scholarly journals OH level populations and accuracies of Einstein-<i>A</i> coefficients from hundreds of measured lines

2020 ◽  
Vol 20 (9) ◽  
pp. 5269-5292 ◽  
Author(s):  
Stefan Noll ◽  
Holger Winkler ◽  
Oleg Goussev ◽  
Bastian Proxauf
Keyword(s):  
Population Distribution ◽  
Rotational Temperature ◽  
Energy Levels ◽  
Population Data ◽  
Rotational Level ◽  
Echelle Spectrograph ◽  
High Quality ◽  
Emission Layer ◽  
Order Of Magnitude ◽  
Upper Level

Abstract. OH airglow is an important nocturnal emission of the Earth's mesopause region. As it is chemiluminescent radiation in a thin medium, the population distribution over the various roto-vibrational OH energy levels of the electronic ground state is not in local thermodynamic equilibrium (LTE). In order to better understand these non-LTE effects, we studied hundreds of OH lines in a high-quality mean spectrum based on observations with the high-resolution Ultraviolet and Visual Echelle Spectrograph at Cerro Paranal in Chile. Our derived populations cover vibrational levels between v=3 and 9, rotational levels up to N=24, and individual Λ-doublet components when resolved. As the reliability of these results critically depends on the Einstein-A coefficients used, we tested six different sets and found clear systematic errors in all of them, especially for Q-branch lines and individual Λ-doublet components. In order to minimise the deviations in the populations for the same upper level, we used the most promising coefficients from Brooke et al. (2016) and further improved them with an empirical correction approach. The resulting rotational level populations show a clear bimodality for each v, which is characterised by a probably fully thermalised cold component and a hot population where the rotational temperature increases between v=9 and 4 from about 700 to about 7000 K, and the corresponding contribution to the total population at the lowest N decreases by an order of magnitude. The presence of the hot populations causes non-LTE contributions to rotational temperatures at low N, which can be estimated quite robustly based on the two-temperature model. The bimodality is also clearly indicated by the dependence of the populations on changes in the effective emission height of the OH emission layer. The degree of thermalisation decreases with increasing layer height due to a higher fraction of the hot component. Our high-quality population data are promising with respect to a better understanding of the OH thermalisation process.

scholarly journals OH level populations and accuracies of Einstein-A coefficients from hundreds of measured lines

2019 ◽  
Author(s):  
Stefan Noll ◽  
Holger Winkler ◽  
Oleg Goussev ◽  
Bastian Proxauf
Keyword(s):  
Population Distribution ◽  
Rotational Temperature ◽  
Energy Levels ◽  
Population Data ◽  
Rotational Level ◽  
Echelle Spectrograph ◽  
High Quality ◽  
Emission Layer ◽  
Order Of Magnitude ◽  
Upper Level

Abstract. OH airglow is an important nocturnal emission of the Earth's mesopause region. As it is chemiluminescent radiation in a thin medium, the population distribution over the various roto-vibrational OH energy levels of the electronic ground state is not in local thermodynamic equilibrium (LTE). In order to better understand these non-LTE effects, we studied hundreds of OH lines in a high-quality mean spectrum based on observations with the high-resolution Ultraviolet and Visual Echelle Spectrograph at Cerro Paranal in Chile. Our derived populations cover vibrational levels between v = 3 and 9, rotational levels up to N = 24, and individual Λ-doublet components when resolved. As the reliability of these results critically depends on the Einstein-A coefficients used, we tested six different sets and found clear systematic errors in all of them, especially for Q-branch lines and individual Λ-doublet components. In order to minimise the deviations in the populations for the same upper level, we used the most promising coefficients from Brooke et al. (2016, JQSRT 168, 142) and further improved them with an empirical correction approach. The resulting rotational level populations show a clear bimodality for each v, which is characterised by a probably fully thermalised cold component and a hot population where the rotational temperature increases between v = 9 and 4 from about 700 to about 7,000 K and the corresponding contribution to the total population at the lowest N decreases by an order of magnitude. The presence of the hot populations causes non-LTE contributions to rotational temperatures at low N, which can be estimated quite robustly based on the two-temperature model. The bimodality is also clearly indicated by the dependence of the populations on changes in the effective emission height of the OH emission layer. The degree of thermalisation decreases with increasing layer height due to a higher fraction of the hot component. Our high-quality population data are promising with respect to a better understanding of the OH thermalisation process.

