H(II) centers in natural silica under repeated UV laser irradiations

We investigated the kinetics of H(II) centers (=Ge'-H) in natural silica under repeated 266nm UV irradiations performed by a Nd:YAG pulsed laser. UV photons temporarily destroy these paramagnetic defects, their reduction being complete within 250 pulses. After re-irradiation, H(II) centers grow again, and the observed recovery kinetics depends on the irradiation dose; multiple 2000 pulses re-irradiations induce the same post-irradiation kinetics of H(II) centers after each exposure cycle. The analysis of these effects allows us to achieve a deeper understanding of the dynamics of the centers during and after laser irradiation.Comment: Submitted to Journal of Non Crystalline Solid

Atomic electric dipole moments of He and Yb induced by nuclear Schiff moments

We have calculated the atomic electric dipole moments (EDMs) d of ^3He and ^{171}Yb induced by their respective nuclear Schiff moments S. Our results are d(He)= 8.3x10^{-5} and d(Yb)= -1.9 in units 10^{-17}S/(e{fm}^3)e cm. By considering the nuclear Schiff moments induced by the parity and time-reversal violating nucleon-nucleon interaction we find d(^{171}Yb)~0.6d(^{199}Hg). For ^3He the nuclear EDM coupled with the hyperfine interaction gives a larger atomic EDM than the Schiff moment. The result for ^3He is required for a neutron EDM experiment that is under development, where ^3He is used as a comagnetometer. We find that the EDM for He is orders of magnitude smaller than the neutron EDM. The result for Yb is needed for the planning and interpretation of experiments that have been proposed to measure the EDM of this atom.Comment: 4 page

Application of the zero-range potential model to positron annihilation on molecules

In this paper we use a zero-range potential (ZRP) method to model positron interaction with molecules. This allows us to investigate the effect of molecular vibrations on positron-molecule annihilation using the van der Waals dimer Kr2 as an example. We also use the ZRP to explore positron binding to polyatomics and examine the dependence of the binding energy on the size of the molecule for alkanes. We find that a second bound state appears for a molecule with ten carbons, similar to recent experimental evidence for such a state emerging in alkanes with twelve carbons.Comment: 14 pages, 6 figures, to be published in Nuclear Instruments and Methods

Many-electron tunneling in atoms

A theoretical derivation is given for the formula describing N-electron ionization of atom by a dc field and laser radiation in tunneling regime. Numerical examples are presented for noble gases atoms.Comment: 11 pages, 1 EPS figure, submitted to JETP (Jan 99

