product ion scan

In an MS/MS experiment, mass-selected precursor ions are induced to dissociate into product ions, which are then mass analyzed by a second analyzer. The three common scans in the single-step MS/MS experiment are: product ion scan, precursor ion scan, and then the constant neutral loss scan. In the product ion scan, the first mass analyzer is set at the mass of the selected precursor ion, and then the second  mass analyzer is scanned from that mass downwards. The result is a mass spectrum that contains signals for all the product ions formed from that selected precursor ion.