Internal Conversion Electron Data Calculation ∑ ∑

Communication of Nuclear Data Progress No.25 (2001)

Internal Conversion Electron Data Calculation

ZHOU Chunmei HUANG Xiaolong WU Zhendong China Nuclear Data Center,CIAE, Beijing

【abstract】Calculation method of internal conversion electron energy and their absolute intensity in γ transition is introduced briefly, and its application is also given by using 232Th decay as example.

For nuclear decay, nucleus is in its excited states. It deexcites by means of emitting γ-rays, and decays 1.2 Internal conversion electronic absolute to its ground state. During deexcitation, the transition intensity calculation energy may be transferred to the electrons in different Assumed that absolute intensity of Eγ in nuclear atomic-electronic shells outside nucleus by Coulomb decay is Pγ, its internal conversion coefficients are α interaction between a nucleus and its surrounding i γ γ (i=K,L,M,N,.., shell), and absolute intensities of atomic electrons. For the transitions, there are rays internal conversion electrons are P , then emitted and competing internal conversion electrons. ei α These electrons are called as internal conversion Pei=Pγ ∙ i (2) γ electrons in transitions. The calculation method of Obviously, the following expression can be easy internal conversion electron energy and its absolute deduced from Eq. (2) intensity in γ transition is introduced briefly, and its application is also given by using 232Th decay as = = ⋅α = α = ⋅α (3) Pe ∑ Pei ∑ Pγ i Pγ ∑ i Pγ example. i i i α = ∑α (4) 1 Calculation Method i Where α is total internal conversion coefficient for Eγ

transition; Pe is total internal conversion electronic 1.1 Internal Conversion Electron Energy absolute intensity (photon numbers per 100 parent decays). Calculation In order to calculate the internal conversion electron energy, it is assumed that γ transition energy 1.3 Internal Conversion Coefficients Calculation is Eγ, atomic-electron binding energy in i-th atomic- As mentioned above, in order to calculate internal electronic shell is E , emitting electron energy from i- i conversion electronic intensities of different shells th atomic-electronic shell is E . According to the ei and their total intensity, their partial and total basis of energy balance, then conversion coefficient α , α must be known. − i Eei=Eγ Ei (1) The internal conversion coefficient data of where, i=K,L,M,N,..., atomic-electronic shell. different elements (different nuclear proton numbers

The data of atomic-electronic binding energies Ei Z) in different atomic-electronic shells have been in different shells for different elements (different evaluated[2]. In the tables and charts the γ transition nuclear proton numbers Z) have been evaluated and energies, their transition electric and magnetic can be taken from reference [1]. These atom- multiplicities are given. The code HSICC has been electronic binding energies are tabulated for different written to calculate the internal conversion elements (nuclear proton number Z) and in different coefficients[3]. The calculation is based on spline- atomic-electronic shells (K,L,M,N,..., shell). fitting method interpolating. 70 Communication of Nuclear Data Progress No.25 (2001)

1.4 γ-ray Absolute Intensity Calculation are prepared in the required format of calculation In order to calculate the electronic intensities, the codes; (2) Calculation. At first, internal conversion γ-ray absolute intensity Pγ must be known. Usually γ the relative intensities of radionuclide are measured. coefficients and -ray emitting absolute intensities for γ The γ-ray absolute intensities are required in practical each -ray are calculated. Then internal conversion applications. So the normalization factor N electronic energies and their absolute intensities are (multiplier for conversing relative photon intensity to calculated; photons per 100 decays of parent through the decay (3) Output. The results of calculations are output branching) of γ-ray intensities must be known in in tables and drawings, respectively. decay data evaluations by using data analysis and calculation. The γ-ray absolute intensities (γ-ray 2 Application emitting probabilities per 100 parent decays) can be The application of internal conversion electronic calculated by using the normalization factor. data calculation are shown by taking 232Th decay At present, Table of Isotopes (8-th edition) (1996) × 9 [5] (T1/2=14.05 10 a) as an example. The data are by R.B.Firestone et al. is the best evaluated decay given in Table 2, and the scheme is shown in Fig.2[5]. γ data collection. The relative -ray intensities and From Table 2, it can be seen that the normalization factor of all radionuclei are given in normalization factor of γ-ray relative intensities is 1.0, this book. The data can be retrieved from Evaluated and other data relative to internal conversion Nuclear Structure Data File (ENSDF), which are electronic data calculation are also given. done by the evaluators of International Network of The internal conversion coefficients are Nuclear Structure and Decay Data Evaluation from calculated by using HSICC code. The energies of different countries. internal conversion electrons can be got by using formula (1) on the basis of γ-ray energy in Table 2 1.5 Main Calculation Codes and Calculation and atomic-electronic binding energies of different shells of 232Th. The absolute intensities of internal Flow Chart conversion electrons are calculated by using formula The main calculation codes and their functions (2) from data in Table 2. In Table 3, radiation data of are listed in the Table 1. These codes are mainly from 232Th decay are given, in which are included the International Network of Nuclear Structure and radiation data of α, γ, and their internal conversion Decay Data Evaluation. electrons. From Table 3 it can be seen that the In Fig. 1, flow chart of internal conversion electronic intensities calculation is very important for electronic energies and their absolute intensities heavy nucleus. calculation is given. There are three steps: In Fig. 2, the γ-ray energies, intensities, their (1) Start. Evaluated nuclear decay data file, multipolarities and total internal conversion electron atomic-electronic binding energies data file and intensities are given. evaluated internal conversion coefficients data file

Table 1 Main codes and their functions of electronic data calculation

Codes name Functions HSICC calculation of internal conversion coefficients GABS calculation of γ intensity normalization factor RADLST calculation of internal conversion electronic data ENSDAT table and drawing of data output

Table 2 γ-ray data of 232Th decay

Internal Conversion Coefficients E /keV E /keV I γ-mult. γ L γ α α α α α K L M N... 63.81±0.01 63.82 0.263±0.013 E2 59.92 16.22 5.824 82.0 140.88±0.01 204.69 0.021±0.004 E2 0.287 1.47 0.399 0.145 2.30

Iγ absolute intensities, multiplied 1.0, per 100 parent decays.

71 Communication of Nuclear Data Progress No.25 (2001)

Table 3 Radiation data of 232Th decay

Radiation type Energies/keV Absolute intensities / % α 1 3830. 10 0.063 10 α 2 3950. 8 21.7 13 α 3 4012.3 14 78.2 13 γ 1 63.810 10 0.263 13

eCe1L 44.573 10 15.8 10

eCe1M 58.988 10 4.27 25

eCe1N 62.602 10 1.53 9 γ 2 140.880 10 0.021 4

eCe2K 36.958 13 0.0060 12

eCe2L 121.643 10 0.031 6

eCe2M 136.058 10 0.0084 17

eCe2N 139.672 10 0.0030 6 γ eCe1L is a emitting electron of L -shell from 1-ray.

Fig. 1 Flow chart of internal conversion electronic data calculation

Fig. 2 232Th decay scheme

72 Communication of Nuclear Data Progress No.25 (2001)

It is noted that in Fig. 2, γ0.263 is γ-ray intensity of error propagation method. 0.263, and ε21.5 is total internal conversion electronic intensity 21.5. References

[1] F.B.Firestone, et al., Table of Isotopes (8-edition) (1996), 3 Conclusion Atomic-Electron Binding Energies, P.F37-F39. [2] F.B.Firestone, et al., Table of Osotopes (8-edition) (1996), The calculation method of internal conversion Theoretical Internal conversion Coefficients, P.F1-F32. electronic energies and their absolute intensities is [3] T.W.Burrows, ENSDF Physics Analysis Programs, given. Private communications (1998). In general, the error propagation method is [4] F.B.Firestone, et al., Table of Isotopes (8-edition) (1996), adopted in the uncertainty calculation. The Vol.I A=1-150, Vol. II A=151-266. uncertainties in table 3 were calculated on the basis [5] A.Artna-Cohen, Nuclear Data Sheets, 80, 723 (1997).

Evaluation of Neutron Cross Section Data for 121,123Sb and 127,135I

ZHAO Jingwu SU Weining Department of Physics, Nanjing University, Nanjing

are disperse, the other ten are consistent with each Introduction other in energy range 100 keV to 20 MeV. These data were fitted by polynomial. The calculated data were The data of isotopes, 121,123Sb and 127,135I were recommended in the energy range above 14 MeV. evaluated in several evaluated nuclear data libraries. There are over twenty sets of experimental data But there are some discrepancies in these libraries. for 127I. Except for the data in low energy range, there The data of JENDL-3 is better than others and are only seven sets of experimental data available. contain all files. Even so the data of JENDL-3 are The data from Foster[1], Manero[14], Gorlow[15] and also disagree with the experimental data, especially Miller[7] are consistent with each other in high energy new ones. The neutron cross sections were range and are also consistent with the data from reevaluated in this work. This evaluation is based on Angeli[16] at 14 MeV. The data from Bockelman[9] and both experimental data and calculated data with Merrison[17] are consistent with each other in low SUNF code and compared with the experimental data energy range and are also consistent with the data and other evaluated data from JENDL-3, ENDF/B-6. from Miller at 1 MeV. The data were fitted with polynomial. The calculated data are recommended in the energy range above 14 MeV. 1 Total Cross Section Due to no experimental data for 135I, the calculated data were recommended. There are no any experimental data for 121,123Sb. In Fig.1 is shown the evaluated result and The experimental data of natural Sb were used. compared with JENDL-3 and ENDF/B-6 for natural Except for the data in low energy range, there are Sb. only thirteen sets of experimental data[1~13], of which In Fig.2 is shown the evaluated result and the three from Miller[7], Bockelman[9] and Tabony[11] compared with JENDL-3 and ENDF/B-6 for 127I.