We study detailed mechanisms of chemical reactions in the gas and condensed phases by using laser and molecular beam techniques. In particular, we are interested in identifying primary steps, nascent product state distributions and understanding reaction mechanisms at the molecular level. Our research is relevant to environmental, atmospheric and combustion chemistry as well as to the fundamental chemistry of new energy sources.

Much of our research is concerned with the unimolecular decomposition of free radicals and other transient species. For example, we have studied the photoiniatted decomposition of hydroxyalkyl and chloromethyl radicals, as well as the covalently-bound NO dimer. More recently, emphasis has been placed on the state-specific predissociation of hydrogen-bonded dimers with acids and bases, such as HCl and ammonia. The experimental arrangements include molecular beams and ion and photoelectron imaging, as well as the core-sampling version of time-of-flight translational spectroscopy. Theoretical modeling is important in all our studies and the ongoing collaboration with Prof. Anna Krylov and her iOpenShell Center at USC has resulted in joint experimental-theoretical studies of challenging open-shell systems. Special graduate courses on Electronic Structure Theory and Models of Reaction and Ionization Dynamics prepare students and postdocs for these studies. UHV studies of gas-surface and condensed-phase interactions are carried out in collaboration with Professor Curt Wittig. In current experiments, laser and FTIR spectroscopies are used to interrogate the behavior of thin films of solid water doped with small molecules. Changes in the IR spectroscopy of guest molecules such as carbon dioxide and nitrous oxide reveal transport mechanisms, including trapping and ejection processes and phase explosions relevant to icy bodies in the solar system.

Current Projects

  1. Imaging the predissociation dynamics of hydrogen-bonded clusters

    We study state-specific vibrational predissociation dynamics of hydrogen-bonded dimers and trimers of water, acids and bases. Despite their weak bonding, hydrogen bonds are crucially important in environments ranging from living cells to icy bodies in the solar system. In our studies, the state resolution and detection sensitivity of photofragment ion imaging are exploited to obtain pair-correlated distributions of fragments following laser excitation of a hydrogen-bonded stretch vibration in one of the subunits of the dimer or trimer. Encouraged by our previous results on vibrational predissociation dynamics of several dimers, we are now extending the work to include cyclic trimers as prototypes of vibrational energy dissipation in larger hydrogen-bonded networks. State-specific energy flow patterns that lead to H-bond breaking in dimers and trimers will be inferred from quantum state distributions in the fragments, and bond dissociation energies will be obtained with spectroscopic accuracy. Vibrational predissociation dynamics and mechanisms will be elucidated by comparisons with high-level calculations. Specific systems of current interest include: H(D)Cl-water dimers and mixed cyclic trimers; water and ammonia dimers and trimers; and mixed ammonia-water trimers. Learn More...

    1. Imaging the state-specific vibrational predissociation of the NH3-H2O hydrogen-bonded dimer, A. K. Mollner, B. E. Casterline, L. C. Ch'ng, and H. Reisler, J. Phys. Chem. A. 113, 10174-83 (2009).

    2. Photofragment spectroscopy and predissociation dynamics of weakly bound molecules, Hanna Reisler, Annu. Rev. Phys. Chem. 60, 39-59 (2009).

    3. Imaging the State-Specific Vibrational Predissociation of the Hydrogen Chloride-Water Hydrogen-Bonded Dimer B. E. Casterline, A. K. Mollner, L. C. Ch'ng and H. Reisler. J. Phys. Chem. A, (R. Schinke Festschrift), 114, 9774 (2010)

    4. Imaging H2O Photofragments in the Predissociation of the HCl-H2O Hydrogen-Bonded Dimer, B. E. Rocher-Casterline, A. K. Mollner, L. C. Ch'ng, H. Reisler, J. Phys. Chem. A, 115, 6903 (2011).

    5. Experimental and Theoretical Investigations of Energy Transfer and Hydrogen-Bond Breaking in the Water Dimer, L. C. Ch'ng, A. K. Samanta, G. Czakó, J. M. Bowman, H. Reisler, J. Am. Chem. Soc., 134, 15430 (2012).

    6. Imaging bond breaking and vibrational energy transfer in small water containing clusters, A. K. Samanta, L. C. Ch'ng, H. Reisler, Chem. Phys. Lett., 575, 1 (2013).

