E LECTRONIC T RANSITIONS OF S CANDIUM M ONOXIDE NA WANG, Y.W. NG, and A. S-C. CHEUNG The University...
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Transcript of E LECTRONIC T RANSITIONS OF S CANDIUM M ONOXIDE NA WANG, Y.W. NG, and A. S-C. CHEUNG The University...
ELECTRONIC TRANSITIONS
OF
SCANDIUM MONOXIDE
NA WANG, Y.W. NG, and A. S-C. CHEUNG
The University of Hong Kong
109 Pokfulam Road, Hong Kong SAR, P.R.China
International Symposium on Molecular Spectroscopy69TH MEETING - JUNE 16-20, 2014
CONTENTS
Introduction
Experimental Setup
Results and Discussion
Summary
INTEREST IN STUDYING SCO
Astrophysics
ScO has been found in the spectra of M-type stars, where its
spectrum usually accompanies those of TiO Merrill et al (Astrophys. J. 136, 21 (1962))
Catalysis
Scandium oxide is a good catalyst for selective catalytic reduction of
nitric oxide with methane. Fokema et al (applied catalysis B. 18, 71 (1998))
Spectroscopic interest
Sc atom: ns2(n-1)d1 with only one electron in the d orbital
Molecular and electronic structure of Sc diatomic molecule.
Theoretical studies by using different calculation methods for ground state and low-lying electronic states of ScO had been done.
K. D. Carlson, E. Ludena, C. Moser (J. Chem. Phys. 43, 2408 (1965))
D. W. Green (J. Phys. Chem. 75, 3103 (1971))
Bauschlicher Jr., S. R. Langhoff (J. Chem. Phys. 85, 5936 (1986))
G. H. Jeung, J. Koutecky (J. Chem. Phys. 88, 3747 (1988))
S. M. Mattar (J. Phys. Chem. 97, 3171 (1993))
Experimental Work: L. Åkerlind et al observed the spectrum of ScO for the first time and consider 4Σ as ground state. (L. Åkerlind et al (Arkiv. Fysic. 22, 41 (1962))
The ground state of ScO was confirmed to be X2Σ+ state which followed the unusual hyperfine coupling case bβS. The electronic transitions including A’2Δ – X2Σ+, A2Π – X2Σ+ and B2Σ+ - X2Σ+ transitions were obtained and analyzed successfully by many groups. A. Adams, W. Klemperer, T. M. Dunn (Can. J. Phys. 46 2213 (1968))
C. L. Chalek, J. L. Gole (J. Chem. Phys. 65, 2845 (1976))
P. K. Schenck, W. G. Mallard, J. C. Travis, K. C. Smyth (J. Chem. Phys. 69, 5147 (1978))
W. J. Childs, T. C. Steimle (J. Chem. Phys. 88, 6168 (1988))
S. F. Rice, W. J. Childs, R. W. Field (J. Mol. Spectros. 133, 22 (1989))
J. Shirley, C. Scurlock, T. Steimle (J. Chem. Phys. 93, 1568 (1990))
L. B. Knight Jr., J. G. Kaup, B. Petzoldt, R. Ayyad, T. K. Ghanty, E. R. Davidson(J. Chem. Phys. 110, 565 ( 1999))
S. Mukund, S. Yarlagadda, S. Bhattacharyya, S. G. Nakhate(J. Quantitative Spectroscopy & Radiative Transfer, 113, 2004 (2012))
PREVIOUS STUDIES ON SCO
EXPERIMENTAL SETUP FOR OODR SPECTROSCOPY
Schematic Diagram of Laser Vaporization/ OODR spectroscopy Experimental Setup
Sc rod
LIF/OODRtechniques
Laser Ablation/ReactionWith Free Jet Expansion
EXPERIMENTAL CONDITIONS
Molecular Production:
Sc + O2 (5% in Ar) ScO + etc.
Ablation Laser : Nd:YAG, 10Hz, 532nm, 5mJ
Free Jet Expansion : i) backing pressure: 6 atm O2 (5% in Ar)
ii) background pressure: 1x10-5 Torr
LIF spectrum in the UV region (290 ~ 311nm)
OODR spectrum in Visible and Infrared region (720 ~ 815nm)
Laser systems: Pulsed Dye laser & Optical Parametric Oscillator
laser
OPTICAL-OPTICAL DOUBLE RESONANCE TRANSITION SCHEME
ScO molecules are excited in two stages from ground state to
an intermediate state (B state) by dye laser
from intermediate state to the desired excited state (C state) by OPO laser
Molecules give out fluorescent photon and relax back to the ground state
X2Σ+
B2Σ+
C2Π
Fixed laserpumping
Scanning laser
Detection
RESULTS AND DISCUSSION
32500 33000 33500 34000 34500
Ω‘=1.5
[32.92] 1.5 - X2Σ+(1,0)(2,1)(0,0)
(2,0)
