• kinetic energy release (KER);
  • laboratory frame;
  • center of mass frame;
  • kinetic energy release distribution (KERD);
  • metastable ions;
  • mass-analyzed Ion Kinetic Energy (MIKE);
  • electrospray ionization (ESI);
  • matrix-assisted laser desorption/ionization (MALDI);
  • phase space theory (PST);
  • finite heat bath theory (FHBT);
  • the Gspann parameter;
  • surprisal;
  • organometallic ions;
  • clusters;
  • fullerenes;
  • biomolecules;
  • Coulomb explosion;
  • average KER;
  • Maxwell–Boltzmann-like distribution;
  • avoided crossing;
  • conical intersection;
  • angular momentum;
  • reaction cross-section;
  • detailed balance;
  • density of states;
  • centrifugal barrier;
  • prior distribution;
  • momentum gap law;
  • energy randomization


Kinetic energy releases (KERs) in unimolecular fragmentations of singly and multiply charged ions provide information concerning ion structures, reaction energetics and dynamics. This topic is reviewed covering both early and more recent developments. The subtopics discussed are as follows: (1) introduction and historical background; (2) ion dissociation and kinetic energy release: kinematics; potential energy surfaces; (3) the kinetic energy release distribution (KERD); (4) metastable peak observations: measurements on magnetic sector and time-of-flight instruments; energy selected results by photoelectron photoion coincidence (PEPICO); (5) extracting KERDs from metastable peak shapes; (6) ion structure determination and reaction mechanisms: singly and multiply charged ions; biomolecules and fullerenes; (7) theoretical approaches: phase space theory (PST), orbiting transition state (OTS)/PST, finite heat bath theory (FHBT) and the maximum entropy method; (8) exit channel interactions; (9) general trends: time and energy dependences; (10) thermochemistry: organometallic reactions, proton-bound clusters, fullerenes; and (11) the efficiency of phase space sampling. Copyright © 2001 John Wiley & Sons, Ltd.