global Fitting

# Assigned transitions

microwave

LIF

Total

CHD2O

SEP

microwave:LIF:SEP

Standard Deviation (MHz)microwave

SEPLIF

Global Fitting: mw, LIF & SEP

A 3.1735 (14

)

(B+C)/20.79001 (24

)

Aζt 0.997 (10

)

Dk, DNK, DN ,ηeζt, ηKζt0　 c 　

aζed-53.44 (50

)

aDζed0.0364 (38

)

εaa

-0.8686 (58)

εbc

0.130 (16)

ε1

0.0019 (16)

ε2a

-0.0438 (45)

ε2b -0.0109 d

h1 -

0.00033 (36)

h2 0.1212 (47

)

h1K

-0.00059

1 (65)

h2K

-0.00579

(40)

h1N, h2N, h40　 c 　

ΔE-48.30 (55

)

(B-C)/2 0.02297 (24)

θtilt

-1.94 (17)

εab, εab_asym 0　 c

a. In cm-1, b. 2.5σ in parentheses c. fixed

d.fixed to ε2a*(B+C)/2A

Rotational

Spin-Orbit

CoriolisCentrifugal Distortion

Spin-Rotation

Jahn-Teller

Asym.

ΔE=Ex(A’)-Ey(A”):

Principal Axis Sys. Internal Axis Sys.

ΔE=Eb(A’)-Ec(A”) = +45.09(468)cm-1

ΔE=Ec(A’)-Eb(A”) = -48.30(55)cm-1

Ab initio*: -47cm-1

* B3LYP/6-31+G(d,p) Freq=ReadIsotopes* Not scaled* Cs geometry from: A. V. Marenich, J. E. Boggs, J. Mol. Structure,  780, 163 (2006)

Ab initio*: 43cm-1

Eb(A”)>Ec(A’)

Eb(A’)>Ec(A”)

“mass dependent”

CH2DO

CHD2O

θ<5o

Summary and Future Work

New high-resolution SEP spectra of CHD2O, which connects the and states.

Correlation between now broken Molecular constants for ground electronic

state from the global fitting (mw, LIF, and SEP)

New high-resolution SEP spectra of CHD2O, which connects the and states.

Correlation between now broken Molecular constants for ground electronic

state from the global fitting (mw, LIF, and SEP)

23/2EX 2

1/2EX

and ea d E

SEP spectra of CH2DO and CD3O Vibronic analysis involving dispersed

fluorescence spectra of CHD2O Quantitative analysis and comparison

SEP spectra of CH2DO and CD3O Vibronic analysis involving dispersed

fluorescence spectra of CHD2O Quantitative analysis and comparison

Acknowledgement

Miller GroupGOES @ OSU

Merkt GroupXUV @ ETH

Thank You!

$NSF$

Robert Curl