Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “decays”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Probing the nonexponential decay regime in open quantum systems

The most important law of radioactivity is that of the exponential decay. In the realm of quantum mechanics, however, this decay law is neither rigorous nor fundamental. The deviations from the exponential decay have been observed experimentally at the early stage of a decay process, but there is little evidence for non-exponential behavior at long times. Yet such long-term non-exponentiality is expected theoretically to probe the non-resonant background components of the initial wave function which preserve the structural interference and the memory of how the state was created. In this paper, we propose new observables that can be used for experimental investigations of the post-exponential decay regime, including the decay of threshold resonances, particle correlations in three-body decays, and interference between near-lying resonances. While the specific examples presented in this work pertain to atomic nuclei, the properties of non-exponential decay are generic, i.e., they apply to other many-body open quantum systems, such as hadrons, atoms, molecules, and nanostructures.

6 ≤ A ≤ 19↗
DOE OSTI2024

Quantum Molecular Charge-Transfer Model for Multistep Auger–Meitner Decay Cascade Dynamics

The fragmentation of molecular cations following inner-shell decay processes in molecules containing heavy elements underpins the X-ray damage effects observed in X-ray scattering measurements of biological and chemical materials, as well as in medical applications involving Auger electron-emitting radionuclides. Traditionally, these processes are modeled using simulations that describe the electronic structure at an atomic level, thereby omitting molecular bonding effects. This work addresses the gap by introducing a novel approach that couples Auger–Meitner decay to nuclear dynamics across multiple decay steps, by developing a decay spawning dynamics algorithm and applying it to potential energy surfaces characterized with ab initio molecular dynamics simulations. We showcase the approach on a model decay cascade following K-shell ionization of IBr and subsequent Kβ fluorescence decay. We examine two competing channels that undergo two decay steps, resulting in ion pairs with a total 3+ charge state. This approach provides a continuous description of the electron transfer dynamics occurring during the multistep decay cascade and molecular fragmentation, revealing the combined inner-shell decay and charge transfer time scale to be approximately 75 fs. In conclusion, our computed kinetic energies of ion fragments show good agreement with experimental data.

Ab initio molecular dynamics↗
DOE OSTI2024

β -delayed neutron spectroscopy of Co 70 , 72 ground-state and isomeric-state decays

Here, the β-decaying states of 70,72 Co were studied at the National Superconducting Cyclotron Laboratory using the VANDLE neutron time-of-flight array. The (6 - ,7 - )⁢β-decaying state in 70 Co is near-spherical with a lifetime of 113 ± 7 ms, and the low-spin (1 + ,2 + )⁢β-decaying state is postulated to be the prolate deformed ground state with a lifetime of 508 ± 7 ms. Both decay predominantly to the bound states of 70 Ni. For the first time neutron-emissions from neutron unbound states from both the (6 - ,7 - ) and (1 + ,2 + )⁢β decays were measured. Even with the low statistics data, we were able to disentangle the neutron emission from both decays, which enabled a determination of β-decay strength above the neutron separation energy of 70 Ni. Neutron emission probabilities were measured to be 7.1 ± 1.5% and 9.4 ± 1.7%, respectively, for the (6 - ,7 - ) and (1 + ,2 + ) decays. The decay pattern of the 70 Co is driven by neutron f 5/2 to proton f 7/2 Gamow-Teller transformation. The observed population of neutron unbound states is attributed to the conversion of p 1/2 and p 3/2 neutrons to p 3/2 and p 1/2 protons excited across the Z = 28 closed shell.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Searching for beyond the Standard Model physics using the improved description of 100 Mo $2\nu \beta \beta$ decay spectral shape with CUPID-Mo

