HIGH-RESOLUTION

LASER-INDUCED FLUORESCENCE (LIF) SPECTROSCOPY

OF THE DEUTERATED ISOTOPOMERS

OF THE METHOXY RADICAL

06/20/06

JINJUN LIU, JOHN T. YI AND TERRY A. MILLER

Laser Spectroscopy FacilityDepartment of Chemistry

The Ohio State University

Outline

Talk I (TJ04): Motivation and goals Experiment

Experimental apparatus Calibration method Error analysis and experimental accuracy

CH3O, control and example Simulation and fitting Prediction of microwave transitions

Summary

Talk I (TJ04): Motivation and goals Experiment

Experimental apparatus Calibration method Error analysis and experimental accuracy

CH3O, control and example Simulation and fitting Prediction of microwave transitions

Summary

Talk II (TJ05): CH2DO and CHD2O

Experiment Effective Hamiltonian Transition intensities

CD3O Global fitting (LIF and microwave) Summary and future work Acknowledgment

Talk II (TJ05): CH2DO and CHD2O

Experiment Effective Hamiltonian Transition intensities

CD3O Global fitting (LIF and microwave) Summary and future work Acknowledgment

Motivation

CH3O(X 2E)~

Energy/103cm-1

30

20

10

0

CH3+O(3P)

HCO+H2

CH2OH

CH3O(A 2A1)~

H2CO+H

Alkoxy radicals (RO·) are key components in the oxidation of hydrocarbons both in combustion and in the atmosphere.

Methoxy (CH3O), the simplest alkoxy radical is an interesting molecule for dynamic studies.

CH3OCH2O+H Methoxy has also very important theoretical interest

due to its Jahn-Teller effect, coupled to spin-orbit interaction.

The partial deuteration of the methoxy radical (CHD2O & CH2DO).

Breaks the molecular symmetry. Removes the degeneracy in the electronic ground state. Turns Jahn-Teller effect to pseudo-Jahn-Teller effect. Introduces new terms into the rovibronic Hamiltonian of

CH3O.• Extra vibrational bands.• Different rotational structures.

* J. Han, Y. G. Utkin, H. Chen, L. A. Burns, and R. F. Curl, J. Chem. Phys. 117, 6538 (2002).* A. Geers, J. Kappert, F. Temps, and J. W. Wiebrecht, J. Chem. Phys. 101, 3618(1994)* J. J. Orlando, G. S. Tyndall, T. J. Wallington, Chem. Rev. 103, 4657 (2003)

General hydrocarbon oxidation scheme in the atmosphere.

Chronicle

1984Endo et al,microwave spectrum of CH3O.

1988Foster et al,moderate-resolution LIF of CH3O.

Microwave

LIF

2004Melnik et al,microwave spectrum of CH2DO and CHD2O

1990 Liu et al,high-resolution LIF of CH3O (A state spin-rotation splittings only).

~

2001,Kalinovski,low-resolution LIF of CH2DO and CHD2O

2006,Liu et al,high-resolution LIF of CH3O, CH2DO, CHD2O and CD3O, and global fitting with mw.

ExcimerLaser(XeCl)

Pulse Amplifier

Ar+ Laser 20W CW RingDye Laser

Computer

XeFPhotolysis

Laser

~0.5mJ

~5-10 mJPMT

DoublingCrystal

Experimental Apparatus

Box-Car

Vacuum Chamber

Etalon

Chopper(2KHz)

λ/2 Plate PBS

PD

PD

Calibration System

I2

50cm

~100mW

1-3mW

Lock-in

Lock-in

a. H. Kato et. al., “Doppler-Free High Resolution Spectral Atlas of Iodine Molecule”, Japan Society of the Promotion of Science, (2002) (Experimental)b. B. Bodermann, H. Knöckel, E. Tiemann, IodineSpec4 (2002) (Computational)

CHxD3-xONO+first-run Ne

(75% Ne+25%He)

T~3K

John-Teller active mode. Allowed

due to 2E symmetry of the X state

and the Jahn-Teller distortion.

John-Teller active mode. Allowed

due to 2E symmetry of the X state

and the Jahn-Teller distortion.

