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T-type dwarfs present a broad and shallow absorption feature centred around6950 A in the blue wing of the K doublet at 0.77 micron which resembles indepth and shape the satellite absorption predicted by detailed collisionalbroadening profiles. In our previous work, the predicted line satelliteposition was however somewhat too blue compared to the observed feature. Inthis paper we investigate whether new calculations of the energy surfaces ofthe potentials in the K-H_2 system, including spin-orbit coupling, result in acloser coincidence of the satellite with the observed position. We alsoinvestigate the extent to which CaH absorption bands contribute to the feature.We present model atmospheres and synthetic spectra, including gravitationalsettling for an improved description of depth-dependent abundances ofrefractory elements, and based on new K-H_2 line profiles using improvedinteraction potentials. By comparison with a high signal-to-noise opticalspectrum of the T1 dwarf epsilon Indi Ba, we find that these new models doreproduce the observed feature, while CaH does not contribute for theatmospheric parameters considered. We also find that CaH is settled out so deepinto the atmosphere that even turbulent vertical mixing would appearinsufficient to bring significant amounts of CaH to the photosphere in dwarfslater than ~L5. We conclude that previous identification of the feature at thislocation in T and late L dwarf spectra with CaH was erroneous, as expected onphysical grounds: calcium condenses onto grains in early L dwarfs and thusshould have settled out of the photosphere in cooler brown dwarfs. This findingrevokes one observational verification for the cloud-clearing theory: a gradualclearing of the cloud cover in early T dwarfs.

K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba