Ionization of Rydberg atoms by blackbody radiation

We have studied an ionization of alkali-metal Rydberg atoms by blackbody radiation (BBR). The results of the theoretical calculations of ionization rates of Li, Na, K, Rb and Cs Rydberg atoms are presented. Calculations have been performed for nS, nP and nD states which are commonly used in a variety of experiments, at principal quantum numbers n=8-65 and at the three ambient temperatures of 77, 300 and 600 K. A peculiarity of our calculations is that we take into account the contributions of BBR-induced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of measured ionization rates and shapes of their dependences on n. A Cooper minimum for BBR-induced transitions between bound Rydberg states of Li has been found. The calculated ionization rates are compared with our earlier measurements of BBR-induced ionization rates of Na nS and nD Rydberg states with n=8-20 at 300 K. A good agreement for all states except nS with n>15 is observed. Useful analytical formulas for quick estimation of BBR ionization rates of Rydberg atoms are presented. Application of BBR-induced ionization signal to measurements of collisional ionization rates is demonstrated.Comment: 36 pages, 16 figures. Paper is revised following NJP referees' comments and suggestion

Experimental implementation of a four-level N-type scheme for the observation of Electromagnetically Induced Transparency

A nondegenerate four-level N-type scheme was experimentally implemented to observe electromagnetically induced transparency (EIT) at the $^{87}$Rb D$_{2}$ line. Radiations of two independent external-cavity semiconductor lasers were used in the experiment, the current of one of them being modulated at a frequency equal to the hyperfine-splitting frequency of the excited 5P$_{3/2}$ level. In this case, apart from the main EIT dip corresponding to the two-photon Raman resonance in a three-level $\Lambda$-scheme, additional dips detuned from the main dip by a frequency equal to the frequency of the HF generator were observed in the absorption spectrum. These dips were due to an increase in the medium transparency at frequencies corresponding to the three-photon Raman resonances in four-level N-type schemes. The resonance shapes are analyzed as functions of generator frequency and magnetic field.Comment: 3 pages, 2 figure

Collisional and thermal ionization of sodium Rydberg atoms I. Experiment for nS and nD atoms with n=8-20

Collisional and thermal ionization of sodium nS and nD Rydberg atoms with n=8-20 has been studied. The experiments were performed using a two-step pulsed laser excitation in an effusive atomic beam at atom density of about 2 10^{10} cm^{-3}. Molecular and atomic ions from associative, Penning, and thermal ionization processes were detected. It has been found that the atomic ions were created mainly due to photoionization of Rydberg atoms by photons of blackbody radiation at the ambient temperature of 300K. Blackbody ionization rates and effective lifetimes of Rydberg states of interest were determined. The molecular ions were found to be from associative ionization in Na(nL)+Na(3S) collisions. Rate constants of associative ionization have been measured using an original method based on relative measurements of Na_{2}^{+} and Na^{+} ion signals.Comment: 23 pages, 10 figure

Microwave Spectroscopy of Cold Rubidium Atoms

The effect of microwave radiation on the resonance fluorescence of a cloud of cold $^{85}Rb$ atoms in a magnetooptical trap is studied. The radiation frequency was tuned near the hyperfine splitting frequency of rubidium atoms in the 5S ground state. The microwave field induced magnetic dipole transitions between the magnetic sublevels of the 5S(F=2) and 5S(F=3) states, resulting in a change in the fluorescence signal. The resonance fluorescence spectra were recorded by tuning the microwave radiation frequency. The observed spectra were found to be substantially dependent on the transition under study and the frequency of a repump laser used in the cooling scheme.Comment: 6 pages, 4 figure

Ion detection in the photoionization of a Rb Bose-Einstein condensate

Two-photon ionization of Rubidium atoms in a magneto-optical trap and a Bose-Einstein condensate (BEC) is experimentally investigated. Using 100 ns laser pulses, we detect single ions photoionized from the condenstate with a 35(10)% efficiency. The measurements are performed using a quartz cell with external electrodes, allowing large optical access for BECs and optical lattices.Comment: 14 pages, 7 figure

Signs and Symptoms of Central Nervous System Involvement and Their Pathogenesis in COVID-19 According to The Clinical Data (Review)

Detailed clinical assessment of the central nervous system involvement in SARS-CoV-2 infection is relevant due to the low specificity of neurological manifestations, the complexity of evaluation of patient complaints, reduced awareness of the existing spectrum of neurological manifestations of COVID-19, as well as low yield of the neurological imaging.The aim. To reveal the patterns of central nervous system involvement in COVID-19 and its pathogenesis based on clinical data.Among more than 200 primary literature sources from various databases (Scopus, Web of Science, RSCI, etc.), 80 sources were selected for evaluation, of them 72 were published in the recent years (2016-2020). The criteria for exclusion of sources were low relevance and outdated information.The clinical manifestations of central nervous system involvement in COVID-19 include smell (5-98% of cases) and taste disorders (6-89%), dysphonia (28%), dysphagia (19%), consciousness disorders (3-53%), headache (0-70%), dizziness (0-20%), and, in less than 3% of cases, visual impairment, hearing impairment, ataxia, seizures, stroke. Analysis of the literature data revealed the following significant mechanisms of the effects of highly contagious coronaviruses (including SARS-CoV-2) on the central nervous system: neurodegeneration (including cytokine- induced); cerebral thrombosis and thromboembolism; damage to the neurovascular unit; immune-mediated damage of nervous tissue, resulting in infection and allergy-induced demyelination.The neurological signs and symptoms seen in COVID-19 such as headache, dizziness, impaired smell and taste, altered level of consciousness, bulbar disorders (dysphagia, dysphonia) have been examined. Accordingly, we discussed the possible routes of SARS-CoV-2 entry into the central nervous system and the mechanisms of nervous tissue damage.Based on the literature analysis, a high frequency and variability of central nervous system manifestations of COVID-19 were revealed, and an important role of vascular brain damage and neurodegeneration in the pathogenesis of COVID-19 was highlighted

