The forces between hydrogen molecules in liquid hydrogen are van der Waals forces. These are weak, short-range forces that arise from temporary fluctuations in electron distribution around the molecules.

Specifically, the dominant type of van der Waals force in liquid hydrogen is London dispersion forces. These arise from instantaneous, temporary dipoles that form due to the random movement of electrons.

Here's why hydrogen doesn't exhibit other types of intermolecular forces:

* Hydrogen bonding: Hydrogen bonding requires a hydrogen atom bonded to a highly electronegative atom like oxygen, nitrogen, or fluorine. Hydrogen molecules only contain hydrogen atoms, so hydrogen bonding isn't possible.

* Dipole-dipole forces: These forces occur between polar molecules, which have permanent dipoles. Hydrogen molecules are nonpolar, so dipole-dipole forces are not present.

Therefore, the only significant forces holding hydrogen molecules together in the liquid state are the weak London dispersion forces.