~

LIF Spectrum of CH3O

* S.C.Foster, X.P.Misra, T.D.Lin, C.P.Damo, C.C.Carter, and T.A.Miller, J. Phys. Chem. 92, 5914 (1988)

203610

Rotationally Resolved LIF Spectrum of Band203

Moderate-resolution*

(FWHM~6GHz)

High-resolution(FWHM~300MHz)

* D. E. Powers, M. B. Pushkarsky, and T. A. Miller, J. Chem. Phys. 106, 6863 (1997)

32950 32955 32960 32965 32970 32975 32980

Frequency/cm-1

16482.75 16482.80 16482.85 16482.90 16482.95 16483.00 16483.05 16483.10 16483.15 16483.20 16483.25

Atlas

Frequecy/cm-1

16482.75 16482.80 16482.85 16482.90 16482.95 16483.00 16483.05 16483.10 16483.15 16483.20 16483.25

Iodine

FWHM~30MHz

16482.75 16482.80 16482.85 16482.90 16482.95 16483.00 16483.05 16483.10 16483.15 16483.20 16483.25

Etalon

FSR~478MHz

Finesse~15

32965.5 32965.6 32965.7 32965.8 32965.9 32966.0 32966.1 32966.2 32966.3 32966.4 32966.5

LIF

FWHM~300MHz

b

a

Frequency/cm-1

a. Broader than the other three isotopomers (~250MHz). b. B. Bodermann, H. Knöckel, E. Tiemann, IodineSpec4, Toptica Photonics, Munich, Germany, (2002)

Error Analysis and Calibration Method Computational iodine Atlas (σ~1.5MHz) Density of iodine lines (~1/(10GHz), i.e. separation~20FSRs) Instability of FSR of the etalon (σ~0.05MHz)

Mechanical instability (~-1.5KHz/μm) Drift of the index of refraction of the air (thermal: ~0.5KHz/oC,

flow…) Thermal expansion of the Invar frame of the etalon (~-

0.1KHz/oC) Incident angle

Nonlinearity of cw ring laser (~1%, <2.5MHz(=1/2×500MHz×1%))

Uncertainty of picking up the peaks LIF peaks (~50MHz, dominant) Iodine peaks (~1.5MHz) Etalon fringes (~1.5MHz)

Frequency chirping of the pulsed dye amplifier (~10MHz, affects only T00)*

Computational iodine Atlas (σ~1.5MHz) Density of iodine lines (~1/(10GHz), i.e. separation~20FSRs) Instability of FSR of the etalon (σ~0.05MHz)

Mechanical instability (~-1.5KHz/μm) Drift of the index of refraction of the air (thermal: ~0.5KHz/oC,

flow…) Thermal expansion of the Invar frame of the etalon (~-

0.1KHz/oC) Incident angle

Nonlinearity of cw ring laser (~1%, <2.5MHz(=1/2×500MHz×1%))

Uncertainty of picking up the peaks LIF peaks (~50MHz, dominant) Iodine peaks (~1.5MHz) Etalon fringes (~1.5MHz)

Frequency chirping of the pulsed dye amplifier (~10MHz, affects only T00)*

* I. Reinhard, M. Gabrysch, B. F. Weikersthal, K. Jungmann, and G. Putlitz, Appl. Phys. B., 63, 476 (1996)

Iodine peaks for absolute calibration Etalon fringes for relative calibration Whole spectrum calibrated using cubic spline interpolation

Iodine peaks for absolute calibration Etalon fringes for relative calibration Whole spectrum calibrated using cubic spline interpolation

Experimental Accuracy and Proof

Calibration of iodine peaks comparing with atlas (σ<10MHz)

Reproducibility of different calibrated scans (σ<50MHz) σ depends on the frequency separation between the

calibrated peaks to the closest iodine peaks and/or etalon fringes

Prediction of microwave transitions based on combination differences of LIF spectra

Calibration of iodine peaks comparing with atlas (σ<10MHz)

Reproducibility of different calibrated scans (σ<50MHz) σ depends on the frequency separation between the

calibrated peaks to the closest iodine peaks and/or etalon fringes

Prediction of microwave transitions based on combination differences of LIF spectra

a. Corrected for hyperfine splittings.b. Y. Endo, S. Saito, and E. Hirota, J. Chem. Phys. 81, 122, (1984)