Особенности симптоматики и патогенеза повреждения центральной нервной системы при COVID-19 по данным клинических исследований (обзор)

Detailed clinical assessment of the central nervous system involvement in SARS-CoV-2 infection is relevant due to the low specificity of neurological manifestations, the complexity of evaluation of patient complaints, reduced awareness of the existing spectrum of neurological manifestations of COVID-19, as well as low yield of the neurological imaging.The aim. To reveal the patterns of central nervous system involvement in COVID-19 and its pathogenesis based on clinical data.Among more than 200 primary literature sources from various databases (Scopus, Web of Science, RSCI, etc.), 80 sources were selected for evaluation, of them 72 were published in the recent years (2016-2020). The criteria for exclusion of sources were low relevance and outdated information.The clinical manifestations of central nervous system involvement in COVID-19 include smell (5-98% of cases) and taste disorders (6-89%), dysphonia (28%), dysphagia (19%), consciousness disorders (3-53%), headache (0-70%), dizziness (0-20%), and, in less than 3% of cases, visual impairment, hearing impairment, ataxia, seizures, stroke. Analysis of the literature data revealed the following significant mechanisms of the effects of highly contagious coronaviruses (including SARS-CoV-2) on the central nervous system: neurodegeneration (including cytokine- induced); cerebral thrombosis and thromboembolism; damage to the neurovascular unit; immune-mediated damage of nervous tissue, resulting in infection and allergy-induced demyelination.The neurological signs and symptoms seen in COVID-19 such as headache, dizziness, impaired smell and taste, altered level of consciousness, bulbar disorders (dysphagia, dysphonia) have been examined. Accordingly, we discussed the possible routes of SARS-CoV-2 entry into the central nervous system and the mechanisms of nervous tissue damage.Based on the literature analysis, a high frequency and variability of central nervous system manifestations of COVID-19 were revealed, and an important role of vascular brain damage and neurodegeneration in the pathogenesis of COVID-19 was highlighted.Актуальность пристальной клинической оценки поражения центральной нервной системы вирусом SARS-CoV-2 определяется низкой специфичностью ряда неврологических симптомов, сложностью объективизации жалоб пациента, неоднородной осведомленностью и настороженностью по поводу имеющегося спектра неврологических симптомов COVID-19, низкой частотой патологических изменений по данным нейровизуализации.Цель обзора. Выявление особенностей симптоматики и патогенеза поражения центральной нервной системы при COVID-19 на основе анализа данных клинической практики.Из более 200 первично отобранных источников литературы различных баз данных (Scopus, Web of science, РИНЦ и др.) для анализа выбрали 80 источников, из них — 72 источника, опубликованных в течение последних лет (2016-2020 гг.). Критерием исключения источников служили малая информативность и устаревшие данные.Клиническая картина поражения центральной нервной системы при COVID-19 включает в себя: нарушение обоняния (5-98% случаев), нарушение вкусовой чувствительности (6-89%), дисфонию (28%), дисфагию (19%), количественные и качественные нарушения сознания (3-53%), головную боль (0-70%), головокружение (0-20%), менее 3% случаев — нарушение зрения, слуха, атаксию, судорожный приступ, инсульт. Анализ данных литературы позволил выделить следующие значимые механизмы воздействия высококонтагиозных коронавирусов (в том числе вируса SARS-CoV-2) на центральную нервную систему: нейродегенерация (в том числе цитокининдуцированная); церебральный тромбоз и церебральная тромбоэмболия; повреждение нейрососудистой единицы; иммуноопосредованное поражение нервной ткани, приводящее к развитию инфекционно-аллергического демие-линизирующего процесса.Рассмотрели симптомы поражения нервной системы при COVID-19, такие как головная боль, головокружение, нарушение обоняния и вкусовых ощущений, изменение уровня сознания, бульбарные нарушения (дисфагия, дисфония). Соответственно, проанализировали данные о возможных путях проникновения SARS-CoV-2 в центральную нервную систему и механизмы поражения нервной ткани.По результатам проведенного анализа отечественной и зарубежной литературы показали высокую частоту и полиморфность симптомов поражения центральной нервной системы, а также важную роль сосудистого поражения головного мозга и нейродегенерации в патогенезе COVID-19