Molecular Radiative and Relaxation Processes

University Of California-Irvine, Irvine CA

Investigators

Abstract

Shaul Mukamel of the University of California Irvine is supported by an award from the Theory, Models and Computational Methods program in the Chemistry Division for the design, modeling and analysis of coherent nonlinear multidimensional spectroscopies. Superoperator approaches in Liouville space are being developed and used as computational tools for applications involving interactions of fast-pulsed light and matter: (1) Coherent and incoherent femtosecond single-molecule spectroscopy, including non-equilibrium circumstances with tip and junction current-carrying contacts, (2) multidimensional spectroscopy with entangled photons of quantum fields , (3) charge separation and multi-exciton spectroscopic signatures in molecular chromophore aggregates and quantum dot arrays, and (4) femtosecond coherent anti-Stokes Raman scattering probes of molecular chirality using flexible pulse-polarization strategies. These and numerous other experiments are described using the Liouville approach, and computationally modeled using software SPECTRON created for multidimensional optical electronic and vibrational spectroscopy and made available to the research community. The response of a molecule to different light beams depends on many factors, such as how much the beams overlap with each other and the molecule in both space and time. The PI has developed the tools to calculate the responses under different circumstances, such as when the molecule is also being probed by a scanning tunneling microscope tip or is carrying current between two electrical leads. Each beam can also be a series of pulses repeated very quickly, enriching the collection of responses that can be evoked. Many of the most interesting experiments that can be simulated using the methods and software created by the PI involve definite types of correlations between photons approaching or scattering from the molecular sample, which can consist of even a single molecule. The PIs book "The Principles of Nonlinear Optics" is the principal guidebook for research in this community and is undergoing extensive revision under this award. A steady flow of researchers trained in these methods is produced by the students and postdoctoral fellows mentored by the PI.