Excitation of mercury atoms in nitrogen post-discharge

Abstract

The work presents results obtained during spectroscopic observations of nitrogen DC flowing post-discharges at the total gas pressure of 1000 Pa and at the discharge current of 100 mA. Mercury traces were introduced into the system using auxiliary pure nitrogen flow enriched by mercury vapor. A very low mercury concentration of 3.7 ppb was introduced into the system before the active discharge. The strong quenching of nitrogen pink afterglow was observed but no mercury lines were recorded. Moreover, the vibrational distributions of nitrogen excited states were nearly unchanged. Based on these results, the new experimental set up was created. The introduction point of mercury vapor with higher concentration of 600 ppm was movable during the post discharge up to decay time of 40 ms. Besides three nitrogen spectral systems (first and second positive and first negative), NO^β and NO^γ bands, the mercury line at 254 nm was recorded at these conditions. Its intensity was dependent on the mercury vapor introduction position as well as on the mercury concentration. No other mercury lines were observed. The creation of mercury ³P1 state that is the upper state of the observed mercury spectral line is possible by the resonance excitation energy transfer form vibrationally excited nitrogen ground state N₂(X¹Σ⁺_g, v &equal; 19). The observed results should form a background for the development of a new titration technique used for the highly vibrationally excited nitrogen ground state molecules determination.