Total Internal Conversion Coefficients Research Articles

Precise measurement of αK and αT for the 39.8-keV E3 transition in Rh103 : Test of internal-conversion theory

Neutron-activated sources of $^{103}$Ru and $^{103}$Pd both share the isomeric first-excited state in $^{103}$Rh as a daughter product. From independent measurements of both decays, we have measured the $K$-shell and total internal conversion coefficients, $\alpha_K$ and $\alpha_T$, for the 39.8-keV $E$3 transition, which de-excites that state in $^{103}$Rh, to be 141.1(23) and 1428(13), respectively. When compared with Dirac-Fock calculations, our new results disagree with the version of the theory that ignores the $K$-shell atomic vacancy, which is consistent with our conclusion drawn from a series of measurements on high multipolarity transitions in nuclei with higher $Z$. Calculations that include the atomic vacancy indicate that the transition actually has a small $M$4 component with mixing ratio $\delta$ = 0.023(5).

Precise measurement of αK and αT for the 109.3-keV M4 transition in Te125 : Test of internal-conversion theory

We have measured the K-shell and total internal conversion coefficients (ICCs), alpha_K and alpha_T, for the 109.3-keV M4 transition in 125Te to be 185.0(40) and 350.0(38), respectively. Previously this transition's ICCs were considered anomalous, with alpha values lying below calculated values. When compared with Dirac-Fock calculations, our new results show good agreement. The alpha_K result agrees well with the version of the theory that takes account of the K-shell atomic vacancy and disagrees with the one that does not. This is consistent with our conclusion drawn from a series of high multipolarity transitions.

Test of internal-conversion theory with a measurement in 111Cd

We have measured the K -shell and total internal conversion coefficients for the 150.8-keV E 3 transition in 111 Cd: αK = 1.449(18) and αT = 2.217(26) respectively. The αK value agrees well with Dirac-Fock calculations, in which the effect of the K -shell atomic vacancy is included. It is consistent with our previous precise measurements of αK values, which cover a range of atomic numbers, and extends that range down to Z = 48. The αT measurement, however, disagrees by about two standard deviations from the calculated αT value, whether the atomic vacancy is included or not.

Precise measurement ofαKandαTfor the 150.8-keVE3transition inCd111: Test of internal-conversion theory

We have measured the K-shell and total internal conversion coefficients, alpha_K and alpha_T, for the 150.8-keV E3 transition in 111Cd to be 1.449(18) and 2.217(26) respectively. The alpha_K result agrees well with Dirac-Fock calculations in which the effect of the K-shell atomic vacancy is accounted for; it extends our precision tests of alpha_K calculations to Z = 48, the lowest Z yet measured. However, the result for alpha_T disagrees by about two standard deviations from the calculated alpha_T value, whether or not the atomic vacancy is included.

Decay of 120Sb

Single γ spectra and KX coincidence spectra from 120Sb decay are measured. The total internal conversion coefficients (ICCs) and those on the K-shell are determined for slowed E1 and E2 transitions in 120Sn. Penetration effects are observed for which the penetration parameters are found to be λ1 (89.9 keV, E1) = 3.6 ± 1.6 and λ1 (197.3 keV, E2) = 6 ± 2.

Standardization and determination of the total internal conversion coefficient of In-111

The standardization of 111In by means of a 4πβ-γ coincidence system, composed of a proportional counter in 4π geometry, coupled to a 20% relative efficiency HPGe crystal, for measuring gamma-rays is presented. The data acquisition was performed by means of the software coincidence system (SCS) and the activity was determined by the extrapolation technique. Two gamma-ray windows were selected: at 171keV and 245keV total absorption peaks, allowing the determination of the total internal conversion coefficient for these two gamma transitions. The results were compared with those available in the literature.

High spin states inPr151,153,Sm157, andKr93

High spin states are observed for the first time in the neutron-rich nuclei $^{151,153}\mathrm{Pr}$, $^{157}\mathrm{Sm}$, and $^{93}\mathrm{Kr}$ from the spontaneous fission of $^{252}\mathrm{Cf}$. Twenty new transitions in $^{151}\mathrm{Pr}$, twelve in $^{153}\mathrm{Pr}$, five in $^{157}\mathrm{Sm}$, and four in $^{93}\mathrm{Kr}$ were identified by using x-ray(Pr/Sm)-$\ensuremath{\gamma}$-$\ensuremath{\gamma}$ and $\ensuremath{\gamma}$-$\ensuremath{\gamma}$-$\ensuremath{\gamma}$ triple coincidences. From the measured total internal conversion coefficients ${\ensuremath{\alpha}}_{T}$ of four low-energy transitions in $^{151,153}\mathrm{Pr}$, we determine that two bands in each nucleus have opposite parity. The interlacing $E1$ transitions between the bands suggest a form of parity doubling in $^{151,153}\mathrm{Pr}$. New bands in $^{157}\mathrm{Sm}$ and $^{93}\mathrm{Kr}$ are reported. The half-life of the 354.8 keV state in $^{93}\mathrm{Kr}$ is measured to be 10(2) ns.

Assessment of internal conversion coefficients for anomalous electric dipole transitions

Sound quantitative knowledge of internal conversion coefficients (ICCs) is important when establishing decay schemes. ICCs are normally derived from efficiency tables and calculation, but for anomalous transitions and some electric dipole transitions (E1) in particular, theoretical values can differ considerably from the few available measured values. Experimentally measured ICCs and their ratios have been compiled, and these data have been used to propose a method based on the existence of measured ratios to determine the total ICC for such transitions. Comparisons have been made with the existing measured values, and good agreement was observed within the uncertainty limits.

Activity standardization and nuclear decay data of 109Cd

The activity of a 109Cd solution has been accurately determined without using 109Cd nuclear decay data such as emission probabilities. An ampoule containing this calibrated 109Cd solution was sent to the Bureau International des Poids et Mesures to include the activity result in the database of the International Reference System (SIR). The emission rate of conversion electrons was measured by means of pressurized proportional counters as well as by a liquid scintillation spectrometer. The combination of the results with the photon emission rate measured with the aid of γ-ray spectrometers yields the activity concentration. The measurement results were also used to deduce emission probabilities with high accuracy. For the 88 keV transition, a photon emission probability of p γ = 0.03663 ( 33 ) and a total internal conversion coefficient of α t = 26.30 ( 25 ) were determined.

Dirac–Fock Internal Conversion Coefficients

Internal conversion coefficients (ICCs) obtained from relativistic self-consistent-field Dirac-Fock (DF) calculations are presented. The exchange terms of DF equations are included exactly, both for the interaction between bound electrons and for the interaction between bound and free electrons. Static and dynamic effects resulting from finite nuclear size are taken into account, the latter using the surface current model. Experimental electron-binding energies are used wherever possible. The hole in the atomic shell from which an electron was emitted is not taken into consideration because there is no compelling experimental evidence to warrant it. ICCs are given here for each Z between Z=10 and Z=126; for K, L 1, L 2, and L 3 atomic shells; for nuclear-transition multipolarities E1… E5, M1… M5; and for nuclear-transition energies from ∼1 keV above the L 1 threshold to 2000 keV. Also given are the total ICCs. Accurate (≤5%) experimental ICCs ( K and total) are known for 77 transitions with multipolarities E2, M3, E3, M4, or E5. For these transitions, the theoretical DF values are, on average, about 3% lower than the theoretical relativistic Hartree–Fock–Slater (RHFS) values. The DF values are in better agreement with experimental results than the RHFS values.

New features of the IC(4) code and comparison of internal conversion coefficient calculations

The IC(4) software developed to compare calculated internal conversion coefficients (ICC) has been enhanced by adding new features through the use of Borland Delphi and TeeChart. Particularly, the 3D-graph option enhances the possibilities of analyzing calculated ICC values. For example, the comparison between the results given by three sets of theoretical ICC tables for any arbitrary pair of calculated ICC can be presented in a much clearer manner. Their differences can be displayed as energy vs. atomic number surfaces. Results from the analyses of K-shell and total ICCs for E2, E3, M2, M3, and M4 multipolarity are discussed.

K-SHELL, L-SUBSHELL, AND TOTAL INTERNAL CONVERSION COEFFICIENTS FOR SUPERHEAVY ELEMENTS

Internal conversion coefficients (ICC) were calculated for all atomic subshells of the elements with 104≤Z≤126 for E1–E4 and M1–M4 multipolarities and 20 transition energies between 10 keV and 5 MeV. Presented here are the K-shell, L-subshell, and total ICC. For the higher shells and transition energies 10–1000 keV, the ICC have been deposited at the LANL preprint server (http://xxx.lanl.gov/e-print/nucl-th/0004003).

Internal conversioncoefficients for superheavy elements

Internal conversion coefficients (ICC) were calculated for allatomic subshells of the elements with 104⩽Z⩽126,E1...E4, M1...M4 multipolarities and transition energiesbetween 10 and 1000 keV. The atomic screening was treated in therelativistic Hartree-Fock-Slater model. Tables comprisingalmost 90 000 subshell and total ICC were deposited atthe LANL preprintserver (http://xxx.lanl.gov/e-print/nucl-th/0004003).

Redetermination of the total internal conversion coefficient of the 279 keV transition following the decay of 203Hg

A new measurement of the total internal conversion coefficient of the 279 keV transition following the decay of 203Hg resulted in α=0.2250(12).

Analysis of internal conversion coefficients

An extensive database has been assembled that contains the three most widely used sets of calculated internal conversion coefficients (ICC): [Hager R.S., Seltzer E.C., 1968. Internal conversion tables. K-, L-, M-shell Conversion coefficients for Z=30 to Z=103, Nucl. Data Tables A4, 1-237; Band I.M., Trzhaskovskaya M.B., 1978. Tables of gamma-ray internal conversion coefficients for the K-, L- and M-shells, 10≤ Z≤104, Special Report of Leningrad Nuclear Physics Institute; Rösel F., Fries H.M., Alder K., Pauli H.C., 1978. Internal conversion coefficients for all atomic shells, At. Data Nucl. Data Tables 21, 91-289] and also includes new Dirac–Fock calculations [Band I.M. and Trzhaskovskaya M.B., 1993. Internal conversion coefficients for low-energy nuclear transitions, At. Data Nucl. Data Tables 55, 43-61]. This database is linked to a computer program to plot ICCs and their combinations (sums and ratios) as a function of Z and energy, as well as relative deviations of ICC or their combinations for any pair of tabulated data. Examples of these analyses are presented for the K-shell and total ICCs of the gamma-ray standards [Hansen H.H., 1985. Evaluation of K-shell and total internal conversion coefficients for some selected nuclear transitions, Eur. Appl. Res. Rept. Nucl. Sci. Tech. 11.6 (4) 777–816] and for the K-shell and total ICCs of high multipolarity transitions (total, K-, L-, M-shells of E3 and M3 and K-shell of M4). Experimental data sets are also compared with the theoretical values of these specific calculations.

Absolute disintegration rate measurements of Ga-67

The procedure for determining the 67Ga disintegration rate by means of a 4 πβ– γ coincidence system is described. The main difficulty with this radionuclide is the presence of a meta-stable state with a half-life of 9.1 μs and a total internal conversion coefficient of 0.89. This required several measurements using different electronic dead-times to correct for detection of delayed events. Gamma spectrometry measurements by a HPGe detector were also performed in order to check for impurities.

Isomeric transitions in 69Se and the spin of the ground state.

Isomeric transitions in [sup 69]Se are investigated using charged particle-[gamma] and [gamma]-[gamma] delayed coincidence measurements. A precise three-point angular distribution shows that the decay of the 9/2[sup +] isomer is nearly isotropic, suggesting either significant dealignment during the lifetime of the isomer or a small [ital E]3 admixture in this transition. An improved measurement of the lifetime of the isomer yields a half-life of 960[plus minus]23 ns. The single particle level structure of negative parity states in [sup 69]Se below the 9/2[sup +] isomer is investigated using a recoil shadowing technique. A 39.4 keV gamma ray with a total-internal conversion coefficient of 28.0[plus minus]2.5 is observed deexciting the 5/2[sup [minus]] first excited state, which is found to be isomeric with a half-life of 2.0[plus minus]0.2 [mu]s. The observed lifetime, along with the internal conversion coefficient, suggests [ital E]2 multipolarity for this transition and strongly favors a spin and parity assignment of 1/2[sup [minus]] for the [sup 69]Se ground state.

Systematic errors in the tables of theoretical total internal conversion coefficients

Some of the total internal conversion coefficients presented in widely used tables of Rosel et al. (1978) were found to be erroneous. The errors appear for some low transition energies, all multipolarities, and probably for all elements. The origin of the errors is explained. The subshell conversion coefficients of Rosel et al, where available, agree with the authors calculations to within a few percent.

Comparison of experimental and Dirac-Fock calculated high-multipole-order internal conversion coefficients

A large set of accurately measured E3, M3, E4 and M4 internal conversion coefficients (ICCs) has been compared with various theoretical values. ICCs calculated by considering Dirac-Fock wave functions are found in best agreement with the experimental values, although dependence of their discrepancies on transition energy, multipolarity and parity, as well as on nuclear charge and shell, has been revealed. The ICCs of Rösel et al., after the adjustment of Németh and Veres, proved to be the most successful in reproducing the experimental values. The adjusted ICCs of Rösel et al. are recommended and revision of the ICCs and γ-emission probabilities of isomeric transitions in evaluated data compilations such as Nuclear Data Sheets is suggested. Selection from the contradicting K and total ICCs of the 661.66 keV transition of 137Ba is proposed.

Comment on 'Measurement of conversion coefficients of M3 transition in 60mCo and M4 transition in 90mY'

The total internal conversion coefficient of the 479.53 keV M4 transition in 90mY reported by Krishna Murty et al. (1989) is shown to be incorrect. The corrected value is 0.102+or-0.004. It is shown that in this case the total internal conversion coefficient is inadequate to verify the purity of the transition.