al. 1998) and therefore most likely to exhibit gravity effects (McGovern et al. 2004). In addition, the peculiar T6 dwarf 2MASS 0937+29 (Burgasser et al. 2002) was added to the list because of its apparent lack of K I features in lower resolution spectra. Another late T dwarf (2MASS 2356$-$15, T5.5) was observed after completion of the initial set for comparison to the 2MASS 0937+29. Although the signal-to-noise ratio was sufficient to establish the presence of K I absorption in this T5.5 dwarf, the fainter magnitude ($J=15.8$) and stronger 2o absorption made quantitative analysis too difficult so the spectrum is not shown.

Table 1 provides the complete list of 16 targets and the observing log. Shorthand names such as 2MASS 1507$-$16 are used in the text for simplicity, but the full designations are listed in Table 1. Two targets were known visual doubles at the time of observing, 2MASS 0746+20 (L0.5) and DENIS 0205$-$11 (L7), but in neither case did we have sufficient angular resolution to separate the components. Subsequent to making our observations, DENIS 0205-11 was reported as a possible triple brown dwarf system (Bouy et al. 2005) based on Hubble Telescope images. Burgasser et al. (2005) subsequently found 