Common Vacuum Terminology 3

1. ranges of vacuum：The vacuum region is roughly divided as follows:

                      Pa        Torr

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

2. 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.
3. 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.
4. 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.