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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?
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Rotational and Vibrational Energy Transfer from the First Overtone Stretch of Acetylene
Keith FreelJiande Han
Michael C. Heaven
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.
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?
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
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.
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
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)
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’)
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
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
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)
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.
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)
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)
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
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.
Thank You For Listening
• Advisor: Michael Heaven• Postdoc Fellow: Jiande Han• Group Members: Ivan Antinov, Beau Barker,
Md. Humayun Kabir