KHADIJA JAWAD CLAUDIA I VIQUEZ LYUDMILA SLIPCHENKO AND TIMOTHY S ZWIER 72 nd International Symposium on Molecular Spectroscopy TB10 Department of Chemistry Purdue University West Lafayette IN 47906 ID: 633168
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Slide1
1
The exotic excited state behavior of 3-phenyl-2-propynenitrile
KHADIJA JAWAD
, CLAUDIA I. VIQUEZ,
LYUDMILA SLIPCHENKO, AND TIMOTHY S. ZWIER
72
nd
International Symposium on Molecular Spectroscopy
TB10
Department of Chemistry, Purdue University
West Lafayette, IN 47906Slide2
2
Previous work on photochemical reaction between diacetylene and benzene yielded
phenyldiacetylene
Photochemical reaction between benzene and cyanoacetylene could produce PPN
Spectroscopic signature of PPN important to confirm its productionAssignments difficult to make due to confusion over the identity of the excited state(s) involved
MotivationSlide3
3
Previous Work: R2PI
Possible S
0
-S1 origin at 35,242 cm-1
Sharp peaks up to 37,000 cm
-1
Broad absorptions similar to
phenyldiacetylene
above 37,000 cm
-1
208 nm
292 nmSlide4
4
Experimental: Laser-Induced Fluorescence
Laser Induced Fluorescence ChamberSlide5
5
LIFSlide6
6
Origin Dispersed Fluorescence
Lacks a
1
vibrational fundamentals
1101
a113
0
1
a
1
14
01a13801b2
2401b
13701
b
2
35
0
1
b
2
19
0
1
b
1
36
0
1
b
2
8
0
1
a
1
Points to importance of
vibronic
coupling
Prominent peaks can be assigned to b
2
fundamentals
b
1
vibrations appear alongside corresponding b
2
Possible coupling to S
2
stateSlide7
7
Mode
Symmetry
ExperimentalEOM-CCSD/cc-pVDZ
ν
(cm
-1
)
ν
(cm
-1
)
b
2
69
b
1
75
b
1
192
38
0
1
b
2
212
211
24
0
1
b
1
356
362
14
0
1
a
1
379
366
a
2
402
37
0
1
b
2
482489b1502b15243601b25345383501b2627630b16591301a1686693b1758a28651901b1939933a1969a29811101a110081015
Vibrations of C
3
N group appear in pairs:
b
1
and b
2Slide8
8
Vibrations involved in b
1
-b
2 pairs
n26
75cm-1
n
25
192cm
-1
n
22
524cm
-1
n
39
69cm
-1
n
38
211cm
-1
n
36
538cm
-1Slide9
9
LIF Revisited
+472
ν
37
+205
ν38
+65
+115
+186
+255
0
0
0
35,242 cm-1Slide10
10
Dispersed Fluorescence
Δν
=0 Franck-Condon factors
Geometry similar between ground and excited stateResonant fluorescenceFalse origins
x3Slide11
11
How are b
1
and b
2 fundamentals gaining intensity in emission?Modeling of ν24 (b1)
Strong vibronic
coupling between excited states
EOM-CCSD/cc-
pVDZ
Claudia I.
Viquez
MG10
−1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Displacement
Transition
Symmetry
Oscillator Strength
S
0
– S
1
B
2
0.003233
S
0
– S
2
A
1
0.361093
S
0
– S
3
A
2
0.000000
S
0
– S
4
A
2
0.000000Slide12
12
Conclusions and Future Work
Ground and excited state share similar geometry
Strong
vibronic coupling is responsible for the b2 and b
1
fundamentals
Computational modeling of the electronic spectroscopy in progress
Dispersed fluorescence on more peaks in the excitation spectrum
Photochemically
react
cyanoacetylene
and benzeneSlide13
13
Professor Timothy Zwier
Zwier Group
Professor Lyudmila
SlipchenkoClaudia Viquez Rojas
AcknowledgmentsSlide14
14
S
0
Sample heated to 60°C
Vibrationally
cooled to zero-point levels
Supersonic Expansion
Laser
Ports
2 Stage Ion
Acceleration
Einzel
Lens
Pulsed Valve
MCP
Time-of-Flight Tube
Mass Gate
Pulser
Ion Chamber
Experimental: Resonant Two-photon Ionization (R2PI)Slide15
15
Excited State Lifetime
Bi-exponential decay pattern:
Short-lived component
≤
10 ns
Long-lived component > 800 ns
Excited state calculations using TD-DFT were performed with a
ω
B97X-D basis set at 6-31+G(d) level of theory.
ISC
M
+
+ eSlide16
16
Calculations predict
TDM of S
1
from S0 along c-axisTDM of S2 from S0 along a-axisDye-laser resolution of 0.06 cm-1 Experiment suggests it is not due to S0-S
1
Rotational Band Contour of 35,242cm
-1Slide17
17
How are b
1
fundamentals gaining intensity in emission?
C
2
ν
A
1
A
2
A
1
A
2
B
2
A
1
B
2
A
’
A
”
A
’
A
”
A
’
A
’
A
’
C
s
Oscillator strength
S
0
-S
2
0.2482
S
0
-S
1
0.0021
S
0
S
1S2S3S4S5S6Optimized S1 geometry:In-plane deformationof C3N chainA2A1A1b1a1a1b2a1b
1
S
1
S
2
Vibronic
coupling
S
0
Forbidden in C
2v
A
1
xb
1
=B
1
A
2
xb
2
=B
1
b
2
member of tunneling
doublet can mix with
b
1
fundamentals in
S
2
(A
1
) stateSlide18
18
S
0
-S
1 S0-S2
(LUMO)
(HOMO)
(LUMO)
Molecular Orbitals VisualizedSlide19
19
Calculated Geometry changesSlide20
20
Pertinent Character Tables
C
2
νC
s