A NEW COLLISION-INDUCED TRANSITION IN THE VACUUM ULTRAVIOLET SPECTRUM OF $O_{2}$
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Date
1997
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Ohio State University
Abstract
The collision-induced photoabsorption spectrum of $O_{2}$, pressurised by He, is presented in the 1180-1340 {\AA}-region. In addition to the collision-broadened wings of the dipole-allowed mixed Rydberg-valence transitions, we have found a series of diffuse peaks whose intensities depend linearly on the foreign-gas pressure. The observed peaks have been assigned as the (1,0)-(5,0) bands of the $\Delta A = 2$ collision-induced $3p\pi_{u} ^{3}\Delta_{u}\leftarrow X^{3} \Sigma^{-}_{g}$ Rydberg transition, partly on the basis of comparisons with the photoabsorption spectrum of metastable $O_{2}(^{1}\Delta_{g}).^{h}$ The relative regularity of the spacings between the observed peaks supports the conclusions of Buenker and Peyerimhoff, in an {ab initio} study, that there is little interaction between the $3p\pi_{u} ^{3} \Delta_{u}$ Rydberg state and the $A^{\prime} \ ^{3}\Delta_{u}$ valence state, in contrast to the situation for the corresponding states of $^{3}\Sigma^{-}_{u}$ and $^{3}\Pi_{u}$ symmetries. Although the complexity of this spectral region and the diffuseness of the bands precludes any detailed line-profile analyses, it is clear that the integrated intensity of the $3p\pi_{u} {^{3}}\Delta_{u}\leftarrow X^{3} \Sigma_{g}^{-}$ Rydberg system exceeds that of the collision-induced $A^{\prime}\ ^{3}\Delta_{u}\leftarrow X^{3} \Sigma_{g}$ valence system by at least an order of magnitude. Possible sources for this intensity are discussed.
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$^{h}$P.C. Hill, Ph.D. Thesis, Australian National University, (1991). $^{i}$R.J. Buenker and S.D. Peyerimhoff. Chem. Phys. Lett. 334, 225 (1975). $^{j}$V.L. Dianov. Klokov, Opt. Spectrosc. 21, 233 (1996).
Author Institution: Research School of Physical Sciences and Engineering, The Australian National University
Author Institution: Research School of Physical Sciences and Engineering, The Australian National University