A Linear Trap for Studying the Interaction of Nanoparticles with Supersaturated Vapors

We present and characterize a versatile device for studying the controlled interaction of free nanoparticles with supersaturated vapors. It utilizes an rf-ion trap for storing a cloud (>10 8 particles) of singly charged nanoparticles in the sub 10-nm size regime and combines it with a static supersaturation chamber operating at low pressure in free molecular flow regime. This allows for the stable production of a homogeneous zone of variable saturation that can reach very high levels of supersaturation (S > 10 4 ). Compared with diffusion chambers, much higher saturations and more homogeneous saturation fields can be achieved, and convective flow is not an issue. The analysis of adsorption and nucleation processes on the surface of nanoparticles can be performed by mass spectrometry and optical spectroscopy. We discuss the general function principle of the device and demonstrate that it is well suited for studying water adsorption and deposition ice nucleation on metal oxide nanoparticles under the conditions of the upper atmosphere of the Earth and Mars. Copyright 2015 American Association for Aerosol Research