Halogen lights Gas camping lanterns (the kind with mantles) Lasers Fluorescent lights Electroluminescent panels All of these technologies excite atoms so that they produce photons.

The optical dipole trap is much less invasive, quantum mechanically speaking-it can still excite atoms out of the desired state and destroy the BEC, but the probability is low.

Analytical instruments currently use these plasmas as sources to excite atoms (I use one in my research).

So radio waves penetrate most substances because their frequency is too low to excite the electrons or atoms.

He also used pulses of light to excite atoms in the ruby.

In radiative pumping, infrared photons with higher energies than the maser transition photons preferentially excite atoms and molecules to the upper state in the maser in order to produce population inversion.

An increase in temperature changes the quanta of energy available to excite individual atoms to higher levels, enabling them to emit photons of higher frequencies.

All these processes work on the same basic principle: An outside source of energy excites atoms, causing them to release particles of light called photons.

The light excites atoms in the ruby.

To make it more difficult, you want to excite atoms into the excited state in such a way that in some places they are all excited, and in others, none are excited.