UV Fluorescence of N2 Produced by Forbidden Absorption and Resonant Energy Transfer with Argon

J. B. Nee ； J. C. Yang ； H. K. Chen

《Chinese Journal of Physics》 47卷5期 (2009/10) Pp. 625-632

並列摘要

UV fluorescence is observed in N2 excited by VUV synchrotron radiation, with the strongest signals measured at 105.6 107.6, 109.9, and 124 nm. From the absorption spectrum we find that these are bands of the Tanaka system produced by the forbidden absorption with the transition C^3Π(subscript u)(v'=0-3)←X^1Σ(superscript + subscript g). The N2 (C) state subsequently radiates to the B^3Π(superscript + subscript g) state producing the second positive band (2PB) fluorescence. Additional UV fluores-cence is observed at excited states of Ar and CO presented as impurities in N2 with mixing ratios of 10^(-5). Similar to N2, excited states of Ar at about 11.5 eV can be populated by resonant absorption, and then this can be followed by a collisional transfer of energy to N2 to generate 2PB fluorescence. Among the two possible resonant states of argon, Ar(superscript *)(1P1) is more efficient than Ar(superscript *)(3P1) in producing the 2PB fluorescence through collisions. In addition, the absorption spectrum of the Lyman-Birge-Hopfield system of a^1Π(subscript g)-X^1Σ(superscript + subscript g), and the weaker systems of B'^3Σ(superscript + subscript u)-X^1Σ(superscript + subscript g) and a' X^1Σ(superscript + subscript u)-X^1Σ(superscript + subscript u)-X^1Σ(superscript + subscript g) were also observed.