Download presentation

Presentation is loading. Please wait.

Published byJohanna Merriweather Modified over 3 years ago

1
Alpha-Decay Hindrance Factors. Program ALPHAD. Edgardo Browne Decay Data Evaluation Project Workshop May 12 – 14, 2008 Bucharest, Romania

2
The probability of decay depends on the: Energy of the particle Parent and daughter nuclear structure configurations A useful definition of hindrance factor is: HF = T 1/2 ( ) exp./T 1/2 ( ) theor. Notice that T 1/2 ( ) = T 1/2 / branching. HF depends only on the nuclear structure configurations. The energy dependence has been removed. T 1/2 ( ) theor. is from “The Theory of Alpha Radioactivity,” M.A. Preston, Phys. Rev. 71, 865 (1947!!)

4
HF(0+ to 0+, even-even nucleus) = 1 by definition. All other hindrance factors are relative to this value. Hindrance factors for odd-A and odd-odd nuclei are relative to HF values for the 0+ to 0+ transitions in the neighboring even-even nuclei

5
The Radius Parameter r 0 This parameter is roughly equivalent to the nuclear radius, and it may be determine for each nucleus from the 0+ to 0+ transition in even-even nuclei, and assuming HF=1. See “Review of Alpha-Decay Data from Doubly-Even Nuclei,” Y.A. Akovali, Nucl. Data Sheets 84, 1 (1998).

7
Favored alpha-particle transition in odd-A nuclei If HF < 4 then initial and final levels have the same spin (J) and parity ( ).

8
The radius parameter r 0 (Y. Akovali, Oak Ridge) Odd-N nucleus (Z, A) r 0 (Z, N) = [r 0 (Z, N-1) + r 0 (Z, N+1)]/2 Odd-Z nucleus (Z, A) r 0 (Z, N) = [r 0 (Z-1, N) + r 0 (Z+1, N)]/2 Odd-Odd nucleus (Z, A) r 0 (Z, N) = [r 0 (Z, N-1) + r 0 (Z, N+1)]/2 = [r 0 (Z-1, N+1)+r 0 (Z-1, N-1)+r 0 (Z+1, N+1) +r 0 (Z+1, N-1)]/4

9
Example 219 Rn 215 Po (Odd-N) r 0 (Z=84, N=131) = [r 0 (84, 130) + r 0 (84, 132)] /2 From 1998Ak04: r 0 (84,214) = 1.559 8 r 0 (84,216) = 1.5555 2, therefore r 0 (Z=84, N=131) = 1.557 Use Table 1 – “Calculated r 0 for even-even nuclei” (1998Ak04). Insert R0= … in comment record: CA HF R0=… Run program ALPHAD to calculate hindrance factors. HF(401 keV) = 3.4 (Favored decay).

10
Estimating an -decay branching ~100% HF=1 ? 0+ 2+ 0 474 206 Ra 210 Th 0+9 ms 88 90

11
HF Systematic for Even-even Thorium Nuclei Parent nucleus J Daughter nucleus J HF 210 Th 0+ 206 Ra 2+ ? 228 Th 0+ 224 Ra 2+ 0.92 230 Th 0+ 226 Ra 2+ 1.1 232 Th 0+ 228 Ra 2+ 1.0 We expect HF( 210 Th) ~ 1

12
Z A 90. 210. Q ALPHA E TOTAL ALPHA HALF LIFE RADIUS RZERO TOTAL HALF LIFE ALPHA BRANCH 8.0530 8.0881 1.042E-07 D 9.0867E-13 1.5386 9.000E-03 S 1.000E+00 ENERGY LEVEL ABUNDANCE CALC. HALF LIFE HINDRANCE FACTOR 0.00 1.00E+00 1.04E-07 1.00E+00 474.00 1.00E-01 3.35E-06 3.11E-01 474.00 5.00E-02 3.35E-06 6.22E-01 474.00 3.00E-02 3.35E-06 1.04E+00 474.00 1.00E-02 3.35E-06 3.11E+00 474.00 5.00E-03 3.35E-06 6.22E+00 474.00 3.00E-03 3.35E-06 1.04E+01 474.00 1.00E-03 3.35E-06 3.11E+01 474.00 1.00E-04 3.35E-06 3.11E+02 So (474)~ 3% Computer Program ALPHAD

Similar presentations

OK

A=193 Mass Chain evaluation: A summary IAEA-ICTP Workshop on Nuclear Structure and Decay Data: Theory and Evaluation, Trieste, Italy November 17-28 - 2003.

A=193 Mass Chain evaluation: A summary IAEA-ICTP Workshop on Nuclear Structure and Decay Data: Theory and Evaluation, Trieste, Italy November 17-28 - 2003.

© 2018 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google