G+K 1Σ+/sub g/ double-minimum excited state of H2

We have obtained a Born--Oppenheimer potential curve for the previously uncharacterized third 1Σ+/sub g/ state of H2, using a correlated 20-term wavefunction of generalized James--Coolidge type. We find this potential curve to have a double-minimum character, with the inner (Rydberg-like) and outer (''ionic'') wells having minima at about 1.99 and 3.30 bohr, respectively, and an intervening maximum at 2.76 bohr. Unlike the extensively studied E+F double-minimum state, the outer well here appears to be the deeper, by some 450 cm-1 in our calculation. The inner and outer minima can apparently be associated with spectral lines that in experimental tables have previously been attributed to distinct G and K electronic states. The appropriate spectroscopic term symbol of this combined state is accordingly G+K 1Σ+/sub g/ (1ssigma3dsigma+2pπ2)