predissociation database

The PDDB provides a curated collection of vibrational spectra of molecular ions and weakly bound complexes, with a special focus on infrared predissociation spectroscopy. In this technique, mass-selected ions or clusters are irradiated with intense, tunable infrared radiation, leading to vibrational excitation and subsequent fragmentation. By monitoring fragment yields as a function of wavelength, high-resolution vibrational spectra can be obtained.

The spectroscopic data compiled in PDDB originate primarily from experiments conducted at the Free Electron Laser for Infrared eXperiments (FELIX) laboratory in Nijmegen. The exceptional brightness and tunability of FELIX enable access to a wide spectral range and facilitate the investigation of complex molecular systems, including reactive intermediates, protonated species, and non-covalently bound molecular clusters.

By focusing on infrared predissociation spectroscopy of gas-phase ions and clusters, PDDB complements established spectroscopic databases such as the HITRAN database, CDMS database, NASA JPL database, and the NIST Chemistry WebBook, which predominantly focus on gas-phase absorption or emission spectra under thermal equilibrium conditions. Historical reference data can be found in the classic literature by Gerhard Herzberg and in the compilations by Takehiko Shimanouchi, although these sources generally do not include data on ionic or weakly bound molecular systems.