electronic transitions of yttrium monoxide allan s.-c. cheung, y. w. ng, na wang and a. clark...
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Electronic transitions of Yttrium Monoxide
Allan S.-C. Cheung, Y. W. Ng, Na Wang and A. Clark
Department of ChemistryUniversity of Hong Kong
OSU International Symposium on Molecular Spectroscopy19 June, 2013 (WK11)
Paper: WK11
AcknowledgementsPh.D. Students: Mr. Tony Y. W. Ng
Miss Na Wang
Exchange Student: Mr. Andrew Clark
U. of Edinburgh
Funding Agents:Research Grants Council, HKSAR
Committee on Research & Conference Grants, HKU
IntroductionWhy are we interested in YO and (ZrO and ScO)?
Astrophysical interests Presence in the atmosphere of cool M- and S- type stars
Murty, P. S., Astrophys. Lett. & Comm. 23, 7 (1982)
Murty, P. S., Astrophys. & Space Science 94, 295 (1983) Spectroscopic interests
Molecular and electronic structure (n+1)s2 nd1 model system for studying participation of d orbital Y has 5s2 4d1, Sc 4s2 3d1 and Zr 5s2 4d2 electronic configurations
S.R. Langhoff, et al, Annu. Rev. Phys. Chem. 39, 181 (1988)
IntroductionPrevious studies on YO: Meggers et. al., J. Res. NBS 6, 239 (1931).
First spectrum of YO produced by electric arc discharge.
Chalek et. al., Chem. Phys. 19, 59(1977). Recorded A’2 - X2Σ+ transition in chemiluminescent reactions of YO.Observed weak C2Π - X2Σ+ transition between 280 nm and 320 nm, only low resolution spectrum, no detailed analysis.
•Bernard et. al., Ap. J. Suppl. Ser. 52, 443 (1983).– Emission spectroscopy using hollow cathode discharge technique.
B2Σ+ State re= 1.825 Å
A2Π State re= 1.793 Å
X2Σ+ State re= 1.788 Å•Langhoff et al., J. Chem. Phys. 89, 2160 (1988).
– Theoretical calculations of many doublet and quartet states in the visible and UV region.
Gas-Phase YO Production Method
Laser ablation/reaction free jet expansionMolecule production:
Y + O2 (10% in Ar) → YO + etc.
Ablation Laser : Nd:YAG, 10Hz, 532nm, 5mJ
Free Jet Expansion : i) backing pressure: 6 atm O2 (10% in Ar)
ii) background pressure: 1x10-5 Torr
OODR spectrum in the UV regionLaser system: Pulsed Dye laser &
Optical Parametric Oscillator laser
ExperimentSchematic Diagram of laser vaporization/OODR spectroscopy experimental setup
Optical-Optical Double Resonance Transition Scheme
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 laserDetection:fluorescence
dye laser
OPO laser
Results & Discussion Low resolution LIF spectrum of YO
2Π3/2
2Π1/2
2Σ-
33000 34000 35000
Wavenumber (cm-1)
2Π3/2
2Π1/2
4Σ-
9 vibrational bands have been identified and studied
3393433823
20741B2Σ+
2Π3/2 2Π1/2 4Σ-3384933787
333123324233147
33716
(II) (I) (III)
33734
Detailed transition scheme for reaching the C2Π state via B2Σ+ state
Dye laser
OPO laser
P(1.5), Q(1.5) and R(1.5) are observed Ω’ = 0.5
X2Σ+
B2Σ+
[33.8]2Π1/2J
0.5
R1(0.5)
1.5
1.52.5
R(1.5) Q(1.5)P(1.5)
0.5
OODR spectrum obtained by pumping R1(0.5) of B2Σ+ - X2Σ+ transition
13100 13110
P1(1.5)
Q1(1.5)
Wavenumber (cm-1)
R1(1.5)
33849 band
(I) [33.8]2Π1/2 – B2Σ+ transition
Typical OODR spectrum of 2Π – 2Σ+ transition
Assembled spectrum of [33.8]2Π1/2 – B2Σ+ transition
13100 13110
Wavenumber (cm-1)
8.5
7.5 1.5
8.5
8.5
1.5
8.5
1.5
1.5 8.51.51.5R
12(J)Q
12(J)
P12
(J)
R1(J)
Q1(J)
P1(J)
Confirmation of the Ω value (Ω’ = 1.5) --- First lines
Q(1.5) and R(1.5) lines are observed; No P(1.5) line Ω’ = 1.5
(II) [33.9]2Π3/2 – B2Σ+ transition
OODR spectrum obtained by pumping R1(0.5) of B2Σ+ - X2Σ+ transition
X2Σ+
B2Σ+
[33.9]2Π3/2 J
0.5
R1(0.5)
1.5
1.52.5
R(1.5)Q(1.5)
13190 13200
Q(1.5) R(1.5)
Wavenumber (cm-1)
33934 band
The OODR spectrum indicates the upper state is a 4Σ- state
Analysis is still in progress
12960 12980
Q2(6.5)
P2(6.5)
Wavenumber (cm-1)
Q2(6.5)
P2(6.5)
The OODR spectrum of the 4Σ- - B2Σ- transition
High resolution spectrum [33.7] 4Σ- – X2Σ+ transition
33700 33710
8.5
10.5
6.5
7.5
1.5
1.51.5
P2(J)
Q2(J)
Q1(J)
Wavenumber (cm-1)
R1(J)
2.5
Calculated electronic states of YO Langhoff et al
0
5000
10000
15000
20000
25000
30000
Em
issi
on
X2Σ+
A’2ΔA2Π
B2Σ+
C2Π
a4Φb4Πc4Σ+
e4Σ-
Las
er a
bsor
ptio
nEne
rgy
(cm
-1)
Molecular constants for the states of YO
Upper state T0 (cm-1) B (cm-1) q r (Å)2Π3/2 33934.21 0.3431 0 1.903
33823.48 0.2789 0 2.1112Π1/2 33849.00 0.3195 0.001 1.972
33786.65 0.2959 0 2.049
33311.79 0.2779 0 2.114
33241.75 0.3665 0 1.841
33146.90 0.3671 0 1.840
Upper state T0 (cm-1) B (cm-1) γ r (Å)4Σ- 33715.98 0.2921 0.640 2.062
33734.13 0.2921 0.574 2.062
Summary9 transition bands of YO have been studied by Optical-
Optical Double Resonance Spectroscopy
Spectroscopic properties of the 2Π state have been determined to be:
B = 0.3665 cm-1
r = 1.840 Å
Spin-orbit constant A = 692.46 cm-1
A forbidden transition 4Σ- - B2Σ+ has been observed (further experimental work is needed for understanding this transition in detail)
More work is necessary to characterize the observed states