HIGH-RESOLUTION LASER-INDUCED FLUORESCENCE (LIF) SPECTROSCOPY OF THE DEUTERATED ISOTOPOMERS OF THE...
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Transcript of HIGH-RESOLUTION LASER-INDUCED FLUORESCENCE (LIF) SPECTROSCOPY OF THE DEUTERATED ISOTOPOMERS OF THE...
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.
203 1
06