We demonstrate excitation of photosensitisers (PSs) by accelerated protons to produce fluorescence and singlet oxygen. Their fluorescence follows a pattern similar to the proton energy loss in ...matter, while proton-derived fluorescence spectra match the photon-induced spectra. PSs excited in dry gelatin exhibit enhanced phosphorescence, suggesting an efficient PSs triplet state population. Singlet oxygen measurements, both optically at ~1270 nm and through the photoproduct of protoporphyrin IX (PpIX), demonstrate cytotoxic singlet oxygen generation by proton excitation. The singlet oxygen-specific scavenger 1,4-diazabicyclo2.2.2octane (DABCO) abrogates the photoproduct formation under proton excitation, but cannot countermand the overall loss of PpIX fluorescence. Furthermore, in two cell lines, M059K and T98G, we observe differential cell death upon the addition of the PS cercosporin, while in U87 cells we see no effect at any proton irradiation dose. Our results pave the way for a novel treatment combining proton therapy and "proton-dynamic therapy" for more efficient tumour eradication.
The cascading 3.21 and 4.44 MeV electric quadrupole transitions have been observed from the Hoyle state at 7.65 MeV excitation energy in C12, excited by the C12(p,p′) reaction at 10.7 MeV proton ...energy. From the proton-γ−γ triple coincidence data, a value of Γrad/Γ=6.2(6)×10−4 was obtained for the radiative branching ratio. Using our results, together with ΓπE0/Γ from Eriksen et al. Phys. Rev. C 102, 024320 (2020) and the currently adopted Γπ(E0) values, the radiative width of the Hoyle state is determined as Γrad=5.1(6)×10−3 eV. This value is about 34% higher than the currently adopted value and will impact models of stellar evolution and nucleosynthesis.
The orbital M1 scissors resonance has been measured for the first time in the quasicontinuum of actinides. Particle-γ coincidences are recorded with deuteron and (3)He-induced reactions on (232)Th. ...The residual nuclei (231,232,233)Th and (232,233) Pa show an unexpectedly strong integrated strength of B(M1)=11-15μ(n)(2) in the E(γ)=1.0-3.5 MeV region. The increased γ-decay probability in actinides due to scissors resonance is important for cross-section calculations for future fuel cycles of fast nuclear reactors and may also have an impact on stellar nucleosynthesis.
Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction ...method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of 239Pu in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and γ-emission probabilities for the 240Pu (4He, 4He′) surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected γ-ray transitions, we measure the γ-emission probability. This enlarges the applicability of the surrogate-reaction method.
γ
-ray spectroscopy of fission fragments is a powerful method for studies of nuclear structure properties. Recent results on the spectroscopy of fission fragments, using the combination of the AGATA
...γ
-ray tracking array and the VAMOS++ large acceptance magnetic spectrometer at GANIL, are reported. A comparison of the performance of the large germanium detector arrays EXOGAM and AGATA illustrates the advances in
γ
-ray spectroscopy of fission fragments. Selected results are highlighted for prompt
γ
-ray spectroscopy studies, measurements of short lifetimes of excited states with the Recoil Distance Doppler-Shift method, using both AGATA and VAMOS++ and prompt-delayed
γ
-ray spectroscopy studies using AGATA, VAMOS++ and EXOGAM.
Understanding the evolution of level densities in the crossover from spherical to well-deformed nuclei has been a long-standing problem in nuclear physics. We measure nuclear level densities for a ...chain of neodymium isotopes 142,144−151Nd which exhibit such a crossover. These results represent the most complete data set of nuclear level densities to date for an isotopic chain between neutron shell-closure and towards mid-shell. We observe a strong increase of the level densities along the chain with an overall increase by a factor of ≈150 at an excitation energy of 6 MeV and saturation around mass 150. Level densities calculated by the shell model Monte Carlo (SMMC) are in excellent agreement with these experimental results. Based on our experimental and theoretical findings, we offer an explanation of the observed mass dependence of the level densities in terms of the intrinsic single-particle level density and the collective enhancement.
The
γ
-ray strength function (
γ
SF) and nuclear level density (NLD) have been extracted for the first time from inverse kinematic reactions with the Oslo method. This novel technique allows ...measurements of these properties across a wide range of previously inaccessible nuclei. Proton–
γ
coincidence events from the
d
(
86
Kr
,
p
γ
)
87
Kr
reaction were measured at iThemba LABS and the
γ
SF and NLD in
87
Kr
was obtained. The low-energy region of the
γ
SF is compared to shell-model calculations, which suggest this region to be dominated by M1 strength. The
γ
SF and NLD are used as input parameters to Hauser–Feshbach calculations to constrain
(
n
,
γ
)
cross sections of nuclei using the TALYS reaction code. These results are compared to
86
Kr
(
n
,
γ
)
data from direct measurements.
The structure of low-lying states in the light krypton isotopes 72Kr, 74Kr, and 76Kr has been studied with the finite-range Gogny D1S effective interaction via Hartree–Fock–Bogolyubov based ...calculations within a configuration-mixing formalism treating axial and triaxial quadrupole deformations. The good overall agreement with the experimental low-lying excitation spectra and matrix elements supports the shape coexistence scenario and a transition of the ground-state shape from oblate in 72Kr to prolate in 76Kr. The triaxial degree of freedom is shown to be crucial to reproduce the experimental data in general and the inversion of the oblate and prolate configurations in particular.
The validity of the Brink-Axel hypothesis, which is especially important for numerous astrophysical calculations, is addressed for 116,120,124Sn below the neutron separation energy by means of three ...independent experimental methods. The γ -ray strength functions (GSFs) extracted from primary γ -decay spectra following charged-particle reactions with the Oslo method and with the shape method demonstrate excellent agreement with those deduced from forward-angle inelastic proton scattering at relativistic beam energies. In addition, the GSFs are shown to be independent of excitation energies and spins of the initial and final states. The results provide a critical test of the generalized Brink-Axel hypothesis in heavy nuclei, demonstrating its applicability in the energy region of the pygmy dipole resonance.
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