Spectral profiles of Rb i (top) and Cs i (bottom) atomic lines of Luhman 16AB. The relative fluxes of the two objects have been normalised to the mean pseudo-continuum around Rb i and the Cs iλ852.11 nm lines for a proper comparison. These data are corrected for telluric contribution. The effect of the different T_eff between the components becomes apparent in the slope of the pseudo-continua in the bottom panel. The Cs i λ894.35 nm line is blended with the absorption due to CrH and FeH.