Proton Emission Research Articles

Electromagnetic-radiation effect on alpha decay

The effect of the electromagnetic radiation on the spontaneous charge emission from heavy atomic nuclei is estimated in a model which may be relevant for proton emission and alphaparticle decay in laser fields. Arguments are given that the electronic cloud in heavy atoms screens appreciably the electric field acting on the nucleus and the nucleus “sees” rather low fields. In these conditions, it is shown that the electromagnetic radiation brings second-order corrections in the electric field to the disintegration rate, with a slight anisotropy. These corrections give a small enhancement of the disintegration rate. The case of a static electric field is also discussed.

The partial widths of the 16.1 MeV 2+ resonance in 12C

.The 16.1 MeV 2^{+} resonance in 12C situated slightly above the proton threshold can decay by proton, alpha, and gamma emission. The partial width for proton emission cannot be directly measured due to the low proton energy and the small branching ratio. Instead it must be indirectly derived from other observables. However, due to several inconsistent data the derived partial width varies by almost a factor 2 depending on the data used. Here we trace the majority of this inconsistency to different measurements of the (p,alpha) cross sections. We have remeasured this cross section using modern large area silicon strip detectors allowing to measure all final state particles, which circumvents a normalization issue affecting some of the previous measurements. Based on this we determine Gamma_{p} = 21.0(13) eV. We discuss the implications for other observables related to the 16.1 MeV 2^{+} resonance and for isospin symmetry in the A = 12 system. In addition, we conclude that the dataset currently used for the NACRE and NACRE II evaluation of the 11B(p, 3alpha) reaction should be scaled by a factor of 2/3. This impacts the reaction rate accordingly.

Measuring dynamic fast ion spatial profiles with fusion protons in the Madison Symmetric Torus.

Neutral beam injected fast ions play a dominant role in both the field reversed configuration (FRC) at TAE Technologies and the Madison Symmetric Torus (MST) reversed field pinch (RFP), making fast ion diagnosis a major pillar of both research programs. And as strongly self-organized plasmas, the FRC and RFP similarly exhibit dynamic relaxation events which can redistribute fast ions. Recently, a collaboration between TAE Technologies and the University of Wisconsin was conducted to develop a method for measuring a fast changing fast ion spatial profile with a fusion proton detector and to investigate commonalities between the two plasmas. The steerable detector was designed and built at TAE and installed on MST. The fusion proton emission profile resulting from injection of a 25 kV deuterium neutral beam is measured with better than 5 cm spatial resolution and 100 μs temporal resolution over the course of several 10s of shots. The fast ion density profile, forward modeled by tracing the orbits of the 3 MeV protons through a reconstructed magnetic equilibrium, is observed to flatten during global magnetic tearing mode activity, dropping by 30% in the core and increasing by a similar amount at the edge. The equilibrium profile is observed to be consistent with measurements made with a collimated neutron detector.

Proton acceleration from vacuum-gapped double-foil target with low-contrast picosecond intense laser

Proton emissions from vacuum-gapped cascaded-ultrathin-foil targets irradiated with low-contrast intense picosecond laser pulses were measured. The maximum energy of the proton beam and the laser-to-proton energy conversion efficiency were both increased in comparison with those from the single-layer reference targets. A transition from plateau to exponential profile in proton energy spectral shape was found for the target with a front-foil thickness of above 500 nm. The measured annular x-ray emissions from both target front and rear sides indicate that the proton enhancement could be attributed to the modified preplasma distribution. A simple model and hydrodynamic simulations further show that the optimal acceleration occurs when the front shutter foil is right swelled onto the front surface of the rear source foil by the prepulses at the arrival of the main laser pulse. This cascaded thin-foil target design can be popularized in improving laser-driven proton beams for wide applications.

Calculation of proton radioactivity half-lives

We have investigated the proton radioactivity half-lives of 45 proton emitters within the framework of the Wentzel–Kramers–Brillouin (WKB) method by considering the Bohr–Sommerfeld quantization condition. The orientation angle dependent Woods–Saxon, Coulomb, and spin–orbit potentials and centrifugal potential have been used in calculations. We observed that using the orientation angle dependent formalism decreases the values of calculated half-lives.

