• Book : 559()
• Pub. Date : 2025
• Page : pp.165597
• Keyword :

• Book : 605()
• Pub. Date : 2025
• Page : pp.155459
• Keyword :

• Book : 199(1)
• Pub. Date : 2025
• Page : pp.18-41
• Keyword :

• Book : 181()
• Pub. Date : 2025
• Page : pp.107350
• Keyword :

Abstract

A variational calculation for the energies of the ground and first excited states of a shallow donor impurity in bilayer graphene (BLG) with an open energy gap is presented in this study. It is shown that the binding energies of the lowest states and the distance between them can be tuned in the region of few tens of meV by changing the gap and tight binding parameter $ \gamma _{1} $, which is responsible for the nearest neighboring interlayer coupling. Based on the results obtained, the optical transition of an impurity electron from the ground to the first excited state in BLG is investigated. We find that the oscillator strength of the transition between the lowest energy states $ 1 S \rightarrow 2 P_{x} $ of a shallow donor also depends on the gap and tight binding parameter$ \gamma _{1} $, but is not sensitive to the value of the cutting parameter of the soft Coulomb potential that is proposed. The transitions between shallow impurity levels in BLG can serve as an alternative tunable source of terahertz radiation. The possibility to tune the energy levels of hydrogenic-like impurities can open new ways for either the creation of coherent superpositions of the energy states or the coherent population transfer between them by applying laser pulses.

• Book : 40(1)
• Pub. Date : 2025
• Page : pp.015012
• Keyword :

Abstract

The fusion excitation functions for 12 colliding systems with 96 ≤ Z1Z2 ≤ 608 are analyzed using coupled-channel (CC) calculations based on the M3Y double-folding (DF) potential supplemented with a repulsive potential that takes into account the incompressibility of the nuclear matter. We also applied the polarization effects of hot nuclear matter (PEHNM) on the calculations of the bare nucleus--nucleus interaction potential within the framework of the modified density-dependent Seyler-Blanchard (SB) approach in the T² approximation. Our results reveal that we obtain a nice description of the experimental data of different fusion systems when we use the present theoretical approach to calculate the energy-dependent values of the fusion cross sections. In this paper, the influence of the PEHNM on the surface diffuseness parameter of the Woods-Saxon (WS) potential is also studied. In order to reach this goal, we extract the corresponding values of this parameter based on the modified form of the DF potential (M3Y+Repulsion+polarization). We find that the extracted values are located in a range between a = 0.61 and 0.80 fm at different incident energies. It seems that the polarization effects of hot nuclear matter play a key role in describing the abnormally large values of the nuclear potential diffusenesses in the heavy-ion fusion reactions. Additionally, the regular decreasing trend for the diffuseness parameter of the nucleus-nucleus potential with the increase in the bombarding energies is also observed.

• Book : 77(3)
• Pub. Date : 2025
• Page : pp.035301
• Keyword :

Abstract

Evaporation residue cross-sections have been measured for ¹⁹F+^142,150Nd reactions in the energy range 15% below to 30% above the Coulomb barrier at the Inter-University Accelerator Centre, New Delhi, using the heavy ion reaction analyzer (HIRA). The measured fusion excitation functions were compared with the calculations using the coupled channels code CCFULL, including different couplings of the reactants. Fusion barrier distribution is extracted from the measured fusion cross-sections. Significant enhancement in fusion cross-section is observed in both reactions at sub-barrier energies. Enhancement is larger for the ¹⁹F+¹⁵⁰Nd reaction compared to the ¹⁹F+¹⁴²Nd reaction. The coupling of target excitations alone could not reproduce the observed fusion enhancement in both systems at sub-barrier energies. Calculations have been performed treating ¹⁹F as a vibrational as well as a rotational nucleus. Coupled channels calculations assuming ¹⁹F as a rotor reproduce the fusion excitation function reasonably well in both systems. However, these calculations do not require the coupling of transfer channels despite the presence of positive Q-value transfer channels in both systems. This warrants transfer cross-section measurements in both systems.

• Book : 52(1)
• Pub. Date : 2025
• Page : pp.015106
• Keyword :

Abstract

Cherenkov radiation is emitted during x-ray irradiation in a linear accelerator (LINAC). Cherenkov light contains many short wavelength components, including ultraviolet (UV) light, which is well-known for its bactericidal effects. A similar phenomenon is probable for human cancer cells. To assess the effect of Cherenkov light on cell death in x-ray irradiation, we employed simulations and UV cell survival data. We measured the survival rates of HeLa cells exposed to 254 nm (UVC) and 310 nm (UVB) light to determine the 50% lethal dose (LD50) required to kill 50% of the cells. For other wavelengths, we utilized literature values to establish the relationship between wavelength and LD50. Due to the broad range of the Cherenkov light spectrum, we need LD50 as a function of wavelength to estimate cell survival solely from Cherenkov light. A Monte Carlo simulation was used to calculate the fluence distribution of Cherenkov light in a 300 mm³ phantom comprised of soft tissue, both with and without absorption of visible light. The latter scenario is considered to be most influenced by Cherenkov light. By combining the fluence distribution and the wavelength-LD50 relationship, we determined the distribution of the survival rate. Our findings indicate that, in the absence of absorption, a radiation dose of approximately 90 Gy or greater is necessary for Cherenkov light to have any effect. As a result, the impact of Cherenkov light on cell survival can be considered negligible for typical dose of 2 Gy.

• Book : 11(1)
• Pub. Date : 2025
• Page : pp.015027
• Keyword :

• Book : 1054()
• Pub. Date : 2025
• Page : pp.122992
• Keyword :

• Book : 210()
• Pub. Date : 2025
• Page : pp.109604
• Keyword :