Marcos Dantus - US grants

Marcos Dantus is supported by the Experimental Physical Chemistry Program to study the ultrafast transition state dynamics of unconstrained bimolecular reactions. The primary goal is to gain significant insights into fundamental photoassociation reactions in order to understand better the breaking and formation of chemical bonds in collision processes. Specific projects include real-time dynamical studies of Hg + I2 and Na + HF bimolecular reactions, controlling the impact parameter in photoassociation, and exploring the dependence of photoassociation on the initiating laser pulse characteristics.

Light absorption by a pair of unbound atoms or molecules while they are in proximity can lead them to react to form a new chemical bond. This process is called photoassociation. Outcomes from this research effort will lead to the elucidation of previously unmeasurable aspects of bimolecular chemistry, such as reaction dependence on closeness and orientation of colliding atoms and molecules. This understanding could impact studies of reactions relevant to combustion and atmospheric chemistry, for example. This research program also provides unique education and training opportunities for students at Michigan State University.

In this project funded by the Experimental Physical Chemistry Program of the Chemistry Division, Dantus will use three-pulse, four-wave mixing (FWM) non-linear spectroscopy to study the dynamics of wave packet motion in the ground and excited states of NO2, CF3NO, and N2O4. The purpose of the work is to investigate intramolecular vibrational energy redistribution (IVR) and curve crossing dynamics in polyatomic systems and thereby open up the way for more general, and wider ranging investigations than done heretofore on diatomics. Specific questions to be answered in this research are about the initial steps of energy dissipation and IVR in polyatomics, what is the nature of wave packet localization in phase space for multidimensional systems, and what is the ground state dynamics in systems with chemically significant amounts of energy, up to 12,000 cm-1.

This project deals with fundamental questions of how energy absorbed into specific molecular energy states redistributes itself throughout a molecule in the course of time. A good understanding of these intramolecular processes may lead to the laser control of chemical reactions. This research is undertaken with students and postdoctoral research associates. They will acquire training and knowledge in one the forefront areas of contemporary physical chemistry in preparation for advanced studies or employment in industry, government or academia.

With support from the Major Research Instrumentation (MRI) Program, Marcos Dantus and colleagues in the Department of Chemistry at Michigan State University will develop phase-modulated ultrashort laser pulse technology for probing molecular dynamics, optical switches and materials, and coherent control of multiphoton microscopy. The investigators will develop the necessary technology for two unique systems based on ultrashort femtosecond (fs) pulses with pulse characterization methods with unparalleled sensitivity that is directly linked to active phase and amplitude compensation. System A will be an ultrabroad-bandwidth sub-9 fs laser that will require a specially modified amplitude and phase modulator setup that minimizes dispersion and compensates third and fourth order phase distortions. This source will be used to achieve unprecedented selective excitation of molecular probes, as required for functional imaging, for example, using coherent laser control methods developed at Michigan State University and elsewhere. System B will be an amplified sub-20 fs laser source using a two-dimensional pulse shaper to achieve single-shot nonlinear optical excitation spectra of novel materials and nonlinear chromophores over a broad bandwidth. This will use binary pulse shaping technology combined with a novel two-dimensional optical phase modulator. This development will enhance the speed and accuracy of nonlinear optical spectroscopy by orders of magnitude.

A number of interdisciplinary scientific projects linked to biophysics, telecommunications, and advanced materials, will benefit from the development of these systems.

In this award, funded by the Experimental Physical Chemistry Program of the Chemistry Division, Prof. Marcos Dantus of Michigan State University and his postodoctoral, graduate and undergraduate research students will further investigate the use of multiphoton intrapulse interference (MII) as a means of achieving coherent control of molecular dynamics. In particular, Prof. Dantus and his group will develop phase-shaping methods to allow them to prepare gas-phase molecules in predissociative states and to obtain chemically-selective, microscopic images in biological materials.

Besides the broad impact of the research on other areas of science, Prof. Dantus will continue to provide undergraduate and graduate students with the training that will allow them to continue in careers in science and technology. In addition, Prof. Dantus and his group will continue in their efforts to develop commercially useful technology.

In this SGER award, funded by the Experimental Physical Chemistry Program, Prof. Marcos Dantus of Michigan State University and his graduate and undergraduate student colleagues will conduct exploratory research in the attempt to develop the controlled fragmentation and detection of ionized biological species in the gas phase. They propose to do this through the use of shaped femtosecond laser pulses.