The current experiments searching for neutrinoless double-β ($0\nu \beta \beta$) decay also collect large statistics of Standard Model allowed two-neutrino double-β ($2\nu \beta \beta$ ) decay events. These can be used to search for Beyond Standard Model (BSM) physics via $2\nu \beta \beta$ decay spectral distortions. 100 Mo has a natural advantage due to its relatively short half-life, allowing higher $2\nu \beta \beta$ decay statistics at equal exposures compared to the other isotopes. We demonstrate the potential of the dual read-out bolometric technique exploiting a 100 Mo exposure of 1.47 kg years, acquired in the CUPID-Mo experiment at the Modane underground laboratory (France). We set limits on $0\nu \beta \beta$ decays with the emission of one or more Majorons, on $2\nu \beta \beta$ decay with Lorentz violation, and $2\nu \beta \beta$ decay with a sterile neutrino emission. In this analysis, we investigate the systematic uncertainty induced by modeling the $2\nu \beta \beta$ decay spectral shape parameterized through an improved model, an effect never considered before. This work motivates searches for BSM processes in the upcoming CUPID experiment, which will collect the largest amount of $2\nu \beta \beta$ decay events among the next-generation experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Alpha Decay Chains as Thermal Power Sources: Analysis and Applications for RTGs

Radioactive sources can provide power in remote and environmentally harsh locations such as the arctic or space. The generators powered by such sources are rugged and can withstand extreme temperatures, lack of sunlight, and require no human intervention for multiple years. Radioisotopes are used in thermoelectric generators to provide power at remote sites and deep in space. Isotopes like Pu-238, Cm-244, and Am-241 are used in these generators by NASA for power in space probes and spacecrafts. These power sources deliver a steady supply of energy over extended periods of time. Alpha particles created during decay do not travel far in a material. Their kinetic energy is transferred to heat that we can then convert into energy. Unlike beta and gamma decay, the slower-moving alpha particles stop in the material, making their energy available for use. Energy from these natural decay processes provides a reliable source of power. Spontaneous fission is rare and unreliable, and unlike induced fission processes, alpha decay occurs naturally and does not require external management or ignition. The ideal properties of an isotope for use as a power source depend upon the intended use. For use in an Arctic research base over a period of several years, but less than a decade, an isotope that provides high power output over a shorter lifespan may be the most suitable option. Whereas, for deep space missions where a consistent power source for decades or perhaps more than 100 years is needed that would require a very different isotope. One with a much longer half-life that would provide consistent power throughout that time and survive in that state in for these extended periods of time. These examples represent two extreme sides in terms of time frames. By analyzing the power produced by different radioactive decay processes over time, we can evaluate the suitability of various isotope decay chains for specific uses. Some unstable isotopes undergo a series of radioactive decays, transforming into different isotopes at each step and resulting in a stable isotope. The lists of isotopes in these decay processes are known as decay chains. Some of these chains, illustrated in the figures below, are currently being investigated for use in radioisotope thermoelectric generators (RTGs) designed for a range of operational durations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

β decay of Ba 141

The β-decay strength function of nuclides produced in fission is important as it dictates the distribution of decay energy between electrons, neutrinos, and γ rays and so is critical for calculating decay heat in reactors and for estimating the reactor antineutrino spectrum. Several experimental techniques are available to determine this strength function, including electron spectroscopy, γ-ray calorimetry (TAGS spectroscopy), and detailed, high-resolution spectroscopy with modern large high-purity germanium arrays. This work investigates the decay of the well-known and strongly produced fission fragment 141 Ba. A beam of 141 Cs was implanted at the target position of the Gammasphere and the subsequent decay of the daughter 141 Ba was studied. Extensive decay spectroscopy was possible up to the decay Q value of 3.197(7) MeV, including a significant extension of the level scheme and detailed angular correlation measurements for all levels with greater than 0.25% β feeding. The distribution of the β-decay strength was then inferred and compared to previous calorimetric studies. In conclusion, the agreement was excellent and provides a benchmark for comparing strength function methods and data for a more detailed understanding of the structure of 141 La.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Updated evaluation of potential ultralow Q -value β -decay candidates

“Ultralow” Q-value β decays are referred to as such due to their low decay energies of less than ≈1 keV. Such a low energy decay is possible when the parent nucleus decays to an excited state in the daughter, with an energy close to that of the Q value. These decays are of interest as potential new candidates for neutrino mass determination experiments and as a testing ground for studies of atomic interference effects in the nuclear decay process. In this paper, we provide an updated evaluation of atomic mass data and nuclear energy-level data to identify potential ultralow Q-value β decay candidates. For many of these candidates, more precise and accurate atomic mass data is needed to determine if the Q value of the potential ultralow decay branch is energetically allowed and in fact ultralow. Furthermore, the relevant precise atomic mass measurements can be achieved via Penning trap mass spectrometry.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Weak decays in superheavy nuclei

Superheavy nuclei represent the extreme atoms and nuclides known at the limit of mass and charge. The observed superheavy nuclei are all proton-rich; they decay primarily by emitting 𝛼 particles and by fission with a possible small electron capture (EC) branch. Here, due to the huge atomic numbers and associated relativistic effects, EC decays of superheavy systems are expected to differ from what is known in lighter nuclei. In this letter, using the quantified relativistic nuclear density functional theory and the quasiparticle random-phase approximation with the interaction optimized to experimental EC/𝛽 ± -decay half-lives, and Gamow-Teller resonance energies, we study the EC/𝛽 ± -decays in 𝑍=101–118 nuclei. Both allowed (1 + ) and first-forbidden (0 − ,1 − and 2 − ) transitions are considered. We show that the first-forbidden 1 − transitions dominate the decay rates in almost all studied nuclei. For proton-rich nuclei, EC dominates over 𝛽 + decay. Based on calculations with two relativistic energy density functionals, we identify 45 candidate nuclei in which a competition between weak decays and 𝛼 decay and spontaneous fission is expected.

A ≥ 220↗
DOE OSTI2021

Repetitively pulsed nanosecond discharge plasma decay in propane–oxygen gas mixture in the presence of a heating electric field

Plasma decay in the afterglow of a repetitively pulsed nanosecond discharge in a stoichiometric propane–oxygen mixture was experimentally investigated when a weak heating DC electric field was applied and in its absence. The discharge was ignited at room gas temperature and a pressure of 1–2 Torr and was characterized by low specific energy inputs (<0.004 eV per molecule in one pulse). Using microwave interferometry, the temporal evolution of the electron density during plasma decay was studied, and the effective recombination coefficients were obtained from data processing. It was shown that the rate of plasma decay behaved in a non-monotonic manner with increasing degree of propane oxidation; at first the decay rate grew, then passed through a maximum, fell and saturated in the limit of a large (~2000) number of pulses. In this limit, the effect of the heating DC electric field on the plasma decay decreased with approaching chemical equilibrium. Numerical simulation of the observed effects was performed for low and high oxidation degrees of propane taking into account changes in the composition of positive ions in the plasma. Good agreement was obtained between measurements and calculations of the electron density during plasma decay in these cases. Here it was shown that the formation of cluster ions in the discharge afterglow plays a fundamental role. The plasma decay was controlled by electron recombination with hydrocarbon cluster ion at low oxidation degree of propane and with water cluster (hydrated) ions at high oxidation degree. A hypothesis was proposed to explain the observed nonmonotonic behavior of the plasma decay rate with an increase in the propane oxidation in the discharge, based on the formation of hydrated hydrocarbon ions C x H y + (H 2 O) k at moderate oxidation degrees.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

The decay of HIV under anti-retroviral therapy is biphasic even in humanized mice with just T cells

HIV-1 plasma viral load decays in a biphasic manner during antiretroviral therapy (ART). It was hypothesized that this is due to infection of different cell types, namely CD4+ T cells and macrophages. We studied this possibility directly by modeling the decay of HIV-1 in humanized mice. We utilized previously published data from humanized T-cell only mice (TOM) and myeloid-only mice (MOM) infected with HIV-1 and treated with a potent ART regimen. Viral load decay dynamics were modeled using either a single or a biexponential decay fitted using nonlinear mixed effects techniques. Fits were compared using the corrected Bayesian information criterion (BICc). In TOM, the biphasic model was significantly better than a single-phase decay model (ΔBICc ≈ 16) despite additional parameters. In MOM, the biphasic decay was statistically better, but there was substantial uncertainty because the virus goes below detection very fast. The first-phase half-life was consistent between groups (1.2 days in MOM and 1.3 days in TOM) and similar to the half-life estimated in human infection. The second-phase decay in these mice was minimal likely due to low initial viral loads. Additional analyses with mice containing both CD4+ T cells and macrophages or X4-tropic virus-infected MOM mice confirmed the biphasic pattern, demonstrating the robustness of this result. The biphasic decline in HIV-1 occurs, even with only CD4+ T cells, refuting the hypothesis that distinct cell populations (CD4+ T cells and macrophages) drive each decay phase. These findings support an alternative model in which the observed dynamics arise from intrinsic properties of the viral infection lifecycle rather than from cellular compartmentalization.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

