1 Raised over Fort McHenry on the morning of September 14, 1814, to signal American victory over the British in the Battle of Baltimore; the sight inspired Francis Scott Key to write The Star-Spangled Banner. 2  Preserved by the Armistead family as a memento of the battle.
London dispersion forces are a type of intermolecular force. They are relatively weak. They are also called induce-dipole induce-dipole interactions. 1  Present in non-polar molecules.  Due to non-systematic electron distribution where one molecule induces a dipole on another molecule.
The resulting van der Waals forces can be attractive or repulsive. The term includes: 1  force between two permanent dipoles (Keesom force). 2  force between a permanent dipole and a corresponding induced dipole (Debye force). 3  force between two instantaneously induced dipoles (London dispersion force).