An empirical formula for the half-lives of ground state and isomeric state one proton emission

An empirical formula for the half-life estimates for the one proton transition from ground state and isomeric states of 44 proton emitters is presented. The experimental data of the logarithm of the half-life corresponding to different $\ell$ -values, viz., $ \ell=0$ (8-emitters), $\ell =2$ (14-emitters), and $ \ell =5$ (19-emitters), of different proton emitters are separately fitted as a function of the charge number of the daughter and Q -value. The slopes and the intercept values from the obtained relations are found to vary linearly with the $\ell$ -values for the choices of a particular power value of 0.8 on the $ Z_{1}$ dependence. A linear relation of the slopes and intercepts is obtained as a function of $\ell$ , thus resulting in a simple formula involving only four parameters applicable to different $\ell$ -values. The proton emitters with $\ell =3$ (3-emitters) are not considered for the fitting. The obtained four parameter formula is applied to estimate the half-lives of the proton emitters with l = 3. The predictions of the formula are found to be in good agreement with the experimental data for the proton emitters with $\ell = 3$ . Our calculated values are compared with the available theoretical as well as empirical estimates of the experimentally known proton emitters. Further, the redictions for most possible proton emissions reported earlier are also compared with our calculations using the proposed formula. Because of the good overall agreement with the experimental data as well as with other theoretical/model predictions, this proposed formula may serve as a handy tool for planning new experiments.

Predictions of proton emissions from the isotopes of nuclei with Z = 100–136 using the Coulomb and proximity potential model for deformed nuclei

Using the Coulomb and proximity potential model for deformed nuclei (CPPMDN) the half-lives of proton emissions have been predicted for even and odd Z nuclei in the heavy and superheavy region with Z = 100–136 . The half-lives are also evaluated using the Coulomb and proximity potential model (CPPM) of Santhosh et al., in which both the parent and daughter nuclei are treated as spherical. The Geiger-Nuttall law (G-N) is studied for all cases of proton radioactivity under study. From the observed variation of G-N plots with respect to the Z value of the proton emitter, we obtained a new relation for proton decay half-lives. Using this relation the half-life is evaluated for the experimentally detected 44 proton emitters and is found to agree with the experimental data with a standard deviation of 0.8083s. Also, the half-lives are recalculated for all proton emitters in the heavy and superheavy region using the relation we obtained and we found that the half-lives evaluated using CPPMDN are closer to those obtained using the new relation than CPPM. Through the predictions of decay half-lives of the proton emitters in the heavy and superheavy region, the present phenomenological approach can be used satisfactorily to study alpha decay, cluster radioactivity and proton radioactivity.

Puzzling Two-Proton Decay of ^{67}Kr.

Ground-state two-proton (2p) radioactivity is a rare decay mode found in a few very proton-rich isotopes. The 2p decay lifetime and properties of emitted protons carry invaluable information on nuclear structure in the presence of a low-lying proton continuum. The recently measured 2p decay of ^{67}Kr turned out to be unexpectedly fast. Since ^{67}Kr is expected to be a deformed system, we investigate the impact of deformation effects on the 2p radioactivity. We apply the recently developed Gamow coupled-channel framework, which allows for a precise description of three-body systems in the presence of rotational and vibrational couplings. This is the first application of a three-body approach to a two-nucleon decay from a deformed nucleus. We show that deformation couplings significantly increase the 2p decay width of ^{67}Kr; this finding explains the puzzling experimental data. The calculated angular proton-proton correlations reflect a competition between 1p and 2p decay modes in this nucleus.

Charged particle emissions in high-frequency alternative electric fields

Proton emission, α decay, and cluster radioactivity play an important role in nuclear physics. We show that high-frequency alternative electric fields could deform Coulomb barriers that trap the charged particle, and raise the possibility of speeding up charged particle emissions. They could also cause anisotropic effects in charged particle emissions, and introduce additional terms in the Geiger–Nuttall laws. Our study may further suggest that, for proton emitters like 166Ir, when the electric field is strong, the dominant decay mode could be changed from α decay to proton emission. As high-frequency alternative electric fields correspond to high-frequency laser fields in the dipole approximation, our study could be viewed as a benchmark for future theoretical studies of charged particle emissions in realistic laser fields.

