This project will contribute to the development of control mechanisms of molecular quantum states using laser light. In general, molecules are not spherically symmetric objects, and as a result most collisional processes involving them depend strongly on the relative alignment of the colliding partners. Understanding the basic physics of collisional processes between atoms and molecules is of importance for a number of research areas including chemical reactivity, the dynamics of processes involving ultracold atoms and molecules, and astrophysics of the interstellar medium. Molecules also have an elaborate internal structure due to the innumerable ways in which chemical bonds can be realized. This leads to a rich variety of internal quantum states that often interact with each other. Such interactions can cause changes in the nature of the chemical bond between covalent and ionic and also give can rise to breaking of the chemical bond due to couplings between attractive and repulsive electronic states in the process of predissociation.
In the presence of an electromagnetic field (light), the energy levels of an atom or a molecule are modified ("dressed") by the electromagnetic radiation. One of the goals of this project is to use this phenomenon to study the dynamics of molecular collisional processes by probing selectively the change in the alignment of the molecular rotational angular momentum during collisional processes. Quantum state selectivity will be achieved by removing the degeneracy of the magnetic sublevels of the target rotational state of the molecules using the Autler-Townes (AT) effect of a control laser. In addition, dressing of molecular states by a coupling laser will be used to measure the electronic transition dipole moments and to demonstrate control of predissociation in regions of avoided crossings between covalent and ionic potentials of the lithium dimer. Furthermore, the dressed states approach makes it possible to use the spin-orbit interaction as a tool for molecular valence electron spin polarization. The spin-orbit interaction arises due to the coupling between the internal magnetic moment (spin) of the electrons and the magnetic field caused by the orbital motion of the electrons. The Autler-Townes effect, in this context, will make it possible to switch the molecules between a singlet (antiparallel spins) state and a triplet (parallel spins) state. Realizing this "spin switch" has potential applications in quantum computing.
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.
