Nuclear Absorption of Low-Energy Pions

1971 ◽  
Vol 49 (9) ◽  
pp. 1211-1214 ◽  
Author(s):  
Douglas S. Beder
Keyword(s):  
Numerical Calculation ◽  
Nuclear Matter ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Absorption Rate ◽  
Mean Free Path ◽  
Low Energy ◽  
Absorption Cross ◽  
Nuclear Absorption ◽  
The Mean

We derive an expression for the mean free path of low energy π's traversing nuclear matter, assuming that absorption is dominantly on nucleon pairs. Relating the absorption cross section to the data for the inverse reaction NN → NNπ makes this susceptible to numerical calculation. We also discuss how properly to account for nucleon Fermi motion in calculating the absorption rate.

Differences in photosynthetic activity between coral sections infested and not infested by boring spionid polychaetes

2006 ◽  
Vol 86 (4) ◽  
pp. 727-728 ◽  
Author(s):  
Jeffrey Wielgus ◽  
Oren Levy
Keyword(s):  
Photosystem Ii ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Repetition Rate ◽  
Photosynthetic Activity ◽  
Mean Value ◽  
Absorption Cross ◽  
Physiological Mechanisms ◽  
Coral Colony ◽  
The Mean

A SCUBA-based fast repetition rate fluorometer (FRRF) was used to study differences in the functional absorption cross-section of Photosystem II (σPSII) between areas of a coral colony of Astreoporamyriophthalma that were infested with spionid polychaetes vs areas lacking worms. The mean value of σPSII in infested areas (mean±SD=347.62±30.67 Å2) was significantly higher than in the areas that were not infested (316.32±17.49 Å2; P<0.0001). Several physiological mechanisms are discussed that may contribute to the observed differences.

scholarly journals ABSORPTION CROSS-SECTION IN DE SITTER SPACE

2003 ◽  
Vol 18 (09) ◽  
pp. 617-628 ◽  
Author(s):  
Y. S. MYUNG
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Three Dimensional ◽  
De Sitter Space ◽  
Temperature Limit ◽  
Low Energy ◽  
Massless Scalar ◽  
Cosmological Horizon ◽  
Absorption Cross ◽  
De Sitter

We study the wave equation for a minimally coupled massive scalar in three-dimensional de Sitter space. We compute the absorption cross-section to investigate its cosmological horizon in the southern diamond. Although the absorption cross-section is not defined exactly, it can be determined from the fact that the low-energy s(j = 0)-wave absorption cross-section for a massless scalar is given by the area of the cosmological horizon. On the other hand, the low-temperature limit of j ≠ 0-mode absorption cross-section is useful for extracting information surrounding the cosmological horizon. Finally we mention a computation of the absorption cross-section on the CFT-side using the dS/CFT correspondence.

scholarly journals Photoelectric absorption cross section of silicon near the bandgap from room temperature to sub-Kelvin temperature

AIP Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 025120
Author(s):  
C. Stanford ◽  
M. J. Wilson ◽  
B. Cabrera ◽  
M. Diamond ◽  
N. A. Kurinsky ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Room Temperature ◽  
Absorption Cross ◽  
Photoelectric Absorption

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.

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