| Abstract: | 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. |
