 The silicon dihalide gas molecules can be condensed at low temperatures.For example, if the gaseous SiF2 (difluorosilylene) produced from SiF4 (g) and Si (s) at 1100-1400°C is condensed at temperatures below -80°C and subsequently allowed to warm to room temperature, (SiF2)n is obtained.That reaction was first observed by Donald C. Pease, a DuPont scientist in 1958.