ABSTRACT
In vacuum physics, the major concerns are substances in gas phase and their behavior at vacuum conditions. Ideal gases are gas systems at low pressures in which the differences in behavior between individual chemically different gases vanish. The barometric equation is predicated on the simplified assumption of a constant temperature over the whole gas column. Pressure is one of the principal macroscopic characterizing the gas state. Barometric pressure is the pressure measured by a barometer. The gas amount may be given by a gas mass, number of gas molecules, or molar gas quantity. Gas throughput is the quantity related to the physical phenomena of gas flows. The gas exposure is defined as the number of molecules colliding with a unit area of material surface for time t. In the context of sorption processes, a dissimilar quantity with a different unit was introduced for gas exposure.
