Distinguished Professor

James R. Macdonald Laboratory director Itzik Ben-Itzhak has been named a University Distinguished Professor. Itzik joins a long line of Physics professors who have been so honored. Current Distinguished Professors in the Physics department include Brett Esry, CD Lin, Chris Sorenson and Dean Zollman. Retired or otherwise past professors include Lew Cocke, Pat Richard, Talat Rahman and Bill Reay. Clearly, we're doing something right!

Distinguished Professor is a lifetime title that is the highest honor the University bestows on its faculty for demonstrating their commitment to education through their excellence in teaching, research, creative endeavors and service. Four University faculty members were so honored in 2012.

Itzik's research focuses on the interaction of intense ultrashort laser pulses with molecular ions, with the long-term goal of gaining sufficient understanding of these processes so that they may be controlled at the quantum mechanical level. He also studies the physics of atomic and molecular collisions.

Read more about Itzik's honor in the University press releases, or see the photo gallery of the party thrown for him earlier this month.

Imaging Ultrafast Molecular Dynamics

Real-time images of two atoms vibrating in a molecule have been made by the experimental group of Louis DiMauro at Ohio State University, in collaboration with our own University Distinguished Professor CD Lin and his student Junliang Xu.

The technique illuminates nitrogen or oxygen molecules with intense, ultrafast laser light pulses. The powerful laser electric field both ionizes the molecule and causes some electrons to be rescattered from the parent molecule. The electrons produce a diffraction pattern that can be used to to produce the images with sub-Angstrom precision and exposure times of a few femtoseconds.

The paper, entitled "Imaging ultrafast molecular dynamics with laser-induced electron diffraction" was published in the prestigious journal Nature, and in turn received widespread attention in the popular media. Popular stories can be found on the Gizmodo blog and in the Columbus Dispatch newspaper.

Read more news from the lab, or find still more of our world-class AMO physics publications.

Research Highlights

JRM AMO researchers have recently been recognized for the special merit of papers published in the Journal of Physics B: Atomic, Molecular and Optical Physics.

Matthias Kling contributed to "Attosecond imaging of XUV-induced atomic photoemission and Auger decay in strong laser fields". Published in May 2011, this paper has been chosen as a 2011 Highlight, giving "a taste of the outstanding and excellent research published" by J. Phys. B in 2011. See J. Phys. B 44, 105601 .

Carlos Trallero, CD Lin, AT Le and Cheng Jin were co-authors of "Generation of broad XUV continuous high harmonic spectra and isolated attosecond pulses with intense mid-infrared lasers". This work was chosen in December of 2011 as an IOP Select paper for its "novelty, significance and potential impact on future research". See J. Phys. B 45, 011001 .

Read more news from the lab, or find still more of our world-class AMO physics publications.

Ad Astra!

We are wrapping up the Kansas sesquicentennial celebrations, and the Ad Astra Kansas Initiative is spotlighting 150 Kansas researchers, inventors and engineers from the past to the present who have advanced their field. The latest to be so recognized is our own Associate Professor, Kristan Corwin. She joins our Professor Chii-Dong Lin, who was also so honored this past summer.

The Ad Astra Kansas Initiative is a Hutchinson-based organization that works toward promoting the scientific accomplishments of Kansas researchers and innovators who work in the fields of science, technology, engineering and mathematics. Ad Astra's project, "Science in Kansas: 150 Years and Counting," celebrates the state's sesquicentennial. It is meant to emphasize the importance of science and the career possibilities in research and innovation to K-12 students.

Learn more from the Kansas State University press release or the Ad Astra Kansas Initiative web site.

A New Kind of Laser

Associate Professors Brian Washburn and Kristan Corwin, along with graduate student Andrew Jones have invented a new class of lasers. The laser light is generated by gas confined within hollow "photonic crystal" fibers.

The project is being funded by the Army Research Office, the Air Force Office of Scientific Research, and Precision Photonics Corp. in Colorado. The work is in collaboration with Chris Levy in the K-State Chemistry Department, the University of New Mexico and the University of Bath in the U.K.

Jochim Wins Apker Award

A Kansas State University graduate student is receiving a prestigious physics award for research she did as an undergraduate with the help of the J.R. Macdonald Laboratory.

Bethany Jochim, doctoral student in physics from Pierre, SD, is the recipient of the LeRoy Apker Award, the top undergraduate honor awarded by the American Physical Society. The award recognizes outstanding achievements in physics. Two Apker awards are given annually. Each award consists of $5,000 to the recipient, a travel allowance to the American Physical Society meeting where the award will be presented, and $5,000 to the recipient's undergraduate institution.

Jochim is a 2011 bachelor's graduate of Augustana College in Sioux Falls, SD, where she had a successful career as an undergraduate researcher, working with her advisor, K-State alumnus Eric Wells. She had five research articles published in mainstream peer-reviewed scientific journals. Some of this research work was conducted here at the JRM Lab.

See the full K-State or Augustana press releases.

Ad Astra!

We are currently celebrating the Kansas sesquicentennial, and the Ad Astra Kansas Initiative is spotlighting 150 Kansas researchers, inventors and engineers from the past to the present who have advanced their field. The latest to be so recognized is our own Associate Director for Theoretical Research and University Distinguished Professor, Chii-Dong Lin,

The Ad Astra Kansas Initiative is a Hutchinson-based organization that works toward promoting the scientific accomplishments of Kansas researchers and innovators who work in the fields of science, technology, engineering and mathematics. Ad Astra's project, "Science in Kansas: 150 Years and Counting," celebrates the state's sesquicentennial. It is meant to emphasize the importance of science and the career possibilities in research and innovation to K-12 students.

Learn more from the Kansas State University press release or the Ad Astra Kansas Initiative web site.

Informal Physics

Professor and Ph.D. Brett DePaola’s knack for explaining physics without resorting to math is helping him clarify technology topics for the U.S. Department of State. But that’s about the only parallel between his K-State role and his yearlong stint as a Jefferson Science Fellow.

The program brings professors to Washington, D.C., to advise policymakers on science, technology and engineering.

What DePaola has encountered there is a tireless corps of civil servants who truly rely on him and the other Fellows...

From Informal Physics in the Summer 2011 issue of Influences, a publication of the Kansas State College of Arts & Sciences. Read the complete article or the entire publication in Acrobat (pdf) format.

Electron Ping Pong

An international team of researchers, including our own Matthias Kling, succeeded at the Max Planck Institute of Quantum Optics to control and monitor strongly accelerated electrons from nano-spheres with extremely short and intense laser pulses.

When intense laser light interacts with electrons in nanoparticles that consist of many million individual atoms, these electrons can be released and strongly accelerated. Such an effect in nano-spheres of silica was recently observed by an international team of researchers in the Laboratory for Attosecond Physics (LAP) at the Max Planck Institute of Quantum Optics. The researchers report how strong electrical fields (near-fields) build up in the vicinity of the nanoparticles and release electrons. Driven by the near-fields and collective interactions of the charges resulting from ionization by the laser light, the released electrons are accelerated, such that they can by far exceed the limits in acceleration that were observed so far for single atoms. The exact movement of the electrons can be precisely controlled via the electric field of the laser light.

Read the complete press release from MPI, or the original paper in Nature Physics: Controlled near-field enhanced electron acceleration from dielectric nanospheres with intense few-cycle laser fields.

Lew Cocke Is Retiring

During his exceptional career Lew Cocke made outstanding contributions to atomic, molecular and optical physics. He has been a prolific researcher and mentor who, over many decades, led the scientific work at the J. R. Macdonald Laboratory in the KSU Department of Physics. At the end of this Spring semester, Lew will officially retire as a University Distinguished Professor and become a Professor Emeritus. Even though Lew plans to continue conducting research in the coming years, this juncture of his career is an appropriate time to recognize his contributions to AMO physics. We, as his colleagues, and the KSU Department of Physics, are organizing a celebration of this special occasion with a one-day symposium entitled Chasing attosecond dynamics of atoms and molecules with electrons, ions and lasers - the last forty years.

The Lew Cocke Symposium will be held at the KSU Alumni Center on Monday, 18 April 2011.

Imaging A Chemical Reaction

Gaining complete control over chemical reactions has been the dream of chemists and physicists for decades. To achieve this goal, one must first be able to follow and characterize (or 'image') the dynamics of the coupling between electronic and nuclear motion within molecules on a femtosecond timescale. This has been traditionally achieved using the pump–probe scheme, which involves delaying two ultrashort laser pulses with respect to each other. The first pulse — the pump — creates excited states in molecules to initiate a chemical reaction. These molecules are then imaged by a second pulse — the probe — at different points in time following the excitation. Because ultrashort pump pulses can typically excite only a small fraction of molecules at a time, signals from molecules undergoing chemical transformation are much weaker than signals from ground-state molecules, thus making the task technically challenging.

The full text is found in "Ultrafast optics: Imaging a chemical reaction"
Anh-Thu Le, Chii-Dong Lin
Nature Photonics 4, 671 (2010)

Summer Undergrad Research

The Physics Department and the JRM Lab have just concluded another successful summer Research Experience for Undergraduates (REU). The REU program is funded by the National Science Foundation and is managed here by Professors Kristan Corwin and Larry Weaver. Undergraduates from around the country are mentored through an intensive ten weeks of hands-on work by various faculty members.

The KSU Graduate School and the Division of Communications and Marketing have produced the above video highlighting not only the Physics REU program, but undergrad research across the University. Another KSU press release describes the research of one of our students, Jennifer Black of Southern Polytechnic State University in Georgia, mentored by Professor Brian Washburn.

Ultracold Controlled Chemistry

Two groups have now taken a completely new approach to study chemical transformations of molecules: Steven Knoop and colleagues at the University of Innsbruck in Austria and the Austrian Academy of Sciences, in collaboration with Jose D'Incao at JILA and Brett Esry at Kansas State University, both in the US, reporting in Physical Review Letters, and Silke Ospelkaus and co-workers at JILA and NIST, also in the US. These researchers start with an ensemble of atoms cooled to an ultralow temperature (<10 µK) and confined in an optical potential of a focused laser beam. The atoms are then linked together by a time-varying magnetic field in the work of Knoop et al., or by irradiating the sample of atoms with lasers of two different frequencies in the work of Ospelkaus et al.

From a Physics Viewpoint article by Roman V. Krems, on a recent Physical Review Letters paper by our Brett Esry and his collaborators.

The Attosecond Revolution

The most intuitive way to understand the extreme nonlinear interaction that leads to attosecond pulses is through the semi-classical re-collision model. A strong infrared light pulse illuminating an atom or molecule creates a "free" electron wave packet by multiphoton ionization, usually approximated by tunneling. Tunneling occurs over a range of phases of the fundamental pulse near each crest of the laser electric field - a time window of roughly 300 attoseconds (as). In practice, in the infrared, multiphoton ionization intensities in the range of 10¹⁴ to 10¹⁵ W/cm² are needed, corresponding to peak electric field strengths of 3-10 V/Å...

This article by Paul Corkum and Zenghu Chang was the cover story in the October Optics & Photonics News. It is available in Acrobat form.

Coulomb Explosion of D₂

We present the first systematic wavelength-dependent study of laser Coulomb explosion of deuterium molecules at various peak intensities and polarizations. We measured the kinetic energy spectra of D+ for laser wavelengths in the range 480-2000 nm. In addition to the well-known enhanced ionization channel present for all wavelengths, we observe a new high-energy band at short wavelengths. This new band exhibits wavelength dependence, with fragment energy decreasing with increasing wavelengths until it merges with the enhanced ionization band for 800 nm and longer. We attribute the emergence of this band to a new pathway that involves resonant three-photon coupling to the first excited electronic state of the molecular ion during the Coulomb explosion process. This pathway should be accounted for in controlling molecular dynamics of hydrogen by intense laser pulses.

The full text is found in New Journal of Physics, 10, 83011 (07 Aug 2008).

Femtosecond Dynamics

The direct observation of molecular dynamics initiated by x-rays has been hindered to date by the lack of bright femtosecond sources of short-wavelength light. We used soft x-ray beams generated by high-harmonic upconversion of a femtosecond laser to photoionize a nitrogen molecule, creating highly excited molecular cations. A strong infrared pulse was then used to probe the ultrafast electronic and nuclear dynamics as the molecule exploded. We found that substantial fragmentation occurs through an electron-shakeup process, in which a second electron is simultaneously excited during the soft x-ray photoionization process. During fragmentation, the molecular potential seen by the electron changes rapidly from nearly spherically symmetric to a two-center molecular potential. Our approach can capture in real time and with angstrom resolution the influence of ionizing radiation on a range of molecular systems, probing dynamics that are inaccessible with the use of other techniques.

The full text of this paper is found in Science, 317, 1374 (07 Sep 2007).