BIRD (blackbody infrared radiative dissociation): evolution, principles, and applications

Blackbody infrared radiative dissociation (BIRD) describes the observation of ion-dissociation reactions at essentially zero pressure by the ambient blackbody radiation field, which is usually studied in the ion-trapping ion cyclotron resonance (ICR) mass spectrometer. A brief summary of the historical context and evolution is provided. Focussing on the quantitative observation of the temperature dependence of BIRD rates, methods are developed for connecting BIRD observations with activation parameters and dissociation thermochemistry. Three regimes are differentiated and described, comprising large molecules, small molecules, and intermediate-sized molecules. The different approaches to interpreting BIRD kinetics in those three regimes are discussed. In less than a decade since its inception, this approach to studying gas-phase ions has spread over a wide variety of applications, which are surveyed. Some major areas of activity are: the characterization of solvent-molecule detachment from solvated ions; dissociation reactions of biomolecules (polypeptides, oligonucleotides, complexes involving polysaccharides) and the structural information to be deduced from them; and dissociations of proton-bound and metal-ion-containing complexes. Studies of blackbody-radiation-driven evaporation of water molecules from large water-cluster ions are surveyed briefly. Several techniques related to BIRD are noted, including collisional dissociation in the FT-ICR ion trap; high-pressure thermal dissociation in quadrupole ion traps and in heated inlet capillary regions; hot-filament-assisted dissociation; and infrared multiphoton dissociation (IRMPD).