We have performed CID experiments on a triple quadrupole instrument, lowering the
collision gas pressure by 50 times compared to its conventional value. The results
show that at very low-collision gas pressure, single collisions dominate the spectra.
Indirectly, these results suggest that under conventional conditions, 20–50 collisions
may be typical in CID experiments. The results show a marked difference between low-
and high-pressure CID spectra, the latter being characterized in terms of ‘slow heating’
and predominance of consecutive reactions. The results indicate that under single
collision conditions, the collisional energy transfer efficiency is very high: nearly
100% of the center of mass kinetic energy is converted to internal energy.
