Ab initio calculations of 229Th band-to-band internal conversion rate in 229ThO2
Abstract
We present an ab initio calculation of the band-to-band internal-conversion rate of the ℏωnuc ≈ 8.35 eV isomeric transition in 229ThO2. Because the nuclear transition energy exceeds the electronic band gap of ThO2, the isomer can decay nonradiatively by resonantly promoting a valence electron into the conduction band. We formulate this process as a Brillouin-zone sum over vertical interband transitions weighted by local Th-centered hyperfine matrix elements, which are evaluated directly from all-electron full-potential linearized augmented-plane-wave Bloch spinors. A finite nuclear magnetization model is included to regularize the short-range hyperfine interaction and to account for the Bohr-Weisskopf effect. After applying scissor shifts to span the experimentally reported ThO2 band gaps, we find calculated internal-conversion lifetimes in the range of 1−16 μs. The lifetime increases strongly as the band gap approaches ωnuc because the resonant interband phase space at the nuclear transition energy is reduced. For the larger reported ThO2 gaps, the calculated lifetime is comparable to the measured conversion-electron Mössbauer lifetime [Nature 648, 300 (2025)]. Our analysis implies that choosing solid-state hosts with band-gap values slightly lower than ωnuc can optimize solid-state nuclear clock performance with internal-conversion electron readout.
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BibTeX
@misc{perera2026initio,
title = {{Ab initio calculations of $^229$Th band-to-band internal conversion rate in $^229$ThO$_2$}},
author = {Udeshika C. Perera and H. B. Tran Tan and H. W. T. Morgan and Eric Hudson and Daniel A. Rehn and Andrei Derevianko},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.08941},
eprint = {2607.08941},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.08941},
}
RIS
TY - UNPB
TI - Ab initio calculations of ^229Th band-to-band internal conversion rate in ^229ThO_2
AU - Udeshika C. Perera
AU - H. B. Tran Tan
AU - H. W. T. Morgan
AU - Eric Hudson
AU - Daniel A. Rehn
AU - Andrei Derevianko
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2607.08941
UR - https://arxiv.org/abs/2607.08941
AB - We present an ab initio calculation of the band-to-band internal-conversion rate of the ℏω_nuc ≈ 8.35 eV isomeric transition in ^229ThO_2. Because the nuclear transition energy exceeds the electronic band gap of ThO_2, the isomer can decay nonradiatively by resonantly promoting a valence electron into the conduction band. We formulate this process as a Brillouin-zone sum over vertical interband transitions weighted by local Th-centered hyperfine matrix elements, which are evaluated directly from all-electron full-potential linearized augmented-plane-wave Bloch spinors. A finite nuclear magnetization model is included to regularize the short-range hyperfine interaction and to account for the Bohr-Weisskopf effect. After applying scissor shifts to span the experimentally reported ThO_2 band gaps, we find calculated internal-conversion lifetimes in the range of 1−16 μs. The lifetime increases strongly as the band gap approaches ω_nuc because the resonant interband phase space at the nuclear transition energy is reduced. For the larger reported ThO_2 gaps, the calculated lifetime is comparable to the measured conversion-electron Mössbauer lifetime [Nature 648, 300 (2025)]. Our analysis implies that choosing solid-state hosts with band-gap values slightly lower than ω_nuc can optimize solid-state nuclear clock performance with internal-conversion electron readout.
ER -