    7. Experiment and Theory Elucidate the Multichannel Predissociation Dynamics of the HCl Trimer: Breaking Up Is Hard To Do,J. S. Mancini, A. K. Samanta, J. M. Bowman, H. Reisler,DOI:10.1021/jp5015753 (2014), J. Phys. Chem. A

    8. Experimental and Theoretical Investigations of Energy Transfer and Hydrogen-Bond Breaking in Small Water and HCl Clusters, A. K. Samanta, G. Czako, Y. Wang, J. S. Mancini, J. M. Bowman, H. Reisler, Acc. Chem. Res., 47, 2700-2709, (2014)

  2. Photodissociation and photoionization of radicals and diradicals

    Open shell species such as radicals and diradicals are central to reactive processes in combustion and atmospheric chemistry. Our group is engaged in a long-term program to study several intriguing species, such as hydroxyalkyl radicals and methylene, the prototypical carbene. Our goal is to investigate the dissociation and ionization dynamics of radicals and diradicals for which multiple dissociation pathways, including molecular rearrangements, compete. These studies offer opportunities to address fundamental issues related to their open shell nature and the multitude of nonadiabatic interactions and product channels that characterize these systems.

    We use a variety of laser-based spectroscopic techniques to probe reactants and products and time-of-flight and imaging techniques to elucidate the dynamics. A new addition to our "radical machine" is velocity map slice imaging with a novel design that allows us to "slice" images of light particles such as hydrogen with good resolution. We use both photoelectron and photoion imaging, and the BASEX image reconstruction method that we developed is now the most widely used world-wide in reconstructing photoelectron images.

    The study of open-shell and diradical species poses challenges for both experiment and theory. However, when sophisticated theoretical models are combined with state-of-the-art experimental methods, the evolution from excited state to final products can be followed, including transformations of orbitals, couplings among electronic states, and energy disposal in final products. Collaboration with the theory group of Prof. Anna Krylov at USC is an important aspect of our program. Learn More...

    1. Unimolecular processes in CH2OH below the dissociation barrier: O-H stretch overtone excitation and dissociation, Wei J, Karpichev B, Reisler H, J. Chem. Phys. 125 (3): 34303-34303 (2006).

    2. Electronic spectroscopy and photodissociation dynamics of the 1-hydroxyethyl radical CH3CHOH, B. Karpichev, L.W. Edwards, J. Wei and H. Reisler, J. Phys. Chem. A, 112: 412-418 (2008).

    3. Interacting Rydberg and valence states in radicals and molecules: Experimental and theoretical studies, H. Reisler and A.I. Krylov, Int. Rev. Phys. Chem., 28(2) 267-308 (2009).

    4. Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study, E. Kamarchik, C. Rodrigo, J. M. Bowman, H. Reisler, A. I. Krylov, J. Chem. Phys., 136, 084304 (2012).

    5. Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). II. Velocity map imaging studies, M. Ryazanov, C. Rodrigo, H. Reisler, J. Chem. Phys., 136, 084305 (2012).

    6. Accessing Multiple Conical Intersections in the 3s and 3px Photodissociation of the Hydroxymethyl Radical, C. P. Rodrigo, C. Zhou, H. Reisler,DOI: 10.1021/jp404552g (2013)

    7. Imaging Studies of Excited and Dissociative States of Hydroxymethylene Produced in the Photodissociation of the Hydroxymethyl Radical, C. P. Rodrigo, S. Sutradhar, and H. Reisler, DOI:10.1021/jp505108k (2014), J. Phys. Chem. A

  3. Guest-host interactions of molecules in amorphous solid water (ASW)

    We examine the interactions of thin layers of ice with molecules adsorbed on or embedded in the ice, as well as their bonding to insulating surfaces such as MgO(100) single crystals. In these experiments, done collaboratively with Prof. Curt Wittig, we exploit FTIR spectroscopy, time-of-flight mass spectrometry, and laser and temperature programmed desorption techniques. Specifically, probe molecules such as CO2 and N2O are coadsorbed and used to interrogate interactions in the thin ice layers, such as mobility, transport, "volcano" ejection, segregation and phase explosions. These events are important in interstellar space as well as in heterogeneous chemistry in the atmosphere. Ongoing experiments focus on phase explosion and desorption initiated by infrared laser excitation. Learn More...

    1. Amorphous Solid Water Films: Transport and Guest-Host Interactions with CO2 and N2O Dopants, G. Kumi, S. Malyk, S. Hawkins, H. Reisler, and C. Wittig, J. Phys. Chem. A, 110, 2097-2105 (2006).

    2. Trapping and release of CO2 guest molecules by amorphous ice, S. Malyk, G. Kumi, H. Reisler, and C. Wittig, J. Phys. Chem. A, 111 (51): 13365-13370 (2007).

    3. Amorphous Solid Water (ASW): Pulsed Laser Ablation of ASW/CO2 Thin Films, O. Rebolledo-Mayoral, J. Stomberg, S. McKean, H. Reisler, C. Wittig, J. Phys. Chem. C, 116, 563 (2012).

The Reisler Research Group in August 2014