ON THE POSSIBILITY OF CHEMILUMINESCENCE ACCOMPANING THE Tb<sup>3+</sup> ION REDOX-REACTIONS INITIATED BY THE RADIOLYSIS OF AQUEOUS SOLUTIONS
The possibility of generating excited Tb<sup>3+</sup> ion in reactions involving a hydrated electron (e<sub>aq</sub><sup>-</sup>) and sulfate ion, initiated by radiolysis of terbium chloride aqueous solutions with (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> additives is considered. From a comparison of the photo- and radioluminescence of these solutions, it was concluded that an increase in the Tb<sup>3+</sup> luminescence intensity with an increase in the sulfate ion concentration in both cases is due to the formation of the inner-sphere complex [Tb<sup>3+</sup>(H<sub>2</sub>O)<sub>x</sub>(SO<sub>4</sub><sup>2</sup><sup>-</sup>)<sub>y</sub>]<sup>(3</sup><sup>-</sup><sup> y)+</sup>, which has a higher quantum yield of luminescence than the aquaion [Tb<sup>3+</sup>(H<sub>2</sub>O)<sub>x</sub>]<sup>3+</sup>. The chemiluminescence that is possible in the case of the solution radioirradiation during the reduction by e<sub>aq</sub><sup>-</sup> of the Tb<sup>4+</sup> ion formed as a result of the Tb<sup>3+</sup> oxidation by the radiolytically generated radical ion SO<sub>4</sub><sup>•</sup><sup>- </sup>is not realized. An additional increase in the intensity of terbium radioluminescence is observed in the presence of e<sub>aq</sub><sup>-</sup> selective acceptor, H<sup>+</sup>, in the solution, which is associated with the capture by the proton e<sub>aq</sub><sup>-</sup>, which is an effective quencher of *Tb<sup>3+</sup>. This fact also excludes the existence of chemiluminescence Tb<sup>4+</sup> + e<sub>aq</sub><sup>-</sup> ® *Tb<sup>3+</sup>, otherwise the quenching of the radioluminescence of the terbium ion in the presence of H<sup>+</sup> would be observed. It is concluded that the chemiluminescence mechanism of the Tb<sup>3+</sup> ion luminescence during radiolysis is not realized, and the main source of its radioluminescence is the direct action of ionizing radiation on this ion.