A method of controlling back reactions or recombination reactions of product molecules formed in a photolytic dissociation reaction of reactant molecules of a gas sample, the method comprising: providing a photolytic converter comprising: a converter body defining a reaction chamber and having a central axis: one or more electromagnetic radiation sources in communication with the reaction chamber for dissociating the reactant molecules in the gas sample to form product molecules; one or more inflow conduits for conveying an unprocessed gas sample into the reaction chamber, each said inflow conduit having an inlet configured to be in fluid communication with a source of the gas sample and an outlet in communication with the reaction chamber, one or more outflow conduits for conveying a processed gas sample out of the reaction chamber, each said outflow conduit having an inlet in fluid communication with the reaction chamber and an outlet configured to be in fluid communication with a receptacle for receiving the processed gas sample, wherein the outlet of the one or more inflow conduits are oriented tangentially with respect to the converter body, and wherein the inlet of the one or more outflow conduits is oriented axially with respect to the converter body. introducing the unprocessed gas sample into the reaction chamber through the one or more inflow conduits; initiating the dissociation reaction of the reactant molecules of the unprocessed gas sample in the reaction chamber by irradiation with the one or more electromagnetic radiation sources to form the product molecules; conveying the processed gas sample comprising the product molecules out of the reaction chamber through the one or more outflow conduits, thereby creating a patterned flow of the gas sample in the reaction chamber to reduce disordered and/or turbulent mixing of the reactant molecules and/or product molecules in the gas sample and controlling the back reactions or recombination reactions of product molecules. providing a photolytic converter comprising: a converter body defining a reaction chamber and having a central axis: one or more electromagnetic radiation sources in communication with the reaction chamber for dissociating the reactant molecules in the gas sample to form product molecules; one or more inflow conduits for conveying an unprocessed gas sample into the reaction chamber, each said inflow conduit having an inlet configured to be in fluid communication with a source of the gas sample and an outlet in communication with the reaction chamber, one or more outflow conduits for conveying a processed gas sample out of the reaction chamber, each said outflow conduit having an inlet in fluid communication with the reaction chamber and an outlet configured to be in fluid communication with a receptacle for receiving the processed gas sample, wherein the outlet of the one or more inflow conduits are oriented tangentially with respect to the converter body, and wherein the inlet of the one or more outflow conduits is oriented axially with respect to the converter body. one or more electromagnetic radiation sources in communication with the reaction chamber for dissociating the reactant molecules in the gas sample to form product molecules; one or more inflow conduits for conveying an unprocessed gas sample into the reaction chamber, each said inflow conduit having an inlet configured to be in fluid communication with a source of the gas sample and an outlet in communication with the reaction chamber, one or more outflow conduits for conveying a processed gas sample out of the reaction chamber, each said outflow conduit having an inlet in fluid communication with the reaction chamber and an outlet configured to be in fluid communication with a receptacle for receiving the processed gas sample, wherein the outlet of the one or more inflow conduits are oriented tangentially with respect to the converter body, and wherein the inlet of the one or more outflow conduits is oriented axially with respect to the converter body. introducing the unprocessed gas sample into the reaction chamber through the one or more inflow conduits; initiating the dissociation reaction of the reactant molecules of the unprocessed gas sample in the reaction chamber by irradiation with the one or more electromagnetic radiation sources to form the product molecules; conveying the processed gas sample comprising the product molecules out of the reaction chamber through the one or more outflow conduits, thereby creating a patterned flow of the gas sample in the reaction chamber to reduce disordered and/or turbulent mixing of the reactant molecules and/or product molecules in the gas sample and controlling the back reactions or recombination reactions of product molecules.