rotationally resolved a 2 a 1 —x 2 e electronic spectra of deuterated isotopomers of the methoxy...
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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)
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
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
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