Properties of OH roto-vibrational level populations in the Earth's mesopause region

2020 ◽  
Author(s):  
Stefan Noll ◽  
Holger Winkler ◽  
Oleg Goussev ◽  
Bastian Proxauf
Keyword(s):  
Vibrational Level ◽  
Near Infrared ◽  
Population Distribution ◽  
Echelle Spectrograph ◽  
Emission Layer ◽  
Mesopause Region ◽  
Important Indicator ◽  
Infrared Wavelength ◽  
Cold Component ◽  
Upper Level

&lt;p&gt;Chemiluminescent OH airglow emission dominates the nighttime radiation of the Earth's atmosphere in the near-infrared wavelength regime. It is an important indicator of the state and variability of the mesopause region at about 90 km. However, the interpretation of the line intensities suffers from uncertainties in the knowledge of the complex roto-vibrational level population distribution, which is far from local thermodynamic equilibrium (LTE). For a better understanding, we investigated these populations in detail mainly based on a high-quality high-resolution mean spectrum from the UVES echelle spectrograph at Cerro Paranal in Chile, which allowed us to measure about 1,000 individual lines including numerous resolved &amp;#923;-doublet components between 560 and 1060 nm. As the quality of the currently available sets of OH Einstein-A coefficients is not sufficient for accurate population retrievals, we derived an improved set by a semi-empirical approach, which benefited from the measurement of multiple lines with the same upper level. The resulting populations indicate a clear bimodality for each vibrational level, which is characterised by a cold component indicating the ambient temperature at the OH layer heights and a hot non-LTE component dominating high rotational levels. Our promising two-population fits allowed us to constrain the non-LTE contributions to rotational temperatures based on lines with upper states with low rotational and fixed vibrational quantum number, which are widely used to estimate temperatures in the mesopause region. The bimodality is also clearly indicated by the different population changes depending on the effective altitude of the OH emission layer. Only the cold component significantly decreases with increasing altitude. Our results will be very useful for the challenging modelling of the OH thermalisation process.&lt;/p&gt;

scholarly journals OH populations and temperatures from simultaneous spectroscopic observations of 25 bands

2015 ◽  
Vol 15 (7) ◽  
pp. 3647-3669 ◽  
Author(s):  
S. Noll ◽  
W. Kausch ◽  
S. Kimeswenger ◽  
S. Unterguggenberger ◽  
A. M. Jones
Keyword(s):  
Rotational Temperature ◽  
High Sensitivity ◽  
Molecular Data ◽  
Temporal Variations ◽  
High Spectral Resolution ◽  
Astronomical Observation ◽  
Data Sets ◽  
Echelle Spectrograph ◽  
Emission Layer ◽  
Data Archives

Abstract. OH rotational temperatures are widely used to derive mesopause temperatures and their variations. Since most data sets are only based on a fixed set of lines of a single band, it is important to know possible systematic uncertainties related to the choice of lines. Therefore, a comprehensive study of as many OH bands as possible is desirable. For this purpose, astronomical echelle spectrographs at large telescopes are the most suitable instruments. They offer a wide wavelength coverage, relatively high spectral resolution, and high sensitivity. Moreover, since each ground-based astronomical observation has an imprint of the Earth's atmosphere, the data archives of large astronomical facilities are a treasure for atmospheric studies. For our project, we used archival data of the medium-resolution X-shooter echelle spectrograph operated by the European Southern Observatory at Cerro Paranal in Chile. The instrument can simultaneously observe all OH bands that are accessible from ground. We reduced and analysed a set of 343 high-quality spectra taken between 2009 and 2013 to measure OH line intensities and to derive rotational and vibrational temperatures of 25 bands between 0.58 and 2.24 μm. We studied the influence of the selected line set, OH band, upper vibrational level v′, and the molecular data on the derived level populations and temperatures. The rotational temperature results indicate differences by several degrees depending on the selection. The temperatures for bands of even and odd v′ show deviations which increase with v′. A study of the temporal variations revealed that the nocturnal variability pattern changes for v′ from 2 to 9. In particular, the spread of temperatures tends to increase during the night, and the time of the minimum temperature depends on v′. The vibrational temperatures depend on the range of v′ used for their determination, since the higher vibrational levels from 7 to 9 seem to be overpopulated compared to the lower levels. The vibrational temperature tends to increase during the night, while the intensity decreases. Our results support the assumption that the OH emission altitude depends on v′. Moreover, the emission layer appears to rise in the course of the night, which makes the OH thermalisation less efficient. The derived rotational temperatures and their change with v′ seem to be significantly affected by non-equilibrium populations.

