1. The CP-FTMW Spectrum of Bromoperfluoroacetone
Frank Marshall, David J Gillcrist, Thomas D. Persinger, Stephen Jaeger, Cassandra Hurley, Nelson E Shreve, Nicole Moon, Dr. Smitty Grubbs
Missouri University of Science and Technology

2. Motivation
Previous studies by Cooke and Grubbs over halofluorocarbons and halogenated perfluoroacetones
Not much work over Brominated molecules
Interesting to observe how Bromine bonds change when Fluorinated
Good test for newly completed CP-FTMW

3. Missouri S&T CP-FTMW 6-18 GHz linear frequency sweep (“chirp”)
Expandable to 2-18 GHz with a specific amplifier
4us, 6GHz chirps
Low noise, High fidelity instrument
Minimal number of parts
AWG and Oscilloscope eliminate multiple circuit
23GHz, 100GS/s oscilloscope
40W Solid state power amplifier
50GS/s digitization rate, 20GHz bandwidth AWG

5. Bromoperfluoroacetone
97% Bromoperfluoroacetone purchased from Synquest Laboratories
Liquid sample placed in tube and submerged in ice bath
0.5-1 atm of Argon gas bubbled through the sample
Pulsed into chamber at 1 Hz
30,000 FIDs collected

6. Quantum Chemical Calculations
Geometry Optimizations with Gaussian03
MP2/ G theory level with full electron contribution

7. Frequency (MHz)

8. Analysis Spectra was too dense to easily assign
Spectral density of 1 transition every 6 MHz
We used AABS1 package in tandem with Pickett’s SPFit and SPCat programs
Watson S-reduced Hamiltonian in the Ir representation
Theoretical Parameters from W.C. Bailey2 allowed for more accurate assignment
1)Z. Kisiel, PROSPE – Programs for Rotational SPEctroscopy, URL: kisiel/prospe.htm
2) W. C. Bailey, Bromine Nuclear Quadrupole Coupling Constants in Bromoperfluoroacetone, URL:

9. Analysis Continued 1984 transitions assigned
1068 CF3COC79BrF2 transitions
916 CF3COC81BrF2 transitions
Transitions consist of
R-branch a-type, b-type, c-type
Q-branch b-type
X-type, ∆J = 2 Forbidden Transitions

11. Structure Second Moments No Carbon Kraitchman Coordinates
We do know Bromine position
Contributions of CF2, CF3 to Pcc to second moment have general values3
Confirms experimental structure is similar to theoretical structure
3) R. K. Bohn, J. A. Montgomery, Jr., H. H. Michels, J. A. Fournier, J. Mol. Spectrosc. Article In Press

12. Quadrupole Coupling and Electric Field Gradient
Nuclear Quadrupole Coupling Tensor was diagonalized into χxx, χyy, χzz
χzz values of Bromine and Chlorine are not comparable
Electric field gradients are comparable if we assume z-axis and bond axis are identical

13. Dipole Forbidden Transitions
∆J=2 Transitions
Reported for other molecules with large nuclear quadrupole coupling constants and similar size or rotational constants
Off diagonal quadrupole coupling tensor components
X-type transitions
No change in parity for Ka or Kc
Very rare, only one other instance found4
4) A. Maeda, I. R. Medvedev, F. C. De Lucia, E. Herbst, P. Groner, Astrophys. J. Supp. Ser. 175 (2008) 138

14. Dipole Forbidden Transitions Continued
In Dipole Forbidden Transitions the energy levels are nearly degenerate and highly mixed (from Pickett)
In non diagonalized Hamiltonian matrices, the energy levels share multiple off diagonal elements
We are unclear as to the mechanism behind these dipole forbidden transitions
Typically this is a function of one off diagonal tensor element
X type transitions due to quadrupole coupling have not been previously observed

15. Conclusions
Bromoperfluoracetone has been measured for the first time on a CP- FTMW
The molecule has been fit with a standard semi-rigid and quadrupole Hamiltonian
Experimental structure has been shown to agree with theoretical structure
C-Br bond seems to strengthen with Fluorination
Dipole forbidden transitions have been reported, but the mechanism is unclear
Manuscript submitted to J-Mol-Spec

16. Acknowledgements University of Missouri Research Board Grant
Missouri S&T Startup Financial Support
Stephen A Cooke
Stewart Novick
Dr. Smitty Grubbs