Prof. Dantus and his group will attempting to use shaped ultrafast laser pulses to selectively fragment large biological ions in the gas phase. The ultimate aim of these studies is to obtain structural information of large biomolecules with a programmable laser source. The major impact of this type of instrument would be in biological research. The graduate and undergraduate students working on this will receive stellar training in research that is at the interface of physical and biological science.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

With this award from the Chemistry Research Instrumentation and Facilities: Instrument Development (CRIF:ID) program, Marcos Dantus and his research group from Michigan State University will develop a phase and polarization modulated ultrafast laser source for a broad range of scientific applications. The proposed laser will be capable of generating multiple individually addressable pulses from a single ultrashort pulse. The proposed laser source will be used in a number of projects: 1) a multimodal non-linear imaging microscope; 2) biological and biomedical imaging applications; 3) detection of explosives or pathogens and 4) in-situ chemical analysis of the combustion products in jet turbines. The project will be carried out by a diverse group of scientists, ranging in experience from undergraduate students to professors and research scientists. The work involves collaboration with a number of American industrial partners, as well as with the Air Force Research Laboratory.

New kinds of spectroscopy techniques open up brand new avenues of research. The instrument developed with this award will allow scientists to study the composition and properties of a broad range of materials -- from biological samples to hot combustion gases. Knowledge developed with this kind of tool can lead to: improved medical diagnostics, improved food safety, and better materials for advanced technologies. In addition, the researchers working with Prof. Dantus will receive invaluable training in high technology development, an important skill in today's workforce.

In this EArly-concept Grant for Exploratory Research (EAGER), funded by the Chemical Measurement and Imaging Program of the Division of Chemistry, Professor Marcos Dantus from Michigan State University will investigate a novel approach to the design and construction of femtosecond lasers. The proposed development seeks to exploit the stability and low cost of the telecommunication semiconductor pumped CW lasers to generate ultrashort pulses. The resulting laser should mimic the capabilities of a traditional ultrafast laser, but have greater stability, ruggedness, efficiency and lower cost than the presently available sources. The source will incorporate adaptive pulse compression technology developed by Dantus. The successful demonstration of this new source will lead to its use in the areas of biomedical imaging, sensing, metrology and communications. The new source should be ideal for portable sensing instrumentation given the rugged, compact, and energy efficient components. Nonlinear optical imaging and sensing applications will be used to demonstrate the practical capabilities of the resulting new technology.

The proposed low-cost approach will make ultrafast lasers (primarily used for time-resolved spectroscopy and for nonlinear optical imaging) available to a much wider variety of research laboratories, and boost scientific discovery by increased accessibility and reliance of this technology.

DESCRIPTION (provided by applicant): Improving multiphoton imaging with shaped ultrashort laser pulses Multiphoton imaging has become the standard for deep tissue imaging and has recently been approved for human clinical trials in Germany for the non-invasive diagnosis of skin cancer such as melanoma. There is a pressing need to determine the laser pulse duration dependence of different laser-induced damage mechanisms in order to find the pulse parameters that yield optimal signal with minimal laser damage. For example, pigmented tissue has significant absorption in the near-infrared, which in turn causes thermal damage;on the other extreme, instantaneous three-photon absorption leads to DNA damage in living tissue. For this study we propose using a laser system capable of delivering pulses as short as 10 fs (fifteen times shorter than typical two-photon microscopes) outfitted with a pulse shaper that allows us to change the pulse duration from 10 to 1000 fs by restricting the spectral bandwidth (amplitude shaping) or by stretching the pulse in the time domain (phase shaping). The goal is to evaluate laser induced damage first in tissue phantoms and then in skin tissue specimens and to plot its dependence on laser intensity and pulse duration. These measurements will allow us to define a window of 'optimal performance'for the different tissue samples, conditions for which signal is maximized and damage is minimized. Specific aims of the proposed research are: 1. Evaluate the dependence of laser-induced damage in skin phantoms (melanin-rich samples, cell culture models) on pulse duration and laser power. Quantify the expected yield in signal and mitigation of photodamage due to the optimization of laser pulse duration (10-1000 fs) at the sample. Seek for alternative pulse shaping strategies, other than linear chirp and spectral narrowing, to be used for optimization of multiphoton microscopy imaging (e.g., pulse sequence generation). Compare best results versus those obtained by conventional two-photon microscopes using 100-150 fs pulses. 2. Validate the 'laser-safe operational window'model on various skin tissues and other biological samples. Provide guidelines as to what are the optimum pulse duration and energy conditions for nonlinear optical imaging in those tissues. The use of ultrafast laser sources (with broader-than-conventional spectral bandwidth) and pulse shaping to assess phototoxicity and optimize laser parameters for safe multiphoton imaging of pigment-rich tissues is novel. The long term goal of this project is to further facilitate data acquisition in the biomedical imaging field with minimal perturbation to the living system. This research will impact a number of nonlinear biomedical imaging modalities as well as future diagnostic techniques. In particular, it will benefit to the noninvasive optical biopsy of skin lesions such as melanoma, the studies of wound healing processes, and transdermal drug delivery. PUBLIC HEALTH RELEVANCE: The proposed work will improve biomedical imaging by achieving greater signal, improved contrast and less laser induced damage when imaging living cells. Richer biological information can thus be obtained non- invasively which will help researchers and doctors better understand the morphology and pathology of the cell and disease progression.

