- ranges of vacuum：The vacuum region is roughly divided as follows:
Low vacuum: 105～102 760～1
Medium vacuum: 102～10-1 1～10-3
High vacuum: 10-1～10-5 10-3～10-7
Ultra-high vacuum: <10-5 <10-7
- gas：Substances that are free to occupy any space and are not subject to intermolecular interactions. Note: In vacuum technology, the term "gas" is not strictly applied to non-condensable gases and steam.
- n，m-3 number density of molecules：At a given instant, theChina PVD Plating Machine Suppliers number of molecules in the volume around a point in the gas is divided by that volume.
- ι、λ，m mean free path：The distance that a molecule travels with other gaseous molecules every two consecutive collisions is called free path. The average of quite a number of different free paths is called the average free path.