A New Approach for Calculating the Alpha-Decay Half-Life for the Heavy and Super-heavy Elements and an Exact A Priori Result for Beyllium-8

A new general method for calculating the alpha decay half-life is presented. The method predicts an a priori exact value for the beryllium-8 half-life. Beryllium-8 is an exception to the current alpha decay theory captured in the Geiger-Nuttal law. The new method predicts the beryllium-8 alpha half-life using only constants and measured isotopic mass. The method also reliably predicts all the heavier isotope alpha decay half-lives consistent with the Geiger-Nuttal law. With respect to current theory, the inability of the Geiger-Nuttal Law to predict the alpha-decay half-life in the case of beryllium-8 has led to consideration of other decay mechanisms for this isotope, such as fission for example. One result is that given the consistency of the new method presented here for all isotopes including an exact a priori result for beryllium-8, the evidence strongly suggests that the beryllium-8 decay is in fact an alpha decay. A second result is that the method definitively demonstrates that the entire rest mass of the two helium-4 electrons is converted to energy in the decay process and this energy becomes part of the emitted alpha particle kinetic energy.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2022

Decay Curve Correction Analysis Report

The decay curve analysis that is done on the short-lived radionuclide gas samples is used to differentiate between gaseous radionuclides that have the same characteristic gamma decay energy, 511 kiloelectron-volts (keV). A sample of stack gas is isolated and the total counts in the 511 keV peak are counted repeatedly in 10-second intervals to evaluate the decay rate of the sample over time. Analysis of this decay data required a series of steps. First, a raw data report is generated by the gamma acquisition system, based on an analysis template within the acquisition software. The data report file was then loaded into Microsoft Word, and a macro was used to perform minor formatting (remove colons and insert tabs between data columns) to allow analysis within Excel. The file is then saved as a text file at this point. The text file is then uploaded into Excel and a series of macros are used to add labels, calculate radioactive decay constants, and analyze the gamma decay data using linear regression techniques. The analysis template has been used since 1998 for stack 53000303 (TA-53, building 0003, exhaust stack 03) and 2000 for stack 53000702. The overall process, including the gamma report format and the macros used in Word and Excel for processing the report, had remained unchanged until 2015. In October of 2015, staff made a change to the report template in the gamma acquisition software which resulted in an error in the calculations later performed by the Excel macro. This error was not caught until a more in-depth review of the analysis took place regarding 2020 data. This report covers a much more complete review of the issue that occurred regarding the decay curve analysis, a review of the calculations completed to correct the issue, a review of the updated decay curve analysis process, and recommendations for moving forward.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Uncovering a chirally suppressed mechanism of oνββ decay with LHC searches

Δ L = 2 lepton number violation (LNV) at the TeV scale could provide an alternative interpretation of positive signal(s) in future neutrinoless double beta (0 νββ ) decay experiments. An interesting class of models from this point of view are those that at low energies give rise to dimension-9 vector operators and a dimension-7 operator, both of whose 0 νββ -decay rates are “chirally suppressed”. We study and compare the sensitivities of 0 νββ -decay experiments and LHC searches to a simplified model in this class of TeV-scale LNV that is also SU(2) L × U(1) Y gauge invariant. The searches for 0 νββ decay, which are here diluted by a chiral suppression of the vector operators, are found to be less constraining than LHC searches whose reach is increased by the assumed kinematic accessibility of the mediator particles. For the chirally suppressed dimension-7 operator generated by TeV-scale mediators, in contrast, 0 νββ -decay searches place strong constraints on the size of the new Yukawa coupling. Signals of this model at the LHC and 0 νββ -decay experiments are entirely uncorrelated with the observed neutrinos masses, as these new sources of LNV give negligible contributions to the latter. We find the prospects for the high-luminosity LHC and ton-scale 0 νββ -decay experiments to uncover the chirally-suppressed mechanism with TeV-scale LNV to be promising. We also comment on the sensitivity of the 0 νββ -decay lifetime to certain unknown low-energy constants that in the case of dimension-9 scalar operators are expected to be large due to non-perturbative renormalization.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Probing autoionization decay lifetimes of the 4d−16ℓ core-excited states in xenon using attosecond noncollinear four-wave-mixing spectroscopy

