Atomic electron transitions cause the emission or absorption of photons. Their statistics are Poissonian, and the time between jumps is exponentially distributed. The damping time constant (which ranges from nanoseconds to a few seconds) relates to the natural, pressure, and field broadening of spectral lines. The larger the energy separation of the states between which the electron jumps, the shorter the wavelength of the photon emitted.
In an ion trap, quantum jumps can be directly observed by addressing a trapped ion with radiation at two different frequencies to drive electron transitions. This requires one strong and one weak transition to be excited (denoted  and  respectively in the figure to the right). The electron energy level, , has a short lifetime,  which allows for constant emission of photons at a frequency  which can be collected by a camera and/or photomultiplier tube. State   has a relatively long lifetime  which causes an interruption of the photon emission as the electron gets shelved in state through application of light with frequency    The ion going dark is a direct observation of quantum jumps.