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The JRM stories from the 2009 Physics department newsletter.

Lasers in the James R. Macdonald Laboratory

Atomic Physics Research News

Itzik Ben-Itzhak

The J.R. Macdonald Laboratory has now firmly established AMO (Atomic, Molecular and Optical) ultrafast laser physics as its research theme. Four of our faculty, Lew Cocke, Zenghu Chang, Uwe Thumm and Itzik Ben-Itzhak, were invited to present their research in the central ICOMP-08 conference held in Heidelberg, Germany. Also, we were selected to host the Attosecond Physics international conference in July 2009. Chii-Dong Lin and Zenghu Chang, the co-chairs, are leading our efforts to organize this meeting. Our work also received some attention by the media.

The Kansas Light Source (KLS) continues to serve as our main workhorse, now scheduled essentially 24 hours per day 7 days per week. This laser delivers 25 fs, 800 nm pulses with 3 mJ of energy at one kilohertz. The pulse can be shortened to 6 fs and the phase of the “carrier” of the laser relative to the envelope can be stabilized. Zenghu Chang’s group has been working hard to keep up with the high demand for laser time, while continuously developing new capabilities such as 140 attosecond laser pulses. A “Dazzler”, a device capable of generating “designer” pulses by slicing out or modifying user-chosen slices of the wavelength range of the pulse, has been used by Brett DePaola’s group and by Eric Wells, from Augustana College, to control reaction dynamics of atoms and molecules. We were excited to see Lew Cocke’s collaborative research on the interaction of light with simple molecules in the prestigious Science magazine (Science, v320, p920; and Science, v322, p1081). Lew’s group is conducting similar cutting-edge experiments in our laboratory, in which a train of attosecond pulses is generated and used to probe atoms and molecules. Igor Litvinyuk’s group used intense laser pulses for time-resolved imaging of molecules – Coulomb explosion imaging with COLTRIMS and angle-resolved photo-electron spectra with their new velocity map imaging setup. Vinod Kumarappan has completed the development of his new lab space for molecular alignment and orientation studies. In collaboration with Steve Lundeen from Colorado State Univ. we installed a new permanent-magnet ECR ion source, which has been used already by Itzik Ben-Itzhak’s group in crossed-beam studies of molecular ions and intense laser beams.

The JRML theory effort paralleled our experimental work. For example, Chii-Dong Lin’s group focused on retrieval of target structure information from laser-induced measured rescattered electron momentum distributions, Uwe Thumm’s group focused on time-series analysis of vibrational nuclear wave-packet dynamics in D2+, and Brett Esry’s group focused on a general theory of carrier-envelope phase effects.

After many years in leadership, Distinguished Professor Pat Richard retired and moved with Dea to Florida. Horst Schmidt-Böcking from the Univ. of Frankfurt, Germany, the Davisson-Germer Prize Recipient 2008, was the keynote speaker at Pat’s farewell party, which brought back to K-State many of Pat’s former collaborators. We have had many additional changes in lab personnel. As new postdocs, Jesus Hernandez, a former K-State undergraduate student, has joined Brett Esry’s group after receiving his PhD from Auburn University, Chenghua Zhang from Purdue University has joined Uwe Thumm’s group, Feng He and Kamal Singh from the Max Planck Institute for Complex Systems, Dresden, Germany, have joined Uwe Thumm’s and Lew Cocke’s groups, respectively, and Kun Zhao from the University of Nebraska-Lincoln will join Zenghu Chang’s group soon. A couple of our postdocs moved to new jobs: Chengquan Li now at Coherent Inc., and Goga Veshapidze now at the Institute for Molecular Science in Okazaki, Japan. Five of our graduate students (advisor) received their PhD’s and moved to postdoc or industry positions: Eric Moon (Chang) now at Quantronix Corp., Rajesh Thapa (Corwin) now at IMRA America, Marc Trachy (DePaola) now at Lockheed Martin, Max Sayler (Ben-Itzhak) now at Jena University, Germany, and Predrag Ranitovic who recently received his PhD from Stockholm University on research he conducted at JRML under Lew Cocke's guidance is still at K-state. New graduate students (advisor) in the JRML include: Michael Chini (Chang), Rajesh Kadel (Washburn), Xiao-Ming Ren (Kumarappan), and Mohammad Zohrabi (Ben-Itzhak).

