Electronic Spectroscopy of Transient Molecules

Abstract

The generation and characterization of transient species is a challenge for experimentalists as these species are short‐lived and reactive. Our group has focused on the measurement of the electronic spectra of unstable molecules relevant to astrophysical observations as well as to terrestrial environments. Methods of generating and collecting the electronic spectra of radicals and ions have been developed. By first using a mass‐selected matrix isolation technique, the transitions of these species are obtained in neon matrices, following which the gas‐phase transitions can be sought. To this end, an assortment of techniques is employed, for example, cavity ring‐down and frequency modulation absorption spectroscopy, degenerate four‐wave mixing, resonant multiphoton ionization, and photofragmentation schemes that utilize the cooling capabilities of an ion trap. These gas‐phase‐based approaches are illustrated by the electronic spectra of a number of key species providing detailed information about their electronic structure, thus allowing for direct comparison between astronomical observations and theory. The studies of the carbon chains have led to interesting astrophysical implications for the systems, which could be responsible for the diffuse interstellar bands.

High‐ResolutionFTIRand Diode Laser Spectroscopy of Supersonic Jets

“…The transient species are successively cooled and transported in a collisionless environment. Concentrations of 10 12 radicals cm −3 and 10 10 ions cm −3 are obtainable with these techniques (Mazzotti et al 2008, Guennoun andMaier 2011: Electronic Spectroscopy of Transient Molecules, this handbook).…”

“…They have attributed the rotationally resolved spectrum at 1809 cm −1 to an asymmetric stretching mode of a 13-atom counting linear carbon chain. See also Guennoun and Maier 2011: Electronic Spectroscopy of Transient Molecules, this handbook. Kroto et al (1985) discovered an icosahedral carbon cluster, consisting of 60 carbon atoms, which they called Buckminsterfullerene.…”