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

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

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 components@@@# 23GHz, 100GS/s oscilloscope 40W Solid state power amplifier 50GS/s digitization rate, 20GHz bandwidth AWG

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

Quantum Chemical Calculations Geometry Optimizations with Gaussian03 MP2/6-311++G theory level with full electron contribution

Frequency (MHz)

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: http://info.ifpan.edu.pl/ kisiel/prospe.htm 2) W. C. Bailey, Bromine Nuclear Quadrupole Coupling Constants in Bromoperfluoroacetone, URL: http://nqcc.wcbailey.net/CF3COCF2Br.html

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

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

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

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

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

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

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