The groups of Kristan Corwin and Brian Washburn specialize in nonlinear optics and photonic crystal fibers, and their use for infrared frequency metrology. We have stabilized, for the first time, a fiber laser based on carbon nanotubes which provide the saturable absorber. This frequency comb has been used to characterize an acetylene filled fiber reference. In addition, we further developed the Chromium:forsterite laser comb and improved the sealing of gas in photonic crystal fibers. We have two new Department of Defense funded projects: one to create a molecular gas-filled hollow optical fiber laser, and the second, jointly with Precision Photonics and the University of New Mexico, to develop and commercialize gas filled fiber lasers.

We have had a long parade of excellent colloquium speakers in AMO this year. Leading this group was Nobel Laureate William D. Phillips from NIST/Univ. of Maryland who also presented the Peterson public lecture. Thomas Pfeifer from UC-Berkeley, Hiromichi Niikura from the National Research Council, Canada, Mette Gaarde from the Louisiana State Univ., Eleftherios Goulielmakis from the Max Planck Institute for Quantum Optics, Germany, Katsumi Midorikawa from RIKEN, Japan, Min Xiao from the Univ. of Arkansas, Barry Dunning from Rice Univ., Horst Schmidt-Böcking from the Univ. of Frankfurt, Germany, Donald Umstadter from the Univ. of Nebraska-Lincoln, and the Neff lecture in physics speaker Philip Bucksbaum from Stanford University. Outside speakers at our AMO seminar this year have included Danielle Braje from NIST, Alan Fry from Coherent Company, Barry Dunning from Rice Univ., Kun Zhao from the Univ. of Nebraska-Lincoln, Chang Hee Nam from KAIST, Korea, Akira Suda from RIKEN, Japan, Jeff Nicholson from OFS Labs, Matt Bohn from the Air Force Institute of Technology, and Robert Lucchese from Texas A&M Univ.

Dr. Uwe Thumm Finds a Way to Steer Electrons in a Molecule Using Laser Pulses

Uwe Thumm

Theoretical physicist Uwe Thumm and his colleagues Feng He and Andreas Becker not only work with some of the smallest molecules in the universe, but they now have found a way to control the motion of the molecules' building blocks, electrons and nuclei.

Thumm is a professor of physics at Kansas State University. Feng is a research associate at the K-State physics department, and Becker is a professor at the University of Colorado in Boulder. The collaborators have found a way to steer the movement of electrons in a hydrogen molecule using ultrafast laser pulses. These pulses are so short that their duration is measured in attoseconds -- that's one billionth of a billionth of a second.

In a recent research paper, the three collaborators explained how attosecond laser pulses can be used to direct the motion of an electron inside a hydrogen molecule, and what the measurable consequences of this control over the electron would be. The paper appears this month in Vol. 101 of The Physical Review Letters.

As theoretical physicists, Thumm and his colleagues do not perform experiments, but instead simulate the outcome of present and future experiments by developing mathematical models. These models explain the nature of atoms, molecules, light and their interactions in terms of mathematical equations that are solved with the help of powerful computers.

The researchers' model describes experiments that are currently being performed at various laboratories worldwide, including the J.R. Macdonald Laboratory at K-State.

For the past few years, Thumm and his colleagues studied what happens with the hydrogen molecular ion when it interacts with short laser pulses. They used hydrogen because it's the simplest molecule, although they have now extended their research toward the imaging and control of the much faster moving electrons.

The hydrogen molecular ion has two protons and just one electron that "glues" them together. A few years ago, by performing computer simulations, they found that laser pulses can control the motion of the protons by setting them in motion or slowing them down.

The researchers use a first ultrafast laser to pump the molecule with infrared pulses. The protons vibrate and move apart slowly, but the electron still tries to hang on. The second part of their model uses the laser to probe the particles with a second delayed light pulse to see what happens when the electron fails to keep the protons glued together. The infrared laser pulses create an electric field that puts a force on the electron. Eventually, Thumm said, the electron has to choose which proton it will stick with.

