Aerosol VUV Photoelectron Spectroscopy
The surface and sub-surface region of aerosols plays a critical role in governing their chemical activities and fates, because i) aerosol often exhibit a relatively large surface-to-volume ratio, and ii) most physical and chemical activities of aerosols begin to take place from their surfaces. Photoelectron spectroscopy is a surface sensitive technique. Due to the finite photon penetration depth and the nano-scaled escape length of photoelectrons, the resulting photoelectron spectra often display a strong size dependent effect, with a distinctive surface effect. Such a surface-sensitivity makes the photoelectron spectroscopy an extremely suitable for aerosol characterization.
Prof. Chia C. Wang, the Director of ASRC has successfully developed the aerosol VUV photoelectron spectroscopy, equipped with a high resolution hemispherical energy analyzer. The key components of the system includes:
Adjustable aerodynamics lens (AADL) system
Hemi-spherical electronic energy analyzer (VG Scienta, R3000)
• 9 cm period undulator (U9)
• 6 m cylindrical grating monochromator
• 1016 ~1017 photons/sec/mm2/mrad2 between 5-30 eV with 0.1 % bandwidth
Time-resolved Aerosol Infrared Spectroscopy
Since the physical, chemical and optical properties of aerosols often evolve over time, strongly correlated with the temperature and pressure of the ambient environment and presence of other chemical species, our laboratory has built a set of time-resolved temperature-variable aerosol infrared spectroscopy apparatus. By precisely controlling the temperature and pressure of the aerogel generating cavity, the constituent molecules of the aerogel directly aggregate in the aerogel cavity to form clusters and then nucleates, including homogeneous and heterogeneous nucleation. The phase change process, structural characteristics of aerosol and its correlation with the surrounding environment (such as the type of suspended gas, pressure, temperature and the presence or absence of other particles, etc.) can be analyzed by a time-resolved Fourier Transform Infrared Spectrometer. The key features of this apparatus includes:
- Temperature-controlled low-temperature aerosol in-situ generating cavity
- Adjustable optical path can greatly improve sensitivity and signal-to-noise ratio
- Directly observe the formation of aerosol particles and their structural changes over time and the surrounding environment
Time-resolved Fourier Transform Infrared Spectrometer Time-resolved Fourier Transform Infrared Spectrometer Since the physical, chemical and optical properties of aerosols often change with the temperature and pressure of the surrounding environment, our laboratory has built a set of time-resolved low-temperature aerosols infrared spectrometer. By precisely controlling the temperature and pressure of the aerogel generating cavity, the constituent molecules of the aerogel directly aggregate in the aerogel cavity to form clusters and then nucleates, including homogeneous and heterogeneous nodules (homogeneous and heterogeneous). nucleation). The phase change process, structural characteristics of the aerosol and its correlation with the surrounding environment (such as the type of suspended gas, pressure, temperature, and the presence or absence of other particles, etc.) can be analyzed by a time-resolved Fourier Transform spectrometer (time-resolved Fourier Transform) Infrared Spectrometer).
■ Temperature-controlled low-temperature aerosol in-situ generation cavity.
■ Adjustable light path can greatly improve the sensitivity and signal-to-noise ratio.
■ Directly observe the formation of aerosol particles and their structural changes over time and the surrounding environment
Raman optical tweezers
In order to fully understand and master the generation and evolution mechanism and interface chemistry characteristics of PM2.5 aerosol (including native and derivative), the center has been responsible for the construction of Raman optical tweezers and its application in 107. The application of aerosol science combines optical tweezers technology, Raman spectroscopy and nonlinear spectroscopy to study the chemical properties of aerosols, and achieve the accuracy of single particles. Dr. Arthur Ashkin, the inventor of optical tweezers technology, just won the Nobel Prize in Physics in October 107, which shows the importance of this technology. Optical tweezers technology uses the radiation pressure of light to allow researchers to accurately grasp/move single cells and viral particles. This technology has been widely used in the field of biology, and during the last two decades it has also been extensively employed in the fields of atmospheric chemistry and aerosol science. Our min-review article (link) briefly summarized the recent applications of single aerosol particle trapping techniques to atmospheric chemistry.
We will use the optical tweezers spectroscopy system to explore the role of chemical reactions in the various stages of aerosol formation and how to affect various characteristics of aerosol. This system combines optical tweezers and various optical spectroscopy technologies to detect the molecular spectra, physical and chemical properties of single particles and the dynamic behavior of each phase. Raman spectroscopy and fluorescence correlation spectroscopy allows for determining physical and chemical properties of trapped single aerosol particles, such as radius, refractive index, chemical compositions, concentration, pH and diffusion time. This project will focus on natural organic matter oxidation reactions in aerogel chemistry, such as heterogeneous ozonolysis. Our recent work studied the heterogeneous ozonolysis of aqueous ascorbic acid micro-droplets (link). This project hopes to use the optical tweezers spectroscopy system to deeply analyze the roles played by these reactions and precursor molecules in the various stages of aerogel formation and evolution, and how to couple with the various properties of aerogel.
LiDAR's Application in Aerosol Telemetry
This research plan uses Raman Lidar and Polarized Lidar to observe the spatial distribution of aerosol in the Kaohsiung Xiziwan area, and further analyze the physical and chemical properties of aerosol. The observation results of Raman Lidar and Polarized Lidar can provide the following information at the same time: 1. The spatial distribution of aerosol at different times; 2. The height distribution of humidity in the lower troposphere at different times; 3. Extinction backscatter ratio (Lidar ratio); 4. Depolarization ratio. By comparing the depolarization ratio of water vapor and aerogel, the interaction between aerogel and water vapor can be confirmed, that is, the hygroscopicity of aerogel. By comparing the depolarization ratio and the lidar ratio, it can be shown that aerosols from different sources have different optical properties. The role of aerosol and cloud is also one of our next research focuses. This research, combined with the basic research of light scattering in the laboratory, can help us further obtain more information from the telemetry data and further improve LiDAR's technology. The basic research of light scattering in the laboratory includes the research of aerosol optical tweezers and the sonic levitation experiment being developed by our center.
Sun Yat-sen University Aerosol Science Research Center Aerosol Lidar Measuring Station: You can browse our observed data on this website.
Micro aerosol mass spectrometer
E-BAM Environmental Beta-Attentuation Mass Monitor
ASRC has equipped an E-BAM automatic monitor to continously monitor and sample PM2.5. The data is automatically reported every hour, and updated on the screens installed at several sites on campus.