This is nothing more than a fancy Taylor series for three-dimensional scalar and vector fields.

This ansatz leads to a block structure of the molecular Hamiltonian with respect to the electronic degrees of freedom.

This system has the same spectrum as the electromagnetic field after quantisation.

Caused by the Zitterbewegung, this correction to the Hamiltonian is relevant for s states.

Moving slow and steady by Newton's first law, they are often quickly discarded by atomic and molecular physicists.

This fundamental effect cannot be explained by a semiclassical theory of light-matter interaction.

This property of the electron is 100% more effective than its classical analogue.

By taking a detour, this transition allows to couple states that could otherwise not be connected by a single-photon process.

Beyond the wave vector, this property of the light field gives rise to two additional modes of the corresponding quantised field.

This effect is the strongest relativistic correction for valence electrons of light elements in the presence of an electromagnetic field.

When approximating the dipole transition element as constant, these objects determine which vibrational states will be populated after an electronic transition.

Except for the gluon, this is the only massless and chargeless gauge boson of the standard model.

Similar to its brother in name, the Van't Kruijs opening in chess, this should only be considered when everything else was not enough.

When potential energy surfaces get too close, these objects can no longer be simply ignored.

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