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In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun’s energy and contributing to the discovery of neutrino oscillations, those from proton–proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrinos, demonstrating that about 99 per cent of the power of the Sun, 3.84 × 10 33 ergs per second, is generated by the proton–proton fusion process. Spectral observations of the low-energy neutrinos produced by proton–proton fusion in the Sun demonstrate that about 99 per cent of the Sun’s power is generated by this process. Sun's elusive pp neutrinos tracked down The Sun's energy output derives from a sequence of nuclear reactions that converts hydrogen into helium, most of it from the fusion of two protons (the proton–proton or pp reaction) accompanied by the release of a low-energy neutrino. These neutrinos have proved elusive: only solar neutrinos from secondary reactions had been directly observed. But here the Borexino collaboration reports observations of the pp neutrinos themselves, so providing a direct view of the principal fusion process that powers the Sun.

The ability of protocols based on the B2PLYPD/6-311+G**//B3LYP/6-31+G* method with various schemes for accounting for nonspecific solvation to reproduce C-H, N-H, O-H and S-H acidity in a dimethyl sulfoxide medium is considered. For a selected set of 20 compounds, typical reagents for reactions in superbasic media, the IEFPCM scheme with UFF cavity and α = 1.35 multiplier yields better results than the popular SMD model.

For most of their existence, stars are fuelled by the fusion of hydrogen into helium. Fusion proceeds via two processes that are well understood theoretically: the proton–proton ( pp ) chain and the carbon–nitrogen–oxygen (CNO) cycle 1 , 2 . Neutrinos that are emitted along such fusion processes in the solar core are the only direct probe of the deep interior of the Sun. A complete spectroscopic study of neutrinos from the pp chain, which produces about 99 per cent of the solar energy, has been performed previously 3 ; however, there has been no reported experimental evidence of the CNO cycle. Here we report the direct observation, with a high statistical significance, of neutrinos produced in the CNO cycle in the Sun. This experimental evidence was obtained using the highly radiopure, large-volume, liquid-scintillator detector of Borexino, an experiment located at the underground Laboratori Nazionali del Gran Sasso in Italy. The main experimental challenge was to identify the excess signal—only a few counts per day above the background per 100 tonnes of target—that is attributed to interactions of the CNO neutrinos. Advances in the thermal stabilization of the detector over the last five years enabled us to develop a method to constrain the rate of bismuth-210 contaminating the scintillator. In the CNO cycle, the fusion of hydrogen is catalysed by carbon, nitrogen and oxygen, and so its rate—as well as the flux of emitted CNO neutrinos—depends directly on the abundance of these elements in the solar core. This result therefore paves the way towards a direct measurement of the solar metallicity using CNO neutrinos. Our findings quantify the relative contribution of CNO fusion in the Sun to be of the order of 1 per cent; however, in massive stars, this is the dominant process of energy production. This work provides experimental evidence of the primary mechanism for the stellar conversion of hydrogen into helium in the Universe. Direct experimental evidence of the carbon–nitrogen–oxygen fusion cycle in the Sun is provided by the detection of neutrinos emitted during this process.

The search for neutrino events in correlation with gravitational wave (GW) events for three observing runs (O1, O2 and O3) from 09/2015 to 03/2020 has been performed using the Borexino data-set of the same period. We have searched for signals of neutrino-electron scattering and inverse beta-decay (IBD) within a time window of [Formula omitted] s centered at the detection moment of a particular GW event. The search was done with three visible energy thresholds of 0.25, 0.8 and 3.0 MeV. Two types of incoming neutrino spectra were considered: the mono-energetic line and the supernova-like spectrum. GW candidates originated by merging binaries of black holes (BHBH), neutron stars (NSNS) and neutron star and black hole (NSBH) were analyzed separately. Additionally, the subset of most intensive BHBH mergers at closer distances and with larger radiative mass than the rest was considered. In total, follow-ups of 74 out of 93 gravitational waves reported in the GWTC-3 catalog were analyzed and no statistically significant excess over the background was observed. As a result, the strongest upper limits on GW-associated neutrino and antineutrino fluences for all flavors ( [Formula omitted]) at the level [Formula omitted] have been obtained in the 0.5-5 MeV neutrino energy range.

Experimental search for spontaneous fission and cluster decays of 234 U, 235 U, 236 U and 238 U was carried out with a certified 230-g uranium oxide sample enriched in 235 U to 93.2%. The sample was measured over 46.3 days by using a 70 cm 3 broad energy germanium detector. The search for the fission fragments and their daughters was performed by using γ  quanta of energy > 1.5  MeV expected in β -  decays. No such γ  peaks were observed in the experimental data, thus, upper limits on the fragments’ yields are set. The lower limits on partial half-lives are obtained at the level of 5.0 × 10 10 - 2.6 × 10 17  years for the corresponding cold fission and cluster decay channels. In particular, 5 limits for 235 U and 238 U cold fission exceed the prediction made by S.B. Duarte et al. in framework of the effective liquid drop model by a factor of 1.6–227. Therefore, the obtained results can be used to improve the theoretical frameworks to study the cold fission processes.

