Spherical MgSO4 droplets were deposited by a syringe on the hydrophobic Teflon substrate. Using micro-Raman technique, the laser beam was highly focused twice on the surface and in the center of spherical droplets. The Raman spectra for the surface and the inner of MgSO4 droplets were accord-ingly obtained, suggesting formation of a thin layer of gels on MgSO4 droplets at low relative humidity. The gel layer covered the surface and exhibited a significant delay in response to the change of ambi-ent relative humidity, resulting in the structural difference between the surface and the inner of MgSO4 droplets.
A system for measuring the electric properties of single aerosol droplet is designed and applied to the NaClO4 aerosol droplet in different relative humidity (RH). The conductance and capacitance are ob-tained within the whole RH range, especially in the supersaturated state which cannot be acquired from the bulk solution. These results reflect the situation of ions in the droplet macroscopically and supply useful information for other relative study fields, such as crystallogeny and aerography.
HE KeJuan CHENG Hua ZHU YanYing WANG LiangYu ZHANG YunHong
By using the measuring system previously designed by the authors, the conductance of KCl, NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range, especially in the supersaturation region, which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state. The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCl), 75.7% and 93.3% (NaCl), and 69.9% and 96.6% (NH4Cl), respectively. In addition, it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.
HE KeJuanCHENG HuaZHU YanYingWANG LiangYuZHANG YunHong
One technique based on the difference spectra was developed to study the state of water in supersaturated Mg(NO3)2 aerosols. The technique could be derived from the observation that the Raman scattering and infrared absorbance cross sections of molecular vibrations of interest remain practically constant from diluted solutions to supersaturated aerosols. The spectra of solvated water were obtained and primarily related to the first hydration layers of solute molecules in supersaturated Mg(NO3)2 aerosols. Based on this investigation, a chain structure was proposed to occur in the supersaturated Mg(NO3)2 aerosols at low relative humidities (RHs).
The conformational behaviors of monosodium glutamate （MSG） in a dehydration process were studied by Micro-Raman spectroscopy in combination with Hartree-Fock calculations using 6-3 1＋G^＊ method. The dehydration process of the MSG droplet was performed by decreasing the ambient relative humidity （RH）. The intensity ratio of the 935 cm^-1 band to 884 cm^-1 band （I935/ 1884） kept decreasing when RH decreased. By optimizing the geometries with different fixed dihedral angles, the downtrend of （I935/I884） is found to be due to the reduction of MSG molecular volume.
Jing Jing Shou Guang Zeng Hao Zhang Yun Hong Zhang
