THE $(1)^{1}\Pi_{g}$ STATE OF ${^{39}}K_{2}$ REVISITED

Vibrational levels up to $v=107$ of the $(1)^{1}\\Pi_{g}$ state of ${^{39}}K_{2}$, which dissociates to $K(4s)^{2}S +K(4p)^{2}P_{3/2}$, have been observed in high resolution Fourier transform records of $C^{1}\\Pi_{u}\\rightarrow (1)^{1 \\Pi_{g}}$ fluorescence of potassium molecules in a heatpipe source. From a revised analysis of this system, we have constructed a rotationless RKR potential curve which extends to $R=40.3$ {\\AA} covering 99.2\\% of the $(1)^{1}\\Pi_{g}$ state. Vibrational and rotational constants (at $J=0$) have been calculated from this curve. The parameters describing the coulombic interactions between $K(4s) + K(4p)$ atoms are given in a Hund's case (c) basis. From this work, the dissociation energy $D_{e}$ for the $(1)^{1}\\Pi_{g}$ state is found to be $1290.30 \\pm 0.09 cm^{-1}$ (leading to a new value of $T_{e} = 16203.25 \\pm 0.09 cm^{-1}$ for this state) and the long-range parameters are $M^{2} = 25.30 \\pm 0.02 e^{2}a^{2}_{o},R_{01}= 7261 \\pm 223 e^{2}a^{5}_{o}$. These values are in good agreement with values obtained from the pure long range $0^{+}_{g}$ state analyzed by H. Wang, P.L. Gould and W.C. Stwalley (J. Chem. Phys. 106, 7899 (1997)).