Quantum yield measurement in the chemical reactions of laser-excited Zn and Rb atoms with molecules

Graphical abstract: A new method of determining the rate constants of chemical reactions proceeding with participant of Zn(4p 3P1) and Rb(11P3/2) atoms has been introduced. The method is based on the investigation of the spatial and temporary behavior of the atoms and their interaction with reagent-gas molecules in a carrier gas flow. For the excitation of the atom pulsed monochromatic resonance laser radiation was used. The interaction of electronically excited atoms with reagent-gas molecules causes a decrease in the concentration of atoms owing to chemical and physical quenching processes. Registering the change in the atom concentration at the end of the flow, one can evaluate the rate a constants of the reaction in which of stable chemical compounds forms. These investigations are necessary for the laser isotope separation. - Abstract: In the present paper, we introduce a method for measuring the apparent quantum yield θap and the rate-constant values of the physical kp and chemical kc quenching of electronically excited Zn and Rb atoms by gas molecules. The method is based on measuring the concentration of the atoms at the end of their flow in a mixture with a reagent-gas and a carrier gas, in the region where all quenching and secondary processes are already over. The concentration of the atoms was determined from measured absorbed energy of resonance laser radiation. The rate constants and the cross-sections of the chemical and physical quenching of Zn(3P10) and Rb(11P3/2) atoms with several molecules have been determined. For some collisions the quantum yield was found to be close to unity. The method may find applications in laser photochemical isotope separation and in measuring the rate constants of reactions proceeding with participation of ground state atoms.