A long-term measurement was conducted to search for α, double-α and double-β decays with γ quanta emission in naturally occurring osmium isotopes. This study took advantage of two ultra-low background HPGe detectors and one ultra-low background BEGe detector at the Gran Sasso National Laboratory (LNGS) of the INFN. Over almost 5 years of data were taken using high-purity osmium samples of approximately 173 g. The half-life limits set for α decays of 184 Os to the first 2 + 103.6 keV excited level of 180 W ( T 1/2  ≥ 9.3 × 10 15  yr) and of 186 Os to the first 2 + 100.1 keV of 182 W ( T 1/2  ≥ 4.8 × 10 17  yr) exceed substantially the present theoretical predictions that are at level of T 1/2  ~ (0.6–3) × 10 15  yr for 184 Os and T 1/2  ~ (0.3–2) × 10 17  yr for 186 Os. New half-life limits on the 2EC and ECβ + decay of 184 Os to the ground and excited levels of 184 W were set at level of T 1/2  > 10 16 –10 17  yr; a lower limit on the 2β – decay of 192 Os to the 2 + 316.5 keV excited level of 192 Pt was estimated as T 1/2  ≥ 6.1 × 10 20  yr. The half-life limits for 2α decay of 189 Os and 192 Os were set for the first time at level of T 1/2  > 10 20  yr.

Mechanism of ( E , Z )-1,3-diaryl-2-azadienes stereoselective formation from N -benzylketimines and acetylene in the superbasic KO t -Bu/DMSO environment is considered within the density functional theory on the example of N -benzyl-1-phenylethane-1-imine vinylation.

In this article, we present current results of the experiment searching for double beta decay of 106Cd with the help of an enriched 106CdWO4 crystal scintillator in coincidence with two CdWO4 scintillation detectors. The experiment is carried out at the Gran Sasso underground laboratory of the National Institute for Nuclear Physics (LNGS INFN, Italy). After 1075 days of data-taking, no double-beta effects were observed. New half-life limits have been set for the different modes and channels of double beta processes in 106Cd at the level of limT1/2=1020−1022 years.

The mechanism of intramolecular nucleophilic addition in αβ-unsaturated oximes, as well as the effect of the anionic center hydration with one and two water molecules on the activation barriers of intramolecular cyclization, was studied using the B2PLYP-D2/6-311+G**//B3LYP(D)/6-31+G* method with the solvation effects included within the SMD model. The activation barrier for nucleophilic addition of the anionic center of the oxime group to the carbon skeleton of 3-ethyl-N-hydroxy-5-phenylpenten-3-imine-2 is about 21 kcal/mol. During the hydration of the anionic center with one water molecule, a strong complex is formed, which increases the activation barrier by ∼ 6 kcal / mol. The addition of a second water molecule leads to an even higher activation barrier ( ΔG ‡ = 28 kcal/mol), but promotes the binding of the leaving hydroxide ion.

From 7 naturally occurring Nd isotopes, 5 are unstable in relation to α decay. If an excited level of the daughter nucleus is populated, or the daughter nucleus is unstable, γ quanta can be emitted. We used an ultra-low background spectrometry system with 4 high purity germanium (HPGe) detectors (about 225 cm 3 volume each) to search for such decays using a highly purified Nd-containing sample with mass of 2.381 kg. Measurements were performed at the INFN Gran Sasso underground laboratory (with an overburden of about 3600 m w.e.) during 51,237 h. Half-life limits for α decays of 143 Nd and 145 Nd were determined to be T 1/2 ( 143 Nd) > 1.1 × 10 20  year and T 1/2 ( 145 Nd) > 2.7 × 10 19  year at 90% C.L. This is an increase of three and two orders of magnitude, respectively, compared with the most restrictive values currently given in literature. A limit for α decay of 144 Nd to the excited level of 140 Ce with E exc  = 1596.2 keV was determined for the first time as T 1/2 ( 144 Nd →  140 Ce * ) > 9.3 × 10 20  year. Restriction for the α decay of 146 Nd to the excited level of 142 Ce with E exc  = 641.3 keV was increased by 3 orders of magnitude to T 1/2 ( 146 Nd →  142 Ce * ) > 1.4 × 10 21  year. For α and 2 α decays of 148 Nd, first T 1/2 limits were set as 4.2 × 10 18  year and 2.1 × 10 20  year, respectively.