Proton acceleration measurements using fs laser irradiation of foils in the target normal sheath acceleration regime

We present experimental results obtained at the CELIA laboratory using the laser ECLIPSE to study proton acceleration from ultra-intense laser pulses. Several types of targets were irradiated with different laser conditions (focusing and prepulse level). Proton emission was characterized using time-of-flight detectors (SiC and diamond) and a Thomson parabola spectrometer. In all cases, the maximum energy of observed protons was of the order of 260 keV with a large energy spectrum. Such characteristics are typical of protons emitted following the target normal sheath acceleration mechanism for low-energy short-pulse lasers like ECLIPSE.

Intruder configurations of excited states in the neutron-rich isotopes P33 and P34

Author(s): Lubna, RS; Tripathi, V; Tabor, SL; Tai, PL; Kravvaris, K; Bender, PC; Volya, A; Bouhelal, M; Chiara, CJ; Carpenter, MP; Janssens, RVF; Lauritsen, T; McCutchan, EA; Zhu, S; Clark, RM; Fallon, P; MacChiavelli, AO; Paschalis, S; Petri, M; Reviol, W; Sarantites, DG | Abstract: Excited states in the neutron-rich isotopes P33 and P34 were populated by the O18+O18 fusion-evaporation reaction at Elab=24 MeV. The Gammasphere array was used along with the Microball particle detector array to detect γ transitions in coincidence with the charged particles emitted from the compound nucleus S36. The use of Microball enabled the selection of the proton emission channel. It also helped in determining the exact position and energy of the emitted proton; this was later employed in kinematic Doppler corrections. 16 new transitions and 13 new states were observed in P33 and 21 γ rays and 20 energy levels were observed in P34 for the first time. The nearly 4π geometry of Gammasphere allowed the measurement of γ-ray angular distributions leading to spin assignments for many states. The experimental observations for both isotopes were interpreted with the help of shell-model calculations using the (0+1)ω PSDPF interaction. The calculations accounted for both the 0p-0h and 1p-1h states reasonably well and indicated that 2p-2h excitations might dominate the higher-spin configurations in both P33 and P34.

Similarity-based attribute weighting methods via clustering algorithms in the classification of imbalanced medical datasets

In the fields of pattern recognition and machine learning, the use of data preprocessing algorithms has been increasing in recent years to achieve high classification performance. In particular, it has become inevitable to use the data preprocessing method prior to classification algorithms in classifying medical datasets with the nonlinear and imbalanced data distribution. In this study, a new data preprocessing method has been proposed for the classification of Parkinson, hepatitis, Pima Indians, single proton emission computed tomography (SPECT) heart, and thoracic surgery medical datasets with the nonlinear and imbalanced data distribution. These datasets were taken from UCI machine learning repository. The proposed data preprocessing method consists of three steps. In the first step, the cluster centers of each attribute were calculated using k-means, fuzzy c-means, and mean shift clustering algorithms in medical datasets including Parkinson, hepatitis, Pima Indians, SPECT heart, and thoracic surgery medical datasets. In the second step, the absolute differences between the data in each attribute and the cluster centers are calculated, and then, the average of these differences is calculated for each attribute. In the final step, the weighting coefficients are calculated by dividing the mean value of the difference to the cluster centers, and then, weighting is performed by multiplying the obtained weight coefficients by the attribute values in the dataset. Three different attribute weighting methods have been proposed: (1) similarity-based attribute weighting in k-means clustering, (2) similarity-based attribute weighting in fuzzy c-means clustering, and (3) similarity-based attribute weighting in mean shift clustering. In this paper, we aimed to aggregate the data in each class together with the proposed attribute weighting methods and to reduce the variance value within the class. Thus, by reducing the value of variance in each class, we have put together the data in each class and at the same time, we have further increased the discrimination between the classes. To compare with other methods in the literature, the random subsampling has been used to handle the imbalanced dataset classification. After attribute weighting process, four classification algorithms including linear discriminant analysis, k-nearest neighbor classifier, support vector machine, and random forest classifier have been used to classify imbalanced medical datasets. To evaluate the performance of the proposed models, the classification accuracy, precision, recall, area under the ROC curve, κ value, and F-measure have been used. In the training and testing of the classifier models, three different methods including the 50–50% train–test holdout, the 60–40% train–test holdout, and tenfold cross-validation have been used. The experimental results have shown that the proposed attribute weighting methods have obtained higher classification performance than random subsampling method in the handling of classifying of the imbalanced medical datasets.

Spectroscopy of excited states of unbound nuclei Ar30 and Cl29

Several states of proton-unbound isotopes $^{30}$Ar and $^{29}$Cl were investigated by measuring their in-flight decay products, $^{28}$S+proton+proton and $^{28}$S+proton, respectively. A refined analysis of $^{28}$S-proton angular correlations indicates that the ground state of $^{30}$Ar is located at $2.45^{+0.05}_{-0.10}$ MeV above the two-proton emission threshold. The theoretical investigation of the $^{30}$Ar ground state decay demonstrates that its mechanism has the transition dynamics with a surprisingly strong sensitivity of the correlation patterns of the decay products to the two-proton decay energy of the $^{30}$Ar ground state and the one-proton decay energy as well as the one-proton decay width of the $^{29}$Cl ground state. The comparison of the experimental $^{28}$S-proton angular correlations with those resulting from Monte Carlo simulations of the detector response illustrates that other observed $^{30}$Ar excited states decay by sequential emission of protons via intermediate resonances in $^{29}$Cl. Based on the findings, the decay schemes of the observed states in $^{30}$Ar and $^{29}$Cl were constructed. For calibration purposes and for checking the performance of the experimental setup, decays of the previously-known states of a two-proton emitter $^{19}$Mg were remeasured. Evidences for one new excited state in $^{19}$Mg and two unknown states in $^{18}$Na were found.

Fast Atom Ionization in Strong Electromagnetic Radiation

Abstract The Goeppert–Mayer and Kramers–Henneberger transformations are examined for bound charges placed in electromagnetic radiation in the non-relativistic approximation. The consistent inclusion of the interaction with the radiation field provides the time evolution of the wavefunction with both structural interaction (which ensures the bound state) and electromagnetic interaction. It is shown that in a short time after switching on the high-intensity radiation the bound charges are set free. In these conditions, a statistical criterion is used to estimate the rate of atom ionization. The results correspond to a sudden application of the electromagnetic interaction, in contrast with the well-known ionization probability obtained by quasi-classical tunneling through classically unavailable non-stationary states, or other equivalent methods, where the interaction is introduced adiabatically. For low-intensity radiation the charges oscillate and emit higher-order harmonics, the charge configuration is re-arranged and the process is resumed. Tunneling ionization may appear in these circumstances. Extension of the approach to other applications involving radiation-induced charge emission from bound states is discussed, like ionization of molecules, atomic clusters or proton emission from atomic nuclei. Also, results for a static electric field are included.

Erratum: Reinvestigation of the excited states in the proton emitter 151Lu : Particle-hole excitations across the N=Z=64 subshell [Phys. Rev. C 96 , 064307 (2017)

Erratum: Reinvestigation of the excited states in the proton emitter <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow /><mml:mn mathvariant="bold">151</mml:mn></mml:msup><mml:mi mathvariant="bold">Lu</mml:mi></mml:mrow></mml:math> : Particle-hole excitations across the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="bold-italic">N</mml:mi><mml:mo>=</mml:mo><mml:mi>Z</mml:mi><mml:mo>=</mml:mo><mml:mn>64</mml:mn></mml:mrow></mml:math> subshell [Phys. Rev. C <b>96</b> , 064307 (2017)

β-delayed γ decay of 20Mg and the [formula omitted] breakout reaction in Type I X-ray bursts

Certain astrophysical environments such as thermonuclear outbursts on accreting neutron stars (Type-I X-ray bursts) are hot enough to allow for breakout from the Hot CNO hydrogen burning cycles to the rapid proton capture (rp) process. An important breakout reaction sequence is 15O(α,γ)19Ne(p,γ)20Na and the 19Ne(p,γ)20Na reaction rate is expected to be dominated by a single resonance at 457 keV above the proton threshold in 20Na. The resonance strength and, hence, reaction rate depends strongly on whether this 20Na state at an excitation energy of 2647 keV has spin and parity of 1+ or 3+. Previous 20Mg (Jπ=0+) β+ decay experiments have relied almost entirely on searches for β-delayed proton emission from this resonance in 20Na to limit the log ft value and, hence, Jπ. However there is a non-negligible γ-ray branch expected that must also be limited experimentally to determine the log ft value and constrain Jπ. We have measured the β-delayed γ decay of 20Mg to complement previous β-delayed proton decay work and provide the first complete limit based on all energetically allowed decay channels through the 2647 keV state. Our limit confirms that a 1+ assignment for this state is highly unlikely.

