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
OutlineOutline• Introduction
• Experimental Setup
• Results
• Summary
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
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
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
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
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
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
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
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
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)
-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
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
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
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
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
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
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
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
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
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
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
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