(b)
4Σ+ - X2Σ+(1,0)(0,0)[33.41] 0.5 - X2Σ+
wavenumber/cm-1
(1,1) (0,0) (1,0)
(a)
Ω‘=0.5
2Σ+
4Σ+
Low resolution broadband spectrum: (a) direct LIF spectroscopy, (b) OODR spectroscopy
Only v”=o can be observed for OODR spectrum
[32.85] 4∑+V1
0
[33.41] 0.5V1
0[32.92] 1.5 V
1
0
[33.36] 0.5 [33.37] 1.5 [33.39] 1.5[33.49] 1.5
[34.00] 2∑+ [34.01] 2∑+[34.15] 2∑+
B2∑+
X2∑+
626.2
cm-1
55
9.7
cm-1 51
1.3cm
-1
Pulsed Dye Laser
13 electronic transitions have been recorded and analyzed
There are four different types of electronic states have been identified:Ω’ = 0.5, Ω’ = 1.5, 2Σ+ and 4Σ+ states
(I) [33.4]0.5 – B2Σ+ transition
12830 12840 12850
Wavenumber/cm-1
R14
(1.5)Q14
(1.5)P14
(1.5)
OODR spectrum obtained by pumping R14(0.5)
P(1.5), Q(1.5) and R(1.5) are observed Ω’ = 0.5
X2Σ+ 0.5
B2Σ+
[33.4]0.5
1.5
0.5
1.5
2.5 J
R14(0.5)
R14
(1.5
)
Q14
(1.5
)
P14
(1.5
)
High resolution LIF spectrum of (0, 0) band of [33.4] 0.5 – X2Σ+ electronic state
33380 33390 33400 33410 33420
13.5
0.5
23.5
0.5
17.5 0.5
13.5 1.5
18.5
Q24
(J)
Q23
(J)Q
14(J)
Q13
(J)
R24
(J)
R23
(J)R
14(J)
R13
(J)
P24
(J)P
23(J)
P13
(J)
In
ten
sity
Wavenumber/cm-1
P14
(J)1.5
(II) [32.9]1.5 – B2Σ+ transitionOODR spectrum obtained by pumping R23(0.5)
Only P(1.5), and R(1.5) are observed Ω’ = 1.5
X2Σ+ 0.5
B2Σ+
[32.9]1.5
1.5
1.5
2.5 J
R23(0.5)
R23
(1.5
)
Q23
(1.5
)
12340 12345 12350 12355 12360
R23
(1.5)
Wavenumber/cm-1
Q23
(1.5)
(III) [34.1] 2Σ+ – B2Σ+ transition
X2Σ+ 6.5
B2Σ+
[34.1] 2Σ+
5.5
4.5
6.5 J
P14(6.5)
R14
(5.5
)
P14
(5.5
)
13580 13590
P14
(5.5)
R14
(5.5)
Wavenumber
OODR spectrum obtained by pumping P14 (6.5)
12270 12280 12290
TR41
(3.5)RQ31
(3.5)
PQ11
(3.5)
Wavenumber/cm-1
RP41
(3.5)
OODR spectrum obtained by pumping P14 (4.5) and P23(5.5) respectively
(IV) [32.85] 4Σ+ – B 2Σ+ transition
12270 12280 12290
PR12
(4.5)
RR32
(4.5)
RQ42
(4.5)
PP32
(4.5)
Wavenumber/cm-1
NP12
(4.5)
F4
F1
F3
F1F2
F1F2
F1F2
4
3
55.54.5
4.53.53.52.5
efefef
__
++__
N J
B 2Σ+
F1F2
F1F2
F1F25
4
43
32 3.5
4.5
5.55.5
4.5
3.5fe
fe
fe
+_
+_
_+
F1F22
1 2.52.5
fe
_+
PQ
11(3
.5)
PP
21(3
.5)
RR
21(3
.5)
NP
12(4
.5)
PQ
22(4
.5)
PR
12(4
.5)
N J
3.5
4.5
5.5
F3F4
F3F4
F3F4
5
5
67
6
4
5.5
4.5
3.5fe
fe
fe
_+
+_
+_
2.5 F3F44
32.5
fe
_+
RP
41(3
.5)
RQ
31(3
.5)
TR
41(3
.5)
PP
32(4
.5)
RQ
42(4
.5)
RR
32(4
.5)
N J
[32.8] 4Σ+
Energy level diagram for the 4Σ+ – 2Σ+ transition
Molecular constants for observed upper states of ScO
Upper statev' νo B' q ro(Å) Remarks
[33.49] 1.5 0 33496.68 0.3788 0.0028 1.941[33.39] 1.5 0 33395.60 0.3599 - 1.992[33.37] 1.5 0 33372.82 0.3863 - 1.922 Perturbed[32.92] 1.5 1 33429.90 0.3552 - 2.005 Perturbed
0 32918.64 0.4452 - 1.791
[33.37] 0.5 0 33368.59 0.3036 - 2.168 Perturbed[33.41] 0.5 1 33971.30 0.4359 -0.0015 1.810
0 33411.59 0.4367 - 1.808 Perturbed
Upper state v' νo B' γ ro(Å)
[34.16] 2Σ+ 34156.96 0.3957 0.0049 1.899[34.01] 2Σ+ 34008.39 0.4190 -0.2898 1.846 Perturbed[34.00] 2Σ+ 34001.56 0.4271 -0.3012 1.828 Perturbed
Upper state v' νo B' γ λ ro(Å)
[32.85] 4Σ+ 1 33480.10 0.4125 1.07 0.16 1.860 Perturbed 0 32853.23 0.4382 1.03 0.53 1.805
(8σ)2(3π)4(9σ)1 X
2Σ+
(8σ)2(3π)4(1δ)1 A 2Δ
(8σ)2(3π)4(4π)1 A′ 2Π
(8σ)2(3π)4(10σ)1 B
2Σ+
Molecular Configuration Diagram of ScO molecule
(8σ)2(3π)3(9σ)1(1δ)1 2Πi(2), 4Πi
2Φi(2), 4Φi
(8σ)2(3π)3(9σ)1(4π)1 2Σ+(2), 4Σ+
, 2Σ-
(2)
4Σ-, 2Δ(2), 4Δi
(8σ)2(3π)3(9σ)1(10σ)1 2Πi(2), 4Πi
SUMMARYNew electronic states of ScO in the high energy
region have been studied using LIF and OODR Spectroscopy.
Thirteen vibronic transition bands were observed and analyzed. Accurate molecular constants were determined.
A 4Σ+ – 2Σ+ forbidden transition was identified and studied.
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