RELATIVISTIC CALCULATION OF THE RADIATIVE TRANSITION PROBABILITIES AND LIFETIMES OF EXCITED STATES FOR THE RUBIDIUM ATOM IN A BLACK-BODY RADIATION FIELD

We present the results of relativistic calculation of the radiative transition probabilities and excited states lifetimes for a heavy Rydberg atomic systems in a black-body (thermal) radiation field on example of the rubidium. As theoretical approach we apply the combined generalized relativistic energy approach and relativistic many-body perturbation theory with ab initio Dirac zeroth approximation. There are obtained the calculational data for the radiative transition probabilities and excited states lifetimes, in particular, the rubidium atom in the Rydberg states with principal quantum number n=10-100. It is carried out the comparison of obtained theoretical data on the effective lifetime for the group of Rydberg nS states of the rubidium atom at a temperature of T = 300K with experimental data as well as data of alternative theoretical calculation based on the improved quasiclassical model. It is shown that the accuracy of the theoretical data on the radiative transition probabilities and excited states lifetimes is provided by a correctness of the corresponding relativistic wave functions and accounting for the exchange-correlation effects.

On the effective lifetime of Bs → μμγ

We consider the $$ {B}_s^0 $$ B s 0 → μ+μ−γ effective lifetime, and the related CP-phase sensitive quantity $$ {A}_{{\Delta \Gamma}_s}^{\mu \mu \gamma} $$ A ΔΓ s μμγ , as a way to obtain qualitatively new insights on the current B-decay discrepancies. Through a fit comparing pre- to post-Moriond-2021 data we identify a few theory benchmark scenarios addressing these discrepancies, and featuring large CP violation in addition. We then explore the possibility of telling apart these scenarios with $$ {A}_{{\Delta \Gamma}_s}^{\mu \mu \gamma} $$ A ΔΓ s μμγ , once resonance-modeling and form-factor uncertainties are taken into account. We do so in both regions of low and high invariant di-lepton mass-squared q2. For low q2, we show how to shape the integration range in order to reduce the impact of the ϕ-resonance modelling on the $$ {A}_{{\Delta \Gamma}_s}^{\mu \mu \gamma} $$ A ΔΓ s μμγ prediction. For high q2, we find that the corresponding pollution from broad-charmonium resonances has a surprisingly small effect on $$ {A}_{{\Delta \Gamma}_s}^{\mu \mu \gamma} $$ A ΔΓ s μμγ . This is due to a number of cancellations, that can be traced back to the complete dominance of semi-leptonic operator contributions for high q2 — at variance with low q2 — and to $$ {A}_{{\Delta \Gamma}_s}^{\mu \mu \gamma} $$ A ΔΓ s μμγ behaving like a ratio-of-amplitudes observable. Our study suggests that $$ {A}_{{\Delta \Gamma}_s}^{\mu \mu \gamma} $$ A ΔΓ s μμγ is — especially at high q2 — a potentially valuable probe of short-distance CP-violating effects in the very same Wilson coefficients that are associated to current b → s discrepancies. Its discriminating power, however, relies on progress in form-factor uncertainties. Interestingly, high q2 is the region where $$ {B}_s^0 $$ B s 0 → μ+μ−γ is already being accessed experimentally, and the region where form factors are more accessible through non-perturbative QCD methods.

Estimated Effective Lifetime Risks of Radiation-Induced Thyroid Cancer in Computed Tomography (CT) Brain Examination

Thyroid is one of the most radiosensitive organs in the human body. Although the scanning range of brain computed tomography (CT) does not include lower neck region, there is possibility for thyroid to be irradiated due to scattered radiation because of its location near to the external beam collimation. The objective of this study was to evaluate effective lifetime risk of radiation-induced thyroid cancer in young adults following brain CT examination. A total of 306 patient data within the age range between 18 and 39 years old were retrospectively analysed. Absorbed dose of the thyroid organ was obtained through the input of data using WAZA- ARI v2. Effective lifetime risk was calculated by multiplying equivalent dose of the thyroid organ with the lifetime attributable cancer risk adapted from Biological Effects in Ionising Radiation (BEIR) Report V11. The effective lifetime risks were recorded as 0.45 ± 0.70 per 100 000 and 0.93 ± 1.52 per 100 000 for single and multiple exposures, respectively. In terms of gender, woman data (0.99 ± 0.76; 1.95 ± 2.15) were found higher as compared to man data (0.13 ± 0.39; 0.35 ± 0.45) for both single and multiple exposure. The percentage difference of effective lifetime risks between single and multiple exposures was up to 107%. The effective lifetime risk noted in this study may be low, however, the long-term risk of cancer development should be considered. This study serves as preliminary reference when revising clinical protocol especially in those involving repeated exposures in young adult patients. Future study should include other radiosensitive organs exploring the effective lifetime risk of radiation induced cancer following CT procedure.

High Performance Predictable Quantum Efficient Detector Based on Induced-Junction Photodiodes Passivated with SiO2/SiNx

We performed a systematic study involving simulation and experimental techniques to develop induced-junction silicon photodetectors passivated with thermally grown SiO2 and plasma-enhanced chemical vapor deposited (PECVD) SiNx thin films that show a record high quantum efficiency. We investigated PECVD SiNx passivation and optimized the film deposition conditions to minimize the recombination losses at the silicon–dielectric interface as well as optical losses. Depositions with varied process parameters were carried out on test samples, followed by measurements of minority carrier lifetime, fixed charge density, and optical absorbance and reflectance. Subsequently, the surface recombination velocity, which is the limiting factor for internal quantum deficiency (IQD), was obtained for different film depositions via 2D simulations where the measured effective lifetime, fixed charge density, and substrate parameters were used as input. The quantum deficiency of induced-junction photodiodes that would be fabricated with a surface passivation of given characteristics was then estimated using improved 3D simulation models. A batch of induced-junction photodiodes was fabricated based on the passivation optimizations performed on test samples and predictions of simulations. Photodiodes passivated with PECVD SiNx film as well as with a stack of thermally grown SiO2 and PECVD SiNx films were fabricated. The photodiodes were assembled as light-trap detector with 7-reflections and their efficiency was tested with respect to a reference Predictable Quantum Efficient Detector (PQED) of known external quantum deficiency. The preliminary measurement results show that PQEDs based on our improved photodiodes passivated with stack of SiO2/SiNx have negligible quantum deficiencies with IQDs down to 1 ppm within 30 ppm measurement uncertainty.

Influence of low-energy proton irradiation on the effective lifetime in the space charge region of silicon n+-p junctions

The effect of low-energy proton irradiation on the pulse characteristics of silicon n+-p-p+ structures is analyzed. It is shown that irradiation with protons with an energy of 180 keV and a dose of 1015 cm−2 creates a region with an effective lifetime of 5.5·10−8 s in the space charge region of the n+-p junction. Such elements can be used to create high-speed photodiodes with an operating modulation frequency of 18 MHz.

Modelling of voltage changes in the n-p junction in the pulse mode

The article presents the results of modeling the effect of the effective lifetime in the space charge region (SCR) of the n+-p junction on the impulse characteristics of silicon structures. The model is based on solving the fundamental system of differential equations for the transport of charge carriers in inhomogeneous semiconductors. The calculated time dependences of the voltage change in the SCR for a pulse voltage change on the n+-p-p+ structure correspond to the experimental data.

Highly oxygenated organic molecules produced by the oxidation of benzene and toluene in a wide range of OH exposure and NO_<i>x</i> conditions

Oxidation of aromatic volatile organic compounds (VOCs) leads to the formation of tropospheric ozone and secondary organic aerosol, for which gaseous oxygenated products are important intermediates. We show, herein, the experimental results of highly oxygenated organic molecules (HOMs) produced by the oxidation of benzene and toluene in a wide range of OH exposure and NOx conditions. The results suggest that multigeneration OH oxidation plays an important role in the product distribution, which likely proceeds more preferably via H subtraction than OH addition for early generation products from light aromatics. More oxygenated products present in our study than in previous flow tube studies, highlighting the impact of experimental conditions on product distributions. The formation of dimeric products, however, was suppressed and might be unfavorable under conditions of high OH exposure and low NOx in toluene oxidation. Under high-NOx conditions, nitrogen-containing multifunctional products are formed, while the formation of other HOMs is suppressed. Products containing two nitrogen atoms become more important as the NOx level increases, and the concentrations of these compounds depend significantly on NO2. The highly oxygenated nitrogen-containing products might be peroxyacyl nitrates, implying a prolonged effective lifetime of RO2 that facilitates regional pollution. Our results call for further investigation on the roles of high-NO2 conditions in the oxidation of aromatic VOCs.

Does model complexity improve pricing accuracy? The case of CoCos

In this study, we analyze whether model complexity improves accuracy of CoCo pricing models. We compare the out-of-sample pricing ability of four models using a broad dataset that contains all CoCos which were issued between January 1, 2013 and May 31, 2016 in euros. The regarded models include the standard model from De Spiegeleer and Schoutens (J Deriv 20:27–36, 2012), a modified version enriched by credit risk, an extended model that accounts for the effective lifetime of the CoCo, and a trading model, solely based on historic market prices but no pricing theory at all. For a normal market environment, the simple trading model provides a higher pricing accuracy than the theory-based models. Under distress, however, a theory-based model with a sufficiently high complexity is required.

Nanostructure, optical and optoelectronic properties of silver nanoparticle-based chemical etching on monocrystalline silicon for solar cell applications

Introduction: Silver nanoparticle (AgNP)-based chemical etching is applied to produce silicon nanowires (SiNWs) on monocrystalline silicon. Methods: The effect of etching time on the production of silicon nanowires and on optical and optoelectronic properties was studied. Results: Using this approach, surface recombination velocity (Seff) and the effective lifetime (τeff) evolution of SiNWs after passivation were improved, and SiNWs obtained in the optimal time of 20 min, exhibited shallow reflection of 1% in the wavelength range of 300–1100 nm. Conclusion: Thus, passivated solar cell-based SiNWs in an HF/HNO3/H2O solution were essential for increasing the efficiency of solar cell-based SiNWs from 9% to nearly 15%.