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

<p>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 Λ-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.</p>

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.

A full decade (2009-2019) of continuous nightglow observations from the NUV to the NIR

2021 ◽  
Author(s):  
Wolfgang Kausch ◽  
Stefan Noll ◽  
Stefan Kimeswenger ◽  
Sabine Moehler
Keyword(s):  
Wavelength Range ◽  
Near Infrared ◽  
Data Set ◽  
Mesopause Region ◽  
Infrared Wavelength ◽  
Near Ultraviolet ◽  
Very Large Telescope ◽  
Medium Resolution ◽  
Wide Wavelength Range ◽  
Atomic Lines

&lt;p&gt;The airglow emission of the mesopause region comprises molecular bands and atomic lines in the near-ultraviolet to the near-infrared wavelength range, e.g. the prominent roto-vibrational OH bands, a weak FeO/NiO continuum, the green OI line, the NaD doublet and some others. Since ground-based astronomical facilites observe through the Earth's atmosphere, the fingerprint of these emissions is visible in astronomical spectra taken with a telescope.&lt;br&gt;We have assembled a comprehensive data set of about 100,000 spectra in total taken between 1st of October 2009 and 30th of September 2019 with the X-shooter spectrograph, which is mounted at the Very Large Telescope in the Chilean Atacama desert (24.6&amp;#176;S, 70.4&amp;#176;W). This instrument provides medium-resolution spectra covering the entire wavelength range from 0.3 to 2.5&amp;#956;m simultaneously by incorporating three spectral subranges (UVB: 0.3-0.56&amp;#956;m; VIS: 0.56-1.02&amp;#956;m; NIR: 1.02-2.5&amp;#956;m).&lt;/p&gt;&lt;p&gt;The X-shooter instrument was continuously in operation during the covered period and frequently used by astronomers. Thus, the temporal coverage of the available observations is very dense for astronomical data allowing various airglow studies on time scales from minutes to a full decade. Due to the simultaneously observed wide wavelength range, individual airglow emitters as well as correlations between them can be investigated in detail (cf. Noll et al. 2021, this session, for more information).&lt;/p&gt;&lt;p&gt;In this presentation we describe the properties and the calibration of this unique data set.&lt;/p&gt;

Model studies on vibrationally-rotationally excited hydroxyl molecules in the mesopause region

2020 ◽  
Author(s):  
Justus Notholt ◽  
Holger Winkler ◽  
Stefan Noll
Keyword(s):  
Near Infrared ◽  
Measurement Data ◽  
Model Parameters ◽  
Chemical Production ◽  
Echelle Spectrograph ◽  
Mesopause Region ◽  
Rotational States ◽  
Model Studies ◽  
Temperature Component ◽  
Remotely Sense

&lt;p&gt;One of the standard methods to remotely sense the temperature of the mesopause region is based on spectroscopic measurements of near-infrared emissions of vibrationally-rotationally excited hydroxyl molecules, and to calculate &amp;#160;rotational temperatures. For the interpretation of the retrieved temperatures, the aspect of rotational thermalization is of great importance. We present results of a first-principle kinetic model of vibrationally-rotationally excited hydroxyl molecules which accounts for chemical production and loss processes as well as radiative and collision-induced vibrational-rotational transitions. The model allows one to assess deviations of the rotational populations from local thermodynamic equilibrium, and to identify the key parameters which control the rotational thermalization processes. The model simulations reproduce the observed bimodality in temperatures, i.e. a cold temperature component dominating the population of low rotational states, and a hot temperature component dominating higher states. The model results are compared to measurement data from the UVES echelle spectrograph at Cerro Paranal in Chile (Presentation EGU2020-3169) which allows us to confine free model parameters such as the rotational state changes in vibrational quenching process.&lt;/p&gt;

scholarly journals Stripping of the Positive-tone Diazonaphthoquinone / Novolak Resist using Laser Irradiation from Visible to Near Infrared Wavelength

