OutgassingRaten

OutgassingRaten is an uncommon rendering of the term outgassing rate, used in vacuum science and materials engineering. The standard term is outgassing rate, sometimes expressed per unit area as q'' or as a total rate Q for a chamber.

Definition and units: The outgassing rate per area, q'', is the amount of gas released from a material into a vacuum per unit area per unit time. Common units are Torr·L·s⁻¹·cm⁻². The total outgassing from a chamber equals q'' multiplied by its exposed area.

Causes and factors: Outgassing primarily arises from desorption of adsorbed water, hydrocarbons, and other volatile species from surfaces. Materials such as polymers and elastomers tend to outgas more than metals. Temperature, surface cleanliness, storage history, and coatings influence the rate; bakeout and surface treatments can significantly reduce it.

Measurement and management: Outgassing is measured by methods such as rate-of-rise tests, where the pressure increase in a sealed chamber is monitored, and by dedicated tools like quartz crystal microbalances or mass spectrometry. Values vary widely by material and conditioning, from well below 1e-12 Torr L s⁻¹ cm⁻² to higher levels.

Significance: In vacuum systems, outgassing sets the achievable base pressure, affects surface contamination, and can degrade optics, detectors, and seals. Good material selection, cleaning, bakeout, and proper venting are standard practices to minimize it in laboratories, semiconductor equipment, and spacecraft payloads.