72 nd International Symposium on Molecular Spectroscopy June 2024 2016 UrbanaChampaign IL USA FB05 Frank E Marshall Nicole Moon Thomas D Persinger David J Gillcrist N E Shreve William C Bailey and ID: 629138
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Slide1
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
72nd International Symposium on Molecular SpectroscopyJune 20-24, 2016, Urbana-Champaign, IL, USA; FB05
Frank E. Marshall, Nicole Moon, Thomas D. Persinger, David J. Gillcrist, N. E. Shreve, William C. Bailey and G. S. Grubbs IISlide2
Background
Pictures from C. T. Dewberry, G. S. Grubbs II, and S. A. Cooke,
J.
Molec
.
Spectrosc
. 257 (2009) 66.
Observed
Δ
J
=3 due to
χ
ab
Slide3
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
.
328
(2016) 59.Slide4
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?Slide5
Target Molecule: 3-Bromo-1,1,1,2,2-Pentafluoropropane
Multiple conformers, smaller rotational constants
trans
gaucheSlide6
Theory
Parameter
r
opt
/ MHzre / MHz
A25412545
B566566
C556.556
χ
aa
515.4
515.7
χ
bb
-195.3
-195.1
χ
cc
-320.2
-320.6
|
χ
ab
|
297.3
298.2
trans
-79
Parameter
r
opt
/ MHz
r
e
/ MHz
A
1919
1924
B
733
733
C
659
660
χ
aa
230.7
232.4
χ
bb
-58.1
-59.2
χ
cc
-172.6
-173.2
χ
ab
372.0
372.5
χ
ac268.6269.2χbc190.0189.6
gauche-79
MP2/6-311+G(3df,3pd)Slide7
Experiment
CP-FTMW: Ran in “U”-tube approximately 40 cm away from nozzle with 6
psig
Ar backing gas6-12 GHz and 12-18 GHz with 4 µs chirps
170k FIDs obtained at 1 FID/1 Hz gas pulseSlide8
ResultsSlide9
Results
~ 1 transition / MHz!!!!Slide10
Fits (How did I do that?)
Trans-79Slide11
Fits (How did I do that?)
Trans-81Slide12
Off-Diagonal Testing
Trans only had
χab with no dipole forbidden transitions currently assignedWe want to monitor pathways to observe limits
Gauche is neededSlide13
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 waySlide14
Acknowledgements
http://nqcc.wcbailey.net/Publ_N.html