Precise energy measurements of the first-excited state in ¹⁹⁷ Au

Abstract

The energy of the first-excited state in 197 Au has been measured with high precision using conventional γ-ray spectroscopy with HPGe detectors. A γ77 keV line of 197 Au and K β lines of Au are overlapped almost completely and such measurements present a very serious challenge. The coincidence measurements have been applied, first, with the γ77 keV line for the precise energy calibration using Kα and K β lines of Au, secondly, with Kα lines of Au for the precise energy measurement of the first-excited state in 197 Au. Our current result is 77.339 ± 0.003 keV, confirming the observations of the recent 197 Au NEET experiment performed at SPring-8, while, according to available nuclear data, the energy of the first-excited state in 197 Au is 77.351 ± 0.002 keV.

Precise measurement of energy of the first excited state of 115 Sn (E exc ≃ 497.3 keV)

“…This value is in a good agreement with the evaluated data in ref. [3]: 497.334 (22) keV. However, it differs by 3.4σ from the recent result E exc = 497.316 (7) keV [17].…”

“…A list of other potentially interesting candidates with low Q * β values is given in [13][14][15][16]; it should be noted that they are not observed yet, and Q β values are known with the low accuracy of ∼1 keV (or worse). The uncertainty of 24 eV in the Q * β value is defined mainly by the 22 eV uncertainty in our knowledge of the energy of the 115 Sn excited level: E exc = 497.334 (22) keV [3]. The situation is even paradoxical to some extent: we know the absolute values of 115 In and 115 Sn masses of ∼100 GeV (and their difference) with better accuracy than the level energy of ∼0.5 MeV.…”

“…The total uncertainty of the determination of the 115 Sb line was calculated as the square root of quadratically added uncertainty of the line E γ = 477.6035 keV − 2 eV, calibration uncertainty −2 eV, and weighted average statistical uncertainty −1.1 eV, which results in the final value of 3 eV. Similar procedures for processing the spectra were used in our previous work [22] for precise measurement (with 3 eV uncertainty) of the energy of the first excited level of 197 Au.…”

Induced acceleration of the decay of the 31-yr isomer of 178m2 Hf using bremsstrahlung radiation

“…Only recently this disagreement was finally resolved [23], confirming reliably the smaller value 39 ± 3 eV.…”

Nuclear Excitation by Electron Transitions

“…In both cases, the transitions are of the M1 multipolarity. As to the energy of the nuclear 1/2 + level, it is 77.351 keV according to [8] and 77.339 ± 0.003 keV according to the last precision measurements [9]. The corresponding mismatch of the nuclear (E (n) 0 ) and atomic (E (a) 0 ) transition energies, defined as…”