Coupling between modulated Mie scattering and photoacoustic signal generation in optically trapped, single aerosol particles
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Date
2022
Publication Type
Conference Paper
ETH Bibliography
yes
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Abstract
Photoacoustic spectroscopy and photothermal spectroscopy are two common methods to probe aerosol particle absorption coefficients and can be performed both on aerosol ensembles and on the single particle level. With photothermal spectroscopy typically changes in the particle’s light scattering pattern upon heating or cooling are observed with photo-diodes or cameras. In photoacoustic spectroscopy, the acoustic response to periodic light absorption is recorded e.g. with a microphone. Although both methods are closely related through their excitation process, the detection pathways are quintessentially different. In our single particle optical trapping setup, however, we observe a previously unnoticeable, unidirectional coupling between modulated Mie scattering (result of the photothermal effect) and photoacoustic spectroscopy. The coupling manifests itself via differently shaped, sudden features in the acoustic signal. Our analysis suggests a non-trivial interaction between light scattering of single, optically trapped particles and the photoacoustic signal generation based on interactions of light with the acoustic resonator’s walls. Measurements over several trapping powers and photoacoustic excitation powers support this conclusion. How the coupling manifests itself, such as shape and strength, can be conclusively explained by the structure of the particle’s momentary phase function (scattering intensity) calculated by classical Mie theory. This allows us to formulate conditions to either utilise or minimise the coupling effects in future experiments.
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Publication status
published
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Book title
Optical Trapping and Optical Micromanipulation XIX
Journal / series
Volume
12198
Pages / Article No.
1219805
Publisher
SPIE
Event
SPIE Nanoscience + Engineering 2022
Edition / version
Methods
Software
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Date collected
Date created
Subject
Optical trapping; Optical tweezers; Mie scattering; Photoacoustic spectroscopy; Photothermal spectroscopy; Single-particle; Aerosols
Organisational unit
03961 - Signorell, Ruth / Signorell, Ruth
Notes
Funding
200306 - How weak intermolecular interactions govern the formation and properties of clusters and aerosol droplets (SNF)
ETH-42 18-1 - A new single-droplet approach to the determination of evaporation coefficients (ETHZ)
ETH-42 18-1 - A new single-droplet approach to the determination of evaporation coefficients (ETHZ)
Related publications and datasets
Is supplemented by: https://doi.org/10.3929/ethz-b-000554822