Optical deformation of single aerosol particles

Area of Science:

• Atmospheric aerosol science
• Aerosol-cloud interactions
• Optical physics

Background:

• Accurate measurement of physicochemical properties of microscopic particles is vital for atmospheric aerosol science and aerosol-cloud interaction models.
• Optical tweezers offer a platform for isolating and measuring individual particles.
• Radiation pressure in optical tweezers causes particle deformation, though typically unobservable by microscopy.

Purpose of the Study:

• To measure small deformations in optically trapped aqueous droplets.
• To determine the surface tension of atmospheric aerosols.
• To apply the developed method to aqueous organic and inorganic aerosol systems.

Main Methods:

• Utilizing cavity-enhanced Raman scattering and thermal locking to detect micro-deformations.
• Employing light-scattering calculations and a physical model balancing hydrostatic, surface tension, and optical pressures.
• Applying the technique to optically trapped micron-sized aqueous droplets.

Main Results:

• Successfully measured nanometer-scale deformations in optically trapped droplets.
• Accurately determined surface tension of aqueous organic and inorganic aerosols.
• Demonstrated the feasibility of the cavity-enhanced Raman scattering and thermal locking technique for surface tension measurements.

Conclusions:

• Cavity-enhanced Raman scattering and thermal locking provide a novel method for measuring droplet deformation and surface tension.
• The developed approach enables accurate surface tension determination for atmospheric aerosols.
• This technique advances the understanding of aerosol properties relevant to climate modeling.