A vacuum chamber is never perfectly empty. A small number of atoms or molecules always remain, and measuring the tiny pressures they exert is critical. For instance, semiconductor manufacturers create microchips in vacuum chambers that must be almost entirely devoid of atomic and molecular contaminants, and so they need to monitor the gas pressure in the chamber to ensure that the contaminant levels are acceptably low.
Click here for original story, Research team demonstrates a new ‘primary standard’ for measuring ultralow pressures
Source: Phys.org