# THE $b{^{3}}\Pi_{u0}$ STATE OF $^{39}K_{2}$

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 Title: THE $b{^{3}}\Pi_{u0}$ STATE OF $^{39}K_{2}$ Creators: Ross, A. J.; Martin, F.; Crozet, P.; Lyyra, A. M.; Li, Li; Bergeman, T.; Amiot, C.; Manaa, M. Riad Issue Date: 2002 Publisher: Ohio State University Abstract: New observations of the $b{^{3}}\Pi_{u0}$ state of $K_{2}$ have been made by laser induced fluorescence spectroscopy, following single colour OODR excitation with a cw Ti:sapphire laser. Fourier transform spectra revealed two pieces of a progression of the $2 {^{3}}\Pi_{g} \rightarrow b {^{3}}\Pi_{u0}$ system, beginning around 14250 $cm^{-1}$, at $v = 0$, and terminating at 7200 $cm^{-1}$. The two pieces were unfortunately separated by very strong $A \rightarrow X$ emission, which dominated the region $8000 - 12000 cm^{-1}$, so that no measurements could be made for many intermediate vibrational levels. The triplet emission in the visible region was severely affected by spin-orbit interactions with $A^{1} \Sigma^{+}_{u}$, whilst the infrared part of the spectrum was much less perturbed. The intermediate part of the potential is known only through the interactions of the $A^{1} \Sigma^{+}_{u}$ and $b{^{3}}\Pi_{u}$ states. The spin-orbit interaction between the A and b states up to $v_{b} = 90$ has been modelled using an ab initio calculation of the spin-orbit function, which shows a notable dip as a function of R. This model allowed us to assign the vibrational quantum numbers in the infrared part of the fluorescence spectrum : the observations cover $89 \leq v \leq 118$. We are fitting the available A and b state data to $Y_{ij}$ parameters. At present, we have achieved fits (with a standard deviation of $0.025 cm^{-1}$) of about 1000 term values or combination differences, corresponding to levels up to $5500 cm^{-1}$ above the minimum of the b state. We intend to continue the fits over a further $1500 cm^{-1}$ to incorporate all the data, reaching term values $500 cm^{-1}$ below the 4S + 4P threshold. An asymptotic calculation of the Hund's case c) $0_{u}^{+}$ states should be able to extend a deperturbed potential curve for the b state sufficiently accurately to allow the assignment of existing photoassociation data. URI: http://hdl.handle.net/1811/20546 Other Identifiers: 2002-TA-04