They are potentially very efficient and high powered due to a small quantum defect.

He later did important work on the Quantum Defect Theory.

At a fixed pump frequency, the higher the quantum defect, the lower is the upper bound for the power efficiency.

The quantum defect correction can be associated with the presence of a distributed ionic core.

The term quantum defect is ambiguous.

The small quantum defect makes ytterbium a prospective dopant for efficient lasers and power scaling.

The resulting shift of the energy levels is represented mathematically as an angular momentum dependent quantum defect, δ:

The energy of Rydberg states can be refined by including a correction called the quantum defect in the Rydberg formula.

At given frequency of pump and given frequency of lasing, the quantum defect .

The existence of a non-zero quantum defect was attributed to electron-electron repulsion, which clearly does not exist in the isolated hydrogen atom.

This constant is now known as the Rydberg constant, and m is known as the quantum defect.

The final simplification requires that the time-dependent perturbation does not couple the diabatic states; rather, the coupling must be due to a static deviation from a coulomb potential, commonly described by a quantum defect.

In laser science, the term quantum defect refers to the fact that the energy of a pump photon is generally higher than that of a signal photon (photon of the output radiation).

Such quantum defect has dimension of energy; for the efficient operation, the temperature of the gain medium (measured in units of energy) should be small compared to the quantum defect.

The quantum defect of a laser can be defined as part of the energy of the pumping photon, which is lost (not turned into photons at the lasing wavelength) in the gain medium at the lasing.

Additional terms in the potential energy expression for a Rydberg state, on top of the hydrogenic Coulomb potential energy require the introduction of a quantum defect, δ, into the expression for the binding energy:

The quantum defect of a Rydberg atom refers to a correction applied to the equations governing Rydberg atom behavior to take into account the fact that the inner electrons do not entirely screen their associated charge in the nucleus.

Direct pumping of the upper Nd laser level at 885-nm (rather than at the more traditional broad 808-nm band) offers the potential of improved performance through a reduction in the lasing quantum defect, thereby improving system efficiency, reducing cooling requirements, and enabling further TEM00 power scaling.

By introducing the quantum defect d as an empirical parameter, the energy levels of a generic atom were well approximated by the formula , in the sense that one could reproduce fairly well the observed transitions levels observed in the X-ray region (for example, see the empirical discussion and derivation in Moseley's law).