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Eden, James G. Shannon, David Charles 2011-05-07T12:32:25Z 2011-05-07T12:32:25Z 10000-01-01 1989 Molecular inter-Rydberg transitions of the rare gas dimers (He$\sb2$ through Kr$\sb2$) have been observed both through intra-cavity and multi-pass laser absorption spectroscopy. All five Hund's case (c) members of the A5p$\pi\sb{\rm u}$ manifold ($\sim$490-530 nm), predicted by the guidelines established by Mulliken (J. Chem. Phys., 52, 5170 (1970)) for Xe$\sb2$ and later adapted by Chang and Setser (J. Chem. Phys., 69, 3885 (1978)) for Ar$\sb2$, have been tentatively assigned. The molecular transitions originate from A4s$\sigma\sb{\rm g}$ (1$\sb{\rm u},0\sbsp{\rm u}{-}$) and terminate on the A$\sp2\Sigma\sbsp{\rm 1/2u}{+}$ ion core, $\sp3\Pi\sb{\rm g}$-derived (5p Rydberg electron) states (ranked in ascending energy): $0\sbsp{\rm g}{-},\ 0\sbsp{\rm g}{+},\ 2\sb{\rm g},\ 1\sb{\rm g},$ and $1\sb{\rm g}$. Transitions involving three of these are strongly red degraded (revealing that $\rm R\sb{e}4s(1\sb{u},\ 0\sbsp{u}{-}) < R\sb{e}5p(0\sbsp{g}{-})\ \leq\ R\sb{e}(0\sbsp{g}{+})\ <\ R\sb{e}(1\sb{g}-upper))$ whereas the bands associated with the 2$\sb{\rm g}$ and lowest 1$\sb{\rm g}$ levels are not. Analysis of newly-observed hot bands ($\Delta$v $\equiv$ v$\sp\prime$ - v$\sp{\prime\prime}$ $<$0) yields the following vibrational constants for A4s$\sigma\sb{\rm g}$(1$\sb{\rm u},\ 0\sbsp{\rm u}{-}):\ \omega\sb{\rm e}\sp{\prime\prime}$ = 297.2 $\pm$ 1.0 cm$\sp{-1}$, $\omega\sb{\rm e}\sp{\prime\prime}\rm x\sb{\rm e}\sp{\prime\prime}$ = 3.3 $\pm$ 0.4 cm$\sp{-1}$, $\omega\sb{\rm e}\sp{\prime\prime}\rm y\sb{\rm e}\sp{\prime\prime}$ = 0.08 $\pm$ 0.05 cm$\sp{-1}$. Several clear vibrational sequences are observed and tentative assignments for the A5p$\pi\sb{\rm u}$ separated atom limits are reported. The $0\sbsp{\rm g}{-},\ 0\sbsp{\rm g}{+},\ 2\sb{\rm g},\ 1\sb{\rm g}$, and $1\sb{\rm g}$ (upper) states apparently correlates (in the separated atom limit) with Ar($\sp1$S$\sb0$) + Ar5p (1/2) $\sb1$, (5/2) $\sb2$, (5/2) $\sb3$, and (3/2) $\sb1$, respectively, which is consistent with the known 4p, 5p $\to$ 4s oscillator strengths, the Ar 3p$\sp5$ 5p fine structure splittings, and the measured energy defects between the A5p$\pi\sb{\rm u}$ substates. Rather than being degenerate at small R, the 0$\sbsp{\rm g}{-}$ and 0$\sbsp{\rm g}{+}$ states of the A5$\pi\sb{\rm u}$ manifold are split by 247 cm$\sp{-1}$ near R$\sb{\rm e}$. Additionally, the A5p$\sigma\sb{\rm u}$ $\gets$ A4s$\sigma\sb{\rm g}$(1$\sb{\rm u}$, 0$\sbsp{\rm u}{-}$) (v = 0,1) transitions are also observed. Presumably correlated with Ar 5p (5/2) $\sb2$ + $\sp1$S$\sb0$ in the separated atom limit, calculations show that the A5p$\sigma\sb{\rm u}$ (0$\sbsp{\rm g}{-}$) state dissociation energy (D$\sb0$ $\cong$ 1.0 eV) is noticeably smaller than that for the A5p$\pi\sb{\rm u}$ levels (D$\sb0$ $\cong$ 1.26 $\pm$ 0.01 eV). The lowest energy Anp$\pi\sb{\rm u}$ $\gets$ Ans$\sigma\sb{\rm u}$(1$\sb{\rm u}$, 0$\sbsp{\rm u}{-}$) (n = 3$-$5) transitions in the heavier noble gases (Ne through Kr) have been observed with a multi-pass discharge absorption apparatus. Comparison of these transitions with regard to atomic number indicates that dissociative states arising from the ns$\sp\prime$ (1/2) $\sb0$ and ns$\sp\prime$ (1/2) $\sb1$ + $\sp1$S$\sb0$ atomic asymptotes are most likely responsible for the predissociation observed in the associated Anp$\pi\sb{\rm u}$ manifolds. The A4p$\pi\sb{\rm u}$ manifold of argon is perturbed to a far greater extent by dissociative curve crossings than the analogous manifolds in either neon or krypton. Attempts to investigate the ungerade molecular Rydberg states of Ar$\sb2$ using a resonant, two color sequential absorption process with the A4p$\pi\sb{\rm u}$(1$\sb{\rm g}$, 2$\sb{\rm g}$) states as intermediates were unsuccessful. Finally, an as yet unidentified band of absorptions in discharge pumped helium, requiring the presence of two strong optical fields of differing wavelengths, is reported and discussed. Made available in DSpace on 2011-05-07T12:32:25Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9011013.pdf: 2494862 bytes, checksum: 3e3d43d8330cc5d3891fbc41bdb6f4f2 (MD5) Previous issue date: 1989 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:42:22Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:18:25-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9011013 (UMI)AAI9011013 http://hdl.handle.net/2142/20212 eng Copyright 1989 Shannon, David Charles Chemistry, Physical Time-resolved absorption spectroscopy of the rare gas dimer Rydberg states text Electrical and Computer Engineering Electrical and Computer Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.