scholarly journals OH populations and temperatures from simultaneous spectroscopic observations of 25 bands

2014 ◽  
Vol 14 (23) ◽  
pp. 32979-33043 ◽  
Author(s):  
S. Noll ◽  
W. Kausch ◽  
S. Kimeswenger ◽  
S. Unterguggenberger ◽  
A. M. Jones
Keyword(s):  
Rotational Temperature ◽  
High Sensitivity ◽  
Molecular Data ◽  
Temporal Variations ◽  
High Spectral Resolution ◽  
Astronomical Observation ◽  
Echelle Spectrograph ◽  
Emission Layer ◽  
Clear Trend ◽  
Data Archives

Abstract. OH rotational temperatures are widely used to derive mesopause temperatures and their variations. Since most data sets are only based on a fixed set of lines of a single band, it is important to know possible systematic uncertainties related to the choice of lines. Therefore, a comprehensive study of as many as possible OH bands is desirable. For this purpose, astronomical echelle spectrographs at large telescopes are the most suitable instruments. They offer a wide wavelength coverage, relatively high spectral resolution, and high sensitivity. Moreover, since each ground-based astronomical observation has an imprint of the Earth's atmosphere, the data archives of large astronomical facilities are a treasure for atmospheric studies. For our project, we used archival data of the medium-resolution X-shooter echelle spectrograph operated by the European Southern Observatory at Cerro Paranal in Chile. The instrument can simultaneously observe all OH bands that are accessible from ground. We reduced and analysed a set of 343 high-quality spectra taken between 2009 and 2013 to measure OH line intensities and to derive rotational and vibrational temperatures of 25 bands from OH(8-2) to OH(9-7). We studied the influence of the selected line set, OH band, upper vibrational level v′, and the molecular data on the derived level populations and temperatures. The rotational temperature results indicate differences by several degrees depending on the selection. There is a discrepancy for bands of even and odd v′, which increases with v′. A study of the temporal variations revealed that the v′ from to 2 to 9 show a clear trend in the change of the variability pattern. In particular, the spread of temperatures tends to increase during the night, and the time of the minimum temperature depends on v′. The vibrational temperatures depend on the range of v′ used for their determination, since the higher vibrational levels from 7 to 9 seem to be overpopulated compared to the lower levels. The vibrational temperature tends to increase during the night, while the intensity decreases. Our results support the assumption that the OH emission altitude depends on v′. Moreover, the emission layer appears to rise in the course of the night, which makes the OH thermalisation less efficient. The derived rotational temperatures and their change with v′ seem to be significantly affected by non-equilibrium populations.

scholarly journals Population cluster data to assess the urban-rural split and electrification in Sub-Saharan Africa

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Babak Khavari ◽  
Alexandros Korkovelos ◽  
Andreas Sahlberg ◽  
Mark Howells ◽  
Francesco Fuso Nerini
Keyword(s):  
World Bank ◽  
Population Distribution ◽  
Population Data ◽  
Sub Saharan Africa ◽  
Demographic And Health Surveys ◽  
Middle Income ◽  
Disease Response ◽  
The World Bank ◽  
The World ◽  
Urban Rural

