SiCl

SiCl, or silicon monochloride, is a diatomic radical consisting of silicon bonded to chlorine. It is a transient species that is mainly observed in the gas phase under high-temperature conditions, such as flames, plasmas, and certain laboratory spectroscopic studies. As a radical, SiCl contains an unpaired electron and is therefore paramagnetic.

In terms of structure, SiCl is a diatomic molecule with a single Si–Cl bond. The electronic ground state of SiCl is characteristic of many silicon-containing radicals, and its spectrum shows transitions that can be detected by various spectroscopic methods. The molecule is generally less stable than higher silicon chlorides like SiCl2 and SiCl4 and is thus short-lived outside of controlled environments.

Formation and detection of SiCl occur in high-temperature silicon–chlorine chemistry and related gas-phase processes. It has been identified using techniques such as laser-induced fluorescence, absorption spectroscopy, microwave spectroscopy, and mass spectrometry after selective ionization. These methods enable the study of its vibrational and rotational transitions and help determine its spectroscopic constants.

Reactivity is a defining feature of SiCl. It rapidly reacts with oxidants and moisture, tending to form more oxidized silicon species and hydrogen chloride. Consequently, SiCl is typically a fleeting intermediate rather than a stable product in silicon–chlorine chemistry. It is of interest in plasma processing, combustion research, and astrochemical contexts where transient silicon-containing radicals are present.

See also: SiCl2, SiCl4, silicon chloride.