With this award, the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Marcos Dantus of Michigan State University to conduct experimental work looking at the early-time dynamics of photoexcited molecules in solution. Professor Dantus and his group are pushing the technology to be able to make measurements of single molecules in solution. The ultimate goal of research like this is to obtain a better understanding of the ways that electronically excited molecules lose their energy through reaction or relaxation. The graduate and undergraduate students, many from underrepresented groups, working on this project will receive world-class training in lasers and optics. A unique aspect of Professor Dantus' research is that many of the innovations that he has made with NSF support have resulted in new products in the marketplace. Student researchers will benefit from working with this entrepreneurial mentor. In helping to train the next generation of scientists, Prof. Dantus will continue to work with undergraduate students as well as high school students to conduct research in his laboratory.

Prof. Marcos Dantus and his research group will use shaped femtosecond laser pulses to probe the early-time dynamics of photoexcited molecules in solution. The ultimate goals of the research are to answer the questions: (1) Can intermolecular (solvation) and intramolecular dephasing be decoupled? and (2) For how long do molecules retain electronic coherence in the absence of ensemble averaging? The experimental work will benefit from a collaboration with a prominent theorist, Professor Shaul Mukamel, in this research area. This work will lead to novel multidimensional spectroscopic measurements based on a single broadband shaped laser pulse.
Theory and numerical simulation of the results will advance our knowledge and predictability related to laser-molecule interactions. This study will result in knowledge about coherence timescale that can be valuable for controlling photochemical processes and understanding of natural and synthetic photosynthetic systems.

The Division of Chemistry supports a workshop entitled "Workshop on Chemical Sciences Needs for Mid-Scale Instrument Development" organized by Professor Marcos Dantus of Michigan State University and Paul Bohn of the University of Notre Dame. This workshop brings together a diverse group of 35 participants from a broad range of institutions and geographic areas to discuss opportunities for instrument usage in the "mid-scale" range. These discussions focus on instrument development activities that meet the needs of the chemistry community.

Workshop addresses the following objectives: define national needs in the chemical sciences for mid-scale instrument development, organize needs assessment around chemical grand challenge problems, and develop a report specifying prioritized objectives in chemistry. The broader impacts are addressed by dissemination of the findings and recommendations which start a broader conversation among key stakeholders in the US chemical sciences community, including instrument developers, facility managers, and users, as well as federal agencies supporting chemical sciences.