AbstractHuman settlements are usually nucleated around manmade central points or distinctive natural features, forming clusters that vary in shape and size. However, population distribution in geo-sciences is often represented in the form of pixelated rasters. Rasters indicate population density at predefined spatial resolutions, but are unable to capture the actual shape or size of settlements. Here we suggest a methodology that translates high-resolution raster population data into vector-based population clusters. We use open-source data and develop an open-access algorithm tailored for low and middle-income countries with data scarcity issues. Each cluster includes unique characteristics indicating population, electrification rate and urban-rural categorization. Results are validated against national electrification rates provided by the World Bank and data from selected Demographic and Health Surveys (DHS). We find that our modeled national electrification rates are consistent with the rates reported by the World Bank, while the modeled urban/rural classification has 88% accuracy. By delineating settlements, this dataset can complement existing raster population data in studies such as energy planning, urban planning and disease response.

scholarly journals Developing an evidence assessment framework and appraising the academic literature on migrant health in Malaysia: a scoping review

BMJ Open ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. e041379
Author(s):  
Allard Willem de Smalen ◽  
Zhie X Chan ◽  
Claudia Abreu Lopes ◽  
Michaella Vanore ◽  
Tharani Loganathan ◽  
...  
Keyword(s):  
Scoping Review ◽  
Multiple Correspondence Analysis ◽  
Population Data ◽  
Good Health ◽  
Migrant Health ◽  
High Quality ◽  
Level Of Evidence ◽  
Cross Sectional ◽  
Academic Literature

BackgroundA large number of international migrants in Malaysia face challenges in obtaining good health, the extent of which is still relatively unknown. This study aims to map the existing academic literature on migrant health in Malaysia and to provide an overview of the topical coverage, quality and level of evidence of these scientific studies.MethodsA scoping review was conducted using six databases, including Econlit, Embase, Global Health, Medline, PsycINFO and Social Policy and Practice. Studies were eligible for inclusion if they were conducted in Malaysia, peer-reviewed, focused on a health dimension according to the Bay Area Regional Health Inequities Initiative (BARHII) framework, and targeted the vulnerable international migrant population. Data were extracted by using the BARHII framework and a newly developed decision tree to identify the type of study design and corresponding level of evidence. Modified Joanna Briggs Institute checklists were used to assess study quality, and a multiple-correspondence analysis (MCA) was conducted to identify associations between different variables.Results67 publications met the selection criteria and were included in the study. The majority (n=41) of studies included foreign workers. Over two-thirds (n=46) focused on disease and injury, and a similar number (n=46) had descriptive designs. The average quality of the papers was low, yet quality differed significantly among them. The MCA showed that high-quality studies were mostly qualitative designs that included refugees and focused on living conditions, while prevalence and analytical cross-sectional studies were mostly of low quality.ConclusionThis study provides an overview of the scientific literature on migrant health in Malaysia published between 1965 and 2019. In general, the quality of these studies is low, and various health dimensions have not been thoroughly researched. Therefore, researchers should address these issues to improve the evidence base to support policy-makers with high-quality evidence for decision-making.

The sensitization of laser-induced heat of Er3+ doped Y2O3 nanocrystals by codoped with Mn2+

2015 ◽  
Vol 29 (22) ◽  
pp. 1550158
Author(s):  
Yunfeng Bai ◽  
Minjie Luan ◽  
Linjun Li ◽  
Zhelong He ◽  
Dongyu Li
Keyword(s):  
Power Density ◽  
Thermal Emission ◽  
Energy Levels ◽  
Excitation Power ◽  
Threshold Power ◽  
Excitation Power Density ◽  
Ir Laser ◽  
Order Of Magnitude ◽  
Low Threshold ◽  
Density Threshold

Low threshold power density cw laser-induced heat has been observed in [Formula: see text] and [Formula: see text] codoped [Formula: see text] nanocrystals under excitation by a 980 nm IR laser. Codoped [Formula: see text] remarkably reduces the power density threshold of laser-induced heat compared with [Formula: see text] doped [Formula: see text] nanocrystals. When the excitation power density exceed [Formula: see text], [Formula: see text] codoped [Formula: see text] nanocrystals emit strong blackbody radiation. The thermal emission of [Formula: see text] should originate from the multiphonon relaxation between neighboring energy levels. One additional UC-PL enhancement is observed. The UC-PL intensity can be enhanced by an order of magnitude through high temperature calcination caused by light into heat.

