electronic transition of ruthenium monoxide na wang, y. w. ng and a. s.-c. cheung department of...
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Electronic Transition of Electronic Transition of Ruthenium MonoxideRuthenium Monoxide
Na Wang, Y. W. Ng and A. S.-C. CheungDepartment of Chemistry
The University of Hong Kong
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OutlineOutline• Introduction
• Experimental Setup
• Results
• Summary
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IntroductionIntroductionWhy we study diatomic Transition Metal Monoxides?
• Transition metal monoxides play important roles in catalysis, and high temperature chemistry
• Diatomic transition metal molecule is the simplest model for studying more complicated transition metal compounds
• The near degeneracy of the d orbitals and the various spin configurations give rise to many low-lying electronic states with high spin multiplicity
increase complexity in identifying ground state
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Previous Studies on RuOPrevious Studies on RuO• Raziunas et al.(J. Chem. Phys. 43 1010 (1965))
o Studied the emission spectrum of RuO molecule by using a low-current dc arc as the light source
o Reported ground state of RuO as 3Σ+ state o Obtained the bond length to be 1.70Å.
• Scullman and Thelin (J. Mol. Spec. 56 64 (1975) )o Performed emission experiment using a hollow cathode lamp o Analyzed three subsystems called “5526Å”, “5532Å” and “5544Å” o Obtained the bond length as 1.718Å.
• Krauss and Stevens (J. Chem. Phys. 82 5584 (1985) )o Calculated the electronic structure of RuO using Multi-Configuration Self-Consistent-
Field (MC-SCF) wavefunctionso Predicted a 5Δ state ground state for RuO
Ground state of RuO is not confirmed yet
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Gas-Phase Gas-Phase RuO RuO Production MethodProduction Method
Laser ablation/reaction free jet expansion
Molecule production:
Ru + N2O (~6% in Ar) → RuO + etc.
Ablation Laser : Nd:YAG, 10Hz, 532nm, 5mJ
Free Jet Expansion : i) backing pressure: 6 atm N2O (~6% in Ar)
ii) background pressure: 1x10-5 Torr
LIF spectrum in the visible region
Laser system: Optical Parametric Oscillator laser
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Experimental SetupExperimental SetupSchematic Diagram of Laser Vaporization/ LIF Experimental Setup
Digital Delay/ Pulse Generator
Pulsed valve Controller
Nd:YAG Laser
Laser BeamVaporization laser Beam
Trigger
To Diffusion Pump
Ru rod
N2O in Argon
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MonochromatorMonochromator
• Fix the wavelength of the OPO laser to pump the molecules
• Scan the grating in monochromator
• Wavelength resolved fluorescence spectrum
v’
v”
0
012
ΔG3/2
ΔG1/2
Excitation Laser
Scanning grating
ΔG1/2 ΔG3/2
Wavelength resolved fluorescence spectrum
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MonochromatorMonochromator• Serve as an optical filter
• Set the grating in monochromator at a particular wavelength
• Only small spectral region is detected by PMT
• Remove unwanted scattering light
8
Total fluorescence spectrumWithout monochromator filtering
Filtered fluorescence spectrumWith monochromator filtering
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ResultsResultsThis work reported the
• [18.1] Ω = 4 – X 5Δ4 (“5526Å” system)
• [16.0] Ω = 5 – X 5Δ4
• [18.1] Ω = 3 – X 5Δ3 (“5532Å” system)
• [15.8] Ω = 4 – X5Δ3
transitions of RuO in the spectral region between 540-680nm using laser induced fluorescence (LIF) spectroscopy
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Observed transitions of RuOObserved transitions of RuO
X5Δ4X5Δ3
[16.0]5Φ5
[18.1]Ω=4
[15.8]5Φ4
[18.1] Ω=3
v10
v0
v0
v10
v10
v10
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18075 18085
15
4R(J)
Q(J)415
12
Wavenumber (cm-1)