Isolated proton bunch acceleration by a petawatt laser pulse

Often, the interpretation of experiments concerning the manipulation of the energy distribution of laser-accelerated ion bunches is complicated by the multitude of competing dynamic processes simultaneously contributing to recorded ion signals. Here we demonstrate experimentally the acceleration of a clean proton bunch. This was achieved with a microscopic and three-dimensionally confined near critical density plasma, which evolves from a 1 µm diameter plastic sphere, which is levitated and positioned with micrometer precision in the focus of a Petawatt laser pulse. The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV and narrow energy spread (down to 25%) showing almost no low-energetic background. Together with three-dimensional particle-in-cell simulations we track the complete acceleration process, evidencing the transition from organized acceleration to Coulomb repulsion. This reveals limitations of current high power lasers and viable paths to optimize laser-driven ion sources.

Predictions on the modes of decay of odd [formula omitted] superheavy isotopes within the range [formula omitted

The decay modes of 1051 odd Z superheavy nuclei within the range 105 ≤Z≤ 135, and their daughter nuclei are studied by comparing the alpha decay half-lives with the spontaneous fission half-lives. The alpha decay half-lives are calculated using the Coulomb and proximity potential model for deformed nuclei (CPPMDN) proposed by Santhosh et al. (2011) and the spontaneous fission half-lives are obtained with the shell-effect dependent formula of Santhosh et al. (Santhosh and Nithya, 2016). For a theoretical comparison, the alpha decay half-lives are also computed with the Coulomb and proximity potential model (CPPM), Viola–Seaborg–Sobiczewski semi-empirical relation (VSS), Universal curve of Poenaru et al. (UNIV), the analytical formula of Royer, and the Universal decay law of Qi et al. (UDL). The predicted decay modes and half-lives were compared with the available experimental results. The proton and neutron separation energies are calculated to identify those nuclei, which decay through proton and neutron emission. From the entire study of odd Z superheavy elements, it is seen that among 1051 nuclei, 233 nuclei exhibit proton emission and 18 nuclei exhibit neutron emission. 56 nuclei are stable against alpha decay with negative Q value for the decay. 92 nuclei show alpha decay followed by spontaneous fission and 9 nuclei show alpha decay followed by proton emission. 39 nuclei decay through full alpha chain and 595 nuclei decay through spontaneous fission. We hope that the study will be very useful for the future experimental investigations in this field.

A formula for half-life of proton radioactivity**Supported by National Natural Science Foundation of China (11435014, 11405223, 11675265, 11575112), the 973 Program of China (2013CB834401, 2013CB834405), National Key Program for S&T Research and Development (2016YFA0400501), the Knowledge Innovation Project (KJCX2-EW-N01) of Chinese Academy of Sciences, the Funds for Creative Research Groups of China (11321064) and the Youth Innovation Promotion Association of

We present a formula for proton radioactivity half-lives of spherical proton emitters with the inclusion of the spectroscopic factor. The coefficients in the formula are calibrated with the available experimental data. As an input to calculate the half-life, the spectroscopic factor that characterizes the important information on nuclear structure should be obtained with a nuclear many-body approach. This formula is found to work quite well, and in better agreement with experimental measurements than other theoretical models. Therefore, it can be used as a powerful tool in the investigation of proton emission, in particular for experimentalists.

Fabrication and characterization of porous opaque PMMA foils to be laser irradiated producing ion acceleration

In this study, the effect of pore size in the opaque poly(methyl methacrylate) and its composition is investigated by optical measurements as well as Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analyses. The enhancement of the absorption coefficient induced by the presence of micrometric beads makes these porous thin foils high absorbent to IR radiation and suitable to be laser irradiated in order to generate a hot plasma rich in proton emission. The presented results indicate that the high optical transparency of PMMA foils can be strongly reduced by the presence of the micrometric acrylic beads and that the presence of high Z-metallic nanoparticles, such as gold, embedded in the polymer enhances the acceleration of emitted ions. The fabricated advanced targets have been irradiated by lasers at low intensity (Messina University) and at high intensity (PALS Research Infrastructure in Prague) generating plasma accelerating high proton yield and energy.