Carrier relaxation in Si/SiO2_2 quantum dots

Carrier relaxation due to both optical and nonradiative intraband transitions in silicon quantum dots in SiO$_2$ has been considered. Interaction of confined holes with optical phonons has been studied. The Huang-Rhys factor is calculated for such transitions. The probability of intraband transition of a confined hole emitting several optical phonons is estimated.Comment: 8 pages, 2 figures, submitted as an extended abstract to the E-MRS Spring Meeting 200

Сервіси Blogger та YouTube у дистанційному курсі «Система управління базами даних Microsoft Access»

The article is devoted to the coverage of the course “Database management system Microsoft Access”, an educational blog review “The development of a creative child. ІCТ”, which is used as an auxiliary tool for promoting a course and teacher in the Internet, structural analysis of this blog is made. The channel location is set on YouTube video hosting and how it is used in the course on databases. Attention is drawn to the fact that theoretical and practical material is considered on real, implemented informational and analytical systems. To prepare students for the Olympiads and provide methodological help teachers of computer science are looking at tasks from databases that were offered at the All-Ukrainian Olympiads on Information Technologies, especially II, III and IV stages (offline and online Olympiads), which are located in open access to the blog and YouTube channel. The main focus of the article is devoted to the practical side of teaching teachers of computer science, experience in using the above technologies.Стаття присвячена висвітленню курсу «Система управління базами даних Microsoft Access», огляду освітнього блогу «Розвиток креативного дитини. ІCТ », який використовується в якості допоміжного інструменту для просування курсу і вчителі в Інтернеті, проведено структурний аналіз цього блогу. Розташування каналу встановлюється на відеохостингу YouTube і як воно використовується в курсі по базах даних. Звертається увага на те, що теоретичний і практичний матеріал розглядається на реальних, впроваджених інформаційно-аналітичних системах. Для підготовки студентів до олімпіад і надання методичної допомоги вчителя інформатики розглядають завдання з баз даних, які пропонувалися на Всеукраїнських олімпіадах з інформаційних технологій, особливо II, III і IV етапів (оффлайн і онлайн-олімпіади), які розташовані у відкритому доступі до блогу і каналу YouTube. Основна увага в статті приділено практичній стороні навчання викладачів інформатики, досвіду використання вищевказаних технологій

Thermally Activated Emission from Direct Bandgap-Like Silicon Quantum Dots

Due to the covalent character of silicon-carbon (Si-C) bond, C-linked molecules on the silicon quantum dot (SiQD) surface lead to dramatic changes in wavefunctions of the excited electron-hole pairs. Some of the optical transitions are strongly modified and attain direct bandgap-like character, giving rise to bright phonon-less fast decaying emission, while many other transitions keep their typical indirect bandgap character. It appears that in C-terminated SiQDs, with diameter larger than ∼2 nm, the most efficient recombination occurs from states slightly above the ground state. This leads to thermal activation of the fast emission, dominating the photoluminescence from these SiQDs. On the other hand, in the smallest SiQDs of less than 2 nm, the lowest excited states have the direct bandgap-like character and therefore their emission becomes gradually dominant at lower temperatures, as indeed supported by our experimental observations

Individual glow bands of Mn²⁺ ions photoluminescence in plastically deformed ZnS single crystals

The spectra of a photoluminescence (PL) in plastically deformed (PD) ZnS:Mn single crystals are investigated. It is shown that the PD processes cause change of a quantitative ratio between separate types of glow manganese centres (MC) as a result of their local symmetry rearrangement. After decomposing of PL integral spectra by individual PL bands using the cumulative distribution Gauss function, the nature of a ratio change between PL MC of different types is established. The individual with the peaking in the range 618-620 nm is discovered

Measurement of W Polarisation at LEP

The three different helicity states of W bosons produced in the reaction e+ e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation

Measurement of W Polarisation at LEP

The three different helicity states of W bosons produced in the reaction e+ e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation

Study of the e+e- -> Ze+e- process at LEP

The cross section of the process e+e- -> Ze+e is measured with 0.7fb^-1 of data collected with the L3 detector at LEP. Decays of the Z boson into quarks and muons are considered at centre-of-mass energies ranging from 183GeV up to 209GeV. The measurements are found to agree with Standard Model predictions, achieving a precision of about 10% for the hadronic channel

Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays

Bose-Einstein correlations of both neutral and like-sign charged pion pairs are measured in a sample of 2 million hadronic Z decays collected with the L3 detector at LEP. The analysis is performed in the four-momentum difference range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be smaller than that of charged pions. This result is in qualitative agreement with the string fragmentation model

Lambda and Sigma0 Pair Production in Two-Photon Collisions at LEP

Strange baryon pair production in two-photon collisions is studied with the L3 detector at LEP. The analysis is based on data collected at e+e- centre-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated luminosity of 844 pb-1. The processes gamma gamma -> Lambda Anti-lambda and gamma gamma -> Sigma0 Anti-sigma0 are identified. Their cross sections as a function of the gamma gamma centre-of-mass energy are measured and results are compared to predictions of the quark-diquark model

Search for a Higgs Boson Decaying to Weak Boson Pairs at LEP

A Higgs particle produced in association with a Z boson and decaying into weak boson pairs is searched for in 336.4 1/pb of data collected by the L3 experiment at LEP at centre-of-mass energies from 200 to 209 GeV. Limits on the branching fraction of the Higgs boson decay into two weak bosons as a function of the Higgs mass are derived. These results are combined with the L3 search for a Higgs boson decaying to photon pairs. A Higgs produced with a Standard Model e+e- --> Zh cross section and decaying only into electroweak boson pairs is excluded at 95% CL for a mass below 107 GeV