scholarly journals On the total absorption cross-section of galaxies - II: The case of λ cosmologies and covering factor variation

1998 ◽  
pp. 3-7
Author(s):  
M.M. Cirkovic ◽  
S. Samurovic
Keyword(s):  
Cosmological Constant ◽  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Observational Cosmology ◽  
Total Absorption ◽  
Absorption Cross ◽  
Normal Galaxies ◽  
Previous Discussion ◽  
Inner Parts

In this work we expand the previous discussion of the plausibility of hypothesis of origin of the Ly? forest absorption systems in haloes of normal galaxies in connection with the HubbleDeepField (HDF) data. It is shown that simplistic approach to absorption cross-sections of galaxies with no luminosity scaling is in strong violation of empirical statistics up to redshift of z ? 3.5. Realistic variation of the covering factor in order to account for its increase in the inner parts of observed haloes leads to even bigger discrepancy. Cosmologies with finite cosmological constant are briefly discussed and compared to ? = 0 case. Ways to improve agreement with observational data are indicated. This problem is highly illustrative of the basic tenets of modern observational cosmology.

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

scholarly journals Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

2020 ◽  
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martin ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Time Resolved ◽  
Flight Mass Spectrometry ◽  
Iodine Oxides ◽  
Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) ×  10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3 

scholarly journals Determination of the absorption cross sections of higher-order iodine oxides at 355 and 532 nm

2020 ◽  
Vol 20 (18) ◽  
pp. 10865-10887
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martín ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Particle Formation ◽  
Absorption Cross ◽  
Iodic Acid ◽  
Iodine Oxides ◽  
532 Nm

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layers and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x=2, 3, 5, y=1–12 at λ=355 nm by combining pulsed laser photolysis of I2∕O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross-section determinations are those presenting the strongest signals in the mass spectra, where signals containing four iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355nm,IO= (1.2±0.1) ×10-18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are σ355nm,I2O3<5×10-19 cm2 molec.−1, σ355nm,I2O4= (3.9±1.2)×10-18 cm2 molec.−1, σ355nm,I3O6= (6.1±1.6)×10-18 cm2 molec.−1, σ355nm,I3O7= (5.3±1.4)×10-18 cm2 molec.−1, and σ355nm,I5O12= (9.8±1.0)×10-18 cm2 molec.−1. Photodepletion at λ=532 nm was only observed for OIO, which enabled determination of upper limits for the absorption cross sections of IxOy at 532 nm using OIO as an actinometer. These measurements are supplemented with ab initio calculations of electronic spectra in order to estimate atmospheric photolysis rates J(IxOy). Our results confirm a high J(IxOy) scenario where IxOy is efficiently removed during daytime, implying enhanced iodine-driven ozone depletion and hindering iodine particle formation. Possible I2O3 and I2O4 photolysis products are discussed, including IO3, which may be a precursor to iodic acid (HIO3) in the presence of HO2.

scholarly journals Effects of black carbon morphology on the brown carbon absorption estimation: from numerical aspects

2020 ◽  
Author(s):  
Jie Luo ◽  
Yongming Zhang ◽  
Qixing Zhang
Keyword(s):  
Fractal Dimension ◽  
Numerical Method ◽  
Black Carbon ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Accurate Estimation ◽  
Total Absorption ◽  
Absorption Cross ◽  
Brown Carbon ◽  
Carbon Absorption

Abstract. In this work, we developed a numerical method to investigate the effects of black carbon morphology on the estimation of brown carbon (BrC) absorption using the Absorption Ångström exponent (AAE) method. Pseudo measurements of the total absorption were generated based on several morphologically mixed black carbon (BC) models, then the BrC absorption was inferred based on different AAE methods. By comparing the estimated BrC absorption with True BrC absorption, we found that both AAE = 1 and Mie AAE methods do not provide accurate estimation for the BrC absorption, and the estimated BrC absorption can deviate several times from True BrC absorption. The newly proposed Wavelength Dependent AAE (WDA) method does not necessarily improve the estimations, sometimes it may even provide worse estimations than the AAE = 1 and Mie AAE methods. Fixing the fractal dimension to be 1.8, the deviation between the estimated BrC mass absorption cross-section (MAC) and True BrC MAC can reach approximately 9 m2/g, which is far more than brown carbon MAC itself. Therefore, the estimation of BrC absorption based on the AAE method should carefully consider the morphological effects of BC. Our findings highlight the BC morphological effects on the BrC absorption estimation.

Alkyl-triphenylamine end-capped triazines with AIE and large two-photon absorption cross-sections for bioimaging

2014 ◽  
Vol 2 (31) ◽  
pp. 6353-6361 ◽  
Author(s):  
Yuting Gao ◽  
Yi Qu ◽  
Tao Jiang ◽  
Hao Zhang ◽  
Nannan He ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Two Photon Absorption ◽  
Two Photon

Three alkyl-triphenylamine end-capped triazines (ATT-(1–3)) with AIE were synthesized, and the two-photon absorption cross section of ATT-3 was 10 003 GM.

Contribution of L Shell to the Total Absorption Cross Section in Aluminum

1969 ◽  
Vol 40 (7) ◽  
pp. 3046-3047 ◽  
Author(s):  
R. Haensel ◽  
B. Sonntag ◽  
C. Kunz ◽  
T. Sasaki
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Total Absorption ◽  
Absorption Cross

Absorption cross-sections of atmospheric gases for use in aeronomy

1969 ◽  
Vol 47 (10) ◽  
pp. 1823-1834 ◽  
Author(s):  
Robert E. Huffman
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Emission Lines ◽  
Current Status ◽  
Absorption Cross ◽  
Atmospheric Gases ◽  
Ionization Cross ◽  
Atmospheric Absorption ◽  
Ionization Cross Sections

The current status of absorption cross-section measurements for aeronomic use is reviewed. Recommended values for the gases O2, N2, O, and O3 are given at wavelengths where there is strong atmospheric absorption in the 3500–10 Å region. A table of absorption and ionization cross-sections at important solar emission lines is given. The problem of insufficient resolution at some wavelengths is discussed, and information on photolysis products is given where available.

Sign in / Sign up

Export Citation Format

Share Document