Thumm and his colleagues were surprised to find that for certain laser pulses the electron can move in the opposite direction from what they anticipated.

"Our naive expectation was that the electron would follow the laser electric force," Thumm said. "That's what other simulations predicted, and they agree with classical physics and common intuition."

For instance, if you're pulling on a shopping cart, the cart will move in the direction of the force -- in this case, toward you. But at the quantum level, the rules are different.

The researchers found that sometimes the electron moves in the direction of the force, but sometimes not. Thumm, He and Becker found that the electron picks the proton on the left or the one of the right depending on the intensity of the laser pulse. Knowing which intensity will make the electron move to the left or the right gives physicists the ability to steer the electrons by setting the laser pulse to a specific intensity.

Thumm said this finding is not only a contribution to basic physics research, but it also could help chemists better understand and possibly control chemical reactions.

"We would like to see a 'molecular movie' that shows the redistribution of electrons in time -- within attoseconds -- during a chemical reaction," he said. "It would promote our understanding of basic processes that eventually enable life: electrons bind atoms to simple molecules, such as the hydrogen molecule or water. Through many chemical reactions, these simple molecules react with each other and eventually form huge bio-molecules that make life, as we know it, possible."

One possible commercial application of the finding, Thumm said, could be helping companies become more efficient in producing a desired chemical compound while minimizing unwanted byproducts in the reaction.

KSU Physics Undergrad, Samuel Fahrenholtz, Received Honorable Mention Honor for Goldwater Scholarship

Three Kansas State University students are recipients of 2008 Barry M. Goldwater Scholarships, while a fourth student has been recognized as an honorable mention for the award.

The winners are Michelle Higgins, Manhattan; William Carlson, Overland Park; and Scott McCall, Parker, Colo. Samuel Fahrenholtz, Tribune, received honorable mention honors.

The three K-State students are among 321 students from across the nation to receive the Goldwater Scholarship this year, which are awarded for academic merit. The scholarships are worth up to $7,500 annually for a student's final one or two years of undergraduate studies. This year's recipients were selected from a field of 1,035 mathematics, science and engineering students who were nominated by the faculties of colleges and universities nationwide.

"Congratulations to these superb K-State students, who continue this university's rich tradition of national scholarship excellence," said Jon Wefald, K-State president. "The Goldwater Scholarship places a high value on undergraduate research experience, and at K-State, we have long made opportunities for undergraduate research a priority. The efforts of our dedicated and supportive faculty also are helping our students achieve at this highest level."

With three Goldwater recipients this year, K-State students have now won 63 Goldwater Scholarships. K-State remains first in the nation among state universities in Goldwater Scholarship winners. Among all universities, K-State is tied for third place with Duke. Princeton has 68 and Harvard has 67 Goldwater scholars.

All four K-State students plan careers in research.

Higgins, a senior in nutritional sciences and biochemistry, plans to pursue a doctorate in pharmacology. Her career goal is to conduct translational research in drug discovery and development at the university level.

Carlson, a junior who is majoring in mathematics, wants to do research in math analysis and teach at a university after earning his Ph.D.

McCall is a sophomore in biochemistry and biology. After earning his medical degree and doctorate in pharmacology, he would like to conduct novel pharmaceutical research, especially using synthetic medicine chemistry for clinical integration in clinical medicine.

Fahrenholtz, a senior in physics, plans to pursue a doctorate and conduct research in the area of medical physics, teaching at the graduate level and performing clinical work pertinent to his research.

