collision gas

https://doi.org/10.1351/goldbook.12362
Inert gas used for collisional excitation or a reactive gas used for ion/molecule reactions.
See also: buffer gas
Source:
PAC, 2013, 85, 1515. (Definitions of terms relating to mass spectrometry (IUPAC Recommendations 2013)) on page 1531 [Terms] [Paper]