ВОСПАЛИТЕЛЬНЫЕ ИЗМЕНЕНИЯ ГОРТАНИ У ДЕТЕЙ С ОСТРЫМИ РЕСПИРАТОРНЫМИ ВИРУСНЫМИ ИНФЕКЦИЯМИ

This article is dedicated to the connection between laryngealinflammatory pathology and influenza/common cold.The purpose is to study the frequency of different form of laryngitis in children with common cold/ influenza, influenced of carried laryngitis within common cold on laryngeal structures and also the effectiveness of preventive measures against acute respiratory infections.Material and methods are the results of the examination (including laryngeal endoscopy) and analysis of medical files of 3169 patients and also the data of the annual report of one Moscow semi-clinic.Results. Inflammation laryngeal pathology was revealed in 152 (4,79%) cases, in 129 (84,9%) – non-obstructive. 91 patient (59,8%) belonged to category “frequently and often sick”. The recurrent episodes were seen in patients with both forms of laryngitis. Different laryngeal pathology (laryngitis, vocal nodules) was seen after common cold treatment with 43,5% obstructive and 18,63% non-obstructive laryngitis patient as well as dysphonia in 3-14% getting worse with the following common cold episodes. The preventative measures carried among patients with laryngitis allowed to decrease spreading of this pathology notwithstanding the fact of annual growth of common cold in children.Conclusion. Thus taking to account the high circulation of respiratory viruses the absence of specific preventative measures and the especial role of viruses in development all forms of laryngitis it is recommended to include special drugs in preventative techniques of laryngitis prophylactics. Different methods of non-specific prophylactic are effective in decreasing the amount of common cold episodes, decrease the frequency and severity all forms of laryngitis in children and also tend to stabilize/normalize the voice quality in different laryngeal pathology children.Статья посвящена взаимосвязи воспалительной патологии гортани и ОРВИ/гриппа.Цель: изучить частоту встречаемости различных форм ларингита у детей с респираторной острой вирусной инфекцией; влияние перенесенного ларингита на фоне ОРВИ на состояние структур гортани у детей, а также эффективность профилактических мероприятий против ОРВИ/гриппа в отношении различных форм ларингита.Материалы и методы: результаты обследования и анализа амбулаторных карт 3169 пациентов, а такжеданные годового отчета одной из детских поликлиник г. Москвы.Результаты: воспалительная патология гортани была выявлена у 152 (4,79%) пациентов, у 129 пациентов (84,9%) – необструктивная. 91 пациент (59,8%) относился к категории «часто и длительно болеющие» дети. Рецидивы наблюдались у пациентов с обеими формами ларингита (60,90% (ОЛ) и 62,02% (НОЛ)). Органическая патология гортани сохранялась после проведенного лечения у 43,5%, перенесших обструктивную форму, и 18,63%, перенесших необструктивную форму, как и изменение тембра голоса (у 3–14% пациентов), ухудшаясь при очередной респираторной вирусной инфекции. Профилактические мероприятия, проводимые среди пациентов, перенесших различные формы ларингита, позволили снизить распространенность данной патологии, несмотря на ежегодный рост заболеваемости ОРВИ у детей в аналогичный временной период.Заключение:учитывая высокую циркуляцию возбудителей респираторных инфекций, отсутствие специфической профилактики (кроме гриппа), а также особую роль вирусов в развитии различных форм ларингита, рекомендуется включать в технологии профилактики ОРВИ и гриппа препараты различных механизмов действия и форм выпуска, в том числе и в организованных детских коллективах. Различные методы неспецифической профилактики эффективны в снижении заболеваемости респираторными вирусными инфекциями, уменьшают частоту возникновения и тяжесть течения различных форм ларингита у детей, а также способствуют нормализации/улучшению качества голоса у детей с различной патологией гортани

Multiphoton detachment of electrons from negative ions

A simple analytical solution for the problem of multiphoton detachment from negative ions by a linearly polarized laser field is found. It is valid in the wide range of intensities and frequencies of the field, from the perturbation theory to the tunneling regime, and is applicable to the excess-photon as well as near-threshold detachment. Practically, the formulae are valid when the number of photons is greater than two. They produce the total detachment rates, relative intensities of the excess-photon peaks, and photoelectron angular distributions for the hydrogen and halogen negative ions, in agreement with those obtained in other, more numerically involved calculations in both perturbative and non-perturbative regimes. Our approach explains the extreme sensitivity of the multiphoton detachment probability to the asymptotic behaviour of the bound-state wave function. Rapid oscillations in the angular dependence of the $n$-photon detachment probability are shown to arise due to interference of the two classical trajectories which lead to the same final state after the electron emerges at the opposite sides of the atom when the field is close to maximal.Comment: 27 pages, Latex, and PostScript figures fig1.ps, fig2.ps, fig3.ps, accepted for publication in Phys. Rev.

On determination of electronic-vibro-rotational term values of diatomic molecules from measured wavenumbers

A method is proposed for determining rovibronic term values of diatomics from experimental data on the wavenumbers of electronic-vibro-rotational spectral lines. In contrast to existing techniques, the new one is based on the Rydberg-Ritz principle only. It is shown that a link between a set of rovibronic term values and a set of wavenumbers of observed rovibronic spectral lines appears when three and more different electronic-vibrational states are pairwise-connected by radiative transitions. The method differs from known techniques in several aspects, namely, it: 1) doesn't need any assumptions concerning an internal structure of a molecule; 2) doesn't involve any intermediate parameters (as molecular constants in traditional techniques); 3) gives an opportunity to use in one-stage optimization procedure all available experimental data obtained for various band systems, by various authors, and in various works; 4) provides in an interactive mode the opportunity to select the experimental values, eliminating rough errors, to revise wrong identifications of spectral lines and to compare various sets of experimental data for mutual consistency; 5) allows to obtain not only an optimal set of rovibronic term values, but also the error bars depending on quantity and quality of existing experimental data. Necessary precondition for use of this method is a preliminary identification of electronic-vibro-rotational lines to certain electronic-vibro-rotational radiative transitions. For this purpose one has to use traditional methods of the analysis of molecular spectra.Comment: 10 pages, 2 figures, in Russia