Department of Chemistry, University of Georgia

Aggregation in Helium Droplets

Abstract: The first beam of helium droplets was reported in the 1961 paper Strahlen aus kondensiertem Helium im Hochvakuum by Von E. W. Becker and co-workers [1]. However, molecular spectroscopy of helium-solvated dopants wasn’t realized until 30 years later in the laboratories of Scoles and Toennies [2,3].

It has now been over two decades since this early, seminal work on doped helium droplets, yet the field of helium droplet spectroscopy is still fresh with vast potential. Analogous in many ways to cryogenic matrix isolation spectroscopy, the helium droplet is an ideal environment to spectroscopically probe difficult to prepare molecular species, such as radicals, carbenes and ions. The quantum nature of helium at 0.35 K often results in molecular spectra that are sufficiently resolved to evoke an analysis of line shapes and fine-structure that demands rigorous “effective Hamiltonian” treatments. This lecture will focus on our successful attempts to efficiently dope organic molecular radicals and carbenes into helium droplets. The properties of these systems have been probed with infrared laser spectroscopy.