Physics Department News Archive
November 16 , 2005
Summer Research Published
Sioux Falls - The results of a summer research project worked on by four Augustana College undergraduates has been published in this month's issue of Physical Review A. The study, conducted from June of 2004 to August of 2005, is a basic measurement highlighting the wave-particle duality of matter. Recent work by a multi-institutional collaboration, including Augustana College and Kansas State University , pointed out that when a passing charged particle removes both electrons from a hydrogen molecule, the two nuclei of the molecule essentially act as coherent sources of outgoing electron waves. This situation is analogous to Young's famous double-slit interference experiment with light, and, as with light, interference effects are seen as the electron waves propagate. As a result, the electrons are more likely to be removed from the hydrogen molecules if the molecule is aligned perpendicular to the incoming beam of charged particles.
In the follow-up experiment, the Augustana students focused on the case where only one electron was removed from the hydrogen molecule. When removing only one electron, the interaction between the incident charged particle and the molecule is typically weaker, and less momentum is transferred to the electron. According to the de Broglie relation, as momentum decreases, the electron wavelength increases. The longer wavelengths are less likely to produce interference effects. In fact, the present experiment shows that the probability of removing a single electron from the hydrogen molecule does not depend on the molecular alignment.
"I enjoyed working on this project. Being able to make such an intricate measurement is really exciting", says Nora Johnson, the lead author of the paper. Johnson began work on this project during the summer of 2004. The main results published in the article were obtained by Johnson during an experiment conducted over spring break in March. A subsequent experiment in July by Johnson and fellow Augustana students Jamie Kapplinger, Mike Lundy, and Ryan Mello, along with Kansas State undergraduate Eli Parke, confirmed the results. The students then constructed a theoretical model for the process, and found good agreement with their experimental data. Since interference effects can be an extremely sensitive probe of the position of individual nuclei in molecules, this technique might one day be used as a time-dependent probe of molecular motion.
The work was conducted at the J.R. Macdonald Laboratory located on the campus of Kansas State University . The Augustana students were supervised by Eric Wells, who maintains a long-standing collaboration with KSU faculty members Itzik Ben-Itzhak and Kevin Carnes.
The article [Nora G. Johnson, R.N. Mello, Michael E. Lundy, J. Kapplinger, Eli Parke, K.D. Carnes, I. Ben-Itzhak, and E. Wells, "Single ionization of hydrogen molecules by fast protons as a function of the molecular alignment", Phys. Rev. A 72, 052711 (2005) ] is the second in Physical Review for Johnson, a major accomplishment for any undergraduate. The Dell Rapids native is a 2005 graduate of Augustana, and is currently a graduate student in physics at Kansas State. She is the daughter of Lawrence and Diane Johnson. Ryan Mello is a senior physics major from Casper , Wyoming . He is the son of Mary and Frank Mello. Mike Lundy, the son of Tamara and Phil Lundy, is a sophomore physics major from Sioux Falls. Jamie Kapplinger is a senior carrying a triple major in physics, chemistry, and biology. He is from Spring Grove, MN, and is the son of Kim and Nolie Kapplinger.
Major funding for the experiment was provided by the Research Corporation through a Cottrell College Science Award and by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. The Physical Review is a journal of the American Physical Society, and Physical Review A is the section of this journal dedicated to atomic, molecular, and optical physics research. Physical Review is stringently peer-reviewed and is generally regarded as the most prestigious physics-only journal in the world.
- Nora G. Johnson et al., Phys. Rev. A 72 , 052711 (2005).
- A.L. Landers et al., Phys. Rev. A 70 , 042702 (2004).
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Students from the Augustana College / Kansas State University collaboration in front of beamline LA15 in the Macdonald Laboratory at KSU. From left to right: Ryan Mello (Augustana, '06), Mike Lundy (Augustana, '08), Eli Parke (KSU, '07), Nora Johnson (Augustana alumni, now a KSU graduate student), and Jamie Kapplinger (Augustana, '06).