J" parity'' K'' Σ'' Predicted Experimentala, b ResidualMHz MHz MHz

0.5 0 0 0.5 82449 82469 -201.5 0 0 0.5 137350 137449 -991.5 1 1 0.5 137482 137563 -811.5 -1 1 0.5 137482 137486 -42.5 0 0 0.5 192401 192430 -292.5 1 1 0.5 192539 192458 812.5 -1 1 0.5 192539 192611 -72

61Standard Deviation (in MHz):

J" parity'' K'' Σ'' Predicted Experimentala, b ResidualMHz MHz MHz

0.5 0 0 0.5 82449 82469 -201.5 0 0 0.5 137350 137449 -991.5 1 1 0.5 137482 137563 -811.5 -1 1 0.5 137482 137486 -42.5 0 0 0.5 192401 192430 -292.5 1 1 0.5 192539 192458 812.5 -1 1 0.5 192539 192611 -72

61Standard Deviation (in MHz):

Based on the propagation of all experimental errors, an estimation of accuracy σ~50MHz

Based on the propagation of all experimental errors, an estimation of accuracy σ~50MHz

Experimental

Simulation

CH3O, 320 Band

73 transitions HEFF = HROT + HCOR + HSO + HSR 11 Constants

Ground state (2e, Hund’s case a) A”, B”, Aζt”, aζed”, ε aa”, εbc” Excited state (2a, Hund’s case a) A’, B’, εaa’, εbc’ Te

M_|_:M||=1:0 T=3K Standard deviation = 41MHz

73 transitions HEFF = HROT + HCOR + HSO + HSR 11 Constants

Ground state (2e, Hund’s case a) A”, B”, Aζt”, aζed”, ε aa”, εbc” Excited state (2a, Hund’s case a) A’, B’, εaa’, εbc’ Te

M_|_:M||=1:0 T=3K Standard deviation = 41MHz

Rotational

Coriolis interaction

Spin-rotation interaction

Spin-orbit interaction

90 transitions 13 Constants

Ground state (2e, Hund’s case a):

A”, B”, Aζt”, aζed”, ε aa”, εbc” Excited state (2e, Hund’s

case a): A’, B’, Aζt’, εaa’, εbc’, ε1’ Te

M_|_:M||=1:2 Standard deviation =

74MHz

90 transitions 13 Constants

Ground state (2e, Hund’s case a):

A”, B”, Aζt”, aζed”, ε aa”, εbc” Excited state (2e, Hund’s

case a): A’, B’, Aζt’, εaa’, εbc’, ε1’ Te

M_|_:M||=1:2 Standard deviation =

74MHz

Experimental

Simulation

CH3O, 610 Band

Molecular Constants

microwave+LMRa

320 61

0

A 154960 154411 155220B 27931.14 27863.85 27922.49

Aζt 54330 54605 54382

aζed -1865980 -1864914 -1865924

εaa -40930 -36942 -40920

εbc -1428 -2640 -1323

Te cm -132934 32544

A 152824 145974B 21686.85 21991.01

Aζt 19248

εaa 37 -182

εbc 363 372

ε1c 63

c. Absolute value only.

Molecular Constants of CH3O (in MHz)

LIFb

a. Y. Endo, S. Saito, and E. Hirota, J. Chem. Phys. 81, 122, (1984) b. This work

Gro

un

d S

tate

Ex

cit

ed

Sta

te

microwave+LMRa

320 61

0

A 154960 154411 155220B 27931.14 27863.85 27922.49

Aζt 54330 54605 54382

aζed -1865980 -1864914 -1865924

εaa -40930 -36942 -40920

εbc -1428 -2640 -1323

Te cm -132934 32544

A 152824 145974B 21686.85 21991.01

Aζt 19248

εaa 37 -182

εbc 363 372

ε1c 63

c. Absolute value only.

