rotational and vibrational energy transfer from the first overtone stretch of acetylene keith freel...
DESCRIPTION
Purpose: Optically Pumped Molecular Gas Lasers R 3μmμm 80 cm 2 m CaF 2 window detector/ spectrometer R~ 3μmμm C 2 H 2, 2 Torr ns OPO R (7) ( ) 3 μm A.V.V. Nampoothiri, A Ratanavis, N. Campbell, and W. Rudolph. Optics Express, 18(3), 2010, p )Total removal from rotational levels 2)Rotational Energy Transfer 3)Vibrational Energy Transfer To what states? How fast?TRANSCRIPT
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Rotational and Vibrational Energy Transfer from the First Overtone Stretch of Acetylene
Keith FreelJiande Han
Michael C. Heaven
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Purpose:Optically Pumped Molecular Gas Lasers
3100 3120 3140 3160 31800
1
2
3
4
5
Am
plitu
de (a
rb. u
nits
)
Wavelength (nm)
R ~90% @ 3 μm
80 cm
2 m
CaF 2
window
detector/spectrometer
R~ 90%@ 3 μm
C2H2, 2 Torrns OPO
R (7)
00000
10100
(01002100000003201020 )
3 μm
A.V.V. Nampoothiri, A Ratanavis, N. Campbell, and W. Rudolph. Optics Express, 18(3), 2010, p1946.
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Purpose:Optically Pumped Molecular Gas Lasers
3100 3120 3140 3160 31800
1
2
3
4
5
Am
plitu
de (a
rb. u
nits
)
Wavelength (nm)
R ~90% @ 3 μm
80 cm
2 m
CaF 2
window
detector/spectrometer
R~ 90%@ 3 μm
C2H2, 2 Torrns OPO
R (7)
00000
10100
(01002100000003201020 )
3 μm
A.V.V. Nampoothiri, A Ratanavis, N. Campbell, and W. Rudolph. Optics Express, 18(3), 2010, p1946.
1) Total removal from 10100 rotational levels
2) Rotational Energy Transfer
3) Vibrational Energy Transfer
• To what states?• How fast?
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IR-UV-DR (Time Resolved) Spectroscopy
Three types of experiments1. UV scan2. IR scan3. Time delay scan
(00000)00 X S+g
(10100)00
Direct Excitation: (V”, J”, K”) (V,J,K) V’, J’, K’Indirect Transfer: (V”, J”, K”) (V,J,K)init (V,J,K)final (V’,J’,K’)
A 1Au (v3’ + v5’)
LIF
(v1v2v3v4v5)l> 5 ns
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Spectroscopy of Acetylene
n”1
n”2
n”3
n”4
n”5
S+g
S+g
S+u
Pg
Pu
Ground State X S+g (D∞h) First Excited State A 1Au (C2h)
n'1 CH sym str
n'2 CC stretch
n'3 trans bend
n’4 torsion
n'5 CH anti str
n‘6 cis bend
ag
ag
ag
au
bu
bu
3372.85 cm-1
Watson. J Molec. Spec. 95, 1982, 101. Merer. Mol. Phys. 101(4-5), 2003, 663.
1974.32 cm-1
3288.39 cm-1
612.87 cm-1
730.33 cm-1
2880.5 cm-1
768.26 cm-1
2857.41 cm-1
764.91 cm-1
1047.55 cm-1
1386.9 cm-1
Tobiason. J. Chem. Phys. 99(2), 1993, 928.Herman et al. J. Phys. Chem. Ref. Data, Vol. 32, No. 3, 2003. Also MF07.
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Experimental Setup
LIF Flow CellPM
TExcimer pumped Dye Laser with Doubling Crystal
Nd:Yag pumped OPO/OPA
Computer
Boxcar with Preamp
Optics/Filters
Pump1.5 mm
Probe250 nm
Delay Generator
~ 0.1 Torr C2H2
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1. UV Scan – 20 ns delay
(00000)00X S+g
(10100)00
A 1Au (v3’ + v5’)
J=4
J=14J=12J=10J=8J=6
nm (Simulation - PGopher)
P R
Q(6) Q(10)Q(14)
R-branch
P(7)P(11)P(9)
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J=4
J=14J=12J=10J=8J=6
nm (Simulation - PGopher)
P R
Q(6) Q(10)Q(14)
R-branch
P(6)P(10)P(8)
1. UV Scan – 220 ns delay
(00000)00X S+g
(10100)00
A 1Au (v3’ + v5’)
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Density Of States
cm-1 cm-1
Vibrational Rotational
0.3 states/cm-1 > 6 states/cm-1
Herman et al. J. Phys. Chem. Ref. Data, Vol. 32, No. 3, 2003.
10100
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Vibrational Energy Transfer
nm (UV Scan)
(00000)00 X S+g
(10100)
A 1Au (v1’ + v3’)
a = c1|00200> - c2|11020>b = c2|00200> + c1|11020>
A-Xb A-Xa
Band heads
Obs. (Odd DJ)Pumped J=8
Calc. PGopher
10100 Xa + 41 cm-1
10100 Xb + 53 cm-1
Herman et al. J. Phys. Chem. Ref. Data, Vol. 32, No. 3, 2003. Merer. Mol. Phys. 101(4-5), 2003, 663.
g
u
g
g
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2. IR Scan Experiment
1505 1510 1515 1520 1525 1530 1535IR wavelength (nm)
120 ns 220 ns
(00000)00 X S+g
(10100)00
A 1Au (v3’ + v5’)
IR Scan
UV Fixed
R(13)P(15)
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3. Time ScanTotal Removal From 10100 (J=2 – J=16)
ns
J Ki/10-10
(cm3 s-1)+/- 0.3
Crim
2 7.6 NA
4 7.9 NA
6 6.5 NA
8 8.4 8.2
10 8.6 8.5
12 8.8 9.0
14 8.8 10.9
16 8.7 8.8
I(t) = A exp (-Kint)
J. D. Tobiason, Ph.D. thesis, University of Wisconsin-Madison, 1992.
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RET kinetics – measuring kif
J kiJ=14/10-10 (cm3
s-1)+/- 0.3
14 8.6 (Total Removal)
2 0.7
4 1.0
6 1.3
8 1.3
10 1.4
12 1.7
16 1.3
18 0.9
20 0.5
Nf(t)/No = If (t) = (kif /Ki)[1-exp(-Kint)] Ki = total removal rate from ikif = state to state removal rate from i to f
0 100 200 (ns)
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0 400 800 1200 1600 2000 2400 2800 3200
20 and 220 ns UV Scans with Simulation for assignmentBackground Considerations
Q(16)
Q(12)Q(8)
Q(20)
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20 and 220 ns UV Scans with Simulation for assignmentBackground Considerations
Q(16)
Q(12)Q(8)
Q(20)
Payne. Z. Phys. Chem. 219, (2005) 601–633Payne. J. Phys. Chem. A, Vol. 110(9), (2006) 3307
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Conclusions
• IR-UV DR spectroscopy has been used to identify VET and RET
• Total removal rates were measured from the 10100 state and match previous measurements.
• VET to the 00200/11020 diad was observed.• Measured State-to-State RET rates are too
large due to complex ET pathways.
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Thank You For Listening
• Advisor: Michael Heaven• Postdoc Fellow: Jiande Han• Group Members: Ivan Antinov, Beau Barker,
Md. Humayun Kabir