Transcript Document

Isomerization, Perturbations, Calculations and the
S1 State Of C2H2
J. H. Baraban, P. B. Changala, J. R. P. Berk,
R. W. Field, J. F. Stanton, A. J. Merer
Happy Birthday, C2H2!
J. Stark and P. Lipp.
ZPC, 86(1):36, 1913.
Theory and Spectroscopy
C. K. Ingold and G. W. King. J. Chem. Soc., pg. 2715, 1953.
I. G. Ross. Trans. Faraday Soc., 48:973, 1952
Theory and Spectroscopy 2
A. J. Merer, N. Yamakita, S. Tsuchiya,J. F. Stanton, Z. Duan, and R. W. Field. Mol. Phys., 101:663, 2003.
trans conformer of S1 C2H2
- Franck-Condon active
- Totally symmetric
trans
bend
torsion
cis
bend
-
+
+
-
- Non-totally symmetric bends
- Darling-Dennison resonance and Coriolis
coupling form bending polyads:
Near-prolate top:
S1 C2H2 cis-trans Isomerization Primer
cis bend, q6
cis T0
44870
1
2
3
4
5
6
ETS ≈ 4979
Fundamental Frequencies
Mode
EOM-CCSDT
Expt.
Calc.
trans- Obs.
T0
CH sym. str.
2884.76
2880.08
4.68
42197.57
CC str.
1383.23
1386.9
-3.67
trans bend
1062.04
1047.55
14.49
torsion
730.65
764.9
-34.25
CH antisym. str.
2860.52
2857.4
3.12
cis bend
755.3
768.26
-12.96
Curvilinear Calc.-Obs.
25 (3D)
12 (1D), <1 (3D)
<1 (3D)
trans bend, q3
1
1
1 2 B
5000
Barrier Proximal States
1
1
1 3
1
cm
1
1 3 B
E /
1
1
1 B
3
2
2
2 3
1
1 3
1
1
3
1
2 3
3000
2
2
1
2 3
1
1
2 B
2000
2

0
2 B
1


0
2
2
1
2
2
2
1
1
1
2
1
2
1
1
1
3 B
1000
3 B
3
2
B
3
1
3
3 B
B
1
2
3 B
1
1
3 B

1
2 3 B
1
3
3
4
2 B
4
3 B
1
2
3 B
1
3
2

2
3 B
2 3 B
1
2
3
1
3
4
3 B

3 B
2 3 B
2 B
B
2
2
5
1
2 B
3
2
1
3
1
12
2 3 B
2 B
1
5 B
4
4
3 B
3 5
1
1
1
1
B
2
3 B
2 3 B
1
2
1
3
3
1
1
2
2 B
1
4
1
5
6
2
2 5
3
1
3 B
2 B
1
2 3
1 B
1
5 B
1
2
4000
3
1
B
3 5 B
2 3
1
3 5
1
2 5 B
1
1
2
1
1
2
2
1
1 2
2
5
B3
B2
B1
1
ETS
Fitting the Barrier Height
1100
E(v+1)-E(v) (cm-1)
1000
ETS= 4592 ± 2 cm-1
900
800
700
600
Fits to Experimental 3n62 T0 data
500
ETS= 4695 ± 36 cm-1
400
ETS= 4852 ± 5 cm-1
300
0
1000
2000
3000
4000
½[E(v+1)+E(v)]-E(0) (cm-1)
5000
6000
B2 polyad: K- and J- structures
44100
-1
E / cm
42 0f (ag)
43760
E / cm-1
-1.05J(J+1)
Observed
Calculated
3e
K=2
3f
44000
4161 0e (bg)
43740
43900
1f
1e
43720
1e
43800
1f
42
K=2
1 1
46
43700
6
2
0
62 0f (ag)
43700
1
2
Merer et al. JCP, 129:054304, 2008.
3
4
K
0
20
40
60
80
J(J+1)
B3 polyad: K- and J- structures
45000
1 2
44560
-1
E / cm
Observed
0f (bu)
-1
E / cm
- 1.05J(J+1)
Calculated
46
2 1
46
0e (au)
K=2
4
44 800
44520
1
3
3
44480
44600
1
2e
2e 2f
1 2
46
2 1
46
4
0e (au) 2f
3
3
63
0f (bu)
1e
1f
44440
44400
0
1
2
Merer et al. JCP, 129:054304, 2008.
3
K
4
0
20
40
60
80
J(J+1)
4
3
6
K-staggering in cis 3161
Merer et. al., J. Chem. Phys, 134, 244310, 2011.
K-staggerings come from tunneling
splittings
J. T. Hougen and A. J. Merer. JMS, 267:200, 2011.
J. H. Baraban et. al. JCP, 134:244311, 2011.
J. T. Hougen. JMS, 278:41, 2012.
K-staggerings come from tunneling
splittings
K-staggerings come from tunneling
splittings
K-staggerings come from tunneling
splittings
180o
K-staggerings come from tunneling
splittings
180o
K-staggerings come from tunneling
splittings
180o
Even K states only with symmetric
tunneling component
K-staggerings come from tunneling
splittings
180o
Odd K states only with antisymmetric
tunneling component
E(K) ∝ K2 . . . ?
TvK - Tv0
(TvK – Tv0)/K2
17.77
17.77
67.96
16.99
151.32
16.81as
A - B ≈ 16.46
A - B ≈ 16.40
A - B ≈ 17 ✓
A - B ≈ 22.77 !
Todd-Teven= +6.31 cm-1
J. C. Van Craen, M. Herman, R. Colin, and J. K. G. Watson. JMS, 111(1):185, 1985.
Summary
• Two types of barrier-proximal perturbations
– Isomerization dip
– K-staggerings
– Together these two types of information can
characterize the barrier
• K-staggerings a particular challenge
– complicate assignments
– difficult to understand/predict
• New experiments and calculations needed
Acknowledgements
Field Group Members:
Collaborators:
Dr. Adam Steeves
Dr. Hans Bechtel
Jun Jiang
Peter Richter
G. Barratt Park
Prof. J. F. Stanton (UT-Austin)
Prof. A. J. Merer (UBC/IAMS)
Dr. J. T. Hougen (NIST)
B. Broderick (WSU)
Prof. A. Suits (WSU)
Funding
DOE
NSF GRFP