Richard E. Rosati

Absolute yields of CO(a′ 3Σ+, d 3Δi,e 3Σ−)+O from the dissociative recombination of CO2+ ions with electrons

The flowing afterglow technique has been applied to the dissociative recombination CO2++e−→CO*+O, in order to determine the radiative cascade contribution from high-energy triplet states of CO, (a′ 3Σ+), (d 3Δi), and (e 3Σ−), to the total yield of the long-lived (a 3Π) state. The yields of the a′, d, e states were found to be approximately 18%, 20%, and 0.3%, respectively, of the total CO(a) yield, which leads us to conclude that (38±8)% of the total CO(a) yield is due to radiative cascading, rather than direct formation. When combined with our previously reported total CO(a) yield of 0.29±0.10, the absolute yields of the triplet states become f(a′)=0.053±0.024, f(d)=0.057±0.022, and f(e)∼9×10−4.

Optical Spectroscopy of Recombining Ions in Flowing Afterglow Plasmas

Spectroscopy has been an important tool in studies of dissociative recombination (DR) for many years. The early work by Biondi1 and coworkers established the dissociative nature of the process by demonstrating the Doppler broadening of spectral lines due to the momentum that is imparted to the separating recombination fragments. In more recent work, spectroscopic methods have been used to identify products of DR of diatomic and polyatomic ions and to quantitatively measure yields for specified states of radiating recombination products. The formation of products in radiating states is of potential interest for the interpretation of planetary spectra and perhaps those observed from interstellar clouds, and of course, experimenters hope that identification of product states will lead to new insights into the mechanisms of recombination.