One of the challenges in chemistry is to produce specific products from chemical reactions using light. If this objective can be achieved, a wide range of technologies would be advanced, from energy conversion (e.g., light to electricity or synthetic fuel) to chemical sensing, to general improvement of chemical process efficiency. In this project supported by the Chemical Structure, Dynamics and Mechanisms-A Program of the Division of Chemistry, Professors Marcos Dantus and Benjamin Levine of Michigan State University are using a combination of experiment and theoretical modeling to design laser light pulses that can result in specific chemical reactions. The light pulses are typically a few femtoseconds in duration (a femtosecond is one-quadrillionth of a second), and can be designed ("shaped") to contain a desired range of light wavelengths (a range of colors), or even change wavelength over the pulse duration. Depending on their shape, the light pulses affect the motions of electrons inside the molecules in different ways. Since electrons form the bonds between the atoms of a molecule, it is possible to control how the bonds break and re-form. In other words, the shape of the laser light pulses can control the outcome of chemical reactions. The graduate and undergraduate students involved in this project learn about light-matter interactions and collaborate with groups that consider these phenomena from different perspectives (spectroscopists theorists, and synthetic chemists). The researchers regularly include high school students in their research efforts and work closely with programs aimed at increasing the number of underrepresented students who pursue graduate study and research careers.

This project implements a novel strategy for achieving coherent control of the energy flow and reactivity of large organic molecules in the condensed phase. Recognizing that different electronic excited states undergo different chemical reactions, shaped laser pulses are being used to (a) populate electronic states with desirable reactivities, and (b) minimize the probability of spontaneous transition out of the desired electronic state (e.g. internal conversion). In pursuit of (b), quantum control strategies that range from semi-classical (driving the vibrational wave packet along a particular reaction coordinate) to quantum strategies with no classical analogue are being used.For example, topological effects near intersections between electronic states can be exploited to influence the reaction outcome and strong coupling, for example when potential energy surfaces are dressed by the light field. In such cases, the natural energy flow is altered and the molecular system?s coherence with the driving field can be enhanced. Advanced quantum dynamical simulations are enabling the determination of causal relationship between the structure of the initial wave packet and reaction outcomes, thus informing subsequent experiments. Successful control of internal conversion are tracked by the fluorescence yield from higher excited states. Subsequently, similar strategies are used to drive dissociative reactions in a series of dyes, which release a highly efficient fluorophore only when excited to a higher excited state. Together, this combined experimental and theoretical effort is elucidating strategies to maximize the fraction of photon energy needed to drive a condensed phase chemical reaction.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

The ability to predict and control the outcome of chemical reactions is essential for many areas of modern physics, chemistry and biology. This ability requires detailed knowledge of how individual atoms in molecules move to break, form, or rearrange chemical bonds between them during the reaction. This research project aims at obtaining high-resolution movies of such atomic motion. Since the atoms involved in chemical reactions move extremely fast, typically on a time scale of few tens of femtoseconds (one femtosecond is one millionth of a billionth of a second), ultrashort, femtosecond laser pulses are the only experimental tools capable of recording such movies in real time. However, because of the quantum nature of atoms and molecules, the outcome of any molecular reaction is not deterministic: even if one measurement precisely captures the positions of all atoms at a given time, the same measurement will have different outcomes if repeated several times, even under exactly identical conditions. The acquisition of a high-power laser system delivering a hundred thousand pulses (each shorter than 10 femtoseconds) per second will enable repeating such measurements millions of times, which is needed for the creation of a quantum-mechanical molecular movie. Each frame of a movie then reflects the probability of every possible configuration of atoms at different stages of the reaction, instead of a fixed picture of a molecule. Such movies will advance our understanding of fundamental chemical processes and provide input for applications in areas of national priority, ranging from efficient energy conversion and storage to synthesis of novel materials, drug design and molecular electronics. This project is jointly funded by the Major Research Instrumentation program and the Established Program to Stimulate Competitive Research (EPSCoR).


Within this project, a broad range of photochemical processes, including photodissociation and isomerization, charge transfer reactions and formation of van der Waals clusters, will be studied. For each of these processes, the main scientific goal is to image the time-dependent molecular geometry and simultaneously characterize the evolving electronic structure of the molecule. This will be achieved by employing several complementary time-resolved techniques, including photoelectron spectroscopy and ion momentum imaging, inner-shell and laser-induced photoelectron diffraction, as well as ion beam techniques and Fourier-transform spectroscopy for characterization of the neutral fragments. For all these techniques, the key technical aspect facilitating simultaneous characterization of electronic and nuclear degrees of freedom will be the coincident detection of several reaction products, enabled by the high repetition rate of the acquired laser. At the same time, its high average power of several hundred watts will enable the efficient conversion of the emitted near-infrared radiation to a broad range of different wavelengths (from long-wavelength infrared to extreme ultraviolet and soft x-rays) needed for initiating and probing the reactions to be studied.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.