Volume 19 - 2010
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Microwave Spectroscopy

Student Develops




the Study of Molecules

By Mellina Stucky

The use of laser technology with rotational spectroscopy made the University of North Texas the university of choice for Garry “Smitty” Grubbs II, who wanted to pursue graduate work in chemistry after completing a bachelor’s degree at Texas A&M University.

With rotational spectroscopy, as light is imposed on molecules in a vacuum, the molecules start to spin in conjunction with one another and then randomly fall out of sync.

Grubbs says the work of UNT’s Stephen Cooke, assistant professor of chemistry, with lasers and microwave spectroscopy specifically interested him.

“There aren’t many labs that have microwave spectrometers,” says Grubbs, a fourth-year doctoral student. “If you have one, it’s because you built it. You can’t just go out and buy one.”

Nuts and Bolts

Grubbs’ graduate research involves designing, constructing and using spectrometers to study the rotational transitions of molecules.

Traditionally, microwave spectroscopy uses light in the microwave frequency to determine the shapes of gas phase molecules. Grubbs is improving the available instrumentation to measure more molecules and expand the regions of light in which these measurements can be made.

Garry “Smitty” Grubbs II

Doctoral student Garry “Smitty” Grubbs II designs and constructs spectrometers to study the rotational transitions of molecules. He attended the 59th Nobel Laureate Meetings in Lindau, Germany, last summer.

Photo by: Mike Woodruff

He has designed a novel broadband microwave spectrometer with a laser ablation source. His broadband technique allows him to measure gas-phase molecules with high precision and accuracy in a shorter period of time while using less sampling material.

“I never thought I would be using wrenches and hammers to do chemistry,” says Grubbs, who first experienced UNT as a high school student through Upward Bound and its math and science program. “I think of my work as a way to use my creative mind in the design and building of this instrumentation.”

Because each molecule has its own spectrum, the instruments Grubbs builds allow him to study the general chemistry and make-up of the molecules, accurately identifying distances between their bonded atoms and differentiating isotopic species.

Through an electronic circuit and with the use of horn antennae to broadcast, he can rapidly produce microwaves over a broadband region up to 4GHz. In other words, using his technique, he is able to perform the spectroscopy at least 1,000 times faster than before.

“This speeds up the process so much that I can accomplish in one experiment what traditionally takes many experiments to accomplish,” Grubbs says.

Measuring Matter

By determining the rotational constants of each sample studied and mapping the spectra, he is finding out more about the energetic properties of gas-phase molecules. The expanded instrumentation also will allow him to measure molecules not currently studied as well as matter not typically in gas form.

His research, in collaboration with doctoral student Chris Dewberry and master’s student Kerry Etchison, requires knowledge of chemistry, physics, electronic engineering and software development as well as problem solving skills.

“There are so many things that can go wrong during an experiment,” he says. “There could be a problem with the vacuum, the electronics, the computer program or the sample. It’s a trouble-shooter’s dream.”

Grubbs’ technique and growing expertise in the field is impressive, says Sean A. Peebles, an associate professor of chemistry at Eastern Illinois University who spent two months working in Cooke’s lab in 2007. Peebles and Grubbs were working on a chirped-pulse Fourier-transform microwave spectrometer — the only instrument of its kind outside of the University of Virginia at that time.

“I worked closely with Smitty on this instrument, which he had been largely responsible for constructing, and I was impressed with his grasp of the instrumentation and his organized approach to research,” Peebles says. “Since being back at my home institution, we have constructed a similar instrument, and Smitty has been extremely helpful in answering our questions. He is always happy to lend assistance and offer ideas.”

Nobel Laureates

Last summer, Grubbs had the opportunity to meet Nobel Prize winner Harold Kroto at the 59th Nobel Laureate Meetings in Lindau, Germany.

Grubbs was one of 74 students in the nation to earn a $6,000 award from Oak Ridge Associated Universities to attend the annual meetings, which provide a global forum for young researchers to exchange ideas and knowledge with generations of scientists.

Kroto, an English chemist, was awarded the 1996 Nobel Prize for chemistry along with Richard E. Smalley and Robert F. Curl for their joint discovery of buckminsterfullerene or buckyball, a previously unknown form of carbon.

“There are three Nobel Prize winners in my field. Being able to meet one of them at the Lindau meetings was a wonderful opportunity,” Grubbs says.

“Getting to network with fellow scientists was invaluable. I never thought I would be encouraged by so many people of stature to go out and use my creativity and knowledge of science to try and change the world.”

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