Chemical reactions on catalytic surfaces play a vital role in many industrial operations, such as the production of artificial fertilisers. Surface chemistry can even explain the destruction of the ozone layer, as vital steps in the reaction actually take place on the surfaces of small crystals of ice in the stratosphere. The semiconductor industry is yet another area that depends on knowledge of surface chemistry. It was thanks to processes developed in the semiconductor industry that the modern science of surface chemistry began to emerge in the 1960s. This science requires advanced high-vacuum experimental equipment as the aim is to observe how individual layers of atoms and molecules behave on the extremely pure surface of a metal, for instance. It must therefore be possible to determine exactly which element is admitted to the system. Contamination could jeopardise all the measurements. Acquiring a complete picture of the reaction requires great precision and a combination of many different experimental techniques. This book presents the latest research in the field.