scholarly journals Application of quinoline derivatives in third-generation photovoltaics

2021 ◽  
Author(s):  
Gabriela Lewinska ◽  
Jerzy Sanetra ◽  
Konstanty W. Marszalek
Keyword(s):  
Solar Cells ◽  
Polymer Solar Cells ◽  
Energy Levels ◽  
Photovoltaic Cells ◽  
Third Generation ◽  
Quinoline Derivatives ◽  
Emission Layer ◽  
Light Emitting ◽  
Photovoltaic Applications ◽  
Architecture And Design

AbstractAmong many chemical compounds synthesized for third-generation photovoltaic applications, quinoline derivatives have recently gained popularity. This work reviews the latest developments in the quinoline derivatives (metal complexes) for applications in the photovoltaic cells. Their properties for photovoltaic applications are detailed: absorption spectra, energy levels, and other achievements presented by the authors. We have also outlined various methods for testing the compounds for application. Finally, we present the implementation of quinoline derivatives in photovoltaic cells. Their architecture and design are described, and also, the performance for polymer solar cells and dye-synthesized solar cells was highlighted. We have described their performance and characteristics. We have also pointed out other, non-photovoltaic applications for quinoline derivatives. It has been demonstrated and described that quinoline derivatives are good materials for the emission layer of organic light-emitting diodes (OLEDs) and are also used in transistors. The compounds are also being considered as materials for biomedical applications.

scholarly journals Diffracted Light Contrast: Improving the Resolution of a Basic Light Microscope by an Order of Magnitude

2006 ◽  
Vol 14 (6) ◽  
pp. 10-15
Author(s):  
W. Barry Piekos
Keyword(s):  
Epithelial Cells ◽  
Light Microscope ◽  
Depth Of Field ◽  
High Quality ◽  
Surface Lattice ◽  
Buccal Epithelial Cells ◽  
Order Of Magnitude ◽  
Student Laboratory ◽  
Light Contrast ◽  
Very High

The discovery that the diffracted light from a convex edge can be used to form a very high-quality, shadowcast image on any light microscope has led to a device and method, diffracted-light contrast (DLC), which will allow shadowcast imaging to be routinely performed on student/laboratory microscopes (Piekos, 1999, 2003). The surface lattice of Surirella gema was easily resolved, and micrographs comparing the subcellular details of buccal epithelial cells viewed with DLC vs. Nomarski DIC showed that, on the microscopes used, DLC was superior in both the detail it rendered and depth of field. Although the images presented revealed DLC to be an excellent technique, the full capabilities of the technique were not known at the time.

Influence of Hot Electron Scattering and Electron–Phonon Interactions on Thermal Boundary Conductance at Metal/Nonmetal Interfaces

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Ashutosh Giri ◽  
Brian M. Foley ◽  
Patrick E. Hopkins
Keyword(s):  
Phonon Scattering ◽  
Energy Levels ◽  
Golden Rule ◽  
Energy Coupling ◽  
Hot Electron ◽  
Nonequilibrium Electron ◽  
Simplified Approach ◽  
Thermal Boundary Conductance ◽  
Order Of Magnitude ◽  
Unique Mechanism

It has recently been demonstrated that under certain conditions of electron nonequilibrium, electron to substrate energy coupling could represent a unique mechanism to enhance heat flow across interfaces. In this work, we present a coupled thermodynamic and quantum mechanical derivation of electron–phonon scattering at free electron metal/nonmetal substrate interfaces. A simplified approach to the Fermi's Golden Rule with electron energy transitions between only three energy levels is adopted to derive an electron–phonon diffuse mismatch model, that account for the electron–phonon thermal boundary conductance at metal/insulator interfaces increases with electron temperature. Our approach demonstrates that the metal-electron/nonmetal phonon conductance at interfaces can be an order of magnitude larger than purely phonon driven processes when the electrons are driven out of equilibrium with the phonons, consistent with recent experimental observations.

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