Professor Robert J. Levis




Dr. Dmitri Romanov

Dmitri Romanov, PhD



Dr. Aleksey I Filin

Aleksey Filin, PhD

Investigation of radioactive signatures by Impulsive Raman Spectroscopy for remote detection of radioactive materials.

Investigation of novel methods of growing semiconductor quantum dots in glass matrix by ultra-short laser pulse. The method is perspective for creation of three-dimensional quantum dot superstructures.






Johanan Odhner

Johanan Odhner, Ph.D.

The applications of femtosecond laser filament-based standoff/remote spectroscopy and control of atmospheric chemistry motivate my studies of the fundamental process of laser filamentation in order to better understand how to control and direct the process. Particularly interesting for spectroscopy is the pulse shortening that occurs during filamentation, which results in excitation of all Raman-active modes present in the propagation medium, leading to the generation of molecule-specific signatures. Continuum generation by filamentation also acts as a source of intrinsically short pulses that cover the entire visible range, making it a good source for time-resolved spectroscopy.


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Katharine Moore Tibbetts, Ph.D.

The goal of my research is to control chemical reactions induced by strong field femtosecond laser pulse excitation of gas- and condensed-phase molecules. In the gas phase, I use time-resolved spectroscopy to induce specified dissociation reactions in small molecules by selectively populating electronic excited states of their radical cations. In acetophenone, excitation to the second electronic excited state of the radical cation yields selective loss of a methyl group, while excitation to higher-lying excited states results in loss of the acetyl group. I have also demonstrated the preparation of noble metal nanoparticles with controlled sizes and shapes by strong field excitation of aqueous solutions of noble metal salts. The current focus of this research is to understand the mechanisms underlying nucleation of noble metal clusters induced by excitation of metallic precursor complex and surrounding water molecules.



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Jieutonne Archer

My research focuses on validating various methods employing laser electrospray mass spectrometry (LEMS) for the quantitative study of non-covalent protein-ligand interactions. LEMS has proven to be effective in the analysis of native protein samples. Its ability to analyze unprepared solid and liquid samples makes it ideal for biologically sensitive analytes. The use of a temperature-controlled stage to simulate natural environmental temperatures or even to assess temperature related stresses on biological systems also adds to the versatility of LEMS. I believe that my research can help to further prove that LEMS is an ideal tool that can be used to study biologically relevant molecular phenomena within the realm of mass spectrometry.


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Jerry Barney

My research focuses on the ultrafast dynamics of polyatomic molecules under intense visible and IR excitation. Time-of-flight mass spectrometry is used as a detector for the photoionization of molecules subject to strong-field femtosecond laser pulses. Specifically I am interested in the photoionization and subsequent photodissociation of acetophenone and similarly structured molecules. The photodissociation mechanism for acetophenone is known, and the parent ion population has been shown to depend on excitation wavelength. Interrogating this system under different circumstances (wavelength, pulse duration, pulse shape) is my current focus in the Levis group.


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Colin Fitzpatrick

Ultrafast lasers present a unique manner of exerting control over chemical reactions. The focus of this research is to modify or create novel materials using femtosecond pulses. The photo-isomerization of azobenzene has previously been used to induce motion on the nanometer and Angstrom scale, using the rotation from trans to cis or cis to trans. However, most applications have only utilized a single species of azobenzene and are therefore limited to simple binary functions. By modifying azobenzene with different side-groups and tailoring laser pulses to selectively excite different derivatives we can induce complex motions and build intricate and versatile molecular machines. We are also exploring controlled surface chemistry of carbon. Graphitic carbon is normally not highly reactive, unless under extreme conditions like high heat or with strong acids. The aim is to use high-energy pulses to control surface the functionalization by adding more reactive moieties. These chemically active groups would then allow the unique mechanical properties of macroscopic carbon structures to be incorporated into a diversified range of materials in less extreme conditions.


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Reggie Fisher

Reginald Fisher studies the production and detection of molecules that may be generated as a byproduct of nuclear decay by impulsively stimulated Raman spectroscopy.  This includes decay signatures such as oxygen cations or ozone produced by other means.  Femtosecond filamentation is of particular interest both as source of these signatures and as a means of their detection.  The goal of this research is both to understand the mechanism of the production of these signatures and their relation to the ongoing processes involved as well as to provide a method for detection of nuclear decay events.


Stantosh Karki

Santosh Karki

My research focuses on the use of femtosecond laser vaporization to transfer the condensed phase protein molecules into the electrospray plume consisting of a charge altering agent (e.g. supercharging/charge reducing buffer), to study the conformational change of proteins. I am currently working on the investigation of lifetime of laser-vaporized droplet that it spends with the electrospray plume to better understand the kinetics of protein unfolding/refolding in the current system. The study also involves the investigation of possible ionization mechanism of biomolecules in the LEMS process.


