Self-assembling of the neutral intermediate with chemically bound argon in photoexcited van der Waals complex Ar-I₂

Photodissociation of the van der Waals complex Ar-I₂ after excitation into the Rydberg states of I₂ has been investigated with velocity map imaging of photofragments. Formation of the translationally hot ions of argon Ar⁺ with three modes in kinetic energy distribution has been revealed. The measured dependence of the kinetic energy of Ar⁺ on the pumping photon energy indicates the appearance of Ar⁺ from three channels of the photodissociation of the linear intermediate Ar⁺-I-I^- containing chemically bound argon. These channels are (1) dissociation into Ar⁺+ I₂ ^-; (2) three-body dissociation into (Ar⁺)* + I* + I^-, with (Ar⁺)* and I* being the ²P_1/2 states of the species; and (3) two-body electron photodetachment, giving rise to Ar⁺ + I₂ + e. Three indicated channels are similar to those established for the photodissociation of trihalide anions. This similarity confirms the conclusion on the formation of the Ar⁺-I-I^- intermediate, which is isoelectronic to the trihalide anion Cl-I-I^-. The mechanism of the Ar⁺-I-I^- formation involves two-photon excitation of the complex Ar-I₂ into the Rydberg state of I₂ converted into the ion-pair state and further electron transfer from Ar to I⁺ of the ion-pair state. The self-assembling of the structure making the formation of the Ar⁺-I-I^- intermediate energetically accessible is confirmed by modeling the dynamics in the excited linear complex Ar-I₂. Photoexcitation of the van der Waals complexes of noble gases with halogens into the ion-pair states of halogen is supposed to be a promising approach for generating the new chemical compounds of noble gas atoms.