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 Thu Jul 18 22:10:58 2019, Jenn, e768s, OTHER, General, Fixed, , Previous Papers 
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 Sat Jul 20 11:33:01 2019, Christian, e768s, OTHER, General, Fixed, , Previous Papers - gamma decays from states in the 4-MeV region
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Sat Jul 20 12:06:00 2019, Christian, e768s, OTHER, General, Fixed, , Previous Papers - gamma decays from states in the 4-MeV region
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Sat Jul 20 12:57:41 2019, Christian, e768s, OTHER, General, Fixed, , Previous Papers - gamma decays from states in the 4-MeV region
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Sun Jul 21 17:57:08 2019, Christian, e768s, OTHER, General, Fixed, , Previous Papers - gamma decays from states in the 4-MeV region
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Mon Jul 22 10:10:02 2019, Christian, e768s, OTHER, General, Fixed, , Previous Papers - alpha-branching ratios for states in the 4-MeV region
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Thu Jul 25 11:05:18 2019, Francois de Oliveira, e768s, OTHER, General, Fixed, , Previous Papers - alpha-branching ratios for states in the 4-MeV region
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Message ID: 5252
Entry time: Mon Jul 22 10:10:02 2019
In reply to: 5223
Reply to this: 5320
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| Author: |
Christian |
| ExpNbr: |
e768s |
| Type: |
OTHER |
| Category: |
General |
| Status: |
Fixed |
| Target-Source: |
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| Subject: |
Previous Papers - alpha-branching ratios for states in the 4-MeV region |
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Branching ratio data overview from Tan et al. (PRL 2007, attached):
Ex/MeV B_alpha
4.03 2.9(21)e-4
4.14/4.20 1.2(5)e-3
4.38 1.2(3)e-3
4.55 0.07(2)
In the spectra so far, we are very clearly seeing the 4.14/4.20 MeV doublet. We may also be seeing some indication of the 4.38, 4.55 and/or 4.60 MeV states above 4 MeV (4.14, 4.27, and 4.36 MeV respectively, as dominant lines). Note that we have no alpha-branching-ratio data for the 4.60MeV state, and that most likely the gamma-ray events we currently see above 4MeV are the 4.14MeV and 4.36MeV lines (4.38 and 4.60 MeV states).
Comments to lifetimes from Mythili et al., (PRC 2008, attached). The relevant lifetimes are for the states between 4.14 and 4.55. Only dominant errors are given, for details, see attached table:
Pre-2008 Mythili
Ex/MeV lifetime/fs lifetime/fs
4.14 18(+2/-3) 14(4)
4.20 43(+12/-9) 38(+20/-10)
4.38 5(+3/-2) <5.4 (95% CL)
4.55 15(+11/-5) 19(4)
In combination:
4.38 MeV: Branching ratio is fairly well known. Lifetime is very poorly known, if at all. We have 7 counts so far (provisional), in the 4.14 MeV peak after about 3 days of beam on target.
4.55 MeV: Branching ratio is fairly well known. Lifetime is fairly well known, but it is not clear that we see this decay.
4.14/4.20: Lifetimes is known reasonably well for 4.14, poorly for 4.20, and differ by about a factor of 2-4 (within error). Branching ratio is only known in combination between the two. This complicates normalisation to these two states greatly, as we would in principle have to assume any combination of this contribution from 4.14, 4.20, or combined. In their paper (Tan 2007), they do state for this measurement that: "The measured􏰑 peak [in the alpha-spectrum] seems to be lower in energy than the simulated one, indicating that these decay events are more likely from the 4.14-MeV state.". Looking at the spectrum they refer to, however, I would not say that this is in any way a clear cut argument (and they do state it with some hesitation).
In summary: because of the overlap of the 4.14 and 4.20 states in the branching ratio data [which I should admit that I had missed when investigating the previous data and results earlier] it will be much harder than expected to cross check normalisation of the data based on the observed lifetimes and alpha branching ratios for 19Ne resonances.
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