Arthur D. Little Physical Chemistry Seminar

Title: Big Atmosphere, Little Droplets, Tiny Atoms: What Helium Evaporation from Soapy Water Can Teach Us About Aerosols

Abstract: Sea spray droplets are complex beasts that contain surface-active organic molecules in addition to water and NaCl. 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 salts and surfactants in solution. These excess 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 surfactants goes a long way!
This seminar will include hands-on soapy water activities. Please bring a water bottle with you if you have one.