Spectroscopic Determination of Quenching Cross-Sections of Excited Mercury Atoms (63P1, 63P0) in Molecular Collisions

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Abstract
The concentrations of Hg(63P1) and (63P0) atoms, [Hg1*] and [Hg0*], were determined from the absorptions of 4358 and 4047 Å lines in the Ar-diluted mercury vapor in the presence of several quenching molecules, under the radiation of 2537 Å emission. An apparent absorption intensity was not proportional to [Hg1*] or [Hg0*], and was sensitive to the ratio of the spectral half-width of the light source to that of the absorption line. Therefore, a method to correct an absorption intensity was proposed. The relation of [Hg1*] to [Q], a concentration of quenching molecules, is explained well by the Stern-Volmer equation. The value of [Hg0*] increases with [Q] until it reaches a maximum at a certain value of [Q], and a further increase of [Q] results in a decrease of [Hg0*]. These findings are explained well by the following mechanism: (1) Hg+hν→Hg1*, (2) Hg1*→Hg+hν, (3) Hg1*+Q→Hg+Q, (4) Hg1*+Q→Hg0*+Q, (5) Hg0*+Q→Hg+Q, (6) Hg0*→Hg (by collisions with a wall). The respective values of cross-sections (σ2) of N2, CO, and NO for process (3) are ≤0.03, 0.60, and 20 Å2, and those for process (4) are 0.36, 2.1 and 5 Å2, and those for process (5) are ≤3.6×10−4, 0.15 and 8.0 Å2.