Sample pair modulation studies of molecular fragmentation in plasmas

Abstract

An automated sampllng loop system Is presented for modulatlng plasmas with aiternatlng transient inJectlons of two gaseous compounds of wldely dlffering bond energies. Measuring the intenslty ratio at a slngie atomic emission wavelength for the two compounds leads to cancellatlon of all terms In the Elnsteln-Boltrmann emisslon intensity law except the number of free atoms liberated upon fragmentation. The experimentally measured lntenslty ratio therefore equals the free atom ratio for the two compounds. Comparison of thls ratlo wlth known formula stolchiornetry Indicates the extent of fragmentatlon Induced by the plasma for the stablest molecule of the sample palr. The atmospherlc pressure argon inductively coupled plasma Is studied as an example with 0, (bond energy 5.1 eV) and C E O (bond energy 11.1 eV) as the modulation pair. For atomlc oxygen liberated at certain argon flow rates and radlo frequency power levels, the measured near-infrared emisslon lntenslty ratio converges on the value predlcted from formula stolchlometry. Thls indlcates quantltatlve carbon monoxlde dlssociation.