matrix isolation database

The MIDB provides a curated collection of vibrational spectra of small molecules, with a special focus on infrared spectroscopy under matrix-isolation conditions. In this technique, molecules are embedded in inert, cryogenic matrices (e.g., neon, argon, krypton, or xenon), where they are efficiently isolated from one another and stabilized at temperatures typically below 20 K. This approach significantly simplifies vibrational spectra by suppressing molecular rotation, collisional broadening, and chemical reactivity, thereby facilitating spectroscopic investigations.

MIDB is designed to teach and illustrate central aspects of vibrational spectroscopy in the infrared region. For each molecule listed below, this includes detailed descriptions of molecular symmetry, vibrational mode nomenclature, and interactive visualizations of molecular vibrations through animated normal modes, as well as comprehensive tables of vibrational frequencies, raw spectroscopic data, and further molecule-specific details. Beyond its educational purpose, the frequency tables provide valuable reference data for the interpretation of experimental spectra of related molecules and for benchmarking high-level quantum-chemical calculations. Potential energy surfaces (PES) used for the presented calculations are available in the /pes archive.

By focusing on matrix-isolation spectroscopy, MIDB complements established online spectroscopic databases, such as the HITRAN database, CDMS database, NASA JPL database, and the NIST Chemistry WebBook, which primarily provide extensive data for gas-phase spectra. Historical reference spectra can also be found in the classic literature by Gerhard Herzberg (Vol. I, Vol. II, Vol. III) and in the datasets compiled by Takehiko Shimanouchi for the National Bureau of Standards (Vol. I, Vol. II, Vol. III, Consolidated). Note that some of these historical datasets may be partially outdated.