Abstract: Determination of Auger electron excitation cross sections and ranges using proton-excited x-rays

1974 ◽  
Vol 11 (1) ◽  
pp. 278-278 ◽  
Author(s):  
P. B. Needham ◽  
T. J. Driscoll
Keyword(s):  
Cross Sections ◽  
Auger Electron ◽  
Electron Excitation ◽  
X Rays ◽  
Excitation Cross Sections

Determination of absolute two-photon excitation cross sections by in situ second-order autocorrelation

1995 ◽  
Vol 20 (23) ◽  
pp. 2372 ◽  
Author(s):  
Chris Xu ◽  
Winfried Denk ◽  
Jeffrey Guild ◽  
Watt W. Webb
Keyword(s):  
Cross Sections ◽  
Second Order ◽  
Two Photon ◽  
Photon Excitation ◽  
Excitation Cross Sections ◽  
Two Photon Excitation

Destruction of C2H4O2 isomers in ice-phase by X-rays: Implication on the abundance of acetic acid and methyl formate in the interstellar medium

2017 ◽  
Vol 13 (S332) ◽  
pp. 418-424
Author(s):  
Marina G. Rachid ◽  
K. Faquine ◽  
S. Pilling
Keyword(s):  
Acetic Acid ◽  
Cross Sections ◽  
Methyl Formate ◽  
X Rays ◽  
Formation Cross Section ◽  
X Ray ◽  
Synchrotron Light ◽  
The Difference ◽  
Astrophysical Ices

AbstractC2H4O2 isomers, methyl formate (HCOOCH3), acetic acid (CH3COOH) and glycoaldehyde (HOCH2CHO), have been detected in a lot of sources in ISM. However, their abundances are very different, with methyl formate much more abundant than the other two isomers. This fact may be related to the different destruction by ionizing radiation of these molecules. The goal of this work is experimentally study the photodissociation processes of methyl formate and acetic acid ices when exposed to broadband soft X-ray from 6 up to 2000 eV. The experiments were performed coupled to the SGM beamline in the Brazilian Synchrotron Light Source (LNLS/CNPEM) at Campinas, Brazil. The simulated astrophysical ices (12K) were monitored throughout the experiment using infrared vibrational spectroscopy. The analysis of processed ices allowed the determination of the effective destruction cross sections of the parent molecules as well as the effective formation cross section of daughter molecular species. The relative abundance between acetic acid and methyl formate (NCH3COOH/NHCOOCH3) in different astronomical scenarios and their column density evolution in the presence of X-rays were calculated and our results suggests that such radiation field can be one of the factors that explain the difference in the isomers C2H4O2 abundances. We also quantified the daugther species after the establishment of a chemical equilibrium in the samples.

Intensity and Distribution of Background X-rays in Wavelength Dispersive Spectrometry III

1989 ◽  
Vol 33 ◽  
pp. 521-529
Author(s):  
Tomoya Arai ◽  
Takashi Shoji
Keyword(s):  
Spectroscopic Analysis ◽  
Electron Excitation ◽  
Major Elements ◽  
X Rays ◽  
Fundamental Feature ◽  
X Ray ◽  
Wavelength Dispersive Spectrometry ◽  
Low Concentrations ◽  
Ppm Level

In the spectroscopic analysis of composite elements by x-ray fluorescence (XRF), it is the fundamental feature of this method that the background x-ray intensity is lower than that with electron excitation. However, the background x-rays of this method, which consist of Thomson (Rayleigh) and Compton scattered x-rays from the primary radiation, impair the analytical performance at the ppm level. In order toinvestigate the intensity of the background x-rays precisely,the study was conducted in two parts. The first part compared the measured and theoretically calculated x-ray intensities for Rh Kα and Rh Kβ peaks from various materials. The second part examined the determination of low concentrations of lead,arsenic and colonium in steel samples. The variation in the background x-ray intensities of the analyzed elements was found to be caused by the variation of the major elements and a correction equation for it is derived.

scholarly journals On the Interpretation of the Relative Intensities of the Solar XUV Lines of Lithium-Like Ions

1972 ◽  
Vol 14 ◽  
pp. 738-739
Author(s):  
D. R. Flower
Keyword(s):  
Cross Sections ◽  
Electron Excitation ◽  
Energy Separation ◽  
Temperature Structure ◽  
Isoelectronic Sequence ◽  
Ionization Equilibrium ◽  
Excitation Cross Sections ◽  
Powerful Means ◽  
Intensity Ratios ◽  
Equilibrium Calculations

The relative intensities of the 2s–2p and 2l–3l′ (l=0, l′= 1; l= 1, l′ = 0, 2) solar XUV lines of ions in the lithium isoelectronic sequence are sensitive to electron temperature because of the large energy separation of the 2p and 3/’ levels. Recent observations of these lines for three members of the sequence, O+5, Ne+7 and Mg+9 (Heroux and Cohen, 1971), consequently provide a potentially powerful means of studying the temperature structure of the upper chromosphere-corona transition region. These observations have been examined in the light of recent calculations of the electron excitation cross-sections for the relevant transitions (Flower, 1971). It is found that the observed intensity ratios are systematically greater than values calculated assuming that all the lines of a given ion are produced at essentially the same temperature, namely, the temperature for which the ionization equilibrium calculations of Jordan (1969) predict that emission in the lines is most highly favoured. Part of the discrepancy is removed if this assumption is dropped and the emission in each line is calculated separately before taking the ratio. These two calculations do not yield the same result because there is a high temperature tail in the ionization curve of the lithium-like ions which results in the transitions of higher excitation energy, the 2l–3l′ transitions, being enhanced relative to the 2s–2p transition. The unsatisfactory agreement between theory and observation could have important implications for current theories of the ionization equilibrium, but, before definite conclusions can be reached, further observations of the same type need to be made and remaining uncertainties in the cross-sections to be resolved.

Threshold-energy region in the electron-excitation cross sections of the sodium resonant transition

1993 ◽  
Vol 48 (2) ◽  
pp. 1189-1194 ◽  
Author(s):  
C. H. Ying ◽  
F. Perales ◽  
L. Vušković ◽  
B. Bederson
Keyword(s):  
Cross Sections ◽  
Energy Region ◽  
Threshold Energy ◽  
Electron Excitation ◽  
Resonant Transition ◽  
Excitation Cross Sections

Electron Excitation Cross Sections for the SiiTransitions 3s23p34So→ 3s23p32Do,2Po, and 3s3p44P

1997 ◽  
Vol 484 (2) ◽  
pp. 979-984 ◽  
Author(s):  
C. Liao ◽  
Steven J. Smith ◽  
D. Hitz ◽  
A. Chutjian ◽  
S. S. Tayal
Keyword(s):  
Cross Sections ◽  
Electron Excitation ◽  
Excitation Cross Sections
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