Pandemonium effect

According to this, the energy levels of the daughter nucleus can be populated in two ways: The total gamma rays emitted by an energy level (IT) should be equal to the sum of these two contributions, that is, direct beta feeding (Iβ) plus upper-level gamma de-excitations (ΣIi).

Since the only magnitude that can be measured are the gamma intensities ΣIi and IT (that is, the amount of gammas emitted by the daughter with a certain energy), the beta feeding has to be extracted indirectly by subtracting the contribution from gamma de-excitations of higher energy levels (ΣIi) to the total gamma intensity that leaves the level (IT), that is: The pandemonium effect appears when the daughter nucleus has a large Q value, allowing the access to many nuclear configurations, which translates in many excitation-energy levels available.

Measuring these gamma rays with high-resolution detectors may present two problems: These two effects reduce how much of the beta feeding to the higher energy levels of the daughter nucleus is detected, so less ΣIi is subtracted from the IT, and the energy levels are incorrectly assigned more Iβ than present: When this happens, the low-lying energy levels are the more affected ones.

Some of the level schemes of nuclei that appear in the nuclear databases[3] suffer from this Pandemonium effect and are not reliable until better measurements are made in the future.

One possible solution is to use a calorimeter like the total absorption spectrometer (TAS), which is made of a scintillator material.

Schematic showing how the pandemonium effect can affect the results in an imaginary decay to a nucleus that has 3 levels. If this effect is large, feeding to high-lying levels is not detected, and more beta feeding is assigned to the low-lying energy levels.