Dissociation degree of nitrogen molecule in low-pressure microwave-discharge nitrogen plasma with various rare-gas admixtures

Abstract

The dissociation degree of nitrogen molecules is examined in a microwave discharge nitrogen–rare gas mixture plasma with a total discharge pressure of 1 Torr, by actinometry measurement. Although the spectral line from the excited nitrogen atoms is overlapped by the band spectrum of the N2 first positive system (1PS), the subtraction of the 1PS spectrum fitted theoretically can successfully extract the atomic nitrogen line, which enables actinometry measurement. The nitrogen dissociation degree decreases with increasing mixture ratio of Ar to Kr, whereas it increases with He, which is attributed to the variations in the electron temperature and density. When we dilute the nitrogen with neon, however, we find an anomalous increase in the nitrogen dissociation degree by several orders of magnitude even at a downstream region in the discharge tube. The reason for the dissociation enhancement upon adding neon is discussed in terms of atomic and molecular processes in the plasma.

Nonequilibrium characteristics in the rotational temperature of CO excited states in microwave discharge CO2 plasma

“…The vibrational temperatures of both CO 3PS and CO Ångstrom bands is found to be in the range of T v ; 0.2-0.4 eV, which is approximately the same as that for other molecules observed in the microwave discharge plasmas, such as N 2 1PS, N 2 2PS, O 2 A-band, and so on. [34][35][36][37][38]43,45,49) As already shown in the previous subsections, the CO 3PS was well described with the unique rotational temperature T r , while that of the CO Ångstrom band showed anomalous behavior, i.e. it had two rotational temperatures corresponding to the bulk part T r bulk and high-energy tail part T r tail .…”

“…These observed values are considerably common to the microwave discharge plasmas of any gaseous species in the present device. 34,35,39,40,43) The characteristics of the nonequilibrium were considered to have been caused by the low ionization degree and the resultant electron collisions with atoms and molecules, which were more essential than the Coulomb collisions between the charged species.…”

“…It is identical to the one applied in the previous experiments. [34][35][36][37][38][39][40][41][42][43][44][45][46] The magnetron generates a microwave with a frequency of 2.45 GHz, as a general-purpose variable output microwave oscillator with its output of 0.2-4.9 kW equipped with a built-in isolator. It was connected to the discharge tube via a set of waveguides with a power monitor and a 3-stub tuner, which was finally terminated with a movable short-circuited plunger.…”

Sustainable Non‐Thermal Plasma‐Assisted Nitrogen Fixation—Synergistic Catalysis

“…Recent examples include microwave-discharge [31,32] andd ielectric-barrier-discharge (DBD) plasma. Recent examples include microwave-discharge [31,32] andd ielectric-barrier-discharge (DBD) plasma.…”

“…The nitrogen dissociation mechanisms and kinetics under variousp lasma environments was also studied and discussed. Recent examples include microwave-discharge [31,32] andd ielectric-barrier-discharge (DBD) plasma. [33] Table 1s ummarized the main dissociative reactions in the DBD and microwavep lasmas.…”