2012 ◽  
Vol 25 (6) ◽  
pp. 741-746 ◽  
Author(s):  
Tomosumi Kamimura ◽  
Hiroki Muraoka ◽  
Yuki Yamana ◽  
Yoshiaki Matsura ◽  
Hideo Horibe
Keyword(s):  
Laser Irradiation ◽  
Near Infrared ◽  
Infrared Wavelength

Hybridization-sensitive fluorescence control in the near-infrared wavelength range

2011 ◽  
Vol 9 (11) ◽  
pp. 4199 ◽  
Author(s):  
Shuji Ikeda ◽  
Hiroyuki Yanagisawa ◽  
Akiko Nakamura ◽  
Dan Ohtan Wang ◽  
Mizue Yuki ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Near Infrared ◽  
Infrared Wavelength

Growth and Properties of Pulsed Laser Deposited K3Li2Nb5O15 Thin Films

2007 ◽  
Vol 351 ◽  
pp. 184-188 ◽  
Author(s):  
Zu Sheng Zhan ◽  
Yan Sheng Gong ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Near Infrared ◽  
Ambient Pressure ◽  
Tungsten Bronze ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Optical Studies ◽  
Tetragonal Tungsten Bronze ◽  
Infrared Wavelength ◽  
Optimum Parameters ◽  
Substrate Temperatures

Potassium lithium niobate (KLN: K3Li2Nb5O15) films have been deposited on quartz glass by Pulsed laser deposition (PLD) technique using a stoichiometric KLN target as starting materials. By investigating the effects of both the oxygen pressure and the substrate temperature on the structure of KLN films, optimum parameters have been identified for the growth of high-quality KLN films. At 10Pa oxygen ambient pressure, tetragonal tungsten-bronze-type structure of KLN films with (310) preferred orientation can be achieved at substrate temperatures in the range of 700-800°C. Optical studies indicate that the films are highly transparent in the visible-near-infrared wavelength range.

scholarly journals Mode Sensitivity Exploration of Silica–Titania Waveguide for Refractive Index Sensing Applications

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7452
Author(s):  
Muhammad A. Butt ◽  
Andrzej Kaźmierczak ◽  
Cuma Tyszkiewicz ◽  
Paweł Karasiński ◽  
Ryszard Piramidowicz
Keyword(s):  
Refractive Index ◽  
High Performance ◽  
Near Infrared ◽  
Sol Gel ◽  
Cost Effective ◽  
Dip Coating ◽  
Infrared Wavelength ◽  
Refractive Index Sensing ◽  
Sensing Applications ◽  
Coating Method

In this paper, a novel and cost-effective photonic platform based on silica–titania material is discussed. The silica–titania thin films were grown utilizing the sol–gel dip-coating method and characterized with the help of the prism-insertion technique. Afterwards, the mode sensitivity analysis of the silica–titania ridge waveguide is investigated via the finite element method. Silica–titania waveguide systems are highly attractive due to their ease of development, low fabrication cost, low propagation losses and operation in both visible and near-infrared wavelength ranges. Finally, a ring resonator (RR) sensor device was modelled for refractive index sensing applications, offering a sensitivity of 230 nm/RIU, a figure of merit (FOM) of 418.2 RIU−1, and Q-factor of 2247.5 at the improved geometric parameters. We believe that the abovementioned integrated photonics platform is highly suitable for high-performance and economically reasonable optical sensing devices.

scholarly journals Near-infrared wavelength intersubband transitions in GaN∕AlN short period superlattices

2006 ◽  
Vol 89 (15) ◽  
pp. 151112 ◽  
Author(s):  
E. A. DeCuir ◽  
Emil Fred ◽  
B. S. Passmore ◽  
A. Muddasani ◽  
M. O. Manasreh ◽  
...  
Keyword(s):  
Near Infrared ◽  
Intersubband Transitions ◽  
Infrared Wavelength ◽  
Short Period ◽  
Short Period Superlattices
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