The decay of core-excited states is a sensitive probe of autoionization dynamics and correlation effects in many-electron systems, occurring on ultrafast timescales. Xenon, with its dense manifold of autoionizing resonances that can be coupled with near-infrared light, provides a platform to investigate these processes. In this work, the autoionization decay lifetimes of 4d-16ℓ (ℓ = s, p, d, …) core-excited states in xenon atoms are probed with extreme ultraviolet (XUV) attosecond noncollinear four-wave-mixing (FWM) spectroscopy. The 4d{5/2,3/2}-16p XUV-bright states (optically dipole-allowed) exhibit decay lifetimes of ∼6 fs, which is consistent with spectator-type decay. In contrast, the 4d{5/2,3/2}-16s and 4d{5/2,3/2}-16d XUV-dark states (optically dipole forbidden) show longer decay lifetimes of ∼20 fs. Photoionization calculations confirm that all core-hole states with 4d character should decay via spectator channels in ≤6 fs, suggesting that the apparently longer dark-state decay times arise from an alternative mechanism. A few-level simulation of the FWM process shows that the inclusion of a nearby, longer-lived dark state can mimic the experimental FWM signal, suggesting population cycling with a second electronic state with non-4d character. Ab initio calculations support the presence of such multielectron excited states in the 60-70 eV range. These results demonstrate that FWM signals can encode coupled-state dynamics when probing complex systems, highlighting the importance of combining theoretical and experimental approaches to disentangle accurate core-level decay pathways and lifetimes.

Puskar, Nicolette G↗
DOE OSTI2023

Biphasic decay of intact SHIV genomes following initiation of antiretroviral therapy complicates analysis of interventions targeting the reservoir

The latent reservoir for HIV-1 in resting CD4 + T cells persists despite antiretroviral therapy (ART) and precludes cure. Reservoir-targeting interventions are evaluated in ART-treated macaques infected with simian immunodeficiency virus (SIV) or simian-human immunodeficiency virus (SHIV). Efficacy is determined by reservoir measurements before and after the intervention. However, most proviruses persisting in the setting of ART are defective. In addition, intact HIV-1 and SIV genomes undergo complex, multiphasic decay observable when new infection events are blocked by ART. Intervention-induced elimination of latently infected cells must be distinguished from natural decay. Here, we address these issues for SHIV. We describe an intact proviral DNA assay that allows digital counting of SHIV genomes lacking common fatal defects. We show that intact SHIV genomes in circulating CD4 + T cells undergo biphasic decay during the first year of ART, with a rapid first phase (t 1/2 = 30.1 d) and a slower second phase (t 1/2 = 8.1 mo) that is still more rapid that the slow decay observed in people with HIV-1 on long-term ART (t 1/2 = 3.7 y). In SHIV models, most interventions are tested during 2nd phase decay. Natural 2nd phase decay must be considered in evaluating interventions as most infected cells present at this time do not become part of the stable reservoir. In addition, for interventions tested during 2nd phase decay, a caveat is that the intervention may not be equally effective in people with HIV on long-term ART whose reservoirs are dominated by latently infected cells with a slower decay rate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

