Student Kyle Larson (left) and Physics professor Len Keeler test components in the atomic physics lab
Classical representation of electrons
A diagram of the apparatus Keeler is constructing to study highly excited atoms. |
New UMM physics faculty member Len Keeler jokingly explains his interest in
atomic physics as the result of being “a big control freak.” He
enjoys manipulating atoms to do what he wants them to do. “This is one of those little things that entertains me,” he laughs. But it’s more than just control. It’s also the chance to build equipment to do the manipulating. Early in his career as a physicist, Keeler discovered he was adept at working with lab equipment. That natural talent served him well from the start. “My career was started in a whimsical dare,” Keeler recalls. “My new graduate advisor left for six months and he told me to work on assembling an accelerator. When he came back, it worked! I’d built it from the pieces laying around in the lab. So I guess you could say I got started in atomic physics because of the equipment; voltage, vacuum pumps, accelerators and things like that.” Currently, Keeler is working with physics student Kyle Larson to create the equipment needed to study highly excited atoms. With the limited resources at a small undergraduate university, it’s a good thing Keeler knew how to build the equipment for UMM’s first atomic physics lab. For starters, he decided to work with laser-diode technology. “This technology is going to be used in the next generation super high density DVD players. It’s relatively inexpensive because it’s going to be mass marketed. Until two years ago, there was no such thing as a laser diode that could emit blue light. It’s a higher frequency,” Keeler explains. Knowing that this technology was coming, Keeler began to research possible applications. He discovered that the frequency of the blue laser was the perfect wave length to excite potassium atoms. This was good news because potassium, like other alkaline metals, has a single valence electron. That one electron’s orbit encircles all the other electrons orbiting the atom’s nucleus. “It’s simple. So it’s easier to do the theory,” says Keeler. That’s important for working with highly excited atoms because the computations required in the research are formidable.” Normally, the rules of quantum mechanics are applied to atoms because of their small size. Yet, in many cases, quantum mechanics calculations become almost impossible for highly excited atoms because of the computer capability needed. “For example, when I do computations now for lithium atoms in the range of N=20 to 30, the computation for what I’m doing takes 1 1/2 weeks on a standard state-of-the-art PC,” says Keeler. “The computation time increases dramatically as the atom gets larger. Another research group I know of is doing excited lithium atom computation with a super computer cluster. It takes them weeks to do computations in the N=50 to 60 range. “So when it comes to mathematically describing atoms in the 200 to 500 range, it seems impossible. BUT…when the atom becomes that large, the approximation of classical mechanics starts to work and we can actually compute the spectrum of highly highly excited atoms in electric fields with classical mechanics. Fundamentally, we’re testing the approximation of classical mechanics under these conditions.” If the assumption is correct that classical mechanics applies in these conditions, Keeler can take his experimental data and use it to map out the classical path of the excited valence electron in an atom. “This is pretty astounding to be able to experimentally determine the classical trajectories of an electron,” he notes. “Large atomic physics labs do this with other atoms, but the laser equipment is expensive. We only needed a couple thousand dollars to get started. That we can make highly excited atoms at all is remarkable.” So far, Keeler has built two laser systems, equipment for temperature and current control and optical feedback. Kyle Larson worked hard last summer helping Keeler get the lab ready for the highly excited atoms project. “Kyle’s been remarkably helpful for having started this project in the summer of his sophomore year,” Keeler notes. “I schematic a circuit and a week later, Kyle has it built. He’s also machining parts for the optics. It’s great experience. You know, data-taking is interesting but there’s a deeper level of understanding the equipment when you build it yourself.” |
|
The University of Minnesota is an equal opportunity educator and employer.
University of Minnesota Online Privacy Statement
©2004 by the Regents of the University of Minnesota
Edited and maintained by Carol Ford(fordcj@morris.umn.edu)
Last Modified: Friday, September 28, 2007
Page URL: http://www.morris.umn.edu/academic/science/news/phys2.html