Helium 4 dimer in nanotubes

The ground state of the helium 4 dimer is considered using the Monte Carlo technique. In a cylinder with a hard core wall, binding depends on its radi us. For a small radius binding occurs as in the one-dimensional case. With an increase of the radius, the binding becomes stronger, reaches its maximu m value, and then slowly diminishes. In conical geometry, that may be reali zed as a generalization of a cylindrical one, this dependence of the bindin g energy on the radius might lead to an effective force which tends to move the molecule toward the region of minimal energy. Thus, in channels, with nonhomogeneous cross-sections, the particles move easier in dimer form. In addition, the square of the momentum and of the particle separation along t he cylinder axis and in the plane perpendicular to it are calculated as wel l.