1. AN INVESTIGATION OF THE DIPOLE FORBIDDEN TRANSITION EFFECTS IN BROMOFLUOROCARBONS AS IT PERTAINS TO 3-BROMO-1,1,1,2,2-PENTAFLUOROPROPANE USING CP-FTMW SPECTROSCOPY
Frank E. Marshall, Nicole Moon, Thomas D. Persinger, David J. Gillcrist, N. E. Shreve, William C. Bailey and G. S. Grubbs II
72nd International Symposium on Molecular Spectroscopy
June 20-24, 2016, Urbana-Champaign, IL, USA; FB05

2. Background Observed ΔJ =3 due to χab
Pictures from C. T. Dewberry, G. S. Grubbs II, and S. A. Cooke, J. Molec. Spectrosc (2009) 66.

3. Bromoperfluoroacetone
Pictures and table from F. E. Marshall, D. J. Gillcrist, T. D. Persinger, S. Jaeger, C. C. Hurley, N. E. Shreve, N. Moon, and G. S. Grubbs II, J. Molec. Spectrosc (2016) 59.

4. Questions Where is the limit to forbidden transitions structurally?
How do conformations affect dipole forbidden transition pathways?
What can be learned from the dipole forbidden transition pathways?

5. Target Molecule: 3-Bromo-1,1,1,2,2-Pentafluoropropane
gauche
trans
Multiple conformers, smaller rotational constants

6. Theory MP2/6-311+G(3df,3pd) trans-79 gauche-79 Parameter ropt / MHz
re / MHz A
2541
2545 B
566 C
556
.556
χaa
515.4
515.7
χbb
-195.3
-195.1
χcc
-320.2
-320.6
|χab|
297.3
298.2
Parameter
ropt / MHz
re / MHz A
1919
1924 B
733 C
659
660
χaa
230.7
232.4
χbb
-58.1
-59.2
χcc
-172.6
-173.2
χab
372.0
372.5
χac
268.6
269.2
χbc
190.0
189.6
MP2/6-311+G(3df,3pd)

7. Experiment
CP-FTMW: Ran in “U”-tube approximately 40 cm away from nozzle with 6 psig Ar backing gas
6-12 GHz and GHz with 4 µs chirps
170k FIDs obtained at 1 FID/1 Hz gas pulse

8. Results

9. Results
~ 1 transition / MHz!!!!

10. Fits (How did I do that?)
Trans-79

11. Fits (How did I do that?)
Trans-81

12. Off-Diagonal Testing
Trans only had χab with no dipole forbidden transitions currently assigned
We want to monitor pathways to observe limits
Gauche is needed

13. Off-Diagonal Testing
Pathway tests could result in sign determination of off-diagonals
Three-wave chirality experiments are analogous and should be able to be harnessed in same way

14. Acknowledgements