Atomic, Molecular & Optical Physics (AMO) Projects
Imaging Molecular Dynamics Induced by Intense Ultrashort Laser Pulses (Experimental)
E-mail: ibi@phys.ksu.edu
During the 2023 REU program, our research group will be involved in a variety of projects in which undergraduate students can participate in, contribute to our research progress, and in the process gain research experience. I have briefly outlined below a couple of projects that would best fit an REU student. We expect these projects to provide hands-on experience in and out of the laboratory, involve students in different aspects of advanced laser-matter interaction measurements ranging from designing and testing of experimental setups to interpreting results for publication. In addition to their REU project, undergraduate students can get involved in other summer projects within our group1. Our research group includes my graduate student, Naoki Iwamoto, and post-doctoral fellow, Chandan Bagdia. The REU student will interact with the entire group while working closely with one person.
For a couple of decades, we have been studying the interaction of intense ultrafast laser pulses with fast molecular ion beams through the application of a coincidence three-dimensional momentum imaging technique [1]. We have recently upgraded our imaging setup to facilitate studies of molecules having both light and heavy fragments, which have been previously limited to a heavy-to-light mass ratio of about 6 [2]. A second position- and time-sensitive detector to detect the light ion was added, while the heavy and neutral fragments are detected on the existing detector. Employing this upgraded setup, we are exploring fragmentation of hydrocarbons, like CHn+, as well as simpler diatomic molecules, such as HeH+ and OH+. In parallel, we are refining the calibration of the new imaging setup and determining its capabilities and limitations. To that end, the REU student will perform simulations of the ion trajectories needed for calibration of the momentum-imaging setup and analyze test data taken in different configurations of the new apparatus. The same HD+ dissociation data used for calibration also includes some intriguing phenomena that we may pursue if fast progress on this project is achieved.
Another upgrade that we are working on involves the development of a higher density ion-beam target. The low density of a typical ion beam is the limiting factor in our experiments, as it leads to much lower counting rates than possible in gas phase measurements. In this case the REU student is expected to be involved in tests of a new ion beam bunching scheme, employing TOF spectrometry techniques [3]. Bunching the ion current is expected to significantly increase the target density of our ion-beam target, provided that the ion bunches can be efficiently produced and synchronized with the laser pulses.
References
[1] A.M. Sayler et al., J. Phys. B 47, 031001 (2014); J. McKenna et al., Phys. Rev. Lett. 103, 103004 (2009); I. Ben-Itzhak et al., Phys. Rev. Lett. 95, 073002 (2005);
[2] L. Graham et al., Phys. Rev. A 91, 023414 (2015)
[3] Ben Berry et al., Rev. Sci. Instrum. 86, 046103 (2015); J. McKenna et al., Phys. Rev. A 84, 043425 (2011); I. Ben-Itzhak, S.G. Ginther, and K.D. Carnes, Nucl. Instrum. Methods B 66, 401 (1992).
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1 It is important to note that the specific involvement of the REU student in any of the projects will depend on the qualifications and interests of the student as well as our needs at the time.
Computational Ultrafast Dynamics for Molecules (Theory)
E-mail: lgreenman@phys.ksu.edu
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 2023 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.
Modeling Quantum Dynamics in Intense Laser-Molecule Interaction (Theory)
Chii-Dong Lin/Isaac Yuen (postdoc)
E-mail: cdlin@phys.ksu.edu or iyuen@phys.ksu.edu
When a molecule is illuminated by an intense laser pulse, a range of exciting quantum phenomena can occur, including ionization and breakup. In this project, you will gain hands-on experience in modeling these dynamics for simple systems in various conditions. You will develop proficiency in coding with Python, using the command line in the terminal, and running calculations on a supercomputer. These skills will be highly valuable in your future academic and professional pursuits. If you are interested in theoretical physics, our project on modeling quantum dynamics will suit you well.
Studying Ultrafast Molecular Dynamics in Pump-probe Experiments with Femtosecond Lasers (Experiment)
Daniel Rolles and Artem Rudenko
E-mail: rolles@phys.ksu.edu
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 2023 REU program, we offer a project focused on performing pump-probe experiments at the James R. Macdonald Laboratory using intense femtosecond laser pulses in the ultraviolet (UV) to near-infrared (NIR) spectral range. The main goal of these experiments will be to trace the time evolution of molecular reactions induced by either the UV or the NIR light pulse, primarily using a technique called ‘Coulomb explosion imaging’ [4-6]. Within the course of the project, the REU student will gain practical, hands-on experience working with ultrafast optics (in particular the characterization of femtosecond laser pulses), 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.
[1] S. Pathak et al., Nature Chemistry 12, 795-800 (2020).
[2] Y. Malakar et al., Phys. Chem. Chem. Phys. 21, 14090-14102 (2019).
[3] D. Rolles et al., Journal of Visualized Experiments 140, e57055 (2018).
[4] S. Bhattacharyya et al., J. Phys. Chem. Lett. 13, 5845 (2022).
[5] R. Boll et al., Nature Physics 18, 423-428 (2022).
[6] F. Ziaee et al., Phys. Chem. Chem. Phys., in press (2023).