| Autor: |
G. M. Ewart, N. K. Sherman |
| Rok vydání: |
1983 |
| Předmět: |
|
| Zdroj: |
Physical Review C. 27:1011-1031 |
| ISSN: |
0556-2813 |
| DOI: |
10.1103/physrevc.27.1011 |
| Popis: |
Cross sections sigma/sub kappa/ for pair creation by photons on Ta and Bi nuclei were deduced with 1% uncertainty between 3 and 28 MeV from total absorption measurements which were combined with data already published from the same apparatus. The gamma ray spectrometer consisted of a photoneutron time-of-flight detector and a liquid deuterium target. Energy resolution varied from 0.6% at 6 MeV (40 keV) to 1.9% at 25 MeV. At 10 MeV, sigma/sub kappa/(Bi) is (13.04 +- 0.07) b, exceeding by 1.7% a value calculated for Bi from a theoretical result for uranium which assumes a point nucleus but is otherwise exact. New tables of atomic cross sections agree closely with our measurements for Ta and Bi up to 10 MeV. The agreement in the case of Ta remains good at higher energies where older tables significantly underestimate the pair cross sections of heavy elements. For Bi the experimental sigma/sub kappa/ exceed even the new tabulated values by (0.8 +- 0.7) % around 20 MeV. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
