Cross Section Measurements for Photodetachment or Photodissociation of Ions Produced in Gaseous Mixtures of O2, CO2,and H2O,

摘要

A drift tube mass spectrometer coupled with a continuous laser photon source has been used to study photodissociation of thermal energy positive ion clusters. Absolute photodissociation cross sections have been measured for the singly charged positive ion of molecular oxygen clustered to one and two water molecules, clustered to molecular oxygen, and clustered to one carbon dioxide molecule. Upper limits have been established for the photodissociation cross sections of the atomic hydrogen positive ion clustered to one through four water molecules. All of these measurements have been made at room temperature and for low field conditions (10 or 14.3 x 10(-21) volt-square meter). Photon wavelengths ranging from 676.4 nm to 454.4 nm were studied. The hydrated proton clusters were found to have small or zero cross sections. The single molecules of water and carbon dioxide clustered to the molecular oxygen cation have cross sections which behave similarly over part of the photon energy range. Near 2.60 eV both ions have cross sections approaching 6 x 10 (-22) square meter. The photodissociation of the molecular oxygen cation-carbon dioxide cluster produces a singly charged carbon dioxide cation photofragment. From the appearance of the fragment an upper bound on the dissociation energy of the molecular oxygen ion cluster to carbon dioxide was place at 0.46 eV. (Author)