Converted electrons are emitted as gammas Particular case of 190Po->186Pb, 1 alpha + 2 conversion electrons (E0 transitions only). Gammas are observed instead of electrons. The following macro can be executed with the rdecay01 example to reproduce the issue. Output histograms "1" and "3" contain electron and gamma spectra respectively. ############# # macro for rdecay01 # /control/cout/ignoreThreadsExcept 0 /control/verbose 2 /run/verbose 1 # /gun/particle ion /gun/ion 84 190 /process/had/rdm/nucleusLimits 190 190 84 84 # /tracking/verbose 2 /run/beamOn 1 /tracking/verbose 0 # /analysis/setFileName Po190 /analysis/h1/set 1 150 0. 1500 keV #e+ e- /analysis/h1/set 2 150 0. 1500 keV #neutrino /analysis/h1/set 3 2200 0. 2200 keV #gamma /analysis/h1/set 6 100 0. 2500 keV #EkinTot (Q) /analysis/h1/set 7 150 0. 15e3 keV #P balance /analysis/h1/set 8 100 0. 100. year #time of life /analysis/h1/set 9 100 1. 3. MeV #EvisTot # /run/printProgress 10000 /run/beamOn 300000 ##################### The effect is subtle in general, but it is present for all isotopes I tested. In general, the gamma intensity of calibration sources increases if EC is enabled.
Hello Alvaro, in this case, we have a reaction: 190Po->186Pb[X] + alpha, where X = 0 (96.4%), 536 keV (3.3%), 655 keV (0.3%). In G4LEVELGAMMADATA/z82.a186 the probability of internal conversion (IC) is zero for the two last cases. This was reported earlier in the old problem report #1986 for Pb186 and Pb188. There was a claim that low-level IC probability should be nearly 100% but there was no reply on what are correct numbers. In order to fix both problem reports properly, it would be good to know experimental data on IC: 1) what is it the total IC probability for these isomeres? 2) what are partial probabilities for different levels K-, L-, M-? If data are not well defined it is possible to change from 0% to 100% internal conversion for these levels but we have to know information about data. Because we are in the release phase of Geant4 11.2, these information is needed urgently. VI
Hi Vladimir, Thanks a lot for checking this issue. The transitions are marked as E0 in ENSDF, thus the de-excitation happens by converted electrons always. I understood from the documentation that the IC coefficients are calculated according to a model. I learnt yesterday that those coefficients are provided within the G4 data library, not calculated at runtime. Comparing latest version with older PhotonEvaporation4.0/z82.a186, I notice that the list of coefficients was previously set to zero, but those zeroes disappear in the latest version of the data. Maybe this decay was wrongly defined in previous versions as well and it was a bad benchmark. I have checked calibration radioactive source 207Bi, and the e- and gamma spectra look good to me. Just one detail: if internal conversion is disabled, gamma intensity increases (probably assumes the intensity of the conversion as gamma). This may lead to confusion, given the fact is disabled by default. Sorry for creating too inflated problem, it is likely it can be solved easily.
Hello Alvaro, if these transitions should be pure electron conversion then we have two possibilities: 1) correct these levels by hand 2) introduce in the level reader the fix for these levels only Is it possible to see more levels with E0? I suspect that in our converter E0 is considered incorrectly and we have instead of 100% IC 0% IC. Vladimir
Hi Vladimir, There are many cases where E0 transitions happens, for example in isotopes of Hg, Pb, Po, Rn, Maybe a nice case to be tested is the decay 182Hg->178Pt, which populates 0+ and 2+ excited states, and de-excites via E0 transition @ 442 keV, or E2 transitions @ 252 keV, @ 170 keV. It seems to be well known in ENSDF Thank you for your time. Alvaro
Hello Alvaro, the 1st simple attempt to fix this problem introduce a new more serious problem, so nothing fixed for 11.2. Now it is a work item for 2023. Vladimir
It is work item for 2024.
