David A. Micha
Professor of Chemistry and Physics

Quantum Theory Project
Department of Chemistry
University of Florida

VOICE: (352) 392-6977

EMAIL: micha@qtp.ufl.edu

HOMEPAGE: http://www.qtp.ufl.edu/~micha/

Research Interests

Our research deals with theoretical and computational aspects of molecular and materials sciences, with emphasis on the unified treatment of physical and chemical kinetics using quantum molecular dynamics. It includes collision-induced and photoinduced phenomena in the gas phase, clusters, and at solid surfaces. Our aim is to provide a fundamental approach to molecular dynamics, where electronic and nuclear motions are consistently coupled to account for quantal effects. We use quantum and statistical mechanics, mathematical, and computational methods, to describe time-dependent phenomena (such as femtosecond dynamics and spectra) in both simple and complex molecular systems.
In particular:

Quantum molecular dynamics.
• Energy transfer, electron transfer and reactions in gas phase molecular collisions.
• Energy transfer, electron transfer and reactions of molecules at solid surfaces.
• Intermolecular forces in ground and excited electronic states.
• Spectra and dynamics in atomic clusters.
• Photodissociation of polyatomic molecules.
• Photodesorption of molecules from solid surfaces.
• Light emission in collisions of ions with atoms and solid surfaces.

Theoretical methods.
• Time-dependent many-electron theory; time-dependent molecular orbital and time-dependent Hartree-Fock approaches to molecular phenomena.
• Few-body and many-body theory of molecular collisions; collisional time-correlation approach to many-atom collisions.
• Statistical mechanics of response and rate processes.
• Density matrix theory of relaxation, dissipation and fluctuations in extended molecular systems.

Computational methods.
• Numerical methods for the solution of differential and integral equations of scattering.
• Variational methods for scattering and time-dependent states.
• Path integral and wavepacket propagation in quantum dynamics.
• Constrained simulated annealing and constrained molecular dynamics.
• Operator algebra methods for solving operator differential equations.
• Numerical methods for the solution of the Liouville-von Neumann differential equation for the density operator.
• Integration of stochastic differential equations for coupled quantal and classical degrees of freedom, and of the generalized Langevin equations.
• Integration of differential equations for coupled fast and slow degrees of freedom. The "relax-and-drive" method.
• Calculation of molecular one- and two-electron integrals for travelling atomic basis functions.

Computer visualization and animation of molecular interactions.
• Animation of the temporal evolution of both nuclear motions and electronic densities using nuclear trajectories and isocontours of electronic densities.
• Animation of electronic transitions and electron transfer obtained from time-dependent molecular orbitals.
• Animation of light emission in collisions of ions involving electronic rearrangement and the related transient dipoles.

Recent Publications

D. A. Micha "Density Matrix Theory and Computational Aspects of Quantum Dynamics in an Active Medium", Intern. J. Quantum Chem. 80, 394-405(2000).

S. Miret-Artes, D. A. Micha, and D. Beksic, "Spectral Line Shapes in Dissipative Systems: Molecules Adsorbed on Metal Surfaces", J. Chem. Phys. 114, 4690-95 (2001).

D. A. Micha and A. Santana, "Adsorbate Vibrational Effects on the Photodesorption of CO from Cu(001)", J. Phys. Chem. A 105, 2468-73 (2001).

D. A. Micha and C. D. Stodden, "An Eikonal Treatment of Electronically Diabatic Photodissociation: Branching Rations of CH_3I", J. Phys. Chem. A 105, 2890-96 (2001).

D. A. Micha, A. Santana, and A. Salam, "Nonlinear optical response and yield in the femtosecond photodesorption of CO from the Cu(001) surface: a density matrix treatment", J. Chem. Phys. 116, 5173 (2002)

A. Reyes, D. A. Micha, and K. Runge "First Principles Dynamics of Li+He Collisional Excitation Using Atomic Core Potentials", Chem. Phys. Letters 363 , 441-46 (2002)

D. A. Micha and B. Thorndyke "Dissipative Dynamics in Many-Atom Systems: A Density Matrix Treatment", Intern. J. Quantum Chem. 90 , 759-771 (2002)

D. A. Micha "From Few-atom to Many-atom Quantum Dynamics", Adv. Quantum Chem. 41, 139-159 (2002)

A. Santana and D. A. Micha "Optical Control of Photodesorption with Chirped Femtosecond Pulses: Nonlinear Response Treatment for CO/Cu(001)", Chem. Phys. Lett. 369 (2003) 459-465

D. A. Micha and A. Santana, "Dissipative quantum dynamics with many coupled molecular states: Photodesorption from metal surfaces", J. Phys. Chem., to appear (2003)

A. Reyes, and D. A. Micha "Dynamics of electronic excitation in collisions of alkali atoms with noble-gas atoms using atomic core potentials", J. Chem. Phys., submitted (2003)

A. Reyes, and D. A. Micha "Dynamics of spin-orbit recoupling in collisions of alkali atoms with noble-gas atoms using atomic core potentials", J. Chem. Phys., submitted (2003)