Study of water adsorption on organics crystal surfaces using a modified X-ray photoelectron spectroscopy instrument.

The coupling of a high partial pressure water vapor system to a conventional X-ray photoelectron spectroscopy instrument for use with both organic powders and single crystals is described. The modified chamber serves a dual purpose as both a treatment and sample preparation apparatus. The design utilizes the high- and cryo-temperature capabilities of the existing system to allow investigation of various states of surface water, as well as the interplay between temperature, water, and surface structure of the substrate. Sample handling and methods for compatibility testing are detailed, and data illustrating the application of the modified and integrated capabilities are summarized, detailing novel studies on the state of water on the surface of model organic pharmaceutical salts. In addition to facilitating investigation of the presence of various states of water at the surface of organic material, namely, dissociated versus molecular water, the setup allows the investigation of structural effects of the surface on the state of water.