Juehuan Liu

Juehuan is working on shaping the filamentation, a broadband ultrafast laser pulse that is induced by the laser ionized air. As the front of a near IR laser pulse is for creating ionized air and the back of the pulse is for creating broadband white light, optimizing the shape of the incoming pulse is critical. After obtained a controllable filament with close loop process, it will be used for analyzing.


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Erin McCole

Currently we are investigating atomic and molecular systems by using femtosecond laser filaments to perform strong-field chemistry. Filaments are used in impulsive vibrational and rotational Raman spectroscopy for purposes of point and remote detection of chemical systems of interest, including explosive and radioactive decay signatures. In Filament-Assisted Impulsive Raman (FAIR) Spectroscopy, the filament acts as an impulsive pump pulse to simultaneously excite all the Raman-active modes of the system. In Spectral-to-Temporal Amplitude Mapping Polarization Spectroscopy (STAMPS), the filament is temporally chirped (~65 ps) and used to probe the impulsively excited rotational revivals occurring within the time window of the filament pulse.


Johnny Perez

My research endeavors are multi-faceted. Since joining the Levis Group, and the CAPR, I have had an interest in Biophysics, specifically, what affect do ultrafast lasers have on the structure and function of biological molecules and samples? We are also in the early stages of using LEMS to study proteomics and enzyme catalysis following laser vaporization. In addition, we are designing experiments to understand the dynamics and physics involved in the entrainment of sample into an electrospray droplet plume. Lastly, we are making strides in developing an atmospheric pressure ion mobility chamber that will couple with our mass spectrometer introducing a new and exciting area of research.


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Habib Sistani

My research focuses on sample preparation for laser electrospray mass spectrometry (LEMS) in order to improve the reproducibility of LEMS analyses. The idea is to use electrospray deposition (ESD) technique to make a homogeneous film of analytes. Electrospray deposition is accomplished by using a home built apparatus, which consists of a high voltage power supply, a syringe pump, a needle and a sample substrate. The needle is mounted in a holder and it is biased to a high voltage of approximately +5 kV while the sample substrate is maintained at ground. A spray is formed between the tip of the needle and the substrate. Electrospray deposition results in a homogeneous circular film of sample. The higher sample homogeneity from ESD samples decreases both the within-film of sample and between-films of sample (film-to-film) variability, resulting in a decrease in the relative standard deviation (RSD) for LEMS experiments.


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Fenjian Shi

 I am interested in studying the localization of metabolites in the plant and animal tissue samples using laser electrospray mass spectrometry-mass spectrometry imaging (LEMS-MSI). LEMS-MSI combines the microsampling capability of a near-IR, femtosecond duration laser beam with the high ionization efficiency of an electrospray source for label/matrix-free sample interrogation at a lateral resolution of < 50 µm under ambient conditions. My research thus far has concerned investigating distributional changes and biomarker discovery of a normal or diseased tissue sample using LEMS-MSI and multivariate statistical analysis such as principle component analysis (PCA). I am also involved in collaboration with the IMRA America Inc. to apply a low energy, femtosecond fiber laser to our LEMS source as a universal, affordable and robust approach for the detection of a variety of small and macro biomolecules.


Maryam Tarazkar

The theoretical studies performed in this lab focus on two areas:
1) The development of new methods for calculating nonlinear optical responses of the atoms, molecules, and ions interacting with strong laser field with applications in modeling of femtosecond laser filamentation dynamics, high harmonic generation, etc. In this regard, the quadratic and quartic nonlinear optical responses have been investigated in a series of neutral and ionized atoms as well as diatomic molecular ions by using axillary electric field approach and the ab initio quantum mechanical methods. The results confirm that filament stabilization is induced by the generation of free electrons.

2) Combining quantum mechanical ab initio calculations with pump-probe spectroscopy in order to understand and control the dissociation dynamics in strong field regime. Exploring potential energy surfaces and investigating the role of conical intersections can help to predict possible mechanism for photo-dissociation of polyatomic systems ionized through strong field laser pulses. These theoretical calculations can be used to design new control strategies for selective bond dissociation in molecules and molecular ions.




Tyler Giesen



Sharon Kass




Levis Group, Department of Chemistry, Temple University, Beury Hall 244, 1901 N. 13th Street, Philadelphia, PA 19122    Tel: 215-204-5241     Fax: 215-204-6179
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