# OBSERVATION OF AN UNGERADE RYDBERG STATE OF $^{7}Li_{2}$

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 Title: OBSERVATION OF AN UNGERADE RYDBERG STATE OF $^{7}Li_{2}$ Creators: Ross, A. J.; Martin, F.; Adohi-Krou, A. Issue Date: 2004 Publisher: Ohio State University Abstract: Some weak, collisionally induced transitions have been observed following excitation of the two lowest vibrational levels of the $5d {^{1}}\Pi_{g}$ state of $^{7}Li_{2}$ (produced in a heatpipe source). The transitions were recorded in Fourier transform resolved fluorescence spectra in the near infrared $(7900 - 8800 cm^{-1})$, at an instrumental resolution of $0.08 cm^{-1}$, and they have been assigned as transitions from a Rydberg $^{1}\Pi_{u}$ state to $v = 0, 1$ and 2 of the $1 ^{1}\Delta_{g}$ electronic state. It seems highly likely that the two upper state levels populated through the collisions are $v = 0$ and $v = 1$ of $a ^{1}\Pi_{u}$ state which lies very close in energy to the $5d {^{1}}\Pi_{g}$ state. The energy transfer occurs to $v = 0$ of the $^{1}\Pi_{u}$ state from $v = 0$ of the $5d ^{1}\Pi_{g}$ state, and (at low J only) to $v = 1$ of the $^{1}\Pi_{u}$ state from $v = 1$ of $5d ^{1}\Pi_{g}$. Six bands were analysed: $0-0, 0-1, 0-2, 1-0, 1-1$ and 1-2. The rotational constants of this $^{1}\Pi_{u}$ state are too large to be high levels of the other ungerade Rydberg state of $Li_{2}$ documented in the literature, namely the $D ^{1}\Pi_{u}$ state studied by Theiss and $co-workers^{b}$. They are however sufficiently close to those of the $5d ^{1}\Pi_{g}$ state $(T_{e} = 37257.7 cm^{-1}, B_{e} = 0.48 cm^{-1}, \omega_{e} = 237.4 cm^{-1})$ given in earlier $work^{c}$, that we suggest the Rydberg state is most likely to correlate at long range with $Li(2s) + Li(5p)$ atoms. Principal spectroscopic constants are $T_{o} = 37390.198(5) cm^{-1}, B_{o} = 0.50627(12) cm^{-1}, \Delta G_{v} = 262.4 cm^{-1}$. Description: $^{a}$Permanent address: UFR SSMT Universit\'{e} de Cocody, 22 BP 582 Abidjan 22, Ivory Coast., $^{b}$W. Theiss, H. J. M\""{u}schenborn, and W. Demtr\""{o}der, Chem. Phys. Lett. 174 (1990) $126-132 ^{c}$. R. Bernheim, L. P. Gold, and T. Tipton, J. Chem. Phys. 78 (1983) 3635-3646 Author Institution: Laboratoire de Spectrom\'{e}trie Ionique et Mol\'{e}culaire, (UMR 5579 CNRS), B\^{a}timent A. Kastler, Universit\'{e} Lyon I, Domaine Scientifique de la Doua URI: http://hdl.handle.net/1811/21288 Other Identifiers: 2004-RE-04