5P(J)
The (0,0) band of the [18.1] Ω = 4 – X The (0,0) band of the [18.1] Ω = 4 – X 55ΔΔ33 transition of RuO transition of RuO
• P(5), Q(4), R(4) Ω’ = 4 – Ω” = 4
• [18.1] Ω = 4 – X 5Δ4
4
5
4
5Ω” = 4
J
Ω’ = 4
P(5)R(4) Q(4)
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-1000 -500 0 500 1000 1500
18070 Band
v" =
1Vibrational separation (cm-1)
Laser
865cm-1
Resolved fluorescence spectrum of Resolved fluorescence spectrum of [18.1] Ω = 4 – X [18.1] Ω = 4 – X 55ΔΔ44
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Observed transitions of RuOObserved transitions of RuO
X5Δ4X5Δ3
[16.0]5Φ5
[18.1]Ω=4
[15.8]5Φ4
[18.1] Ω=3
v10
v0
v0
v10
v10
v10
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The (0,0) band of the [15.8] The (0,0) band of the [15.8] 55ΦΦ44 – X – X 55ΔΔ33 transition of RuO transition of RuO
• P(5), Q(4), R(3) Ω’ = 4 – Ω” = 3
• [15.8] 5Φ4 – X 5Δ3
15780 15790
31717 4
8
R(J)
Q(J)
P(J)5
Wavenumber (cm-1)
4
4
5Ω” = 3
JΩ’ = 4
P(5)R(3) Q(4)
3
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Resolved fluorescence spectrum of Resolved fluorescence spectrum of [1[15.85.8] ] 55ΦΦ44 – X – X 55ΔΔ44
-1500 -1000 -500 0 500 1000 1500
Laser
856cm-115790 Band
Vibrational Separation (cm-1)v”
=1
856cm-1
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Summary on molecular Constants for RuO (cmSummary on molecular Constants for RuO (cm-1-1))
Parameter
[18.1] Ω=3 [18.1] Ω=4[15.8] Ω=4
X 5Δ3 X 5Δ4
Toa+18064.99(
2)18881.18(1)
a+15788.25(2)
a 0
ΔG1/2 784.87 795.19 983.69856.27(2
)855.82(
2)
Be 0.3813 0.3822 0.3884 0.4139 0.4148
re (Å) 1.787 1.785 1.771 1.715 1.714
αe 0.0014 0.0011 0.0051 0.0022 0.0035
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Molecular orbital energy level diagramMolecular orbital energy level diagram
Ground State Configuration of RuC: (11σ)2(5π)4(2δ)4 1Σ+
RuC
11σ
5π
12σ6π
13σ
Ru C
4d
5s
2p2δ
σ
δπ
σ
σ
π
RuNN
Ground State Configuration of RuC: (11σ)2(5π)4(2δ)4(12σ)1 2Σ+
Ground State Configuration of RuO: (11σ)2(5π)4(2δ)4(12σ)2 1Σ+
ORuO
(11σ)2(5π)4(2δ)4(12σ)1(6π)1 3Π
Do not contribute to states with Ω =3 or 4
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Molecular orbital energy level diagramMolecular orbital energy level diagram
Ground State Configuration of RuF: (11σ)2(5π)4(2δ)3(6π)3(12σ)1 4Φ9/2
RuF
11σ
5π
12σ
6π
13σ
Ru F
4d
5s
2p2δ
σ
δπ
σ
σ
π
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Molecular orbital energy level diagramMolecular orbital energy level diagram
FeO is isoelectronic to RuO
Ground State Configuration of FeO: (8σ)2(3π)4(1δ)3(9σ)1(5π)2 5Δ
FeO
8σ
3π
9σ4π
10σ
Fe O
3d
4s
2p1δ
σ
δπ
σ
σ
π
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Molecular orbital energy level diagramMolecular orbital energy level diagram
Ground State Configuration of RuO: (11σ)2(5π)4(2δ)3(12σ)1(6π)2 5Δ
RuO
11σ
5π
12σ6π
13σ
Ru O
4d
5s
2p2δ
σ
δπ
σ
σ
π
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Ground State AnalysisGround State Analysis• Ground State Configuration:
(11σ)2(5π)4(2δ)3(12σ)1(6π)1 5Δ
• Number of electrons in δ MO is more than half-filled inverted 5Δ
• Transitions obtained are from lower state Ω = 3 and Ω = 4 inverted 5Δ
Ground State of RuO : X5Δ4
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Comparison of Ru compounds Comparison of Ru compounds Molecule RuB RuC RuN RuO RuF
Electronic configuratio
nδ3 δ4 δ4σ1 δ3σ1π2 δ3π3σ1
Symmetry 2Δ5/21+ 2+ 5Δ4
4Φ9/2
Be (cm-1) 0.5834 0.6072 0.5545 0.4148 0.2866
re (Å) 1.706 1.608 1.571 1.714 1.916
ΔG1/2 (cm-1) 911.0 1029.6 1108.3 855.8 534.0
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SummarySummary• Reported four electronic transition system of RuO
o [18.1] Ω = 4 – X 5Δ4
o [16.0] Ω = 5 – X 5Δ4
o [18.1] Ω = 3 – X 5Δ3
o [15.8] Ω = 4 – X5Δ3
• Ground state symmetry: X 5Δ4
• Equilibrium bond length, re = 1.714Å
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