Internal bremsstrahlung: Exact relativistic independent-particle-approximation calculations

Abstract

We have reformulated the relativistic theory of internal bremsstrahlung in electron capture (IBEC) and developed a numerical code for calculating a transition amplitude for any initial atomic state. All relativistic as well as screening effects are included within the independent-particle approximation. We have shown the advantage of the theory even in the pole-dominance region of the IBEC spectra, thus making it suitable for comparison with the observed spectra in experiments that search for light-and/or heavy-neutrino mass components. In addition, we have applied our code to study the interference effects in the IBEC transition amplitude of ' Ho and found, in agreement with experimental data, a smaller interference suppression than predicted by several recent models.

Absolute intensity of internal bremsstrahlung from the electron capture decay ofI125

“…In our previous work [4] we indicated that the Suric et al calculation [3] reproduces the shape and relative intensity of the partial IB spectra for ' I to within a few percent. The above normalization factor indicates that the Suric calculation essentially reproduces (to within 15%) the absolute intensity of the IB spectrum, as well.…”

“…Several half-lives have now elapsed since the completion of the IB measurement and the source strength has become sufficiently low to allow an absolute calibration. We present in this Brief Report the absolutely calibrated IB spectrum and compare the intensity to the theoretical calculation of Suric et al [3].…”

“…Several half-lives have now elapsed since the completion of the IB measurement and the source strength has become sufficiently low to allow an absolute calibration. We present in this Brief Report the absolutely calibrated IB spectrum and compare the intensity to the theoretical calculation of Suric et al [3].To determine the source activity, the yield of Te K x rays and of the 35.5-keV y ray from the decay of the ' Te isomer were measured using a planar Ge detector with no absorbers and with the source at a distance of 16.5 cm from the detector. The intensities of the Kcr, KP, and 35.5-keV lines were taken respectively as 1.135~0.021, 0.255 0.006, and 0.0658~0.0008 per decay [10].…”

“…Although the calculations reproduced the measured shapes of the IB spectra, the magnitudes were off by factors of 1.5 to 2. Recently, Suric, Horvat, and Pisk [3] developed a code to calculate IBEC matrix elements in an independent-particle approximation, with atomic wave functions obtained from a relativistic self-consistent-field potential. Their calculated spectrum for ' Pt was also lower than the data by about a factor of 2.…”

“…shows the absolutely normalized net IB spectrum together with a fit using Suric et al 's calculation[3] (convoluted with the response function of the detector). The lowest energy used in the fit is 120 keV, which is above the 118.…”