Low-temperature Bessel beam trap for single submicrometer aerosol particle studies

Area of Science:

• Atmospheric Chemistry
• Physical Chemistry
• Optical Physics

Background:

• Understanding aerosol particle phase transitions is crucial for climate and atmospheric processes.
• Previous methods for studying single aerosol particles at low temperatures have limitations.

Purpose of the Study:

• To introduce a novel instrument for studying single aerosol particles at low temperatures.
• To investigate the freezing and evaporation behavior of individual aerosol particles.

Main Methods:

• Utilizing a dual counter-propagating Bessel beams (CPBBs) optical trap for particle levitation.
• Implementing precise temperature control down to 223 K (-50 °C) for aerosol studies.
• Capturing and stably trapping individual submicrometer to micrometer-sized aerosol particles for extended periods.

Main Results:

• Successfully trapped and froze supercooled hexadecane, dodecane, and water droplets (radius ~450 nm to 5500 nm).
• Conducted experiments on homogeneous and heterogeneous freezing, freezing-melting cycles, and evaporation.
• Achieved the first reported observation of the freezing process for levitated single submicrometer droplets using optical trapping.

Conclusions:

• The temperature-controlled CPBB trap is a powerful new tool for single aerosol particle research.
• This technique enables detailed studies of phase transitions in atmospheric aerosols.
• The findings open new avenues for understanding aerosol behavior in the atmosphere.