E.A. Yakushev

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 < or = Z < or = 104, Special Report of Leningrad Nuclear Physics Institute; Rosel 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.

Precise measurement of the KLL and KLX Auger spectra of cadmium from the EC-decay of 111In

Abstract The KLL and KLX Auger spectra of Cd from the EC-decay of 111 In have been analyzed with the 7 eV instrumental resolution using a combined electrostatic spectrometer and a source prepared by a modified Langmuir–Blodgett method. Energies and relative intensities of all the nine well resolved KLL lines have been precisely determined. While the latter quantities were found to be in very good agreement with the relativistic intermediate coupling calculations, the former ones deviate from results of the widely used semi-empirical calculations especially in the case of the absolute energies. The predicted strong influence of the relativistic effects on the KL 1 L 2 ( 3 P 0 ) transition intensity has been proved. Most of the main KLX Auger lines have been well separated and their complex structures have been observed. Accurate energies and intensities obtained for these lines have been compared with results of calculations. The intermediate coupling splitting of the KL 2 L 2 and KL 3 L 3 lines have been revealed. The KLX/KLL, KLN(O)/KLM, and KXY/KLL group intensity ratios have also been determined. A conclusion is made that further finer theoretical investigation on the complex interaction mechanism for two inner-shell vacancies is still very much needed.

First experimental investigation of the KLL Auger spectrum of Ge (Z=32)

Abstract The KLL Auger spectrum of 73 Ge from the electron capture decay of 73 As was measured with 7 eV instrumental resolution using a combined electrostatic spectrometer and a source prepared by a gas-chemical method. The energies and relative intensities of all the nine resolved KLL lines were precisely determined. A rather poor agreement was found between the measured KLL transition energies and predictions of the widely used semiempirical calculations. Our relative KLL transition intensities agree only with results of the relativistic calculations in intermediate coupling with configuration interaction. The predicted influence of the relativistic effects on the KL 1 L 2 ( 3 P 0 ) transition rate was also proven.

An experimental investigation of some KLL and L3MM Auger transitions for Z=58, 59, and 61:: the predicted relativistic effects on the KL1L2(3P0) Auger transition probability proved

Abstract The KL1L2 Auger doublet of 14059Pr and the KLL Auger spectrum of 14561Pm from the electron capture decay of 140Nd and 145Sm, respectively, have been measured with high instrumental resolutions using a combined electrostatic spectrometer and sources prepared by a modified Langmuir–Blodgett method. An exceptional agreement of the determined KL1L2(3P0)/(1P1) intensity ratios of 0.42(2) and 0.45(1) for 140Pr and 145Pm, respectively, with the respective calculated values of 0.419 and 0.450 has proved the predicted strong influence of the relativistic effects on the KL1L2(3P0) transition intensity. While the measured relative intensities of the KLL transitions in 145Pm were found to agree well with the relativistic intermediate coupling calculations, the measured relative energies deviate from results of the widely used semi-empirical calculations. A doublet structure of the KL2L3(1D2) line of 145Pm with a splitting of 18.3(6) eV has been observed. We made an assumption that this structure originates in two different K shell excitation processes. The measured absolute energies of 28 397(3), 29 423.1(26), and 31 542.9(15) eV for the KL2L3 transition in 140Ce, 140Pr, and 145Pm, respectively, were found to be higher by about 20 eV than the semi-empirical values. The most intense L3MM line groups of 145Pm have also been measured but not evaluated. The absolute energy of the L3M4M5(1G4) transition has been determined to be 4342.6(16) eV. The energy of the M1 61.2 keV nuclear transition in 145Pm has been improved to be 61 226.5(17) eV using the measured energy of 16 042.5(15) eV of the K-61.2 conversion line. Values of 19.2(5) and 25.3(9) eV were determined for natural widths of the K shell and KL2L3 transition of 145Pm, respectively.

Development of the ultra-low background HPGe spectrometer OBELIX at Modane underground laboratory

A new ultra low-background spectrometer based on a HPGe detector with a sensitive volume of 600 cm(3) was developed to investigate rare nuclear processes, such as resonant neutrino-less double electron capture (0νEC/EC) and double beta decay processes (2ν2β(−), 2νβ(+)EC, 2νEC/EC) to the excited states of daughter nuclei. The spectrometer was installed at the Modane underground laboratory (LSM, France, 4800 m w.e.). Sensitivity of the spectrometer and its background were tested. A new method for the efficiency calibration in measurements of low-active samples was developed. The spectrometer was used for the measurements of low active materials and samples. Results obtained in 395 h investigation of resonant 0νEC/EC decay of (106)Cd to the 2718 keV and 2741 keV excited states of (106)Pd with ~23.2 g of enriched (106)Cd and 2ν2β(−) decay of (100)Mo sample with a mass of 2588 g to the 0(+), 1130 keV and 2(+), 539.5 keV excited states of (100)Ru are presented.

New search for double electron capture in

A new experiment devoted to searches for double electron capture in 106Cd decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The limit T1/2(2νEC/EC) > 2.0×1020 yr at a 90%confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope 106Cd to 99.57%. The limits T1/2(KL, 2741 keV) > 0.9 × 1020 yr and T1/2(KK, 2718 keV) ≫ 1.4 × 1020 yr at a 90% C.L. on the neutrinoless decay of 106Cd were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope 106Cd.

^{106}

The EDELWEISS experiment is aimed at direct searches for nonbaryonic cold dark matter by means of cryogenic germanium detectors. It is deployed at the LSM underground laboratory in the Frejus tunnel, which connects France and Italy. The results of the experimentmade it possible to set a limit on the spin-independent cross section for the scattering of weak-interacting massive particles (WIMP) at a level of 10−6 pb. Data from 21 detectors of total mass about 7 kg are being accumulated at the present time.

Cd decay with the TGV-2 spectrometer

A new ultra-low-background spectrometer based on a HPGe detector with a sensitive volume of 600 cm 3 was developed to investigate rare nuclear processes, such as resonant neutrino-less double electron capture (0νEC/EC) and double beta decay processes (2ν2β, 2νβEC, 2νEC/EC) to the excited states of daughter nuclei. The spectrometer was installed at the Modane underground laboratory (LSM, France, 4800 m w.e.). Sensitivity of the spectrometer and its background were tested. A new method for the efficiency calibration in measurements of low-active samples was developed. A spectrometer was used for the measurements of low active materials and samples. Results obtained in 395 h investigation of resonant 0νEC/EC decay of Cd to the 2718 keV and 2741 keV excited states of Pd with ~23.2 g of enriched Cd, βEC, EC/EC decays of Ni in measurements of ~21.7 kg sample of natural nickel and 2ν2β decay of Mo sample with the mass of 2588 g to the 0 + , 1130 keV and 2 + , 539.5 keV excited states of 100 Ru are presented.

EDELWEISS experiment: Direct search for dark matter

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.

The Low-Background HPGE Γ-Spectrometer OBELIX for the Investigation of the Double Beta Decay to Excited States

A new experimental run of searching for EC/EC decay of 106Cd was performed at the Modane underground laboratory (4800 m w.e.) using the TGV-2 spectrometer and ∼23.2 g 106Cd with enrichment of 99.57%. The limit on 2νEC/EC decay of 106Cd - T1/2(2νEC/EC) > 3.1×1020 y, at 90% C.L was obtained from the preliminary calculation of experimental data accumulated for 7018 h of measurement. The limits on the resonance neutrino-less double electron capture decay of 106Cd were obtained from the measurement of ∼23.2 g of 106Cd with the low-background HPGe spectrometer OBELIX lasted 395 h - T1/2(KL, 2741 keV) > 0.9×1020 y and T1/2(KK, 2718 keV) > 1.4×1020 y at 90% C.L.