Advancements in Instrumentation for Fourier Transform Microwave Spectroscopy

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The efforts of my research have led to the successful construction of several instruments that have helped expand the field of microwave spectroscopy. The classic Balle-Flygare spectrometer has been modified to include two different sets of antenna to operate in the frequency ranges 6-18 GHz and 18-26 GHz, allowing it to function for a large range without having to break vacuum. This modified FTMW instrument houses two low noise amplifiers in the vacuum chamber to allow for the LNAs to be as close to the antenna as physically possible, improving sensitivity. A new innovative Balle-Flygare type spectrometer, the efficient low ... continued below

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Dewberry, Christopher Thomas August 2011.

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  • Dewberry, Christopher Thomas

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The efforts of my research have led to the successful construction of several instruments that have helped expand the field of microwave spectroscopy. The classic Balle-Flygare spectrometer has been modified to include two different sets of antenna to operate in the frequency ranges 6-18 GHz and 18-26 GHz, allowing it to function for a large range without having to break vacuum. This modified FTMW instrument houses two low noise amplifiers in the vacuum chamber to allow for the LNAs to be as close to the antenna as physically possible, improving sensitivity. A new innovative Balle-Flygare type spectrometer, the efficient low frequency FTMW, was conceived and built to operate at frequencies as low as 500 MHz through the use of highly curved mirrors. This is new for FTMW techniques that normally operate at 4 GHz or higher with only a few exceptions around 2 GHz. The chirped pulse FTMW spectrometer uses horn antennas to observe spectra that span 2 GHz versus the standard 1 MHz of a cavity technique. This instrument decreases the amount of time to obtain a large spectral region of relative correct intensity molecular transitions. A Nd:YAG laser ablation apparatus was attached to the classic Balle-Flygare and chirped pulse FTMW spectrometers. This allowed the study of heavy metal containing compounds. The instruments I constructed and the techniques I used have allowed the discovery of further insights into molecular chemistry. I have seen the effects of fluorinating an alkyl halide by determining the geometry of the carbon backbone of trans-1-iodoperfluoropropane and observing a ΔJ = 3 forbidden transition caused by a strong quadrupole coupling constant on this heavy molecule. The quadrupole coupling tensors of butyronitrile, a molecule observed in space, have been improved. The nuclear quadrupole coupling tensor of difluoroiodomethane was added to a list of variably fluorinated methyl halides upholding a trend for the magnitude of χzz. The study of SrS led to the determination of the Born-Oppenheimer breakdown terms and improving the precision of the SrS internuclear distance. I have also conducted the first pure rotational spectroscopic investigation on an actinide containing molecule, ThO.

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  • August 2011

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  • May 17, 2012, 9:47 p.m.

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  • Dec. 3, 2013, 11:35 a.m.

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Dewberry, Christopher Thomas. Advancements in Instrumentation for Fourier Transform Microwave Spectroscopy, dissertation, August 2011; Denton, Texas. (digital.library.unt.edu/ark:/67531/metadc84308/: accessed February 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .