Atomic, Molecular & Optical Physics (AMO) Projects
Computational ultrafast dynamics for molecules (Theory)
E-mail: lgreenman@phys.ksu.edu
Number of REU participants: 1
The dynamics of molecules interacting with intense, ultrafast, or high-photon-energy laser fields pushes the frontier of complexity that can be described by current theories and computational techniques. However, it is precisely these regimes where we can learn new phenomena for molecules relevant to chemical reactivity and energy conversion. In this project, a 2019 REU student will explore new techniques for understanding molecular interactions on ultrafast timescales and complex dynamical processes.
Together, we will work with experimentalists at the James R. Macdonald Laboratory to understand complex processes by characterizing the potential energy of molecules at distorted geometries and in highly excited states. The student will learn to use state-of-the-art methods from the community of quantum chemistry, where quantum mechanics and applied mathematics are combined and applied to molecules. In the course of this project, we will use some of the most powerful supercomputers in the world including those at the National Energy Research Supercomputing Center (NERSC). Benefits include exposure to computer scripting in languages like Python, basic computer programming in Fortran or C++, and high-performance computational techniques.
Imaging molecular dynamics induced by intense ultrashort laser pulses (Experiment)
Number of REU participants: 1
During the 2019 REU program, our research group will be involved in a variety of projects where undergraduate students can learn interesting physics and contribute to our research progress. Below, we have briefly outlined a project that would best fit an REU student. We expect this project to provide hands-on research experience both in and out of the laboratory, ranging from designing and testing of the experimental setup, to conducting measurements and hopefully preparing the results for publication. In addition to their specific project, the REU students are invited to get involved in other summer projects within our research group. Our research group includes graduate students Bethany Jochim and Travis Severt, who were both REU students in 2010 and 2011, respectively, Professor Kevin Carnes and Professor Itzik Ben-Itzhak.
Ultrafast laser pulses (≤ femtoseconds in pulse duration) provide physicists and chemists with a unique tool to probe the nuclear dynamics of molecules on their natural femtosecond time scale. Our research group utilizes a unique experimental apparatus developed here at K-State to study the fragmentation dynamics of molecular-ion beams by imaging the momentum distributions following the breakup [1-2].
Recently, we began studying the fragmentation of polyatomic molecular ions, such as acetylene (C2H2 +). Unfortunately, due to limitations of our apparatus, we cannot measure hydrogen/proton elimination channels, like H++C2H, efficiently due to large mass difference between the fragments (see Ref. [3] for similar issues in studies of a CD+ beam). To overcome this limitation, we began designing a two-detector imaging system, which allows the light ionic fragments (like H+ and H2 +) to be measured on one detector while the heavy ionic and all neutral fragments are measured on a second detector further downstream.
The goal of this REU project will be to assist Travis in the construction and testing of this two-detector setup. In addition, the student will be involved with deriving the equations for calculating the momenta of the fragments for ideal electric fields, modeling correction factors for the actual electric fields using the commercially available SIMION software, developing a method to simultaneously calibrate both detectors, and participating in the first experiment utilizing the setup, if time permits.
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- I. Ben-Itzhak et al., Phys. Rev. Lett. 95, 073002 (2005).
- J. McKenna et al., Phys. Rev. Lett. 103, 103004 (2009).
- L. Graham et al., Phys. Rev. A 91, 023414 (2015).
Studying ultrafast molecular dynamics in pump-probe experiments with femtosecond lasers (Experiment)
Daniel Rolles and Artem Rudenko
E-mail: rolles@phys.ksu.edu or rudenko@phys.ksu.edu
Number of REU participants: 2
State-of-the-art femtosecond lasers can generate pulses with durations shorter than the time scales of fundamental molecular processes such as dissociation, rearrangement of molecular bonds, and vibrational motion. This can be exploited for creating "movies" of these processes in so-called pump-probe experiments. Here, the first ("pump") laser pulse triggers the reaction of interest, and the second ("probe") pulse, arriving after certain delay time, takes a snapshot of the molecular structure [1-3].
For the 2019 REU program, we offer a project focused on performing pump-probe experiments at the James R. Macdonald Laboratory using an intense femtosecond 800 nm laser, its 3rd and 4th harmonic at 266 and 200 nm, and/or shorter wavelengths created by high harmonic generation. The main goal of these experiments will be to trace the time evolution of the molecular wave packets induced by either the 800 nm or the 266 nm light pulse. Within the course of the project, the REU student will gain practical, hands-on experience working with ultrafast optics (in particular, third/fourth harmonic and high-order harmonic generation and characterization), learn basics of laser interactions with atoms and molecules, get an introduction into electron and ion spectroscopy, and in the data acquisition and data analysis software for pump-probe experiments. The student will be co-mentored by Prof. Daniel Rolles and Prof. Artem Rudenko and work together with graduate students from the Rolles and Rudenko groups.
- Y. Malakar et al., PCCP, in press (2019).
- F. Allum et al., J. Chem. Phys. 149, 204313 (2018).
- D. Rolles et al., Journal of Visualized Experiments 140, e57055 (2018).
