Title: Big Atmosphere, Little Droplets, Tiny Atoms: What Can Helium Evaporation Teach Us About Sea Spray?
Abstract:
Sea spray droplets are complex beasts that contain surface-active organic molecules in addition to water and salts. These aerosol particles behave like little chemical laboratories that transform gases in the atmosphere and alter the concentration of key species, including ozone, the hydroxyl radical, and methane. But what do helium atoms have to with aerosols? Amazingly, when helium atoms are dissolved in sea spray proxies, they evaporate at super-Maxwellian speeds that vary sensitively with the identity of the salts and surfactants in solution. The excess helium kinetic energies teach us about the interfacial morphologies of surfactant-salt-water solutions, which we can explain using two beautiful chemical concepts: the principle of detailed balance and potentials of mean force. We can use what we have learned to discuss how charged surfactants can significantly alter the outcome of reactions in sea spray because they control the segregation of reactive ions to the surface. Just a speck of surfactant goes a long way!
This talk will be accompanied by some fun hands-on activities at your seat. Please bring a water bottle if you have one and prepare to get a bit wet.
Bio:
This seminar is Gil’s last before retirement after being a faculty member in Chemistry for 38 years. He has taught general (103, 115) and physical (561) chemistry, physical chemistry lab (563/4), and surface chemistry (777) many times. Gil has also served the department as physical and general chemistry path chairs, as Associate Chair for Research, and as chair of the chair search, shops, seminar, and faculty search committees. His group has led “Surface Circus – the Wonderful World of Water”, a hands-on science activity for the public. By volunteering over many years at science fairs and schools, he and his group have introduced hundreds of children and their parents and grandparents to the marvels of soapy water (including a family-sized soap bubble chamber).
Gil’s group spearheaded studies of collisions and reactions of gases at the surfaces of liquids using molecular beam scattering techniques. The experiments explore the interfacial analogues of bulk solvation, hydrogen bonding, the “like dissolves like” rule, proton exchange and acid-base reactions, halogen atom transfer, and electron solvation and reaction. Among the most important applications arereactions of sea spray mimics that regulate air quality and climate change (the focus of the talk), the evaporation of fuel in combustion engines, and reactions of surface solvated electrons.
Gil will spend the fall semester as a Visiting Miller Professor at UC-Berkeley to continue studies of gas-liquid reactions.
Live Stream Link: http://128.104.155.144/ClassroomStreams/chemistry1435_stream.html
There will be a reception to follow in the North Tower Atrium