Problem 1795 - RadioactiveDecay lacks factor ln(2) in decay width-half life conversion
Summary: RadioactiveDecay lacks factor ln(2) in decay width-half life conversion
Status: RESOLVED WORKSFORME
Alias: None
Product: Geant4
Classification: Unclassified
Component: processes/hadronic/models/radioactive_decay (show other problems)
Version: other
Hardware: All All
: P5 trivial
Assignee: dennis.herbert.wright
URL:
Depends on:
Blocks:
 
Reported: 2015-10-21 11:05 CEST by osipenko
Modified: 2015-10-28 02:07 CET (History)
1 user (show)

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Description osipenko 2015-10-21 11:05:54 CEST 
RadioactiveDecay database seems to have wrong conversion from decay width into half-life: factor ln(2) is missing. In fact, when the value is divided by ln(2) to get mean lifetime it return a number different from expected.
Comment 1 osipenko 2015-10-21 11:14:14 CEST 
Was seen in RadioactiveDecay3.4, not clear about the last version since decay widths are not more given in the comments and many isotopes are not more included. Why?
Comment 2 osipenko 2015-10-21 14:03:48 CEST 
Some examples:

Be8 - Gamma=6.8 eV --> halflife was 9.6790e-17, now 8.1810e-17, should be 6.7094e-17.

As it is mentioned in the post the error appeared when width in eV was converted into half-life. It does not apply to those nuclei which have half-life directly from database. In the last version of RadioactiveDecay almost all these nuclei were removed, except Be8.

List of wrong half-life for RadioactiveDecay3.4:

5HE (0.60 MeV) z2.a5 7HE (160 keV) z2.a7 9HE (0.30 MeV) z2.a9 10HE (0.3 MeV) z2.a10

5LI (1.5 MeV) z3.a5 10LI (1.2 MeV) z3.a10

6BE (92 keV) z4.a6 8BE (6.8 eV) z4.a8 13BE (0.9 MeV) z4.a13

7B (1.4 MeV) z5.a7 9B (0.54 keV) z5.a9

8C (230 keV) z6.a8

11N (740 keV) z7.a11

12O (0.40 MeV) z8.a12

15F (1.0 MeV) z9.a15 16F (40 keV) z9.a16

16NE (122 keV) z10.a16

all of them had no decay channel too. Probably because of lack of n or p decay channel?
Comment 3 dennis.herbert.wright 2015-10-28 02:07:13 CET 
The factor ln(2) is not missing.  However, in the case of very short lifetimes, the NNDC lists not the half-life but the width in eV.   To get the half-life from this, the factor ln(2) must be included, which it was in the RadioactiveDecay4.1 and 4.2 data.