Ultrahigh vacuum working Techniques

Therefore, in UFIV (p 10 mbar) the monolayer formation time is of the order of minutes to hours or longer and thus of the same length of time as that needed for experiments and processes in vacuum. The practical requirements that arise have become particularly significant in solid-state physics, such as for the study of thin films or electron tube technology. A UFIV system is different from the usual high vacuum system for the following reasons  

To fulfill these conditions, the individual components used in UHV apparatus must be bakeable and extremely leaktight. Stainless steel is the preferred material for UHV components. 

Basically, two independent questions arise concerning the size of a vacuum system  

What effective pumping speed must the pump arrangement maintain to reduce the pressure in a given vessel over a given time to a desired value  

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The non situ experiment pioneered by Sass uses a preparation of an electrode in an ultrahigh vacuum through cryogenic coadsorption of known quantities of electrolyte species (i.e., solvent, ions, and neutral molecules) on a metal surface. " Such experiments serve as a simulation, or better, as a synthetic model of electrodes. The use of surface spectroscopic techniques makes it possible to determine the coverage and structure of a synthesized electrolyte. The interfacial potential (i.e., the electrode work function) is measured using the voltaic cell technique. Of course, there are reasonable objections to the UHV technique, such as too little water, too low a temperature, too small interfacial potentials, and lack of control of ionic activities. ... 

In recent years through a number of spectroscopic and other techniques, great progress has been made in the understanding of catalytic phenomena. However, many of the new spectroscopic techniques are somewhat limited in value because of the necessity to work under conditions very far from the actual conditions of the catalytic process. That is, many of these techniques are used under ultrahigh vacuum (UHV), and the samples are best studied in the form of films, ribbons, or single crystals. Such samples are very different... 

Correlations of in situ and ex situ observations. The characterization methods of surface science have already been established within an electrochemical context, because they can provide structural definition of fine distance scales as well as atomic composition of a surface and, sometimes, vibrational spectroscopy of adsorbates. These ex situ methods normally involve transfer of an electrode from the electrochemical environment to ultrahigh vacuum, and the degree to which they provide accurate information about structure and composition in situ is continuously debated. Additional work is needed to clarify the effect of emersion of samples and their transfer to ex situ measurement environments. The most appropriate experimental course requires observations by techniques that can be employed in both environments. Vibrational spectroscopy, ellipsometry, radiochemical measurements, and x-ray methods seem appropriate to the task. Once techniques suited to this problem are established, emphasis should be placed on the refinement of transfer methods so that the possibilities for surface reconstruction and other alterations in interfacial character are minimized. 

A proper judgment of the validity of these findings, as well as any extension of such work, must rest upon a detailed appreciation of the experiments involved. It is the aim of this article to review the experimental methods upon which these advances have been based—the flash filament technique, flash desorption, field emission and field ion microscopy, and the use of ultrahigh vacuum procedures. 

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