James Valentini

MC 3120

work:+1 212-854-7590

Valentini Research Group
Selected Publications

Research Summary

We are a group of physical chemists who seek molecular-level understanding of how photochemical and bimolecular reactions take place. This understanding is expressed in quantum mechanical and classical mechanical descriptions of how chemical bonds are formed and broken in the process of reaction, i.e., in terms of how the combined, collective motion of the individual atoms carries the system from reactants to products. These descriptions are built on very detailed, quantum-state-resolved experimental measurements that follow the reactions and photochemical transformations one collision at a time. Such knowledge will contribute to a better understanding of chemical systems in which bimolecular and photochemical reactions are of central importance, e.g., combustion, atmospheric chemistry, and biological systems.

Our current focus is the influence of many-body effects on photochemical and bimolecular reactions, specifically the effects of solvation in condensed phase and microsolvation in molecular clusters, and the effects of multiple reaction sites in reactions of polyatomic molecules. Systems of current interest range from photoinduced bond-breaking and bond-making in hydrogen-bonded molecular complexes like (HCl)2, to bimolecular reactions like the H + c-C₆H₁₂ -> H₂+ c-C₆H₁₁ abstraction reaction, to the photochemistry of polyamide and polyolefin polymers.

We use a variety of experimental tools in our research. Laser spectroscopy is at the heart of all our measurements; it is used to both prepare and detect molecules in specific quantum states. Our experiments use lasers to initiate photochemistry, to produce atomic and molecular free radical reactants by photodissociation of stable molecules, and to prepare bimolecular reactant molecules in specific quantum states. Lasers also are used to determine the chemical identity of the products of bimolecular and photochemical reactions, to reveal how the products are distributed over their quantum states, and to follow the time evolution of molecular excited states. All the experiments are highly time-resolved, with time resolutions of ten femtoseconds to ten nanoseconds.

We are primarily experimentalists. However, our experiments are complemented by computational simulations and the development of heuristic models to explain our experimental observations. The simulations and models link our measurements to the molecular-level behavior we aim to elucidate. These theoretical calculations are sometimes done within our own group and at other times by collaboration with theory groups.

Publications
"State-to-State Chemical Reaction Dynamics in Polyatomic Systems: Case Studies," J.J. Valentini, Ann. Rev. Phys. Chem., 52, 1539 (2001)

"Reactions at Suprathreshold Energy: Evidence of a Kinematic Limit to the Internal Energy of the Products," C.A. Picconatto, A. Srivastava, and J.J. Valentini, J. Chem. Phys., 114, 16631671 (2001)

"The H + n-C₅H₁₂/n-C₆H₁₄ -> H2(v¹, j¹) + n-C₅H₁₁/n-C₆H₁₃ Reactions: State-to-State Dynamics and Models of Energy Disposal," C.A. Picconatto, A. Srivastava, and J.J. Valentini, J. Chem. Phys., 114, 48374845 (2001)

"Quantum State Distribution of HCl from the UV Photodissociation of HCl Dimer," C.A. Picconatto, H. Ni, A. Srivastava, and J.J. Valentini, J. Chem. Phys., 114, 70737080 (2001)

"Resonance Raman Studies of Photoinduced Decomposition of Nylon 6,6: Product Identification and Mechanistic Determination," H. Matsui, S.M. Arrivo, and J.J. Valentini, Macromol., 33, 56555664 (2000)

"Dynamics of the Vibrational Predissociation of HCl Dimer," H. Ni, J. Serafin, and J.J. Valentini, J. Chem. Phys., 113, 30553066 (2000)