  I calculate the quantum states for He atom in the potential of an external
groove of the single wall carbon nanotube bundle. The calculated ground state
energy is found to be in fair agreement with the experimental estimate which
suggests that the outer groove site is a preferential site for the adsorption
of He gas in the samples studied experimentally. I also calculate the specific
heat of low-density $^4$He atom gas adsorbed in groove positions. The specific
geometry of the groove and its influence on the adsorbate quantum states and
specific heat are discussed.
