system
Given the following post, respond as if you're commenting on Reddit:
human
How can collisions between molecules in the gas-phase result in cooling i.e. "collisional cooling" when collisions are also used to activate and fragment molecules i.e. "collision-induced dissociation"?

This seems contradicting to me. Can someone explain the difference between a scenario where collisional cooling dominates and a scenario where collisional activation dominates? My particular example is for peptide ions in a mass spectrometer in case different theories apply for different regimes.
gpt
The difference is the kinetic energy involved in collisions.

Collisional cooling: very cold gas in weak trap. Kinetic energy involved in collisions is way smaller than bond energy. Collisions occasionally give individual molecules higher-than-average kinetic energy, enough to exit the trap, at which point they remove that kinetic energy from the system, decreasing the average KE and therefore the temperature.

Collision-induced dissociation: very hot gas, or molecules accelerated toward each other. Kinetic energy involved in collisions is on the order of bond energy.