LASERSPECTROSCOPIC INVESTIGATION OF HIGHER EXCITED ELECTRONIC STATES OF KAr

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1994

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Ohio State University

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First successful measurements on higher excited electronic states of the van der Waals molecule KAr have been performed in a supersonic jet. The higher excited electronic stales $^{2}\Lambda$ are reached in a two-step excitation via the intermediate slate $A^{2}\Pi$ using two tunable cw dye lasers. One laser the pump laser with $\delta \approx 770$ nm, was tuned to a suitable rovibrational line of the $A^{2}\Pi \leftarrow X^{2}\Sigma$ transition populating one rovibrational sublevel of the $A^{2}\Pi$ state. The second probe laser ($\delta \approx 585$ nm) was scanned over a range at about $200 cm^{-1}$. By means of a systematic variation of the pumping transition we found a total of more man 500 lines due to the transition $^{2}\Lambda \leftarrow A^{2}\Pi$. A large part of these lines could be assigned to the rotational structure of vibrational bands leading to vibrational levels of the two $2\Sigma$ states being correlated with the $^{72}S$ and the $^{52}D$ stale of the K-atom. In addition, the parameters of rotation and of spin-orbit coupling could be determined for 6 and 3 vibrational levels due to the $^{2}\Lambda(^{52}D)$ and the $^{2}\Lambda(5^{2}D)$ state, respectively For the $2\Lambda(5^{2}D)$ state an inverted fine structure splitting of around -$0 4 cm^{-1}$ was observed for ail vibrational stales which is in good agreement with the value predicted from the inverted tine structure splitting of the $5^{2}D$ state of The K atom. Up to now the interatomic potentials of the higher excited $2\Lambda$ slates could not be determined from our spectroscopic results as numerous avoided crossings between different potential curves are expected leading to large deviations from the usual ladder of vibrational energies.

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Author Institution: Technische Universit\""{a}t Berlin, Institut f\""{u} Strahlungs- und Kemphysik

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