Gas-liquid interfacial scattering
Lead Research Organisation:
Heriot-Watt University
Department Name: Sch of Engineering and Physical Science
Abstract
This is a PhD research project in Chemistry. It will involve developing new methodology, advancing fundamental understanding, and informing applications of the scattering of gas-phase molecules at liquid surfaces. The development of surface-sensitive methods to study these processes presents a number of serious experimental challenges. One strand of the project will be to advance real-space imaging of the products of gas-liquid scattering. This technique will be applied to the collisions of OH molecules with the surfaces of functionalised organic liquid surfaces, of relevance to the uptake of OH on atmospheric aerosol particles. A parallel strand will be to develop new gas-phase projectiles that can interrogate, through reactive-atoms scattering, the surfaces of complex liquids. This will include, in particular, the development of metal atoms as a probe of the surfaces of technologically important ionic liquids and their mixtures.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509474/1 | 01/10/2016 | 30/09/2021 | |||
| 1963688 | Studentship | EP/N509474/1 | 01/10/2017 | 30/09/2021 | Maksymilian Roman |
| EP/R513040/1 | 01/10/2018 | 30/09/2023 | |||
| 1963688 | Studentship | EP/R513040/1 | 01/10/2017 | 30/09/2021 | Maksymilian Roman |
| Description | We captured images of a packet of hydroxyl radicals (OH) travelling through vacuum toward surfaces of three different atmospherically relevant liquids as well as their subsequent collision and scattering from said surfaces. The liquids included a non-reactive reference polymer (PFPE) as well as two reactive hydrocarbons - squalane and squalene. The technique employed allowed us to image the packet in real-space and real-time eventually producing movies of the scattering process. The shape of the plume of radicals scattering from the surfaces allowed us to infer the distribution of scattering angles as well as the peak speeds of the radicals. These two parameters help with identifying the mechanism with which the scattering occurred - whether impulsive scattering following singular-type collisions or thermal desorption following accommodation on the surface. The range of scattering angles turned out to be very broad regardless of the initial packet angle of approach which would suggest thermal desorption as the dominant mechanism. However, the measured peak speeds were vastly higher than expected for thermal desorption, suggesting impulsive scattering. Studies of the change in internal rotational energy of the molecules before and after the collision also suggested impulsive scattering. These seemingly contradictory outcomes were explained by the roughness of the liquid surface causing the wide range of scattering angles even if the mechanism was impulsive. |
| Exploitation Route | Further students and PDRAs now have a very novel technique of investigating the collisions at liquid surfaces that can lead to new discoveries in terms of the scattering mechanisms as well as the comparison between properties of various liquids. |
| Sectors | Chemicals,Environment |