Quantum Control of Cold Collisions Using Stark-Induced Adiabatic Raman Passage
Abstract
To investigate the stereodynamics in cold molecular scattering, we plan to study quantum state controlled collisions in a supersonically co-expanded beam of two molecular species, where both partners are prepared in specific m quantum states within a desired single vibrational-rotational (v, j) energy eigenstate. Selection of m-states defines molecular orientation with respect to a suitable quantization axis, thus defining the collision geometry at the quantum level. For the scattering experiment a large molecular ensemble will be prepared in the (v, j, m) quantum state using Stark-induced adiabatic Raman passage (SARP), a coherent optical technique which has been extensively developed in our laboratory. Quantum state selection in the input channel is not an option but a requirement for experimentally determining the detailed dynamics of molecular collision. Further state selection will be accomplished by co-expanding colliding partners in a single well collimated supersonic molecular beam, which brings the collision temperature down to a few Kelvin, thus limiting the number of involved input orbital angular momentum states or partial waves. The collision temperature in the range of a few Kelvin is most suitable to observe collision complexes that are formed within the interaction potential and the centrifugal barrier. The co-expansion also defines the direction of the collision velocity within a few mRad, a necessary condition for studying stereochemistry. By studying low energy scattering with controlled quantum states we will learn how the formation of a Van der Waals complex depends on the collision geometry. In the proposed work, we will expand the scope of SARP to allow the high-resolution quantum state selection of diatomic molecules such as HCl, CO, NO, and N2 as well as linear polyatomic molecules like C2H2. We will then study aligned-aligned bimolecular collisions of these molecules and extract the scattering matrix by measuring the quantum states of the scattered molecules for each highly defined quantum state in the input channel. The proposed work will also use SARP in a novel ladder-like fashion to prepare H2 molecules and its isotopomers in a highly excited vibrational level close to the dissociation limit, and study exotic chemical reactions involving the two loosely bound, yet entangled atoms of the vibrationally excited H2.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 21, 2019
- Source ID
- W911NF1910163
Entities
People
- Richard Zare
Organizations
- Army Contracting Command
- Stanford University
- United States Army