25 Siβ + -decay spectroscopy

Background: β-decay spectroscopy provides valuable information on exotic nuclei and a stringent test for nuclear theories beyond the stability line. Purpose: To search for new β-delayed protons and γ rays of 25 Si to investigate the properties of 25 Al excited states. Method: 25 Si β decays were measured by using the Gaseous Detector with Germanium Tagging system at the National Superconducting Cyclotron Laboratory. The protons and γ rays emitted in the decay were detected simultaneously. Here, a Monte Carlo method was used to model the Doppler broadening of 24 Mg γ-ray lines caused by nuclear recoil from proton emission. Shell-model calculations using two newly developed universal sd-shell Hamiltonians were performed. Results: The most precise 25Si half-life to date has been determined. A new proton branch at 724(4) keV and new proton-γ-ray coincidences have been identified. Three 24 Mg γ-ray lines and eight 25 Al γ-ray lines are observed for the first time in 25 Si decay. The first measurement of the 25 Si β-delayed γ-ray intensities through the 25 Al unbound states is reported. All the bound states of 25 Al are observed to be populated in the β decay of 25 Si. Several inconsistencies between the previous measurements have been resolved, and new information on the 25 Al level scheme is provided. An enhanced decay scheme has been constructed and compared to the mirror decay of 25 Na and the shell-model calculations. Conclusions: The measured excitation energies, γ-ray and proton branchings, log $ft$ values, and Gamow-Teller transition strengths for the states of 25 Al populated in the β decay of 25 Si are in good agreement with the shell model calculations, offering gratifyingly consistent insights into the fine nuclear structure of 25 Al.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Strong and Weak C P Tests in Sequential Decays of Polarized Σ 0 Hyperons

The J / ψ , ψ ( 3686 ) → Σ 0 Σ ¯ 0 processes and subsequent decays are studied using the world’s largest J / ψ and ψ ( 3686 ) data samples collected with the BESIII detector. The parity-violating decay parameters of the decays Σ 0 → Λ γ and Σ ¯ 0 → Λ ¯ γ , α Σ 0 = − 0.0017 ± 0.0021 ± 0.0018 and α ¯ Σ 0 = 0.0021 ± 0.0020 ± 0.0022 , are measured for the first time. The strong C P symmetry is tested in the decays of the Σ 0 hyperons for the first time by measuring the asymmetry A C P Σ = α Σ 0 + α ¯ Σ 0 = ( 0.4 ± 2.9 ± 1.3 ) × 10 − 3 . The weak C P test is performed in the subsequent decays of their daughter particles Λ and Λ ¯ . Also for the first time, the transverse polarizations of the Σ 0 hyperons in J / ψ and ψ ( 3686 ) decays are observed with opposite directions, and the ratios between the S -wave and D -wave contributions of the J / ψ , ψ ( 3686 ) → Σ 0 Σ ¯ 0 decays are obtained. These results are crucial to understand the decay dynamics of the charmonium states and the production mechanism of the Σ 0 − Σ ¯ 0 pairs. Published by the American Physical Society 2024

Physics↗
DOE OSTI2021

Search for double-beta decay of $$\mathrm {^{130}Te}$$ to the $$0^+$$ states of $$\mathrm {^{130}Xe}$$ with CUORE

Abstract The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ( $$0\nu \beta \beta $$ 0 ν β β ) in the isotope $$\mathrm {^{130}Te}$$ 130 Te . In this work we present the latest results on two searches for the double beta decay (DBD) of $$\mathrm {^{130}Te}$$ 130 Te to the first $$0^{+}_2$$ 0 2 + excited state of $$\mathrm {^{130}Xe}$$ 130 Xe : the $$0\nu \beta \beta $$ 0 ν β β decay and the Standard Model-allowed two-neutrinos double beta decay ( $$2\nu \beta \beta $$ 2 ν β β ). Both searches are based on a 372.5 kg $$\times $$ × yr TeO $$_2$$ 2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as $$\mathrm {S^{0\nu }_{1/2} = 5.6 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 0 ν = 5.6 × 10 24 yr for the $${0\nu \beta \beta }$$ 0 ν β β decay and $$\mathrm {S^{2\nu }_{1/2} = 2.1 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 2 ν = 2.1 × 10 24 yr for the $${2\nu \beta \beta }$$ 2 ν β β decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at $$90\%$$ 90 % C.I. on the decay half lives is obtained as: $$\mathrm {(T_{1/2})^{0\nu }_{0^+_2} > 5.9 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 0 ν > 5.9 × 10 24 yr for the $$0\nu \beta \beta $$ 0 ν β β mode and $$\mathrm {(T_{1/2})^{2\nu }_{0^+_2} > 1.3 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 2 ν > 1.3 × 10 24 yr for the $$2\nu \beta \beta $$ 2 ν β β mode. These represent the most stringent limits on the DBD of $$^{130}$$ 130 Te to excited states and improve by a factor $$\sim 5$$ ∼ 5 the previous results on this process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