Higgins is working in the K-State College of Veterinary Medicine's pharmacology program, looking for proof of concept by performing immunohistochemistry on prostate tumor sections from treated mice. At K-State, she also was a student lab assistant in 2005 for the department of human nutrition, assisting in a study researching the effects of diet and exercise on cancerous tumor development. She has worked as a research technician in the K-State Nutrient Metabolism Lab, assisting in a glycemic index study investigating glucose absorption and insulin sensitivity. In 2007, she was a National Exchange Student at Oregon State University, where she gained biochemistry research credit by maintaining prostate cancer cell cultures and learning DNA extraction and Western blotting. She also had a Summer Undergraduate Research Fellowship at the University of Kansas Medical Center, where she tested pharmacologic interventions for prostate cancer. She is a member of the K-State women's rowing team, College of Human Ecology honors program, Alpha Chi Sigma professional chemistry fraternity and Phi Kappa Phi honor society. Her others honors include a 2007 Cancer Research Award; Gamma Sigma Delta Honor Society's Outstanding Junior Award in 2007; semester academic honors; Big 12 Conference Commissioner's Honor Roll for multiple semesters; 2007 Phi Kappa Phi Scholarship; K-State department of biochemistry scholarship, 2006-present; Kansas State University Foundation Scholarship, 2004-2008; and a K-State Women's Rowing Athletic Scholarship, 2004-2008. A 2004 graduate of Manhattan High School, she is the daughter of Mary Higgins, Manhattan, and the late Randy Higgins.

Carlson is currently conducting research related to the analysis of particular partial differential equations under the supervision of Ivan Blank, visiting professor of mathematics. A research paper he wrote was published in Quantum Information and Computation. Carlson is a member of several honor societies including Phi Kappa Phi, Pi Mu Epsilon national mathematics society and the National Society of Collegiate Scholars. He was awarded a K-State Presidential Scholarship, a Stromberg scholarship, a Foster scholarship, a Friends of Mathematics scholarship, an IBM Watson Scholarship and an I-Center Undergraduate Research Award. Carlson also participated in a summer 2006 undergraduate research experience at the State University of New York at Potsdam. His research was focused on graph theory and he co-authored the paper "Universal Mixing of Quantum Walks on Graphs" that was published in Quantum Information and Computation. Carlson is a member of several honor societies including Phi Kappa Phi, Pi Mu Epsilon national mathematics society and the National Society of Collegiate Scholars. He has also been a member of the Chess Club, the Physics Club, the Math Club and a founding member of both the Go Club and the KSU Airsoft Team. A 2005 graduate of Shawnee Mission South High School, he is the son of Ron and Diane Carlson, Overland Park.

McCall has received the K-State Legacy Scholarship and the Gamma Sigma Delta First Year Achievement Award. Since fall 2006 he has worked in the organometallic lab of Stefan Kraft, assistant professor of chemistry. McCall is currently researching the development and synthesis of novel ligands designed to use high oxidation state palladium as a catalyst for carbon-hydrogen bond activation, with the ultimate aim of converting natural gas into combustible methanol as an alternative fuel source. He is also beginning work on elucidating the mechanisms of corneal cross-linking as part of surgical healing after LASIK surgery. McCall will pursue that topic this summer with a fellowship at the Mount Desert Island Biological Laboratory in Bar Harbor, Maine. He is a member of the K-State National Intercollegiate Rodeo Association rodeo team. In addition, he represents K-State as a Colorado ambassador. He was a National Forensics League Academic All-American in high school, and recently the American Quarter Horse Youth Association reserve national high point calf-roper, and three-time Rocky Mountain Quarter Horse Youth Association champion calf-roper. A 2006 graduate of Cherry Creek High School, he is the son of Dr. Marc and Lori McCall, Parker, Colo.

Fahrenholtz has participated in undergraduate research with the research group of Itzhak Ben-Itzhak, K-State professor of physics. They are studying the physics of laser-ion and molecule-ion collisions. He is involved in the imaging of the team’s experimental measurements and is currently analyzing proton-water collisions. Fahrenholtz has received a Kansas State University Foundation Scholarship, a Linschied Scholarship, a Dragsdorf Physics Scholarship and a College of Arts and Sciences Scholarship. He also has been active in K-State Concert Band and Brass Ensemble. A member of Farmhouse fraternity and a 2005 graduate of Goddard High School, he is the son of Dr. Randy and Janice Fahrenholtz, Tribune.

Last updated on Monday, 08-Feb-2010