Knowledge Bank

X-ray emission and absorption investigations were known to provide empirical evidence for the failure of the isolated atom model as early as the 1920’s. Prior to World War II substantial progress was also achieved by solid state physicists in using soft x-rays, i.e. valence electron transitions, as a tool for learning about the density of states in simple conductors and insulators. Recent advances in instrumentation and the application of simple molecular bonding concepts indicate that x-ray photon spectroscopy should be a powerful tool in studying structural and bonding problems. This paper will briefly review the fundamental aspects and the instrumentation requirements of molecular x-ray spectroscopy and will contrast the capabilities of photon techniques as compared with photoelectron methods. The paper will also offer a detailed interpretation of the $L2,2$ and $K\beta$ spectra of sulfur and chlorine bearing substances.