Abstract We employ an optical second harmonic generation(SHG) technique to investigate the surface behaviours at the liquid(solid)/vapour interface of the Ga-Bi binary metallic system. In a heating and cooling cycle between 280℃ and room temperature, there is no change of the SH-intensity in the heating process, whereas there exists an abrupt and abnormal change of the SH-intensity in the cooling process. It is interesting to find that a macroscopic Bi-rich solid layer is floating on the surface of the Ga-rich liquid phase just below the monotectic temperature (222℃±2℃) in the cooling process, in spite of the Bi-rich phase being heavier than the Ga-rich phase. On the other hand, different undercooling behaviours are observed at the surface and in the bulk. The behaviours of surface solidification and surface melting are different from those in the bulk.
Received: 27 May 2002
Revised: 19 December 2002
Accepted manuscript online:
PACS:
42.65.Ky
(Frequency conversion; harmonic generation, including higher-order harmonic generation)
Fund: Project supported by the Alexander von Humboldt (AvH) foundation, Germany.
Cite this article:
Wang Cong (王聪), Wang Tian-Min (王天民) Surface behaviour and undercooling in the liquid Ga-Bi binary system detected by optical second harmonic generation 2003 Chinese Physics 12 315
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