N.34 NuDat 2 data selection

The gamma decay data of figures 14.61 and 14.62 were retrieved from NuDat 2, [[12]], October-November 2011.

In the data selection, transitions were ignored if any ambiguity at all was indicated for any of the primary data. The primary data were the initial energy level, the released energy in the transition of interest, the half life, the initial and final spins and parities, the multipole type and order, the relative intensity of the gamma transition of interest, (see below for more), the mixing ratio for transitions of mixed multipole type, the conversion coefficient, (see below for more), and the decay rate in Weisskopf units. If there was a decay process other than gamma decay indicated, the gamma decay percentage had to be given without ambiguity. Indications of ambiguity included parentheses, square brackets, inequalities, tildes, question marks, multiple values, and more.

Note that the given data uncertainties were ignored. That is a weakness of the data, but presumably not really important in view of the very large deviations from theory. Including uncertainties would make processing much more complicated.

As an overall check on the data, the computed transition rate was compared to the one provided in terms of Weisskopf units by NuDat 2 itself. If the difference was less than 5% and there were no other concerns, as discussed below, the transition was accepted automatically. Tests were also performed on whether the initial and final energy levels matched the energy release, and on spin and parity conservation. These tests were mainly to guard against typos in the data base and no violations were observed.

If there were any concerns, the data were printed out. A decision was then made manually on whether to accept the transition as a potential candidate for plotting. If the computed transition rate was substantially, (more than roughly 15%), above the NuDat 2 value, the transition was rejected out of hand. If the computed transition rate was below the NuDat 2 one, it was examined whether the NuDat 2 value was self-evidently missing its correction for other decay types, for the other gamma intensities, the mixing ratio, or the conversion coefficient. That was observed in a relatively small number of cases, usually for a missing conversion coefficient. In all other cases, for a substantial difference in decay rates, over about 15%, the transition was rejected.

Even if the computed decay rate matched the Weisskopf one, various decays were manually rejected. In doing so, if the gamma intensity was not given, it was assumed to be 100% only if there was only one gamma decay out of the energy level. If there were other gamma decays out of the same energy level, their intensities were, based on manual examination, allowed to be omitted (assumed to be zero), specified by an upper limit if small (assumed to be half the upper limit), or specified as approximate if small. If the conversion coefficient was not given, it was manually allowed to be zero if the incompressible ballpark value was below about 10$\POW9,{-4}$. Some initial energy levels with multiple gamma decays were manually rejected if the transition of interest had very low intensity and only one or two digits were given. Mixed transitions were manually examined, but it was not considered cause for rejection as long as a valid mixing ratio was given. If the multipole level was higher than needed, that was also announced, but it too was not taken to be a reason for rejection.

No, in the manual selections, the author did not select the worst nuclei to make physicists look bad.

The plot range from 30 to 3,000 keV (in the plots reduced to 2,500 keV) energy release was divided into 70 segments for which one symbol to plot each. Transitions to plot were selected by comparing them to the selected transitions in the other segments. The selection was designed to achieve a broad coverage of transitions. For plot segments for which there was only one available transition, that transition was immediately selected. Then the program iterated over the segments with more than one potential candidate for plotting. In each segment the best candidate to plot was selected according to the following criteria:

1.
Candidates that were more distant in terms of $Z$ from the currently selected candididates in the other segments received priority. Distance was here defined as the distance from the closest selected nucleus of the other segments. The intention was to cover the entire range of atomic numbers as well as possible.
2.
In case of a tie, nuclei that were different from the most other selected nuclei in terms of either proton or neutron odd/evenness received priority. The intention was to include all variations of even/oddness.
3.
In case of a tie, nuclei that were stable received priority. That was in the hopes that data on stable nuclei might be better quality.
4.
In case of a tie, nuclei that were more different in $A$ from the already selected nuclei received priority.
5.
In case of a tie, a random choice was made between the nuclei in the tie.
Because these criteria depend on the selections in the other segments, iteration was needed. The iterations were terminated if there were no more changes in the selected candidates.

The data on the selected nuclei, including log files, are available in the web version of this document. If you have suggestions on how the data could be improved, let me know.