Jason J. Pajski, Matt Logan, Brian C. Dian 1, Gordon G. Brown, Kevin O. Douglass, Richard D. Suenram and Brooks H. Pate Department of Chemistry, University of Virginia, McCormick Rd., P.O. Box , Charlottesville, VA ) Department of Chemistry, Purdue University, 560 Oval Dr., West Lafayette, IN David F. Plusquellic Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, MD BROADBAND ROTATIONAL SPECTRA OF THE SOMAN-RELATED COMPOUNDS: PINACOLYL ALCOHOL AND PINACOLONE

11 GHz CP-FTMW Spectrometer Pulse Monitor 12 GHz Oscilloscope (40 Gs/s) Free Induction Decay 0.5– 11.5 GHz Arbitrary Waveform Generator Chirped Pulse Frequency Sweep 4 GS/s x GHz TWT Amplifier FID acquisition and Fourier transform 9.9 GHz PDRO 2 GHz Bandwidth Nozzle Sample Feed GHz PDRO

Chemical Warfare Agent Simulants Pinacolone Pinacolyl Alcohol Soman (GD) – nerve agent (cholinesterase inhibitor)

Pinacolyl Alcohol

Pinacolyl Alcohol Constants 1 Calculated with MP2/ G(d,p) ExperimentalCalculated 1 Δ (obs-calc) A (MHz) B (MHz) C (MHz) Δ J (kHz)1.01×10 -3 Δ JK (kHz)1.21×10 -4 Δ K (kHz)-5.64×10 -4 δ J (kHz)2.93×10 -4 δ K (kHz)-4.09×10 -3

Pinacolone A-E splitting

Pinacolone - MP2/cc-pVTZ Rotational constants (MHz): A=3211 B=2334 C=1936 Dipole moment (Debye): μ a = -1.1 μ b = 2.3 μ c = 0.0 Tot= 2.6 Rotational constants (MHz): A = 3218 B = 2322 C = 1935 Top-of-barrier - Planar – E Rel = cm -1 Equilibrium - Non-Planar – E Rel = 0.0 cm -1 Dipole moment (Debye): μ a = -1.1 μ b = 2.4 μ c = 0.0 Tot= 2.6 Rotational constants (MHz): A = 3213 B = 2326 C = 1932 Equilibrium - Planar – E Rel = cm -1 Dipole moment (Debye): μ a = -1.1 μ b = 2.4 μ c = 0.0 Tot= 2.6

13 C Isotopomers Relative Intensity C1.16 % C1.22 % C1.14 % C1.01 % C C2.84 %

Unassigned Line

Qualitative Quantum Mechanical Argument

Pinacolone Constants

Experimental vs. Calculated Parameters for Pinacolone Experimental 1 Calculated 2 Δ (obs-calc) A (MHz) (2) B (MHz) (2) C (MHz) (2) Barrier to rotation (cm -1 ) 122.3(5) Values are for the A-state. 2 Calculated at MP2/cc-pVTZ level.

Conclusions for Pinacolone A-E splittings from methyl rotor Experimental barrier determined to be 122.3(5) cm -1 Pinacolone is dynamically planar Some molecules cool only to next-lowest energy state in a double well with a probability density centered off the c-axis giving rise to extra lines in the spectrum

Acknowledgements Pate Lab Group Members Rick Suenram and David Plusquellic at NIST Funding: NSF Chemistry SELIM Program NSF MRI Program (with Tom Gallagher, UVa Physics) University of Virginia John D. and Catherine T. Macarthur Foundation The Jeffress Trust

Approximate Energy Gap for c-Type Transitions with the Double Well Assumption ΔE ~ 2-4 cm -1 ~ GHz

Pinacolone - MP2/ G(d,p) Rotational constants (MHz): 13 C Isotopomers C C C C C C

Chirped Pulse Generation: x8 Scheme x4 x2 7.5 – 18.5 GHz To Experiment Chirped Pulse Frequency Sweep – MHz Phase locked oscillator 9.9 GHz 10 MHz Rb Oscillator 4 GHz Arb. Waveform Generator Dual Channel Independent Trigger Laser/TWT Trigger Scope Trigger 0-80 dB Programmable Atten. Single Sideband Filter Sweep – GHz Sweep – GHz 19.8 GHz High Power TWT Amplifier x2 Low Power Loop

2 nd Generation Chirped Pulse Design 7.5 – 18.5 GHz To Experiment Chirped Pulse Frequency Phase locked oscillator 13.0 GHz 10 MHz Rb Oscillator Arbitrary Waveform Generator Dual Channel Independent Trigger Laser/TWT Trigger Scope Trigger High Power TWT Amplifier

Chirped Pulse (Linear Frequency Sweep) Excitation Chirped Pulse Instantaneous Frequency:  = sweep rate Need: 11,000 GHz/1  s Synthesizer: 300MHz/1ms Use arbitrary waveform generator as the frequency source Need sweep rates that are 10 5 times faster than standard synthesizers

11 GHz Chirped Pulse Frequency Sweep in TimeFrequency Sweep in Frequency Signal recorded at -60 dB from 1kW TWT

Pinacolyl Alcohol - MP2/ G(d,p) Principal axis orientation: Center Atomic Coordinates (Angstroms) Number Number X Y Z Rotational constants (MHZ):

Pinacolone - MP2/ G(d,p) Principal axis orientation: Center Atomic Coordinates (Angstroms) Number Number X Y Z Rotational constants (MHZ):