Photoelectron Ejection from Aromatic Negative Ions in Rigid Media

A study is made of the photoejection of electrons from negative hydrocarbon ions in a glassy solution of 2-methyl tetrahydrofuran at 77°K. The irradiation leads to a conversion M=→ lim hpM−+e−or M−→ lim hpM+e−.The threshold for photo-oxidation appeared to be dependent on the nature of the aromatic species. By using light with an energy below this threshold the photoreaction can be reversed. The ejected electrons give rise to (i) an optical-absorption band in the near infrared with ε=3–4×104 at the point of maximum absorption (7.7 kK) and (ii) an ESR signal at g=2.002 with a width of 4.5 G. It is shown that the ejected electrons are trapped by cavities in the rigid solvent. A lower limit of about 10−2M is found for the concentration of cavities suitable for trapping electrons.