Radiation of Atoms and Ions of Metals in the Plasma-Chemical Process Initiated by the Radiation of a Powerful Pulsed Gyrotron in Mixtures of Magnesium and Titanium Oxide Powders

Results of spectroscopic measurements of the plasma radiation in microwave discharges in experiments on the synthesis of micro- and nanosized catalytic structures under the action of powerful microwave radiation pulses produced by a gyrotron (the wavelength of 4 mm, the pulse duration of 2–8 ms, and the power of up to 500 kW) on the mixture of magnesium Mg and titanium oxide TiO₂ powders have been presented. The experiments have been carried out in air. The radiation spectra of the microwave discharges have been recorded by a set of AvaSpec spectrometers of different types in the wavelength range from 219 to 920 nm. Spectral lines of neutral atoms and singly ionized ions of magnesium and titanium were recorded. The characteristics of the spectral lines are studied during the interaction of the microwave radiation pulse with the powder mixture and after its termination. The analysis of the obtained results shows that for titanium atoms, the condition of the local thermodynamic equilibrium (LTE) is fulfilled, which allows one to make reliable estimates of the electron temperature of the plasma, which varies from 0.2 to 0.4 eV. At the same time, for titanium ions, the LTE condition is not fulfilled in the microwave discharge. The comparable intensities of the atomic and ionic titanium lines in the discharges at the electron temperature of 0.2–0.4 eV, which is more than one order of magnitude lower than the ionization potential of titan, indicate that the plasma of the microwave discharge in the powder mixture is strongly inhomogeneous. The bands of titanium monoxide TiO recorded in the radiation of the microwave discharge indicate that plasma-chemical reactions occur in the discharge.