Molecular Constants of CH3O (in MHz)

LIFb

a. Y. Endo, S. Saito, and E. Hirota, J. Chem. Phys. 81, 122, (1984) b. This work

Gro

un

d S

tate

Ex

cit

ed

Sta

te

Prediction of Microwave Transitions

J" parity'' K'' Σ'' Predicted Experimentala, b ResidualMHz MHz MHz

0.5 0 -1 0.5 82389 82393 -40.5 0 0 0.5 82455 82469 -141.5 0 -2 0.5 137191 137111 801.5 0 -1 0.5 137320 137324 -41.5 0 0 0.5 137434 137449 -151.5 1 1 0.5 137530 137563 -331.5 -1 1 0.5 137530 137486 442.5 0 -3 0.5 191876 191354 5232.5 0 -2 0.5 192080 191965 1152.5 0 -1 0.5 192257 192258 -12.5 0 0 0.5 192410 192430 -202.5 1 1 0.5 192548 192458 902.5 -1 1 0.5 192548 192611 -632.5 0 2 0.5 192674 192592 81

56Standard Deviation (in MHz):

Based on 320 band

J" parity'' K'' Σ'' Predicted Experimentala, b ResidualMHz MHz MHz

0.5 0 -1 0.5 82389 82393 -40.5 0 0 0.5 82455 82469 -141.5 0 -2 0.5 137191 137111 801.5 0 -1 0.5 137320 137324 -41.5 0 0 0.5 137434 137449 -151.5 1 1 0.5 137530 137563 -331.5 -1 1 0.5 137530 137486 442.5 0 -3 0.5 191876 191354 5232.5 0 -2 0.5 192080 191965 1152.5 0 -1 0.5 192257 192258 -12.5 0 0 0.5 192410 192430 -202.5 1 1 0.5 192548 192458 902.5 -1 1 0.5 192548 192611 -632.5 0 2 0.5 192674 192592 81

56Standard Deviation (in MHz):

Based on 320 band

a. Corrected for hyperfine splittings.b. Y. Endo, S. Saito, and E. Hirota, J. Chem. Phys. 81, 122, (1984)

J" parity'' K'' Σ'' Predicted Experimentala, b ResidualMHz MHz MHz

0.5 0 -1 0.5 82383 82393 -100.5 0 0 0.5 82455 82469 -141.5 0 -2 0.5 137173 137111 621.5 0 -1 0.5 137311 137324 -131.5 0 0 0.5 137431 137449 -181.5 1 1 0.5 137536 137563 -271.5 -1 1 0.5 137536 137486 502.5 0 -3 0.5 191837 191354 4842.5 0 -2 0.5 192056 191965 912.5 0 -1 0.5 192245 192258 -132.5 0 0 0.5 192410 192430 -202.5 1 1 0.5 192557 192458 992.5 -1 1 0.5 192557 192611 -542.5 0 2 0.5 192689 192592 96

54Standard Deviation (in MHz):

Based on 610 band

J" parity'' K'' Σ'' Predicted Experimentala, b ResidualMHz MHz MHz

0.5 0 -1 0.5 82383 82393 -100.5 0 0 0.5 82455 82469 -141.5 0 -2 0.5 137173 137111 621.5 0 -1 0.5 137311 137324 -131.5 0 0 0.5 137431 137449 -181.5 1 1 0.5 137536 137563 -271.5 -1 1 0.5 137536 137486 502.5 0 -3 0.5 191837 191354 4842.5 0 -2 0.5 192056 191965 912.5 0 -1 0.5 192245 192258 -132.5 0 0 0.5 192410 192430 -202.5 1 1 0.5 192557 192458 992.5 -1 1 0.5 192557 192611 -542.5 0 2 0.5 192689 192592 96

54Standard Deviation (in MHz):

Based on 610 band

Summary and Future Work (TJ05)

Ground electronic state constants from the global fitting (LIF and microwave).

Hi-resolution LIF spectra of all other isotopomers.

Ground electronic state constants from the global fitting (LIF and microwave).

Hi-resolution LIF spectra of all other isotopomers.

Hi-resolution LIF apparatus improved by the new calibration system (σ~50MHz).

Hi-resolution LIF spectra of CH3O ( and bands).

Successful simulation and fitting.

Hi-resolution LIF apparatus improved by the new calibration system (σ~50MHz).

Hi-resolution LIF spectra of CH3O ( and bands).

Successful simulation and fitting.

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