Flash spectroscopy with mercury resonance radiation. Part 1.—An experimental method with microwave-pulse excitation

Abstract

A method of producing an intense flash of mercury resonance radiation (2537 Å) was described and application to kinetic absorption spectroscopy was illustrated with a variety of experiments. A powerful pulse of microwave radiation was delivered via a radiating horn to a flash lamp situated at the exit of the horn. The reaction cell was located inside and coaxial with the flash lamp and, with the incident radiation transverse to the lamp, the discharge was naturally confined to the outer annulus. The maximum rate of absorption of resonance radiation in the inner reaction-cell was achieved when the lamp was filled with a He + N₂ mixture. The production of free radicals in the central vessel was investigated by kinetic absorption spectroscopy.

A method of actinometry was described in which CS was produced in the sequence Hg^*+ N₂O → Hg + N₂+ O, O + CS₂→ CS + SO. (iv) Thereby the light absorption per 2.5 µs pulse was recorded as ∼10¹⁴ quanta cm^–3. The absolute rate of (iv) was also measured.

A technique was developed for measuring the fractional quenching of Hg(³P₁) to Hg(³P_o) and the yields of metastable atoms were determined in N₂, CO, CO₂, CH₄, C₂H₆, C₃H₈, n-C₄H₁₀, NH₃ and H₂O. Metastable atom yields in H₂, D₂, NO, N₂O, O₂, H₂S, C₂H₂, CH₃Br, HBr, HCl and HCN were reported to be less than 1 %. The following processes were established spectroscopically: Hg(³P₁)+ H₂S → Hg(¹S_o)+ H + SH, Hg(³P₁)+ H₂→ HgH + H, Hg(³P₁)+ HCL → HgCl + H, Hg(³P₁)+ CS₂→ Hg(¹S_o)+ CS^*₂. It was suggested that the new technique is capable of achieving an analysis of essentially the complete role of metastable atoms, and intermediate mercury complexes, in reactions photosensitized by mercury.