Electric and magnetic deflection of fully field-oriented molecules within superfluid nanodroplets: A probe of simple and complex cold polar molecules

University Of Southern California, Los Angeles CA

Investigators

Abstract

In this project, funded by the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program of the Division of Chemistry, Professor Vitaly Kresin's group from the University of Southern California is using a jet of extremely cold nanoscale droplets of superfluid helium as a tool to probe the electric magnetic properties of individual molecules. A "superfluid" is a fluid that can flow without the internal friction or viscosity of liquids. The cold temperature (a fraction of a degree above absolute zero, which is -273.15 degrees Celsius) and viscosity free condition of superfluid helium makes it possible to use electric or magnetic fields outside the droplet to control the orientation of molecules inside the helium droplet. This in turn makes it possible to measure fundamental properties of these molecules (for example the electric and magnetic "poles" of the molecules). It also makes it possible to understand how molecules aggregate into clusters. The research group is considering the study of a variety of important molecules and their agglomerates, including biological species and "molecular magnets." The broader scientific impacts of the project stem from the fact that electric and magnetic characteristics of biological, molecular-magnet systems are relevant to fields ranging from protein synthesis to quantum computing. Graduate and undergraduate students and postdoctoral researchers are mentored in a highly interdisciplinary area of research and are involved in outreach programs and in science fairs. Undergraduate students gain experience in giving scientific presentations, as they present their work at USC's annual Undergraduate Symposium for Scholarly and Creative Work. Professor Kresin is also involved in the national Society of Physics Students' "Adopt-a-Physicist" program which connects high school classes with professional scientists for conversations and questions about careers, science, school, work, and life balance. Helium nanodroplets are produced by the supersonic expansion of cold helium gas. These droplets pick up guest molecules by passing through pick-up cells and then traverse a strong inhomogeneous electric or magnetic field which both orients the polar impurity and exerts an intense deflecting force. This force is measured by mapping out the beam profile - in this way yielding an experimental readout of the magnitude of the dipole moment of a single ultracold molecule or molecular complex. This technique is applied to amino acids and small peptides, to hydrated acid complexes, to molecular magnets, and to molecular assemblies whose reaction pathways can be custom pre-aligned by the external field. The study and control of cold polar molecule interactions, assemblies, and reactions is attracting considerable interdisciplinary interest in view of their relevance to quantum computing, novel condensate phases, molecular interferometry, and investigations of fundamental symmetries.